/*

  * Matroska file demuxer

  * Copyright (c) 2003-2008 The FFmpeg Project

  *
  * This file is part of FFmpeg.
  *
  * FFmpeg is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
  * version 2.1 of the License, or (at your option) any later version.
  *
  * FFmpeg is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public
  * License along with FFmpeg; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
 /**

  * @file libavformat/matroskadec.c

  * Matroska file demuxer
  * by Ronald Bultje <rbultje@ronald.bitfreak.net>
  * with a little help from Moritz Bunkus <moritz@bunkus.org>

  * totally reworked by Aurelien Jacobs <aurel@gnuage.org>

  * Specs available on the Matroska project page: http://www.matroska.org/.

  */
 

 #include <stdio.h>

 #include "avformat.h"
 /* For codec_get_id(). */
 #include "riff.h"

 #include "isom.h"

 #include "matroska.h"

 #include "libavcodec/mpeg4audio.h"

 #include "libavutil/intfloat_readwrite.h"

 #include "libavutil/intreadwrite.h"

 #include "libavutil/avstring.h"

 #include "libavutil/lzo.h"

 #if CONFIG_ZLIB

 #include <zlib.h>
 #endif

 #if CONFIG_BZLIB

 #include <bzlib.h>
 #endif

 typedef enum {
     EBML_NONE,
     EBML_UINT,
     EBML_FLOAT,
     EBML_STR,
     EBML_UTF8,
     EBML_BIN,
     EBML_NEST,
     EBML_PASS,
     EBML_STOP,
 } EbmlType;
 
 typedef const struct EbmlSyntax {
     uint32_t id;
     EbmlType type;
     int list_elem_size;
     int data_offset;
     union {
         uint64_t    u;
         double      f;
         const char *s;
         const struct EbmlSyntax *n;
     } def;
 } EbmlSyntax;
 
 typedef struct {
     int nb_elem;
     void *elem;
 } EbmlList;
 
 typedef struct {
     int      size;
     uint8_t *data;
     int64_t  pos;
 } EbmlBin;
 

 typedef struct {
     uint64_t version;
     uint64_t max_size;
     uint64_t id_length;
     char    *doctype;
     uint64_t doctype_version;
 } Ebml;
 

 typedef struct {
     uint64_t algo;
     EbmlBin  settings;
 } MatroskaTrackCompression;

 typedef struct {
     uint64_t scope;
     uint64_t type;
     MatroskaTrackCompression compression;
 } MatroskaTrackEncoding;

 typedef struct {
     double   frame_rate;
     uint64_t display_width;
     uint64_t display_height;
     uint64_t pixel_width;
     uint64_t pixel_height;
     uint64_t fourcc;
 } MatroskaTrackVideo;

 typedef struct {
     double   samplerate;
     double   out_samplerate;
     uint64_t bitdepth;
     uint64_t channels;
 
     /* real audio header (extracted from extradata) */
     int      coded_framesize;
     int      sub_packet_h;
     int      frame_size;
     int      sub_packet_size;
     int      sub_packet_cnt;
     int      pkt_cnt;
     uint8_t *buf;
 } MatroskaTrackAudio;

 typedef struct {
     uint64_t num;

     uint64_t uid;

     uint64_t type;

     char    *name;

     char    *codec_id;
     EbmlBin  codec_priv;
     char    *language;

     double time_scale;

     uint64_t default_duration;

     uint64_t flag_default;

     MatroskaTrackVideo video;
     MatroskaTrackAudio audio;
     EbmlList encodings;

 
     AVStream *stream;

     int64_t end_timecode;

 } MatroskaTrack;
 

 typedef struct {

     uint64_t uid;

     char *filename;
     char *mime;
     EbmlBin bin;

 
     AVStream *stream;

 } MatroskaAttachement;
 
 typedef struct {

     uint64_t start;
     uint64_t end;
     uint64_t uid;
     char    *title;

 
     AVChapter *chapter;

 } MatroskaChapter;
 
 typedef struct {

     uint64_t track;
     uint64_t pos;
 } MatroskaIndexPos;
 
 typedef struct {
     uint64_t time;
     EbmlList pos;
 } MatroskaIndex;
 

 typedef struct {

     char *name;
     char *string;

     char *lang;
     uint64_t def;

     EbmlList sub;
 } MatroskaTag;
 
 typedef struct {

     char    *type;
     uint64_t typevalue;
     uint64_t trackuid;
     uint64_t chapteruid;
     uint64_t attachuid;
 } MatroskaTagTarget;
 
 typedef struct {
     MatroskaTagTarget target;
     EbmlList tag;
 } MatroskaTags;
 
 typedef struct {

     uint64_t id;
     uint64_t pos;
 } MatroskaSeekhead;
 

 typedef struct {

     uint64_t start;
     uint64_t length;

 } MatroskaLevel;
 

 typedef struct {

     AVFormatContext *ctx;
 

     /* EBML stuff */

     int num_levels;
     MatroskaLevel levels[EBML_MAX_DEPTH];
     int level_up;
 

     uint64_t time_scale;
     double   duration;
     char    *title;

     EbmlList tracks;

     EbmlList attachments;

     EbmlList chapters;

     EbmlList index;

     EbmlList tags;

     EbmlList seekhead;

 
     /* byte position of the segment inside the stream */

     int64_t segment_start;

     /* the packet queue */

     AVPacket **packets;
     int num_packets;

     AVPacket *prev_pkt;

     int done;

     int has_cluster_id;

 
     /* What to skip before effectively reading a packet. */
     int skip_to_keyframe;

     uint64_t skip_to_timecode;

 } MatroskaDemuxContext;
 

 typedef struct {
     uint64_t duration;
     int64_t  reference;
     EbmlBin  bin;
 } MatroskaBlock;
 
 typedef struct {
     uint64_t timecode;
     EbmlList blocks;
 } MatroskaCluster;
 

 static EbmlSyntax ebml_header[] = {
     { EBML_ID_EBMLREADVERSION,        EBML_UINT, 0, offsetof(Ebml,version), {.u=EBML_VERSION} },
     { EBML_ID_EBMLMAXSIZELENGTH,      EBML_UINT, 0, offsetof(Ebml,max_size), {.u=8} },
     { EBML_ID_EBMLMAXIDLENGTH,        EBML_UINT, 0, offsetof(Ebml,id_length), {.u=4} },
     { EBML_ID_DOCTYPE,                EBML_STR,  0, offsetof(Ebml,doctype), {.s="(none)"} },
     { EBML_ID_DOCTYPEREADVERSION,     EBML_UINT, 0, offsetof(Ebml,doctype_version), {.u=1} },
     { EBML_ID_EBMLVERSION,            EBML_NONE },
     { EBML_ID_DOCTYPEVERSION,         EBML_NONE },
     { 0 }
 };
 
 static EbmlSyntax ebml_syntax[] = {
     { EBML_ID_HEADER,                 EBML_NEST, 0, 0, {.n=ebml_header} },
     { 0 }
 };
 

 static EbmlSyntax matroska_info[] = {
     { MATROSKA_ID_TIMECODESCALE,      EBML_UINT,  0, offsetof(MatroskaDemuxContext,time_scale), {.u=1000000} },
     { MATROSKA_ID_DURATION,           EBML_FLOAT, 0, offsetof(MatroskaDemuxContext,duration) },
     { MATROSKA_ID_TITLE,              EBML_UTF8,  0, offsetof(MatroskaDemuxContext,title) },
     { MATROSKA_ID_WRITINGAPP,         EBML_NONE },
     { MATROSKA_ID_MUXINGAPP,          EBML_NONE },
     { MATROSKA_ID_DATEUTC,            EBML_NONE },
     { MATROSKA_ID_SEGMENTUID,         EBML_NONE },
     { 0 }
 };
 

 static EbmlSyntax matroska_track_video[] = {
     { MATROSKA_ID_VIDEOFRAMERATE,     EBML_FLOAT,0, offsetof(MatroskaTrackVideo,frame_rate) },
     { MATROSKA_ID_VIDEODISPLAYWIDTH,  EBML_UINT, 0, offsetof(MatroskaTrackVideo,display_width) },
     { MATROSKA_ID_VIDEODISPLAYHEIGHT, EBML_UINT, 0, offsetof(MatroskaTrackVideo,display_height) },
     { MATROSKA_ID_VIDEOPIXELWIDTH,    EBML_UINT, 0, offsetof(MatroskaTrackVideo,pixel_width) },
     { MATROSKA_ID_VIDEOPIXELHEIGHT,   EBML_UINT, 0, offsetof(MatroskaTrackVideo,pixel_height) },
     { MATROSKA_ID_VIDEOCOLORSPACE,    EBML_UINT, 0, offsetof(MatroskaTrackVideo,fourcc) },

     { MATROSKA_ID_VIDEOPIXELCROPB,    EBML_NONE },
     { MATROSKA_ID_VIDEOPIXELCROPT,    EBML_NONE },
     { MATROSKA_ID_VIDEOPIXELCROPL,    EBML_NONE },
     { MATROSKA_ID_VIDEOPIXELCROPR,    EBML_NONE },
     { MATROSKA_ID_VIDEODISPLAYUNIT,   EBML_NONE },

     { MATROSKA_ID_VIDEOFLAGINTERLACED,EBML_NONE },
     { MATROSKA_ID_VIDEOSTEREOMODE,    EBML_NONE },
     { MATROSKA_ID_VIDEOASPECTRATIO,   EBML_NONE },
     { 0 }
 };
 
 static EbmlSyntax matroska_track_audio[] = {
     { MATROSKA_ID_AUDIOSAMPLINGFREQ,  EBML_FLOAT,0, offsetof(MatroskaTrackAudio,samplerate), {.f=8000.0} },
     { MATROSKA_ID_AUDIOOUTSAMPLINGFREQ,EBML_FLOAT,0,offsetof(MatroskaTrackAudio,out_samplerate) },
     { MATROSKA_ID_AUDIOBITDEPTH,      EBML_UINT, 0, offsetof(MatroskaTrackAudio,bitdepth) },
     { MATROSKA_ID_AUDIOCHANNELS,      EBML_UINT, 0, offsetof(MatroskaTrackAudio,channels), {.u=1} },
     { 0 }
 };
 
 static EbmlSyntax matroska_track_encoding_compression[] = {
     { MATROSKA_ID_ENCODINGCOMPALGO,   EBML_UINT, 0, offsetof(MatroskaTrackCompression,algo), {.u=0} },
     { MATROSKA_ID_ENCODINGCOMPSETTINGS,EBML_BIN, 0, offsetof(MatroskaTrackCompression,settings) },
     { 0 }
 };
 
 static EbmlSyntax matroska_track_encoding[] = {
     { MATROSKA_ID_ENCODINGSCOPE,      EBML_UINT, 0, offsetof(MatroskaTrackEncoding,scope), {.u=1} },
     { MATROSKA_ID_ENCODINGTYPE,       EBML_UINT, 0, offsetof(MatroskaTrackEncoding,type), {.u=0} },
     { MATROSKA_ID_ENCODINGCOMPRESSION,EBML_NEST, 0, offsetof(MatroskaTrackEncoding,compression), {.n=matroska_track_encoding_compression} },

     { MATROSKA_ID_ENCODINGORDER,      EBML_NONE },

     { 0 }
 };
 
 static EbmlSyntax matroska_track_encodings[] = {
     { MATROSKA_ID_TRACKCONTENTENCODING, EBML_NEST, sizeof(MatroskaTrackEncoding), offsetof(MatroskaTrack,encodings), {.n=matroska_track_encoding} },
     { 0 }
 };
 
 static EbmlSyntax matroska_track[] = {
     { MATROSKA_ID_TRACKNUMBER,          EBML_UINT, 0, offsetof(MatroskaTrack,num) },

     { MATROSKA_ID_TRACKNAME,            EBML_UTF8, 0, offsetof(MatroskaTrack,name) },

     { MATROSKA_ID_TRACKUID,             EBML_UINT, 0, offsetof(MatroskaTrack,uid) },

     { MATROSKA_ID_TRACKTYPE,            EBML_UINT, 0, offsetof(MatroskaTrack,type) },
     { MATROSKA_ID_CODECID,              EBML_STR,  0, offsetof(MatroskaTrack,codec_id) },
     { MATROSKA_ID_CODECPRIVATE,         EBML_BIN,  0, offsetof(MatroskaTrack,codec_priv) },
     { MATROSKA_ID_TRACKLANGUAGE,        EBML_UTF8, 0, offsetof(MatroskaTrack,language), {.s="eng"} },
     { MATROSKA_ID_TRACKDEFAULTDURATION, EBML_UINT, 0, offsetof(MatroskaTrack,default_duration) },
     { MATROSKA_ID_TRACKTIMECODESCALE,   EBML_FLOAT,0, offsetof(MatroskaTrack,time_scale), {.f=1.0} },
     { MATROSKA_ID_TRACKFLAGDEFAULT,     EBML_UINT, 0, offsetof(MatroskaTrack,flag_default), {.u=1} },
     { MATROSKA_ID_TRACKVIDEO,           EBML_NEST, 0, offsetof(MatroskaTrack,video), {.n=matroska_track_video} },
     { MATROSKA_ID_TRACKAUDIO,           EBML_NEST, 0, offsetof(MatroskaTrack,audio), {.n=matroska_track_audio} },
     { MATROSKA_ID_TRACKCONTENTENCODINGS,EBML_NEST, 0, 0, {.n=matroska_track_encodings} },
     { MATROSKA_ID_TRACKFLAGENABLED,     EBML_NONE },
     { MATROSKA_ID_TRACKFLAGFORCED,      EBML_NONE },
     { MATROSKA_ID_TRACKFLAGLACING,      EBML_NONE },
     { MATROSKA_ID_CODECNAME,            EBML_NONE },
     { MATROSKA_ID_CODECDECODEALL,       EBML_NONE },
     { MATROSKA_ID_CODECINFOURL,         EBML_NONE },
     { MATROSKA_ID_CODECDOWNLOADURL,     EBML_NONE },
     { MATROSKA_ID_TRACKMINCACHE,        EBML_NONE },
     { MATROSKA_ID_TRACKMAXCACHE,        EBML_NONE },

     { MATROSKA_ID_TRACKMAXBLKADDID,     EBML_NONE },

     { 0 }
 };
 
 static EbmlSyntax matroska_tracks[] = {
     { MATROSKA_ID_TRACKENTRY,         EBML_NEST, sizeof(MatroskaTrack), offsetof(MatroskaDemuxContext,tracks), {.n=matroska_track} },
     { 0 }
 };
 

 static EbmlSyntax matroska_attachment[] = {

     { MATROSKA_ID_FILEUID,            EBML_UINT, 0, offsetof(MatroskaAttachement,uid) },

     { MATROSKA_ID_FILENAME,           EBML_UTF8, 0, offsetof(MatroskaAttachement,filename) },
     { MATROSKA_ID_FILEMIMETYPE,       EBML_STR,  0, offsetof(MatroskaAttachement,mime) },
     { MATROSKA_ID_FILEDATA,           EBML_BIN,  0, offsetof(MatroskaAttachement,bin) },

     { MATROSKA_ID_FILEDESC,           EBML_NONE },

     { 0 }
 };
 
 static EbmlSyntax matroska_attachments[] = {
     { MATROSKA_ID_ATTACHEDFILE,       EBML_NEST, sizeof(MatroskaAttachement), offsetof(MatroskaDemuxContext,attachments), {.n=matroska_attachment} },
     { 0 }
 };
 

 static EbmlSyntax matroska_chapter_display[] = {
     { MATROSKA_ID_CHAPSTRING,         EBML_UTF8, 0, offsetof(MatroskaChapter,title) },

     { MATROSKA_ID_CHAPLANG,           EBML_NONE },

     { 0 }
 };
 
 static EbmlSyntax matroska_chapter_entry[] = {
     { MATROSKA_ID_CHAPTERTIMESTART,   EBML_UINT, 0, offsetof(MatroskaChapter,start), {.u=AV_NOPTS_VALUE} },
     { MATROSKA_ID_CHAPTERTIMEEND,     EBML_UINT, 0, offsetof(MatroskaChapter,end), {.u=AV_NOPTS_VALUE} },
     { MATROSKA_ID_CHAPTERUID,         EBML_UINT, 0, offsetof(MatroskaChapter,uid) },
     { MATROSKA_ID_CHAPTERDISPLAY,     EBML_NEST, 0, 0, {.n=matroska_chapter_display} },
     { MATROSKA_ID_CHAPTERFLAGHIDDEN,  EBML_NONE },

     { MATROSKA_ID_CHAPTERFLAGENABLED, EBML_NONE },
     { MATROSKA_ID_CHAPTERPHYSEQUIV,   EBML_NONE },
     { MATROSKA_ID_CHAPTERATOM,        EBML_NONE },

     { 0 }
 };
 
 static EbmlSyntax matroska_chapter[] = {
     { MATROSKA_ID_CHAPTERATOM,        EBML_NEST, sizeof(MatroskaChapter), offsetof(MatroskaDemuxContext,chapters), {.n=matroska_chapter_entry} },
     { MATROSKA_ID_EDITIONUID,         EBML_NONE },
     { MATROSKA_ID_EDITIONFLAGHIDDEN,  EBML_NONE },
     { MATROSKA_ID_EDITIONFLAGDEFAULT, EBML_NONE },

     { MATROSKA_ID_EDITIONFLAGORDERED, EBML_NONE },

     { 0 }
 };
 
 static EbmlSyntax matroska_chapters[] = {
     { MATROSKA_ID_EDITIONENTRY,       EBML_NEST, 0, 0, {.n=matroska_chapter} },
     { 0 }
 };
 

 static EbmlSyntax matroska_index_pos[] = {
     { MATROSKA_ID_CUETRACK,           EBML_UINT, 0, offsetof(MatroskaIndexPos,track) },
     { MATROSKA_ID_CUECLUSTERPOSITION, EBML_UINT, 0, offsetof(MatroskaIndexPos,pos)   },

     { MATROSKA_ID_CUEBLOCKNUMBER,     EBML_NONE },

     { 0 }
 };
 
 static EbmlSyntax matroska_index_entry[] = {
     { MATROSKA_ID_CUETIME,            EBML_UINT, 0, offsetof(MatroskaIndex,time) },
     { MATROSKA_ID_CUETRACKPOSITION,   EBML_NEST, sizeof(MatroskaIndexPos), offsetof(MatroskaIndex,pos), {.n=matroska_index_pos} },
     { 0 }
 };
 
 static EbmlSyntax matroska_index[] = {
     { MATROSKA_ID_POINTENTRY,         EBML_NEST, sizeof(MatroskaIndex), offsetof(MatroskaDemuxContext,index), {.n=matroska_index_entry} },
     { 0 }
 };
 

 static EbmlSyntax matroska_simpletag[] = {
     { MATROSKA_ID_TAGNAME,            EBML_UTF8, 0, offsetof(MatroskaTag,name) },
     { MATROSKA_ID_TAGSTRING,          EBML_UTF8, 0, offsetof(MatroskaTag,string) },

     { MATROSKA_ID_TAGLANG,            EBML_STR,  0, offsetof(MatroskaTag,lang), {.s="und"} },
     { MATROSKA_ID_TAGDEFAULT,         EBML_UINT, 0, offsetof(MatroskaTag,def) },

     { MATROSKA_ID_SIMPLETAG,          EBML_NEST, sizeof(MatroskaTag), offsetof(MatroskaTag,sub), {.n=matroska_simpletag} },
     { 0 }
 };
 

 static EbmlSyntax matroska_tagtargets[] = {
     { MATROSKA_ID_TAGTARGETS_TYPE,      EBML_STR,  0, offsetof(MatroskaTagTarget,type) },
     { MATROSKA_ID_TAGTARGETS_TYPEVALUE, EBML_UINT, 0, offsetof(MatroskaTagTarget,typevalue), {.u=50} },
     { MATROSKA_ID_TAGTARGETS_TRACKUID,  EBML_UINT, 0, offsetof(MatroskaTagTarget,trackuid) },
     { MATROSKA_ID_TAGTARGETS_CHAPTERUID,EBML_UINT, 0, offsetof(MatroskaTagTarget,chapteruid) },
     { MATROSKA_ID_TAGTARGETS_ATTACHUID, EBML_UINT, 0, offsetof(MatroskaTagTarget,attachuid) },
     { 0 }
 };
 

 static EbmlSyntax matroska_tag[] = {

     { MATROSKA_ID_SIMPLETAG,          EBML_NEST, sizeof(MatroskaTag), offsetof(MatroskaTags,tag), {.n=matroska_simpletag} },
     { MATROSKA_ID_TAGTARGETS,         EBML_NEST, 0, offsetof(MatroskaTags,target), {.n=matroska_tagtargets} },

     { 0 }
 };
 

 static EbmlSyntax matroska_tags[] = {

     { MATROSKA_ID_TAG,                EBML_NEST, sizeof(MatroskaTags), offsetof(MatroskaDemuxContext,tags), {.n=matroska_tag} },

     { 0 }
 };
 

 static EbmlSyntax matroska_seekhead_entry[] = {
     { MATROSKA_ID_SEEKID,             EBML_UINT, 0, offsetof(MatroskaSeekhead,id) },
     { MATROSKA_ID_SEEKPOSITION,       EBML_UINT, 0, offsetof(MatroskaSeekhead,pos), {.u=-1} },
     { 0 }
 };
 
 static EbmlSyntax matroska_seekhead[] = {
     { MATROSKA_ID_SEEKENTRY,          EBML_NEST, sizeof(MatroskaSeekhead), offsetof(MatroskaDemuxContext,seekhead), {.n=matroska_seekhead_entry} },
     { 0 }
 };
 

 static EbmlSyntax matroska_segment[] = {
     { MATROSKA_ID_INFO,           EBML_NEST, 0, 0, {.n=matroska_info       } },
     { MATROSKA_ID_TRACKS,         EBML_NEST, 0, 0, {.n=matroska_tracks     } },
     { MATROSKA_ID_ATTACHMENTS,    EBML_NEST, 0, 0, {.n=matroska_attachments} },
     { MATROSKA_ID_CHAPTERS,       EBML_NEST, 0, 0, {.n=matroska_chapters   } },
     { MATROSKA_ID_CUES,           EBML_NEST, 0, 0, {.n=matroska_index      } },
     { MATROSKA_ID_TAGS,           EBML_NEST, 0, 0, {.n=matroska_tags       } },
     { MATROSKA_ID_SEEKHEAD,       EBML_NEST, 0, 0, {.n=matroska_seekhead   } },
     { MATROSKA_ID_CLUSTER,        EBML_STOP, 0, offsetof(MatroskaDemuxContext,has_cluster_id) },
     { 0 }
 };
 
 static EbmlSyntax matroska_segments[] = {
     { MATROSKA_ID_SEGMENT,        EBML_NEST, 0, 0, {.n=matroska_segment    } },
     { 0 }
 };
 

 static EbmlSyntax matroska_blockgroup[] = {
     { MATROSKA_ID_BLOCK,          EBML_BIN,  0, offsetof(MatroskaBlock,bin) },
     { MATROSKA_ID_SIMPLEBLOCK,    EBML_BIN,  0, offsetof(MatroskaBlock,bin) },
     { MATROSKA_ID_BLOCKDURATION,  EBML_UINT, 0, offsetof(MatroskaBlock,duration), {.u=AV_NOPTS_VALUE} },
     { MATROSKA_ID_BLOCKREFERENCE, EBML_UINT, 0, offsetof(MatroskaBlock,reference) },
     { 0 }
 };
 
 static EbmlSyntax matroska_cluster[] = {
     { MATROSKA_ID_CLUSTERTIMECODE,EBML_UINT,0, offsetof(MatroskaCluster,timecode) },
     { MATROSKA_ID_BLOCKGROUP,     EBML_NEST, sizeof(MatroskaBlock), offsetof(MatroskaCluster,blocks), {.n=matroska_blockgroup} },
     { MATROSKA_ID_SIMPLEBLOCK,    EBML_PASS, sizeof(MatroskaBlock), offsetof(MatroskaCluster,blocks), {.n=matroska_blockgroup} },

     { MATROSKA_ID_CLUSTERPOSITION,EBML_NONE },
     { MATROSKA_ID_CLUSTERPREVSIZE,EBML_NONE },

     { 0 }
 };
 
 static EbmlSyntax matroska_clusters[] = {
     { MATROSKA_ID_CLUSTER,        EBML_NEST, 0, 0, {.n=matroska_cluster} },

     { MATROSKA_ID_INFO,           EBML_NONE },
     { MATROSKA_ID_CUES,           EBML_NONE },
     { MATROSKA_ID_TAGS,           EBML_NONE },
     { MATROSKA_ID_SEEKHEAD,       EBML_NONE },

     { 0 }
 };
 

 /*

  * Return: Whether we reached the end of a level in the hierarchy or not.

  */

 static int ebml_level_end(MatroskaDemuxContext *matroska)

 {

     ByteIOContext *pb = matroska->ctx->pb;

     int64_t pos = url_ftell(pb);

     if (matroska->num_levels > 0) {

         MatroskaLevel *level = &matroska->levels[matroska->num_levels - 1];

         if (pos - level->start >= level->length) {

             matroska->num_levels--;

             return 1;

         }
     }

     return 0;

 }
 
 /*
  * Read: an "EBML number", which is defined as a variable-length
  * array of bytes. The first byte indicates the length by giving a
  * number of 0-bits followed by a one. The position of the first
  * "one" bit inside the first byte indicates the length of this
  * number.

  * Returns: number of bytes read, < 0 on error

  */

 static int ebml_read_num(MatroskaDemuxContext *matroska, ByteIOContext *pb,

                          int max_size, uint64_t *number)

 {
     int len_mask = 0x80, read = 1, n = 1;
     int64_t total = 0;
 

     /* The first byte tells us the length in bytes - get_byte() can normally

      * return 0, but since that's not a valid first ebmlID byte, we can
      * use it safely here to catch EOS. */
     if (!(total = get_byte(pb))) {
         /* we might encounter EOS here */
         if (!url_feof(pb)) {

             int64_t pos = url_ftell(pb);

             av_log(matroska->ctx, AV_LOG_ERROR,
                    "Read error at pos. %"PRIu64" (0x%"PRIx64")\n",
                    pos, pos);
         }

         return AVERROR(EIO); /* EOS or actual I/O error */

     }
 
     /* get the length of the EBML number */
     while (read <= max_size && !(total & len_mask)) {
         read++;
         len_mask >>= 1;
     }
     if (read > max_size) {

         int64_t pos = url_ftell(pb) - 1;

         av_log(matroska->ctx, AV_LOG_ERROR,
                "Invalid EBML number size tag 0x%02x at pos %"PRIu64" (0x%"PRIx64")\n",
                (uint8_t) total, pos, pos);
         return AVERROR_INVALIDDATA;
     }
 
     /* read out length */
     total &= ~len_mask;
     while (n++ < read)
         total = (total << 8) | get_byte(pb);
 
     *number = total;
 
     return read;
 }
 
 /*
  * Read the next element as an unsigned int.
  * 0 is success, < 0 is failure.
  */

 static int ebml_read_uint(ByteIOContext *pb, int size, uint64_t *num)

 {

     int n = 0;

     if (size < 1 || size > 8)

         return AVERROR_INVALIDDATA;
 

     /* big-endian ordering; build up number */

     *num = 0;
     while (n++ < size)
         *num = (*num << 8) | get_byte(pb);
 
     return 0;
 }
 
 /*
  * Read the next element as a float.
  * 0 is success, < 0 is failure.
  */

 static int ebml_read_float(ByteIOContext *pb, int size, double *num)

 {
     if (size == 4) {
         *num= av_int2flt(get_be32(pb));
     } else if(size==8){
         *num= av_int2dbl(get_be64(pb));

     } else

         return AVERROR_INVALIDDATA;
 
     return 0;
 }
 
 /*
  * Read the next element as an ASCII string.
  * 0 is success, < 0 is failure.
  */

 static int ebml_read_ascii(ByteIOContext *pb, int size, char **str)

 {

     av_free(*str);

     /* EBML strings are usually not 0-terminated, so we allocate one

      * byte more, read the string and NULL-terminate it ourselves. */

     if (!(*str = av_malloc(size + 1)))

         return AVERROR(ENOMEM);

     if (get_buffer(pb, (uint8_t *) *str, size) != size) {

         av_free(*str);

         return AVERROR(EIO);

     }
     (*str)[size] = '\0';
 
     return 0;
 }
 
 /*

  * Read the next element as binary data.
  * 0 is success, < 0 is failure.
  */
 static int ebml_read_binary(ByteIOContext *pb, int length, EbmlBin *bin)
 {
     av_free(bin->data);
     if (!(bin->data = av_malloc(length)))
         return AVERROR(ENOMEM);
 
     bin->size = length;
     bin->pos  = url_ftell(pb);
     if (get_buffer(pb, bin->data, length) != length)
         return AVERROR(EIO);
 
     return 0;
 }
 
 /*

  * Read the next element, but only the header. The contents
  * are supposed to be sub-elements which can be read separately.
  * 0 is success, < 0 is failure.
  */

 static int ebml_read_master(MatroskaDemuxContext *matroska, int length)

 {

     ByteIOContext *pb = matroska->ctx->pb;

     MatroskaLevel *level;
 
     if (matroska->num_levels >= EBML_MAX_DEPTH) {
         av_log(matroska->ctx, AV_LOG_ERROR,
                "File moves beyond max. allowed depth (%d)\n", EBML_MAX_DEPTH);

         return AVERROR(ENOSYS);

     }
 
     level = &matroska->levels[matroska->num_levels++];
     level->start = url_ftell(pb);
     level->length = length;
 
     return 0;
 }
 
 /*
  * Read signed/unsigned "EBML" numbers.

  * Return: number of bytes processed, < 0 on error

  */

 static int matroska_ebmlnum_uint(MatroskaDemuxContext *matroska,
                                  uint8_t *data, uint32_t size, uint64_t *num)

 {

     ByteIOContext pb;
     init_put_byte(&pb, data, size, 0, NULL, NULL, NULL, NULL);
     return ebml_read_num(matroska, &pb, 8, num);

 }
 
 /*
  * Same as above, but signed.
  */

 static int matroska_ebmlnum_sint(MatroskaDemuxContext *matroska,
                                  uint8_t *data, uint32_t size, int64_t *num)

 {
     uint64_t unum;
     int res;
 
     /* read as unsigned number first */

     if ((res = matroska_ebmlnum_uint(matroska, data, size, &unum)) < 0)

         return res;
 
     /* make signed (weird way) */

     *num = unum - ((1LL << (7*res - 1)) - 1);

 
     return res;
 }
 

 static int ebml_parse_elem(MatroskaDemuxContext *matroska,
                            EbmlSyntax *syntax, void *data);

 static int ebml_parse_id(MatroskaDemuxContext *matroska, EbmlSyntax *syntax,
                          uint32_t id, void *data)

 {
     int i;

     for (i=0; syntax[i].id; i++)
         if (id == syntax[i].id)
             break;

     if (!syntax[i].id && id != EBML_ID_VOID && id != EBML_ID_CRC32)

         av_log(matroska->ctx, AV_LOG_INFO, "Unknown entry 0x%X\n", id);
     return ebml_parse_elem(matroska, &syntax[i], data);

 }
 

 static int ebml_parse(MatroskaDemuxContext *matroska, EbmlSyntax *syntax,
                       void *data)

 {

     uint64_t id;
     int res = ebml_read_num(matroska, matroska->ctx->pb, 4, &id);
     id |= 1 << 7*res;

     return res < 0 ? res : ebml_parse_id(matroska, syntax, id, data);

 }
 

 static int ebml_parse_nest(MatroskaDemuxContext *matroska, EbmlSyntax *syntax,
                            void *data)

 {

     int i, res = 0;

     for (i=0; syntax[i].id; i++)
         switch (syntax[i].type) {
         case EBML_UINT:
             *(uint64_t *)((char *)data+syntax[i].data_offset) = syntax[i].def.u;
             break;
         case EBML_FLOAT:
             *(double   *)((char *)data+syntax[i].data_offset) = syntax[i].def.f;
             break;
         case EBML_STR:
         case EBML_UTF8:
             *(char    **)((char *)data+syntax[i].data_offset) = av_strdup(syntax[i].def.s);
             break;

         }

     while (!res && !ebml_level_end(matroska))
         res = ebml_parse(matroska, syntax, data);

     return res;

 }
 

 static int ebml_parse_elem(MatroskaDemuxContext *matroska,
                            EbmlSyntax *syntax, void *data)
 {

     ByteIOContext *pb = matroska->ctx->pb;

     uint32_t id = syntax->id;

     uint64_t length;

     int res;

     void *newelem;

 
     data = (char *)data + syntax->data_offset;
     if (syntax->list_elem_size) {
         EbmlList *list = data;

         newelem = av_realloc(list->elem, (list->nb_elem+1)*syntax->list_elem_size);
         if (!newelem)
             return AVERROR(ENOMEM);
         list->elem = newelem;

         data = (char*)list->elem + list->nb_elem*syntax->list_elem_size;
         memset(data, 0, syntax->list_elem_size);
         list->nb_elem++;
     }
 

     if (syntax->type != EBML_PASS && syntax->type != EBML_STOP)

         if ((res = ebml_read_num(matroska, pb, 8, &length)) < 0)

             return res;
 

     switch (syntax->type) {

     case EBML_UINT:  res = ebml_read_uint  (pb, length, data);  break;
     case EBML_FLOAT: res = ebml_read_float (pb, length, data);  break;

     case EBML_STR:

     case EBML_UTF8:  res = ebml_read_ascii (pb, length, data);  break;

     case EBML_BIN:   res = ebml_read_binary(pb, length, data);  break;

     case EBML_NEST:  if ((res=ebml_read_master(matroska, length)) < 0)

                          return res;
                      if (id == MATROSKA_ID_SEGMENT)
                          matroska->segment_start = url_ftell(matroska->ctx->pb);

                      return ebml_parse_nest(matroska, syntax->def.n, data);

     case EBML_PASS:  return ebml_parse_id(matroska, syntax->def.n, id, data);

     case EBML_STOP:  *(int *)data = 1;      return 1;

     default:         return url_fseek(pb,length,SEEK_CUR)<0 ? AVERROR(EIO) : 0;

     }

     if (res == AVERROR_INVALIDDATA)
         av_log(matroska->ctx, AV_LOG_ERROR, "Invalid element\n");
     else if (res == AVERROR(EIO))
         av_log(matroska->ctx, AV_LOG_ERROR, "Read error\n");
     return res;

 }
 
 static void ebml_free(EbmlSyntax *syntax, void *data)
 {
     int i, j;
     for (i=0; syntax[i].id; i++) {
         void *data_off = (char *)data + syntax[i].data_offset;
         switch (syntax[i].type) {
         case EBML_STR:
         case EBML_UTF8:  av_freep(data_off);                      break;
         case EBML_BIN:   av_freep(&((EbmlBin *)data_off)->data);  break;
         case EBML_NEST:
             if (syntax[i].list_elem_size) {
                 EbmlList *list = data_off;
                 char *ptr = list->elem;
                 for (j=0; j<list->nb_elem; j++, ptr+=syntax[i].list_elem_size)
                     ebml_free(syntax[i].def.n, ptr);
                 av_free(list->elem);
             } else
                 ebml_free(syntax[i].def.n, data_off);
         default:  break;
         }
     }
 }
 

 
 /*
  * Autodetecting...
  */
 static int matroska_probe(AVProbeData *p)
 {
     uint64_t total = 0;
     int len_mask = 0x80, size = 1, n = 1;

     static const char probe_data[] = "matroska";

     /* EBML header? */

     if (AV_RB32(p->buf) != EBML_ID_HEADER)
         return 0;
 
     /* length of header */
     total = p->buf[4];
     while (size <= 8 && !(total & len_mask)) {
         size++;
         len_mask >>= 1;
     }
     if (size > 8)
       return 0;
     total &= (len_mask - 1);
     while (n < size)
         total = (total << 8) | p->buf[4 + n++];
 

     /* Does the probe data contain the whole header? */

     if (p->buf_size < 4 + size + total)
       return 0;
 

     /* The header must contain the document type 'matroska'. For now,

      * we don't parse the whole header but simply check for the
      * availability of that array of characters inside the header.
      * Not fully fool-proof, but good enough. */
     for (n = 4+size; n <= 4+size+total-(sizeof(probe_data)-1); n++)
         if (!memcmp(p->buf+n, probe_data, sizeof(probe_data)-1))
             return AVPROBE_SCORE_MAX;
 
     return 0;
 }
 
 static MatroskaTrack *matroska_find_track_by_num(MatroskaDemuxContext *matroska,
                                                  int num)
 {
     MatroskaTrack *tracks = matroska->tracks.elem;
     int i;
 
     for (i=0; i < matroska->tracks.nb_elem; i++)
         if (tracks[i].num == num)
             return &tracks[i];
 
     av_log(matroska->ctx, AV_LOG_ERROR, "Invalid track number %d\n", num);
     return NULL;
 }
 

 static int matroska_decode_buffer(uint8_t** buf, int* buf_size,
                                   MatroskaTrack *track)

 {

     MatroskaTrackEncoding *encodings = track->encodings.elem;

     uint8_t* data = *buf;
     int isize = *buf_size;
     uint8_t* pkt_data = NULL;

     uint8_t* newpktdata;

     int pkt_size = isize;
     int result = 0;
     int olen;
 

     switch (encodings[0].compression.algo) {

     case MATROSKA_TRACK_ENCODING_COMP_HEADERSTRIP:

         return encodings[0].compression.settings.size;

     case MATROSKA_TRACK_ENCODING_COMP_LZO:
         do {
             olen = pkt_size *= 3;

             pkt_data = av_realloc(pkt_data, pkt_size+AV_LZO_OUTPUT_PADDING);

             result = av_lzo1x_decode(pkt_data, &olen, data, &isize);
         } while (result==AV_LZO_OUTPUT_FULL && pkt_size<10000000);

         if (result)
             goto failed;
         pkt_size -= olen;
         break;

 #if CONFIG_ZLIB

     case MATROSKA_TRACK_ENCODING_COMP_ZLIB: {
         z_stream zstream = {0};
         if (inflateInit(&zstream) != Z_OK)
             return -1;
         zstream.next_in = data;
         zstream.avail_in = isize;
         do {
             pkt_size *= 3;

             newpktdata = av_realloc(pkt_data, pkt_size);
             if (!newpktdata) {
                 inflateEnd(&zstream);
                 goto failed;
             }
             pkt_data = newpktdata;

             zstream.avail_out = pkt_size - zstream.total_out;
             zstream.next_out = pkt_data + zstream.total_out;
             result = inflate(&zstream, Z_NO_FLUSH);
         } while (result==Z_OK && pkt_size<10000000);
         pkt_size = zstream.total_out;
         inflateEnd(&zstream);
         if (result != Z_STREAM_END)
             goto failed;
         break;
     }
 #endif

 #if CONFIG_BZLIB

     case MATROSKA_TRACK_ENCODING_COMP_BZLIB: {
         bz_stream bzstream = {0};
         if (BZ2_bzDecompressInit(&bzstream, 0, 0) != BZ_OK)
             return -1;
         bzstream.next_in = data;
         bzstream.avail_in = isize;
         do {
             pkt_size *= 3;

             newpktdata = av_realloc(pkt_data, pkt_size);
             if (!newpktdata) {
                 BZ2_bzDecompressEnd(&bzstream);
                 goto failed;
             }
             pkt_data = newpktdata;

             bzstream.avail_out = pkt_size - bzstream.total_out_lo32;
             bzstream.next_out = pkt_data + bzstream.total_out_lo32;
             result = BZ2_bzDecompress(&bzstream);
         } while (result==BZ_OK && pkt_size<10000000);
         pkt_size = bzstream.total_out_lo32;
         BZ2_bzDecompressEnd(&bzstream);
         if (result != BZ_STREAM_END)
             goto failed;
         break;
     }
 #endif

     default:
         return -1;

     }
 
     *buf = pkt_data;
     *buf_size = pkt_size;
     return 0;
  failed:
     av_free(pkt_data);
     return -1;
 }
 

 static void matroska_fix_ass_packet(MatroskaDemuxContext *matroska,

                                     AVPacket *pkt, uint64_t display_duration)

 {
     char *line, *layer, *ptr = pkt->data, *end = ptr+pkt->size;
     for (; *ptr!=',' && ptr<end-1; ptr++);
     if (*ptr == ',')
         layer = ++ptr;
     for (; *ptr!=',' && ptr<end-1; ptr++);
     if (*ptr == ',') {

         int64_t end_pts = pkt->pts + display_duration;

         int sc = matroska->time_scale * pkt->pts / 10000000;
         int ec = matroska->time_scale * end_pts  / 10000000;
         int sh, sm, ss, eh, em, es, len;
         sh = sc/360000;  sc -= 360000*sh;
         sm = sc/  6000;  sc -=   6000*sm;
         ss = sc/   100;  sc -=    100*ss;
         eh = ec/360000;  ec -= 360000*eh;
         em = ec/  6000;  ec -=   6000*em;
         es = ec/   100;  ec -=    100*es;
         *ptr++ = '\0';
         len = 50 + end-ptr + FF_INPUT_BUFFER_PADDING_SIZE;
         if (!(line = av_malloc(len)))
             return;

         snprintf(line,len,"Dialogue: %s,%d:%02d:%02d.%02d,%d:%02d:%02d.%02d,%s\r\n",

                  layer, sh, sm, ss, sc, eh, em, es, ec, ptr);
         av_free(pkt->data);
         pkt->data = line;
         pkt->size = strlen(line);
     }
 }
 

 static int matroska_merge_packets(AVPacket *out, AVPacket *in)

 {

     void *newdata = av_realloc(out->data, out->size+in->size);
     if (!newdata)
         return AVERROR(ENOMEM);
     out->data = newdata;

     memcpy(out->data+out->size, in->data, in->size);
     out->size += in->size;
     av_destruct_packet(in);
     av_free(in);

     return 0;

 }
 

 static void matroska_convert_tag(AVFormatContext *s, EbmlList *list,
                                  AVMetadata **metadata, char *prefix)

 {
     MatroskaTag *tags = list->elem;

     char key[1024];
     int i;

 
     for (i=0; i < list->nb_elem; i++) {

         const char *lang = strcmp(tags[i].lang, "und") ? tags[i].lang : NULL;

         if (prefix)  snprintf(key, sizeof(key), "%s/%s", prefix, tags[i].name);
         else         av_strlcpy(key, tags[i].name, sizeof(key));

         if (tags[i].def || !lang) {

         av_metadata_set(metadata, key, tags[i].string);

         if (tags[i].sub.nb_elem)

             matroska_convert_tag(s, &tags[i].sub, metadata, key);

         }
         if (lang) {
             av_strlcat(key, "-", sizeof(key));
             av_strlcat(key, lang, sizeof(key));
             av_metadata_set(metadata, key, tags[i].string);
             if (tags[i].sub.nb_elem)
                 matroska_convert_tag(s, &tags[i].sub, metadata, key);
         }

     }
 }
 
 static void matroska_convert_tags(AVFormatContext *s)
 {
     MatroskaDemuxContext *matroska = s->priv_data;
     MatroskaTags *tags = matroska->tags.elem;
     int i, j;
 
     for (i=0; i < matroska->tags.nb_elem; i++) {
         if (tags[i].target.attachuid) {
             MatroskaAttachement *attachment = matroska->attachments.elem;
             for (j=0; j<matroska->attachments.nb_elem; j++)
                 if (attachment[j].uid == tags[i].target.attachuid)
                     matroska_convert_tag(s, &tags[i].tag,
                                          &attachment[j].stream->metadata, NULL);
         } else if (tags[i].target.chapteruid) {
             MatroskaChapter *chapter = matroska->chapters.elem;
             for (j=0; j<matroska->chapters.nb_elem; j++)
                 if (chapter[j].uid == tags[i].target.chapteruid)
                     matroska_convert_tag(s, &tags[i].tag,
                                          &chapter[j].chapter->metadata, NULL);
         } else if (tags[i].target.trackuid) {
             MatroskaTrack *track = matroska->tracks.elem;
             for (j=0; j<matroska->tracks.nb_elem; j++)
                 if (track[j].uid == tags[i].target.trackuid)
                     matroska_convert_tag(s, &tags[i].tag,
                                          &track[j].stream->metadata, NULL);
         } else {
             matroska_convert_tag(s, &tags[i].tag, &s->metadata, NULL);
         }

     }
 }
 

 static void matroska_execute_seekhead(MatroskaDemuxContext *matroska)

 {
     EbmlList *seekhead_list = &matroska->seekhead;
     MatroskaSeekhead *seekhead = seekhead_list->elem;
     uint32_t level_up = matroska->level_up;

     int64_t before_pos = url_ftell(matroska->ctx->pb);

     MatroskaLevel level;

     int i;

     for (i=0; i<seekhead_list->nb_elem; i++) {

         int64_t offset = seekhead[i].pos + matroska->segment_start;

         if (seekhead[i].pos <= before_pos
             || seekhead[i].id == MATROSKA_ID_SEEKHEAD
             || seekhead[i].id == MATROSKA_ID_CLUSTER)
             continue;

         /* seek */

         if (url_fseek(matroska->ctx->pb, offset, SEEK_SET) != offset)

             continue;
 

         /* We don't want to lose our seekhead level, so we add

          * a dummy. This is a crude hack. */
         if (matroska->num_levels == EBML_MAX_DEPTH) {
             av_log(matroska->ctx, AV_LOG_INFO,
                    "Max EBML element depth (%d) reached, "
                    "cannot parse further.\n", EBML_MAX_DEPTH);
             break;
         }
 
         level.start = 0;
         level.length = (uint64_t)-1;
         matroska->levels[matroska->num_levels] = level;
         matroska->num_levels++;
 

         ebml_parse(matroska, matroska_segment, matroska);

 
         /* remove dummy level */
         while (matroska->num_levels) {
             uint64_t length = matroska->levels[--matroska->num_levels].length;
             if (length == (uint64_t)-1)
                 break;
         }

     }

     /* seek back */

     url_fseek(matroska->ctx->pb, before_pos, SEEK_SET);

     matroska->level_up = level_up;

 }
 

 static int matroska_aac_profile(char *codec_id)

 {

     static const char * const aac_profiles[] = { "MAIN", "LC", "SSR" };

     int profile;
 

     for (profile=0; profile<FF_ARRAY_ELEMS(aac_profiles); profile++)

         if (strstr(codec_id, aac_profiles[profile]))
             break;
     return profile + 1;
 }
 

 static int matroska_aac_sri(int samplerate)

 {
     int sri;
 

     for (sri=0; sri<FF_ARRAY_ELEMS(ff_mpeg4audio_sample_rates); sri++)

         if (ff_mpeg4audio_sample_rates[sri] == samplerate)

             break;
     return sri;
 }
 

 static int matroska_read_header(AVFormatContext *s, AVFormatParameters *ap)

 {
     MatroskaDemuxContext *matroska = s->priv_data;

     EbmlList *attachements_list = &matroska->attachments;
     MatroskaAttachement *attachements;
     EbmlList *chapters_list = &matroska->chapters;
     MatroskaChapter *chapters;

     MatroskaTrack *tracks;

     EbmlList *index_list;
     MatroskaIndex *index;

     int index_scale = 1;

     uint64_t max_start = 0;

     Ebml ebml = { 0 };

     AVStream *st;

     int i, j;

 
     matroska->ctx = s;
 
     /* First read the EBML header. */

     if (ebml_parse(matroska, ebml_syntax, &ebml)

         || ebml.version > EBML_VERSION       || ebml.max_size > sizeof(uint64_t)
         || ebml.id_length > sizeof(uint32_t) || strcmp(ebml.doctype, "matroska")
         || ebml.doctype_version > 2) {

         av_log(matroska->ctx, AV_LOG_ERROR,

                "EBML header using unsupported features\n"
                "(EBML version %"PRIu64", doctype %s, doc version %"PRIu64")\n",
                ebml.version, ebml.doctype, ebml.doctype_version);

         return AVERROR_NOFMT;
     }

     ebml_free(ebml_syntax, &ebml);

 
     /* The next thing is a segment. */

     if (ebml_parse(matroska, matroska_segments, matroska) < 0)

         return -1;

     matroska_execute_seekhead(matroska);

     if (matroska->duration)
         matroska->ctx->duration = matroska->duration * matroska->time_scale
                                   * 1000 / AV_TIME_BASE;

     av_metadata_set(&s->metadata, "title", matroska->title);

     tracks = matroska->tracks.elem;
     for (i=0; i < matroska->tracks.nb_elem; i++) {
         MatroskaTrack *track = &tracks[i];
         enum CodecID codec_id = CODEC_ID_NONE;

         EbmlList *encodings_list = &tracks->encodings;
         MatroskaTrackEncoding *encodings = encodings_list->elem;

         uint8_t *extradata = NULL;
         int extradata_size = 0;
         int extradata_offset = 0;

         ByteIOContext b;

 
         /* Apply some sanity checks. */

         if (track->type != MATROSKA_TRACK_TYPE_VIDEO &&
             track->type != MATROSKA_TRACK_TYPE_AUDIO &&
             track->type != MATROSKA_TRACK_TYPE_SUBTITLE) {
             av_log(matroska->ctx, AV_LOG_INFO,
                    "Unknown or unsupported track type %"PRIu64"\n",
                    track->type);
             continue;
         }

         if (track->codec_id == NULL)
             continue;
 

         if (track->type == MATROSKA_TRACK_TYPE_VIDEO) {
             if (!track->default_duration)
                 track->default_duration = 1000000000/track->video.frame_rate;
             if (!track->video.display_width)
                 track->video.display_width = track->video.pixel_width;
             if (!track->video.display_height)
                 track->video.display_height = track->video.pixel_height;
         } else if (track->type == MATROSKA_TRACK_TYPE_AUDIO) {
             if (!track->audio.out_samplerate)
                 track->audio.out_samplerate = track->audio.samplerate;
         }
         if (encodings_list->nb_elem > 1) {
             av_log(matroska->ctx, AV_LOG_ERROR,
                    "Multiple combined encodings no supported");
         } else if (encodings_list->nb_elem == 1) {
             if (encodings[0].type ||
                 (encodings[0].compression.algo != MATROSKA_TRACK_ENCODING_COMP_HEADERSTRIP &&

 #if CONFIG_ZLIB

                  encodings[0].compression.algo != MATROSKA_TRACK_ENCODING_COMP_ZLIB &&
 #endif

 #if CONFIG_BZLIB

                  encodings[0].compression.algo != MATROSKA_TRACK_ENCODING_COMP_BZLIB &&
 #endif
                  encodings[0].compression.algo != MATROSKA_TRACK_ENCODING_COMP_LZO)) {
                 encodings[0].scope = 0;
                 av_log(matroska->ctx, AV_LOG_ERROR,
                        "Unsupported encoding type");
             } else if (track->codec_priv.size && encodings[0].scope&2) {
                 uint8_t *codec_priv = track->codec_priv.data;
                 int offset = matroska_decode_buffer(&track->codec_priv.data,
                                                     &track->codec_priv.size,
                                                     track);
                 if (offset < 0) {
                     track->codec_priv.data = NULL;
                     track->codec_priv.size = 0;
                     av_log(matroska->ctx, AV_LOG_ERROR,
                            "Failed to decode codec private data\n");
                 } else if (offset > 0) {
                     track->codec_priv.data = av_malloc(track->codec_priv.size + offset);
                     memcpy(track->codec_priv.data,
                            encodings[0].compression.settings.data, offset);
                     memcpy(track->codec_priv.data+offset, codec_priv,
                            track->codec_priv.size);
                     track->codec_priv.size += offset;
                 }
                 if (codec_priv != track->codec_priv.data)
                     av_free(codec_priv);
             }
         }
 

         for(j=0; ff_mkv_codec_tags[j].id != CODEC_ID_NONE; j++){
             if(!strncmp(ff_mkv_codec_tags[j].str, track->codec_id,
                         strlen(ff_mkv_codec_tags[j].str))){
                 codec_id= ff_mkv_codec_tags[j].id;
                 break;

             }

         }

         st = track->stream = av_new_stream(s, 0);

         if (st == NULL)
             return AVERROR(ENOMEM);
 

         if (!strcmp(track->codec_id, "V_MS/VFW/FOURCC")

             && track->codec_priv.size >= 40
             && track->codec_priv.data != NULL) {

             track->video.fourcc = AV_RL32(track->codec_priv.data + 16);
             codec_id = codec_get_id(codec_bmp_tags, track->video.fourcc);

         } else if (!strcmp(track->codec_id, "A_MS/ACM")

                    && track->codec_priv.size >= 18
                    && track->codec_priv.data != NULL) {

             init_put_byte(&b, track->codec_priv.data, track->codec_priv.size,
                           URL_RDONLY, NULL, NULL, NULL, NULL);
             get_wav_header(&b, st->codec, track->codec_priv.size);
             codec_id = st->codec->codec_id;
             extradata_offset = 18;
             track->codec_priv.size -= extradata_offset;

         } else if (!strcmp(track->codec_id, "V_QUICKTIME")
                    && (track->codec_priv.size >= 86)
                    && (track->codec_priv.data != NULL)) {

             track->video.fourcc = AV_RL32(track->codec_priv.data);
             codec_id=codec_get_id(codec_movvideo_tags, track->video.fourcc);

         } else if (codec_id == CODEC_ID_PCM_S16BE) {
             switch (track->audio.bitdepth) {
             case  8:  codec_id = CODEC_ID_PCM_U8;     break;
             case 24:  codec_id = CODEC_ID_PCM_S24BE;  break;
             case 32:  codec_id = CODEC_ID_PCM_S32BE;  break;
             }
         } else if (codec_id == CODEC_ID_PCM_S16LE) {
             switch (track->audio.bitdepth) {
             case  8:  codec_id = CODEC_ID_PCM_U8;     break;
             case 24:  codec_id = CODEC_ID_PCM_S24LE;  break;
             case 32:  codec_id = CODEC_ID_PCM_S32LE;  break;
             }
         } else if (codec_id==CODEC_ID_PCM_F32LE && track->audio.bitdepth==64) {
             codec_id = CODEC_ID_PCM_F64LE;

         } else if (codec_id == CODEC_ID_AAC && !track->codec_priv.size) {

             int profile = matroska_aac_profile(track->codec_id);
             int sri = matroska_aac_sri(track->audio.samplerate);
             extradata = av_malloc(5);
             if (extradata == NULL)
                 return AVERROR(ENOMEM);
             extradata[0] = (profile << 3) | ((sri&0x0E) >> 1);
             extradata[1] = ((sri&0x01) << 7) | (track->audio.channels<<3);
             if (strstr(track->codec_id, "SBR")) {
                 sri = matroska_aac_sri(track->audio.out_samplerate);
                 extradata[2] = 0x56;
                 extradata[3] = 0xE5;
                 extradata[4] = 0x80 | (sri<<3);
                 extradata_size = 5;

             } else

                 extradata_size = 2;

         } else if (codec_id == CODEC_ID_TTA) {

             extradata_size = 30;
             extradata = av_mallocz(extradata_size);
             if (extradata == NULL)
                 return AVERROR(ENOMEM);
             init_put_byte(&b, extradata, extradata_size, 1,
                           NULL, NULL, NULL, NULL);
             put_buffer(&b, "TTA1", 4);
             put_le16(&b, 1);
             put_le16(&b, track->audio.channels);
             put_le16(&b, track->audio.bitdepth);
             put_le32(&b, track->audio.out_samplerate);
             put_le32(&b, matroska->ctx->duration * track->audio.out_samplerate);

         } else if (codec_id == CODEC_ID_RV10 || codec_id == CODEC_ID_RV20 ||
                    codec_id == CODEC_ID_RV30 || codec_id == CODEC_ID_RV40) {

             extradata_offset = 26;
             track->codec_priv.size -= extradata_offset;

         } else if (codec_id == CODEC_ID_RA_144) {

             track->audio.out_samplerate = 8000;
             track->audio.channels = 1;

         } else if (codec_id == CODEC_ID_RA_288 || codec_id == CODEC_ID_COOK ||
                    codec_id == CODEC_ID_ATRAC3) {

             init_put_byte(&b, track->codec_priv.data,track->codec_priv.size,
                           0, NULL, NULL, NULL, NULL);
             url_fskip(&b, 24);
             track->audio.coded_framesize = get_be32(&b);
             url_fskip(&b, 12);
             track->audio.sub_packet_h    = get_be16(&b);
             track->audio.frame_size      = get_be16(&b);
             track->audio.sub_packet_size = get_be16(&b);
             track->audio.buf = av_malloc(track->audio.frame_size * track->audio.sub_packet_h);
             if (codec_id == CODEC_ID_RA_288) {
                 st->codec->block_align = track->audio.coded_framesize;
                 track->codec_priv.size = 0;
             } else {
                 st->codec->block_align = track->audio.sub_packet_size;
                 extradata_offset = 78;

                 track->codec_priv.size -= extradata_offset;

             }

         }

         if (codec_id == CODEC_ID_NONE)

             av_log(matroska->ctx, AV_LOG_INFO,

                    "Unknown/unsupported CodecID %s.\n", track->codec_id);

         if (track->time_scale < 0.01)
             track->time_scale = 1.0;

         av_set_pts_info(st, 64, matroska->time_scale*track->time_scale, 1000*1000*1000); /* 64 bit pts in ns */

         st->codec->codec_id = codec_id;
         st->start_time = 0;
         if (strcmp(track->language, "und"))

             av_metadata_set(&st->metadata, "language", track->language);

         av_metadata_set(&st->metadata, "description", track->name);

         if (track->flag_default)
             st->disposition |= AV_DISPOSITION_DEFAULT;

         if (track->default_duration)
             av_reduce(&st->codec->time_base.num, &st->codec->time_base.den,
                       track->default_duration, 1000000000, 30000);

         if(extradata){
             st->codec->extradata = extradata;
             st->codec->extradata_size = extradata_size;
         } else if(track->codec_priv.data && track->codec_priv.size > 0){

             st->codec->extradata = av_mallocz(track->codec_priv.size +
                                               FF_INPUT_BUFFER_PADDING_SIZE);

             if(st->codec->extradata == NULL)
                 return AVERROR(ENOMEM);
             st->codec->extradata_size = track->codec_priv.size;
             memcpy(st->codec->extradata,
                    track->codec_priv.data + extradata_offset,
                    track->codec_priv.size);

         }

 
         if (track->type == MATROSKA_TRACK_TYPE_VIDEO) {
             st->codec->codec_type = CODEC_TYPE_VIDEO;
             st->codec->codec_tag  = track->video.fourcc;
             st->codec->width  = track->video.pixel_width;
             st->codec->height = track->video.pixel_height;

             av_reduce(&st->sample_aspect_ratio.num,
                       &st->sample_aspect_ratio.den,

                       st->codec->height * track->video.display_width,
                       st->codec-> width * track->video.display_height,
                       255);
             st->need_parsing = AVSTREAM_PARSE_HEADERS;
         } else if (track->type == MATROSKA_TRACK_TYPE_AUDIO) {
             st->codec->codec_type = CODEC_TYPE_AUDIO;
             st->codec->sample_rate = track->audio.out_samplerate;
             st->codec->channels = track->audio.channels;
         } else if (track->type == MATROSKA_TRACK_TYPE_SUBTITLE) {
             st->codec->codec_type = CODEC_TYPE_SUBTITLE;
         }

     }
 

     attachements = attachements_list->elem;
     for (j=0; j<attachements_list->nb_elem; j++) {
         if (!(attachements[j].filename && attachements[j].mime &&
               attachements[j].bin.data && attachements[j].bin.size > 0)) {
             av_log(matroska->ctx, AV_LOG_ERROR, "incomplete attachment\n");
         } else {

             AVStream *st = av_new_stream(s, 0);

             if (st == NULL)
                 break;

             av_metadata_set(&st->metadata, "filename",attachements[j].filename);

             st->codec->codec_id = CODEC_ID_NONE;
             st->codec->codec_type = CODEC_TYPE_ATTACHMENT;
             st->codec->extradata  = av_malloc(attachements[j].bin.size);
             if(st->codec->extradata == NULL)
                 break;
             st->codec->extradata_size = attachements[j].bin.size;
             memcpy(st->codec->extradata, attachements[j].bin.data, attachements[j].bin.size);
 
             for (i=0; ff_mkv_mime_tags[i].id != CODEC_ID_NONE; i++) {
                 if (!strncmp(ff_mkv_mime_tags[i].str, attachements[j].mime,
                              strlen(ff_mkv_mime_tags[i].str))) {
                     st->codec->codec_id = ff_mkv_mime_tags[i].id;
                     break;
                 }
             }

             attachements[j].stream = st;

         }
     }
 
     chapters = chapters_list->elem;
     for (i=0; i<chapters_list->nb_elem; i++)

         if (chapters[i].start != AV_NOPTS_VALUE && chapters[i].uid
             && (max_start==0 || chapters[i].start > max_start)) {

             chapters[i].chapter =

             ff_new_chapter(s, chapters[i].uid, (AVRational){1, 1000000000},
                            chapters[i].start, chapters[i].end,
                            chapters[i].title);

             av_metadata_set(&chapters[i].chapter->metadata,
                             "title", chapters[i].title);

             max_start = chapters[i].start;
         }

     index_list = &matroska->index;
     index = index_list->elem;

     if (index_list->nb_elem
         && index[0].time > 100000000000000/matroska->time_scale) {
         av_log(matroska->ctx, AV_LOG_WARNING, "Working around broken index.\n");
         index_scale = matroska->time_scale;
     }

     for (i=0; i<index_list->nb_elem; i++) {
         EbmlList *pos_list = &index[i].pos;
         MatroskaIndexPos *pos = pos_list->elem;
         for (j=0; j<pos_list->nb_elem; j++) {

             MatroskaTrack *track = matroska_find_track_by_num(matroska,

                                                               pos[j].track);

             if (track && track->stream)
                 av_add_index_entry(track->stream,

                                    pos[j].pos + matroska->segment_start,

                                    index[i].time/index_scale, 0, 0,
                                    AVINDEX_KEYFRAME);

         }
     }
 

     matroska_convert_tags(s);
 

     return 0;

 }
 

 /*
  * Put one packet in an application-supplied AVPacket struct.
  * Returns 0 on success or -1 on failure.
  */
 static int matroska_deliver_packet(MatroskaDemuxContext *matroska,
                                    AVPacket *pkt)
 {
     if (matroska->num_packets > 0) {
         memcpy(pkt, matroska->packets[0], sizeof(AVPacket));
         av_free(matroska->packets[0]);
         if (matroska->num_packets > 1) {

             void *newpackets;

             memmove(&matroska->packets[0], &matroska->packets[1],
                     (matroska->num_packets - 1) * sizeof(AVPacket *));

             newpackets = av_realloc(matroska->packets,
                             (matroska->num_packets - 1) * sizeof(AVPacket *));
             if (newpackets)
                 matroska->packets = newpackets;

         } else {
             av_freep(&matroska->packets);
         }
         matroska->num_packets--;
         return 0;
     }
 
     return -1;
 }
 
 /*
  * Free all packets in our internal queue.
  */
 static void matroska_clear_queue(MatroskaDemuxContext *matroska)
 {
     if (matroska->packets) {
         int n;
         for (n = 0; n < matroska->num_packets; n++) {
             av_free_packet(matroska->packets[n]);
             av_free(matroska->packets[n]);
         }

         av_freep(&matroska->packets);

         matroska->num_packets = 0;
     }
 }
 

 static int matroska_parse_block(MatroskaDemuxContext *matroska, uint8_t *data,
                                 int size, int64_t pos, uint64_t cluster_time,

                                 uint64_t duration, int is_keyframe,
                                 int64_t cluster_pos)

 {

     uint64_t timecode = AV_NOPTS_VALUE;

     MatroskaTrack *track;

     int res = 0;

     AVStream *st;
     AVPacket *pkt;
     int16_t block_time;
     uint32_t *lace_size = NULL;
     int n, flags, laces = 0;
     uint64_t num;
 

     if ((n = matroska_ebmlnum_uint(matroska, data, size, &num)) < 0) {

         av_log(matroska->ctx, AV_LOG_ERROR, "EBML block data error\n");
         return res;
     }
     data += n;
     size -= n;
 
     track = matroska_find_track_by_num(matroska, num);

     if (size <= 3 || !track || !track->stream) {

         av_log(matroska->ctx, AV_LOG_INFO,

                "Invalid stream %"PRIu64" or size %u\n", num, size);

         return res;
     }

     st = track->stream;

     if (st->discard >= AVDISCARD_ALL)

         return res;
     if (duration == AV_NOPTS_VALUE)

         duration = track->default_duration / matroska->time_scale;

     block_time = AV_RB16(data);

     data += 2;

     flags = *data++;
     size -= 3;

     if (is_keyframe == -1)

         is_keyframe = flags & 0x80 ? PKT_FLAG_KEY : 0;

     if (cluster_time != (uint64_t)-1
         && (block_time >= 0 || cluster_time >= -block_time)) {
         timecode = cluster_time + block_time;

         if (track->type == MATROSKA_TRACK_TYPE_SUBTITLE
             && timecode < track->end_timecode)
             is_keyframe = 0;  /* overlapping subtitles are not key frame */

         if (is_keyframe)

             av_add_index_entry(st, cluster_pos, timecode, 0,0,AVINDEX_KEYFRAME);

         track->end_timecode = FFMAX(track->end_timecode, timecode+duration);

     }
 

     if (matroska->skip_to_keyframe && track->type != MATROSKA_TRACK_TYPE_SUBTITLE) {

         if (!is_keyframe || timecode < matroska->skip_to_timecode)

             return res;
         matroska->skip_to_keyframe = 0;
     }
 
     switch ((flags & 0x06) >> 1) {
         case 0x0: /* no lacing */
             laces = 1;
             lace_size = av_mallocz(sizeof(int));
             lace_size[0] = size;
             break;
 

         case 0x1: /* Xiph lacing */

         case 0x2: /* fixed-size lacing */
         case 0x3: /* EBML lacing */

             assert(size>0); // size <=3 is checked before size-=3 above

             laces = (*data) + 1;
             data += 1;
             size -= 1;
             lace_size = av_mallocz(laces * sizeof(int));
 
             switch ((flags & 0x06) >> 1) {

                 case 0x1: /* Xiph lacing */ {

                     uint8_t temp;
                     uint32_t total = 0;
                     for (n = 0; res == 0 && n < laces - 1; n++) {
                         while (1) {
                             if (size == 0) {
                                 res = -1;
                                 break;
                             }
                             temp = *data;
                             lace_size[n] += temp;
                             data += 1;
                             size -= 1;
                             if (temp != 0xff)
                                 break;
                         }
                         total += lace_size[n];
                     }
                     lace_size[n] = size - total;
                     break;
                 }
 
                 case 0x2: /* fixed-size lacing */
                     for (n = 0; n < laces; n++)
                         lace_size[n] = size / laces;
                     break;
 
                 case 0x3: /* EBML lacing */ {
                     uint32_t total;

                     n = matroska_ebmlnum_uint(matroska, data, size, &num);

                     if (n < 0) {
                         av_log(matroska->ctx, AV_LOG_INFO,
                                "EBML block data error\n");
                         break;
                     }
                     data += n;
                     size -= n;
                     total = lace_size[0] = num;
                     for (n = 1; res == 0 && n < laces - 1; n++) {
                         int64_t snum;
                         int r;

                         r = matroska_ebmlnum_sint(matroska, data, size, &snum);

                         if (r < 0) {
                             av_log(matroska->ctx, AV_LOG_INFO,
                                    "EBML block data error\n");
                             break;
                         }
                         data += r;
                         size -= r;
                         lace_size[n] = lace_size[n - 1] + snum;
                         total += lace_size[n];
                     }

                     lace_size[laces - 1] = size - total;

                     break;
                 }
             }
             break;
     }
 
     if (res == 0) {
         for (n = 0; n < laces; n++) {

             if (st->codec->codec_id == CODEC_ID_RA_288 ||
                 st->codec->codec_id == CODEC_ID_COOK ||
                 st->codec->codec_id == CODEC_ID_ATRAC3) {
                 int a = st->codec->block_align;

                 int sps = track->audio.sub_packet_size;
                 int cfs = track->audio.coded_framesize;
                 int h = track->audio.sub_packet_h;
                 int y = track->audio.sub_packet_cnt;
                 int w = track->audio.frame_size;

                 int x;
 

                 if (!track->audio.pkt_cnt) {

                     if (st->codec->codec_id == CODEC_ID_RA_288)
                         for (x=0; x<h/2; x++)

                             memcpy(track->audio.buf+x*2*w+y*cfs,

                                    data+x*cfs, cfs);
                     else
                         for (x=0; x<w/sps; x++)

                             memcpy(track->audio.buf+sps*(h*x+((h+1)/2)*(y&1)+(y>>1)), data+x*sps, sps);

                     if (++track->audio.sub_packet_cnt >= h) {
                         track->audio.sub_packet_cnt = 0;
                         track->audio.pkt_cnt = h*w / a;

                     }

                 }

                 while (track->audio.pkt_cnt) {

                     pkt = av_mallocz(sizeof(AVPacket));

                     av_new_packet(pkt, a);

                     memcpy(pkt->data, track->audio.buf
                            + a * (h*w / a - track->audio.pkt_cnt--), a);

                     pkt->pos = pos;

                     pkt->stream_index = st->index;

                     dynarray_add(&matroska->packets,&matroska->num_packets,pkt);

                 }

             } else {

                 MatroskaTrackEncoding *encodings = track->encodings.elem;

                 int offset = 0, pkt_size = lace_size[n];

                 uint8_t *pkt_data = data;

                 if (encodings && encodings->scope & 1) {

                     offset = matroska_decode_buffer(&pkt_data,&pkt_size, track);

                     if (offset < 0)
                         continue;

                 }
 

                 pkt = av_mallocz(sizeof(AVPacket));
                 /* XXX: prevent data copy... */

                 if (av_new_packet(pkt, pkt_size+offset) < 0) {

                     av_free(pkt);

                     res = AVERROR(ENOMEM);
                     n = laces-1;
                     break;
                 }

                 if (offset)

                     memcpy (pkt->data, encodings->compression.settings.data, offset);

                 memcpy (pkt->data+offset, pkt_data, pkt_size);

                 if (pkt_data != data)
                     av_free(pkt_data);
 

                 if (n == 0)
                     pkt->flags = is_keyframe;

                 pkt->stream_index = st->index;

 
                 pkt->pts = timecode;
                 pkt->pos = pos;

                 if (st->codec->codec_id == CODEC_ID_TEXT)

                     pkt->convergence_duration = duration;

                 else if (track->type != MATROSKA_TRACK_TYPE_SUBTITLE)

                     pkt->duration = duration;

                 if (st->codec->codec_id == CODEC_ID_SSA)

                     matroska_fix_ass_packet(matroska, pkt, duration);

                 if (matroska->prev_pkt &&

                     timecode != AV_NOPTS_VALUE &&

                     matroska->prev_pkt->pts == timecode &&
                     matroska->prev_pkt->stream_index == st->index)
                     matroska_merge_packets(matroska->prev_pkt, pkt);
                 else {

                     dynarray_add(&matroska->packets,&matroska->num_packets,pkt);

                     matroska->prev_pkt = pkt;
                 }

             }

             if (timecode != AV_NOPTS_VALUE)
                 timecode = duration ? timecode + duration : AV_NOPTS_VALUE;

             data += lace_size[n];
         }
     }
 
     av_free(lace_size);

     return res;

 }
 

 static int matroska_parse_cluster(MatroskaDemuxContext *matroska)

 {

     MatroskaCluster cluster = { 0 };
     EbmlList *blocks_list;
     MatroskaBlock *blocks;

     int i, res;

     int64_t pos = url_ftell(matroska->ctx->pb);

     matroska->prev_pkt = NULL;

     if (matroska->has_cluster_id){

         /* For the first cluster we parse, its ID was already read as

            part of matroska_read_header(), so don't read it again */
         res = ebml_parse_id(matroska, matroska_clusters,
                             MATROSKA_ID_CLUSTER, &cluster);

         pos -= 4;  /* sizeof the ID which was already read */

         matroska->has_cluster_id = 0;
     } else
         res = ebml_parse(matroska, matroska_clusters, &cluster);

     blocks_list = &cluster.blocks;
     blocks = blocks_list->elem;

     for (i=0; i<blocks_list->nb_elem; i++)

         if (blocks[i].bin.size > 0)

             res=matroska_parse_block(matroska,
                                      blocks[i].bin.data, blocks[i].bin.size,
                                      blocks[i].bin.pos,  cluster.timecode,

                                      blocks[i].duration, !blocks[i].reference,
                                      pos);

     ebml_free(matroska_cluster, &cluster);

     if (res < 0)  matroska->done = 1;

     return res;
 }
 

 static int matroska_read_packet(AVFormatContext *s, AVPacket *pkt)

 {
     MatroskaDemuxContext *matroska = s->priv_data;
 
     while (matroska_deliver_packet(matroska, pkt)) {
         if (matroska->done)

             return AVERROR_EOF;

         matroska_parse_cluster(matroska);

     }
 
     return 0;
 }
 

 static int matroska_read_seek(AVFormatContext *s, int stream_index,
                               int64_t timestamp, int flags)

 {
     MatroskaDemuxContext *matroska = s->priv_data;

     MatroskaTrack *tracks = matroska->tracks.elem;

     AVStream *st = s->streams[stream_index];

     int i, index, index_sub, index_min;

     if (!st->nb_index_entries)
         return 0;
     timestamp = FFMAX(timestamp, st->index_entries[0].timestamp);

     if ((index = av_index_search_timestamp(st, timestamp, flags)) < 0) {

         url_fseek(s->pb, st->index_entries[st->nb_index_entries-1].pos, SEEK_SET);

         while ((index = av_index_search_timestamp(st, timestamp, flags)) < 0) {
             matroska_clear_queue(matroska);
             if (matroska_parse_cluster(matroska) < 0)
                 break;
         }

     }

     matroska_clear_queue(matroska);

     if (index < 0)
         return 0;

     index_min = index;
     for (i=0; i < matroska->tracks.nb_elem; i++) {
         tracks[i].end_timecode = 0;
         if (tracks[i].type == MATROSKA_TRACK_TYPE_SUBTITLE
             && !tracks[i].stream->discard != AVDISCARD_ALL) {
             index_sub = av_index_search_timestamp(tracks[i].stream, st->index_entries[index].timestamp, AVSEEK_FLAG_BACKWARD);
             if (index_sub >= 0
                 && st->index_entries[index_sub].pos < st->index_entries[index_min].pos
                 && st->index_entries[index].timestamp - st->index_entries[index_sub].timestamp < 30000000000/matroska->time_scale)
                 index_min = index_sub;
         }
     }
 
     url_fseek(s->pb, st->index_entries[index_min].pos, SEEK_SET);

     matroska->skip_to_keyframe = !(flags & AVSEEK_FLAG_ANY);

     matroska->skip_to_timecode = st->index_entries[index].timestamp;

     matroska->done = 0;

     av_update_cur_dts(s, st, st->index_entries[index].timestamp);

     return 0;
 }
 

 static int matroska_read_close(AVFormatContext *s)

 {
     MatroskaDemuxContext *matroska = s->priv_data;

     MatroskaTrack *tracks = matroska->tracks.elem;

     int n;

     matroska_clear_queue(matroska);

     for (n=0; n < matroska->tracks.nb_elem; n++)
         if (tracks[n].type == MATROSKA_TRACK_TYPE_AUDIO)
             av_free(tracks[n].audio.buf);

     ebml_free(matroska_segment, matroska);

 
     return 0;
 }
 
 AVInputFormat matroska_demuxer = {
     "matroska",

     NULL_IF_CONFIG_SMALL("Matroska file format"),

     sizeof(MatroskaDemuxContext),
     matroska_probe,
     matroska_read_header,
     matroska_read_packet,
     matroska_read_close,
     matroska_read_seek,

     .metadata_conv = ff_mkv_metadata_conv,

 };