/*
  * Copyright (c) 2012 Nicolas George
  *
  * 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
  */
 

 #include "libavutil/avassert.h"

 #include "libavutil/avstring.h"

 #include "libavutil/bprint.h"

 #include "libavutil/intreadwrite.h"

 #include "libavutil/opt.h"

 #include "libavutil/parseutils.h"

 #include "libavutil/timestamp.h"

 #include "avformat.h"
 #include "internal.h"

 #include "url.h"

 typedef enum ConcatMatchMode {
     MATCH_ONE_TO_ONE,
     MATCH_EXACT_ID,
 } ConcatMatchMode;
 

 typedef struct ConcatStream {

     AVBSFContext *bsf;

     int out_stream_index;
 } ConcatStream;
 

 typedef struct {
     char *url;
     int64_t start_time;

     int64_t file_start_time;
     int64_t file_inpoint;

     int64_t duration;

     int64_t user_duration;

     int64_t next_dts;

     ConcatStream *streams;

     int64_t inpoint;

     int64_t outpoint;

     AVDictionary *metadata;

     int nb_streams;

 } ConcatFile;
 
 typedef struct {

     AVClass *class;

     ConcatFile *files;
     ConcatFile *cur_file;
     unsigned nb_files;
     AVFormatContext *avf;

     int safe;

     int seekable;

     int eof;

     ConcatMatchMode stream_match_mode;

     unsigned auto_convert;

     int segment_time_metadata;

 } ConcatContext;
 

 static int concat_probe(const AVProbeData *probe)

 {

     return memcmp(probe->buf, "ffconcat version 1.0", 20) ?
            0 : AVPROBE_SCORE_MAX;

 }
 
 static char *get_keyword(uint8_t **cursor)
 {
     char *ret = *cursor += strspn(*cursor, SPACE_CHARS);
     *cursor += strcspn(*cursor, SPACE_CHARS);
     if (**cursor) {
         *((*cursor)++) = 0;
         *cursor += strspn(*cursor, SPACE_CHARS);
     }
     return ret;
 }
 

 static int safe_filename(const char *f)
 {
     const char *start = f;
 
     for (; *f; f++) {
         /* A-Za-z0-9_- */
         if (!((unsigned)((*f | 32) - 'a') < 26 ||
               (unsigned)(*f - '0') < 10 || *f == '_' || *f == '-')) {
             if (f == start)
                 return 0;
             else if (*f == '/')
                 start = f + 1;
             else if (*f != '.')
                 return 0;
         }
     }
     return 1;
 }
 

 #define FAIL(retcode) do { ret = (retcode); goto fail; } while(0)
 
 static int add_file(AVFormatContext *avf, char *filename, ConcatFile **rfile,
                     unsigned *nb_files_alloc)
 {
     ConcatContext *cat = avf->priv_data;
     ConcatFile *file;

     char *url = NULL;

     const char *proto;
     size_t url_len, proto_len;

     int ret;

     if (cat->safe > 0 && !safe_filename(filename)) {
         av_log(avf, AV_LOG_ERROR, "Unsafe file name '%s'\n", filename);

         FAIL(AVERROR(EPERM));

     }

 
     proto = avio_find_protocol_name(filename);
     proto_len = proto ? strlen(proto) : 0;

     if (proto && !memcmp(filename, proto, proto_len) &&

         (filename[proto_len] == ':' || filename[proto_len] == ',')) {
         url = filename;
         filename = NULL;
     } else {

         url_len = strlen(avf->url) + strlen(filename) + 16;

         if (!(url = av_malloc(url_len)))
             FAIL(AVERROR(ENOMEM));

         ff_make_absolute_url(url, url_len, avf->url, filename);

         av_freep(&filename);

     }

 
     if (cat->nb_files >= *nb_files_alloc) {

         size_t n = FFMAX(*nb_files_alloc * 2, 16);

         ConcatFile *new_files;
         if (n <= cat->nb_files || n > SIZE_MAX / sizeof(*cat->files) ||
             !(new_files = av_realloc(cat->files, n * sizeof(*cat->files))))

             FAIL(AVERROR(ENOMEM));

         cat->files = new_files;

         *nb_files_alloc = n;
     }
 
     file = &cat->files[cat->nb_files++];
     memset(file, 0, sizeof(*file));
     *rfile = file;
 
     file->url        = url;
     file->start_time = AV_NOPTS_VALUE;
     file->duration   = AV_NOPTS_VALUE;

     file->next_dts   = AV_NOPTS_VALUE;

     file->inpoint    = AV_NOPTS_VALUE;

     file->outpoint   = AV_NOPTS_VALUE;

     file->user_duration = AV_NOPTS_VALUE;

 
     return 0;

 
 fail:
     av_free(url);
     av_free(filename);
     return ret;

 }
 

 static int copy_stream_props(AVStream *st, AVStream *source_st)
 {
     int ret;
 

     if (st->codecpar->codec_id || !source_st->codecpar->codec_id) {
         if (st->codecpar->extradata_size < source_st->codecpar->extradata_size) {
             ret = ff_alloc_extradata(st->codecpar,
                                      source_st->codecpar->extradata_size);

             if (ret < 0)
                 return ret;
         }

         memcpy(st->codecpar->extradata, source_st->codecpar->extradata,
                source_st->codecpar->extradata_size);

         return 0;

     }

     if ((ret = avcodec_parameters_copy(st->codecpar, source_st->codecpar)) < 0)

         return ret;
     st->r_frame_rate        = source_st->r_frame_rate;
     st->avg_frame_rate      = source_st->avg_frame_rate;
     st->sample_aspect_ratio = source_st->sample_aspect_ratio;

     avpriv_set_pts_info(st, 64, source_st->time_base.num, source_st->time_base.den);

 
     av_dict_copy(&st->metadata, source_st->metadata, 0);

     return 0;
 }
 

 static int detect_stream_specific(AVFormatContext *avf, int idx)
 {
     ConcatContext *cat = avf->priv_data;
     AVStream *st = cat->avf->streams[idx];
     ConcatStream *cs = &cat->cur_file->streams[idx];

     const AVBitStreamFilter *filter;
     AVBSFContext *bsf;

     int ret;

     if (cat->auto_convert && st->codecpar->codec_id == AV_CODEC_ID_H264) {
         if (!st->codecpar->extradata_size                                                ||
             (st->codecpar->extradata_size >= 3 && AV_RB24(st->codecpar->extradata) == 1) ||
             (st->codecpar->extradata_size >= 4 && AV_RB32(st->codecpar->extradata) == 1))
             return 0;

         av_log(cat->avf, AV_LOG_INFO,
                "Auto-inserting h264_mp4toannexb bitstream filter\n");

         filter = av_bsf_get_by_name("h264_mp4toannexb");
         if (!filter) {

             av_log(avf, AV_LOG_ERROR, "h264_mp4toannexb bitstream filter "
                    "required for H.264 streams\n");
             return AVERROR_BSF_NOT_FOUND;
         }

         ret = av_bsf_alloc(filter, &bsf);
         if (ret < 0)
             return ret;

         cs->bsf = bsf;

         ret = avcodec_parameters_copy(bsf->par_in, st->codecpar);
         if (ret < 0)
            return ret;

         ret = av_bsf_init(bsf);
         if (ret < 0)

             return ret;
 

         ret = avcodec_parameters_copy(st->codecpar, bsf->par_out);
         if (ret < 0)
             return ret;

     }
     return 0;
 }
 

 static int match_streams_one_to_one(AVFormatContext *avf)

 {
     ConcatContext *cat = avf->priv_data;
     AVStream *st;

     int i, ret;

     for (i = cat->cur_file->nb_streams; i < cat->avf->nb_streams; i++) {
         if (i < avf->nb_streams) {
             st = avf->streams[i];
         } else {
             if (!(st = avformat_new_stream(avf, NULL)))
                 return AVERROR(ENOMEM);
         }
         if ((ret = copy_stream_props(st, cat->avf->streams[i])) < 0)
             return ret;
         cat->cur_file->streams[i].out_stream_index = i;
     }
     return 0;
 }
 
 static int match_streams_exact_id(AVFormatContext *avf)
 {
     ConcatContext *cat = avf->priv_data;
     AVStream *st;
     int i, j, ret;

     for (i = cat->cur_file->nb_streams; i < cat->avf->nb_streams; i++) {

         st = cat->avf->streams[i];
         for (j = 0; j < avf->nb_streams; j++) {
             if (avf->streams[j]->id == st->id) {
                 av_log(avf, AV_LOG_VERBOSE,
                        "Match slave stream #%d with stream #%d id 0x%x\n",
                        i, j, st->id);

                 if ((ret = copy_stream_props(avf->streams[j], st)) < 0)
                     return ret;
                 cat->cur_file->streams[i].out_stream_index = j;

             }
         }
     }

     return 0;
 }

 static int match_streams(AVFormatContext *avf)
 {
     ConcatContext *cat = avf->priv_data;
     ConcatStream *map;
     int i, ret;
 
     if (cat->cur_file->nb_streams >= cat->avf->nb_streams)
         return 0;
     map = av_realloc(cat->cur_file->streams,
                      cat->avf->nb_streams * sizeof(*map));
     if (!map)
         return AVERROR(ENOMEM);
     cat->cur_file->streams = map;

     memset(map + cat->cur_file->nb_streams, 0,
            (cat->avf->nb_streams - cat->cur_file->nb_streams) * sizeof(*map));

     for (i = cat->cur_file->nb_streams; i < cat->avf->nb_streams; i++) {

         map[i].out_stream_index = -1;

         if ((ret = detect_stream_specific(avf, i)) < 0)
             return ret;
     }

     switch (cat->stream_match_mode) {
     case MATCH_ONE_TO_ONE:
         ret = match_streams_one_to_one(avf);
         break;
     case MATCH_EXACT_ID:
         ret = match_streams_exact_id(avf);
         break;
     default:
         ret = AVERROR_BUG;
     }
     if (ret < 0)
         return ret;

     cat->cur_file->nb_streams = cat->avf->nb_streams;

     return 0;
 }
 

 static int64_t get_best_effort_duration(ConcatFile *file, AVFormatContext *avf)
 {
     if (file->user_duration != AV_NOPTS_VALUE)
         return file->user_duration;
     if (file->outpoint != AV_NOPTS_VALUE)
         return file->outpoint - file->file_inpoint;
     if (avf->duration > 0)
         return avf->duration - (file->file_inpoint - file->file_start_time);
     if (file->next_dts != AV_NOPTS_VALUE)

         return file->next_dts - file->file_inpoint;

     return AV_NOPTS_VALUE;
 }
 

 static int open_file(AVFormatContext *avf, unsigned fileno)
 {
     ConcatContext *cat = avf->priv_data;
     ConcatFile *file = &cat->files[fileno];
     int ret;
 

     if (cat->avf)
         avformat_close_input(&cat->avf);

 
     cat->avf = avformat_alloc_context();
     if (!cat->avf)
         return AVERROR(ENOMEM);
 

     cat->avf->flags |= avf->flags & ~AVFMT_FLAG_CUSTOM_IO;

     cat->avf->interrupt_callback = avf->interrupt_callback;

     if ((ret = ff_copy_whiteblacklists(cat->avf, avf)) < 0)

         return ret;

     if ((ret = avformat_open_input(&cat->avf, file->url, NULL, NULL)) < 0 ||
         (ret = avformat_find_stream_info(cat->avf, NULL)) < 0) {
         av_log(avf, AV_LOG_ERROR, "Impossible to open '%s'\n", file->url);

         avformat_close_input(&cat->avf);

         return ret;
     }
     cat->cur_file = file;

     file->start_time = !fileno ? 0 :
                        cat->files[fileno - 1].start_time +
                        cat->files[fileno - 1].duration;

     file->file_start_time = (cat->avf->start_time == AV_NOPTS_VALUE) ? 0 : cat->avf->start_time;

     file->file_inpoint = (file->inpoint == AV_NOPTS_VALUE) ? file->file_start_time : file->inpoint;

     file->duration = get_best_effort_duration(file, cat->avf);

 
     if (cat->segment_time_metadata) {
         av_dict_set_int(&file->metadata, "lavf.concatdec.start_time", file->start_time, 0);
         if (file->duration != AV_NOPTS_VALUE)
             av_dict_set_int(&file->metadata, "lavf.concatdec.duration", file->duration, 0);
     }
 

     if ((ret = match_streams(avf)) < 0)
         return ret;

     if (file->inpoint != AV_NOPTS_VALUE) {
        if ((ret = avformat_seek_file(cat->avf, -1, INT64_MIN, file->inpoint, file->inpoint, 0)) < 0)
            return ret;
     }

     return 0;
 }
 
 static int concat_read_close(AVFormatContext *avf)
 {
     ConcatContext *cat = avf->priv_data;

     unsigned i, j;

     for (i = 0; i < cat->nb_files; i++) {

         av_freep(&cat->files[i].url);

         for (j = 0; j < cat->files[i].nb_streams; j++) {

             if (cat->files[i].streams[j].bsf)

                 av_bsf_free(&cat->files[i].streams[j].bsf);

         }

         av_freep(&cat->files[i].streams);

         av_dict_free(&cat->files[i].metadata);

     }

     if (cat->avf)
         avformat_close_input(&cat->avf);

     av_freep(&cat->files);
     return 0;
 }
 
 static int concat_read_header(AVFormatContext *avf)
 {
     ConcatContext *cat = avf->priv_data;

     AVBPrint bp;

     uint8_t *cursor, *keyword;

     int line = 0, i;

     unsigned nb_files_alloc = 0;
     ConcatFile *file = NULL;

     int64_t ret, time = 0;

     av_bprint_init(&bp, 0, AV_BPRINT_SIZE_UNLIMITED);
 
     while ((ret = ff_read_line_to_bprint_overwrite(avf->pb, &bp)) >= 0) {

         line++;

         cursor = bp.str;

         keyword = get_keyword(&cursor);
         if (!*keyword || *keyword == '#')
             continue;
 
         if (!strcmp(keyword, "file")) {
             char *filename = av_get_token((const char **)&cursor, SPACE_CHARS);
             if (!filename) {
                 av_log(avf, AV_LOG_ERROR, "Line %d: filename required\n", line);
                 FAIL(AVERROR_INVALIDDATA);
             }
             if ((ret = add_file(avf, filename, &file, &nb_files_alloc)) < 0)

                 goto fail;

         } else if (!strcmp(keyword, "duration") || !strcmp(keyword, "inpoint") || !strcmp(keyword, "outpoint")) {

             char *dur_str = get_keyword(&cursor);
             int64_t dur;
             if (!file) {

                 av_log(avf, AV_LOG_ERROR, "Line %d: %s without file\n",
                        line, keyword);

                 FAIL(AVERROR_INVALIDDATA);
             }
             if ((ret = av_parse_time(&dur, dur_str, 1)) < 0) {

                 av_log(avf, AV_LOG_ERROR, "Line %d: invalid %s '%s'\n",
                        line, keyword, dur_str);

                 goto fail;

             }

             if (!strcmp(keyword, "duration"))

                 file->user_duration = dur;

             else if (!strcmp(keyword, "inpoint"))
                 file->inpoint = dur;

             else if (!strcmp(keyword, "outpoint"))
                 file->outpoint = dur;

         } else if (!strcmp(keyword, "file_packet_metadata")) {
             char *metadata;

             if (!file) {
                 av_log(avf, AV_LOG_ERROR, "Line %d: %s without file\n",
                        line, keyword);
                 FAIL(AVERROR_INVALIDDATA);
             }

             metadata = av_get_token((const char **)&cursor, SPACE_CHARS);
             if (!metadata) {
                 av_log(avf, AV_LOG_ERROR, "Line %d: packet metadata required\n", line);
                 FAIL(AVERROR_INVALIDDATA);
             }

             if ((ret = av_dict_parse_string(&file->metadata, metadata, "=", "", 0)) < 0) {
                 av_log(avf, AV_LOG_ERROR, "Line %d: failed to parse metadata string\n", line);
                 av_freep(&metadata);
                 FAIL(AVERROR_INVALIDDATA);
             }
             av_freep(&metadata);

         } else if (!strcmp(keyword, "stream")) {
             if (!avformat_new_stream(avf, NULL))
                 FAIL(AVERROR(ENOMEM));
         } else if (!strcmp(keyword, "exact_stream_id")) {
             if (!avf->nb_streams) {
                 av_log(avf, AV_LOG_ERROR, "Line %d: exact_stream_id without stream\n",
                        line);
                 FAIL(AVERROR_INVALIDDATA);
             }
             avf->streams[avf->nb_streams - 1]->id =
                 strtol(get_keyword(&cursor), NULL, 0);

         } else if (!strcmp(keyword, "ffconcat")) {
             char *ver_kw  = get_keyword(&cursor);
             char *ver_val = get_keyword(&cursor);
             if (strcmp(ver_kw, "version") || strcmp(ver_val, "1.0")) {
                 av_log(avf, AV_LOG_ERROR, "Line %d: invalid version\n", line);
                 FAIL(AVERROR_INVALIDDATA);
             }
             if (cat->safe < 0)
                 cat->safe = 1;

         } else {
             av_log(avf, AV_LOG_ERROR, "Line %d: unknown keyword '%s'\n",
                    line, keyword);
             FAIL(AVERROR_INVALIDDATA);
         }
     }

     if (ret != AVERROR_EOF && ret < 0)

         goto fail;

     if (!cat->nb_files)
         FAIL(AVERROR_INVALIDDATA);

     for (i = 0; i < cat->nb_files; i++) {
         if (cat->files[i].start_time == AV_NOPTS_VALUE)
             cat->files[i].start_time = time;
         else
             time = cat->files[i].start_time;

         if (cat->files[i].user_duration == AV_NOPTS_VALUE) {

             if (cat->files[i].inpoint == AV_NOPTS_VALUE || cat->files[i].outpoint == AV_NOPTS_VALUE)
                 break;

             cat->files[i].user_duration = cat->files[i].outpoint - cat->files[i].inpoint;

         }

         cat->files[i].duration = cat->files[i].user_duration;

         time += cat->files[i].user_duration;

     }

     if (i == cat->nb_files) {

         avf->duration = time;

         cat->seekable = 1;
     }

     cat->stream_match_mode = avf->nb_streams ? MATCH_EXACT_ID :
                                                MATCH_ONE_TO_ONE;

     if ((ret = open_file(avf, 0)) < 0)

         goto fail;

     av_bprint_finalize(&bp, NULL);

     return 0;
 
 fail:

     av_bprint_finalize(&bp, NULL);

     concat_read_close(avf);
     return ret;
 }
 
 static int open_next_file(AVFormatContext *avf)
 {
     ConcatContext *cat = avf->priv_data;
     unsigned fileno = cat->cur_file - cat->files;
 

     cat->cur_file->duration = get_best_effort_duration(cat->cur_file, cat->avf);

     if (++fileno >= cat->nb_files) {
         cat->eof = 1;

         return AVERROR_EOF;

     }

     return open_file(avf, fileno);
 }
 

 static int filter_packet(AVFormatContext *avf, ConcatStream *cs, AVPacket *pkt)
 {
     int ret;
 

     if (cs->bsf) {
         ret = av_bsf_send_packet(cs->bsf, pkt);

         if (ret < 0) {

             av_log(avf, AV_LOG_ERROR, "h264_mp4toannexb filter "
                    "failed to send input packet\n");

             return ret;
         }

         while (!ret)
             ret = av_bsf_receive_packet(cs->bsf, pkt);

         if (ret < 0 && (ret != AVERROR(EAGAIN) && ret != AVERROR_EOF)) {
             av_log(avf, AV_LOG_ERROR, "h264_mp4toannexb filter "
                    "failed to receive output packet\n");
             return ret;

         }
     }
     return 0;
 }
 

 /* Returns true if the packet dts is greater or equal to the specified outpoint. */
 static int packet_after_outpoint(ConcatContext *cat, AVPacket *pkt)
 {
     if (cat->cur_file->outpoint != AV_NOPTS_VALUE && pkt->dts != AV_NOPTS_VALUE) {
         return av_compare_ts(pkt->dts, cat->avf->streams[pkt->stream_index]->time_base,
                              cat->cur_file->outpoint, AV_TIME_BASE_Q) >= 0;
     }
     return 0;
 }
 

 static int concat_read_packet(AVFormatContext *avf, AVPacket *pkt)
 {
     ConcatContext *cat = avf->priv_data;
     int ret;

     int64_t delta;

     ConcatStream *cs;

     AVStream *st;

     if (cat->eof)
         return AVERROR_EOF;
 

     if (!cat->avf)
         return AVERROR(EIO);
 

     while (1) {

         ret = av_read_frame(cat->avf, pkt);

         if (ret == AVERROR_EOF) {

             if ((ret = open_next_file(avf)) < 0)
                 return ret;
             continue;
         }
         if (ret < 0)
             return ret;

         if ((ret = match_streams(avf)) < 0) {
             return ret;
         }

         if (packet_after_outpoint(cat, pkt)) {
             av_packet_unref(pkt);
             if ((ret = open_next_file(avf)) < 0)
                 return ret;
             continue;
         }

         cs = &cat->cur_file->streams[pkt->stream_index];
         if (cs->out_stream_index < 0) {
             av_packet_unref(pkt);
             continue;
         }

         break;

     }

     if ((ret = filter_packet(avf, cs, pkt)) < 0)

         return ret;

     st = cat->avf->streams[pkt->stream_index];
     av_log(avf, AV_LOG_DEBUG, "file:%d stream:%d pts:%s pts_time:%s dts:%s dts_time:%s",
            (unsigned)(cat->cur_file - cat->files), pkt->stream_index,
            av_ts2str(pkt->pts), av_ts2timestr(pkt->pts, &st->time_base),
            av_ts2str(pkt->dts), av_ts2timestr(pkt->dts, &st->time_base));
 

     delta = av_rescale_q(cat->cur_file->start_time - cat->cur_file->file_inpoint,

                          AV_TIME_BASE_Q,
                          cat->avf->streams[pkt->stream_index]->time_base);
     if (pkt->pts != AV_NOPTS_VALUE)
         pkt->pts += delta;
     if (pkt->dts != AV_NOPTS_VALUE)
         pkt->dts += delta;

     av_log(avf, AV_LOG_DEBUG, " -> pts:%s pts_time:%s dts:%s dts_time:%s\n",
            av_ts2str(pkt->pts), av_ts2timestr(pkt->pts, &st->time_base),
            av_ts2str(pkt->dts), av_ts2timestr(pkt->dts, &st->time_base));

     if (cat->cur_file->metadata) {
         int metadata_len;
         char* packed_metadata = av_packet_pack_dictionary(cat->cur_file->metadata, &metadata_len);
         if (!packed_metadata)
             return AVERROR(ENOMEM);

         ret = av_packet_add_side_data(pkt, AV_PKT_DATA_STRINGS_METADATA,
                                       packed_metadata, metadata_len);
         if (ret < 0) {

             av_freep(&packed_metadata);

             return ret;

         }
     }

 
     if (cat->cur_file->duration == AV_NOPTS_VALUE && st->cur_dts != AV_NOPTS_VALUE) {
         int64_t next_dts = av_rescale_q(st->cur_dts, st->time_base, AV_TIME_BASE_Q);
         if (cat->cur_file->next_dts == AV_NOPTS_VALUE || next_dts > cat->cur_file->next_dts) {
             cat->cur_file->next_dts = next_dts;
         }
     }
 

     pkt->stream_index = cs->out_stream_index;

     return 0;

 }
 

 static void rescale_interval(AVRational tb_in, AVRational tb_out,
                              int64_t *min_ts, int64_t *ts, int64_t *max_ts)
 {
     *ts     = av_rescale_q    (*    ts, tb_in, tb_out);
     *min_ts = av_rescale_q_rnd(*min_ts, tb_in, tb_out,
                                AV_ROUND_UP   | AV_ROUND_PASS_MINMAX);
     *max_ts = av_rescale_q_rnd(*max_ts, tb_in, tb_out,
                                AV_ROUND_DOWN | AV_ROUND_PASS_MINMAX);
 }
 
 static int try_seek(AVFormatContext *avf, int stream,
                     int64_t min_ts, int64_t ts, int64_t max_ts, int flags)
 {
     ConcatContext *cat = avf->priv_data;

     int64_t t0 = cat->cur_file->start_time - cat->cur_file->file_inpoint;

 
     ts -= t0;
     min_ts = min_ts == INT64_MIN ? INT64_MIN : min_ts - t0;
     max_ts = max_ts == INT64_MAX ? INT64_MAX : max_ts - t0;
     if (stream >= 0) {
         if (stream >= cat->avf->nb_streams)
             return AVERROR(EIO);
         rescale_interval(AV_TIME_BASE_Q, cat->avf->streams[stream]->time_base,
                          &min_ts, &ts, &max_ts);
     }
     return avformat_seek_file(cat->avf, stream, min_ts, ts, max_ts, flags);
 }
 
 static int real_seek(AVFormatContext *avf, int stream,

                      int64_t min_ts, int64_t ts, int64_t max_ts, int flags, AVFormatContext *cur_avf)

 {
     ConcatContext *cat = avf->priv_data;
     int ret, left, right;
 
     if (stream >= 0) {
         if (stream >= avf->nb_streams)
             return AVERROR(EINVAL);
         rescale_interval(avf->streams[stream]->time_base, AV_TIME_BASE_Q,
                          &min_ts, &ts, &max_ts);
     }
 
     left  = 0;
     right = cat->nb_files;

 
     /* Always support seek to start */
     if (ts <= 0)
         right = 1;
     else if (!cat->seekable)
         return AVERROR(ESPIPE); /* XXX: can we use it? */
 

     while (right - left > 1) {
         int mid = (left + right) / 2;
         if (ts < cat->files[mid].start_time)
             right = mid;
         else
             left  = mid;
     }
 

     if (cat->cur_file != &cat->files[left]) {
         if ((ret = open_file(avf, left)) < 0)
             return ret;
     } else {
         cat->avf = cur_avf;
     }

 
     ret = try_seek(avf, stream, min_ts, ts, max_ts, flags);

     if (ret < 0 &&

         left < cat->nb_files - 1 &&
         cat->files[left + 1].start_time < max_ts) {

         if (cat->cur_file == &cat->files[left])
             cat->avf = NULL;

         if ((ret = open_file(avf, left + 1)) < 0)
             return ret;
         ret = try_seek(avf, stream, min_ts, ts, max_ts, flags);
     }
     return ret;
 }
 
 static int concat_seek(AVFormatContext *avf, int stream,
                        int64_t min_ts, int64_t ts, int64_t max_ts, int flags)
 {
     ConcatContext *cat = avf->priv_data;
     ConcatFile *cur_file_saved = cat->cur_file;
     AVFormatContext *cur_avf_saved = cat->avf;
     int ret;
 
     if (flags & (AVSEEK_FLAG_BYTE | AVSEEK_FLAG_FRAME))
         return AVERROR(ENOSYS);
     cat->avf = NULL;

     if ((ret = real_seek(avf, stream, min_ts, ts, max_ts, flags, cur_avf_saved)) < 0) {
         if (cat->cur_file != cur_file_saved) {
             if (cat->avf)
                 avformat_close_input(&cat->avf);
         }

         cat->avf      = cur_avf_saved;
         cat->cur_file = cur_file_saved;
     } else {

         if (cat->cur_file != cur_file_saved) {
             avformat_close_input(&cur_avf_saved);
         }

         cat->eof = 0;

     }
     return ret;
 }
 

 #define OFFSET(x) offsetof(ConcatContext, x)
 #define DEC AV_OPT_FLAG_DECODING_PARAM
 
 static const AVOption options[] = {
     { "safe", "enable safe mode",

       OFFSET(safe), AV_OPT_TYPE_BOOL, {.i64 = 1}, -1, 1, DEC },

     { "auto_convert", "automatically convert bitstream format",

       OFFSET(auto_convert), AV_OPT_TYPE_BOOL, {.i64 = 1}, 0, 1, DEC },

     { "segment_time_metadata", "output file segment start time and duration as packet metadata",
       OFFSET(segment_time_metadata), AV_OPT_TYPE_BOOL, {.i64 = 0}, 0, 1, DEC },

     { NULL }
 };
 
 static const AVClass concat_class = {
     .class_name = "concat demuxer",
     .item_name  = av_default_item_name,
     .option     = options,
     .version    = LIBAVUTIL_VERSION_INT,
 };
 
 

 AVInputFormat ff_concat_demuxer = {
     .name           = "concat",
     .long_name      = NULL_IF_CONFIG_SMALL("Virtual concatenation script"),
     .priv_data_size = sizeof(ConcatContext),
     .read_probe     = concat_probe,
     .read_header    = concat_read_header,
     .read_packet    = concat_read_packet,
     .read_close     = concat_read_close,

     .read_seek2     = concat_seek,

     .priv_class     = &concat_class,

 };