/*
  * Live smooth streaming fragmenter
  * Copyright (c) 2012 Martin Storsjo
  *

  * 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 "config.h"
 #include <float.h>
 #if HAVE_UNISTD_H
 #include <unistd.h>
 #endif
 
 #include "avformat.h"
 #include "internal.h"
 #include "os_support.h"
 #include "avc.h"
 #include "url.h"

 #include "isom.h"

 
 #include "libavutil/opt.h"
 #include "libavutil/avstring.h"
 #include "libavutil/mathematics.h"
 #include "libavutil/intreadwrite.h"
 
 typedef struct {
     char file[1024];
     char infofile[1024];
     int64_t start_time, duration;
     int n;
     int64_t start_pos, size;
 } Fragment;
 
 typedef struct {
     AVFormatContext *ctx;
     int ctx_inited;
     char dirname[1024];
     uint8_t iobuf[32768];
     URLContext *out;  // Current output stream where all output is written

     URLContext *out2; // Auxiliary output stream where all output is also written

     URLContext *tail_out; // The actual main output stream, if we're currently seeked back to write elsewhere
     int64_t tail_pos, cur_pos, cur_start_pos;
     int packets_written;
     const char *stream_type_tag;
     int nb_fragments, fragments_size, fragment_index;
     Fragment **fragments;
 
     const char *fourcc;
     char *private_str;
     int packet_size;
     int audio_tag;
 } OutputStream;
 
 typedef struct {
     const AVClass *class;  /* Class for private options. */
     int window_size;
     int extra_window_size;
     int lookahead_count;
     int min_frag_duration;
     int remove_at_exit;
     OutputStream *streams;
     int has_video, has_audio;
     int nb_fragments;
 } SmoothStreamingContext;
 
 static int ism_write(void *opaque, uint8_t *buf, int buf_size)
 {
     OutputStream *os = opaque;
     if (os->out)
         ffurl_write(os->out, buf, buf_size);
     if (os->out2)
         ffurl_write(os->out2, buf, buf_size);
     os->cur_pos += buf_size;
     if (os->cur_pos >= os->tail_pos)
         os->tail_pos = os->cur_pos;
     return buf_size;
 }
 
 static int64_t ism_seek(void *opaque, int64_t offset, int whence)
 {
     OutputStream *os = opaque;
     int i;
     if (whence != SEEK_SET)
         return AVERROR(ENOSYS);
     if (os->tail_out) {
         if (os->out) {
             ffurl_close(os->out);
         }
         if (os->out2) {
             ffurl_close(os->out2);
         }
         os->out = os->tail_out;
         os->out2 = NULL;
         os->tail_out = NULL;
     }
     if (offset >= os->cur_start_pos) {

         if (os->out)
             ffurl_seek(os->out, offset - os->cur_start_pos, SEEK_SET);

         os->cur_pos = offset;
         return offset;
     }
     for (i = os->nb_fragments - 1; i >= 0; i--) {
         Fragment *frag = os->fragments[i];
         if (offset >= frag->start_pos && offset < frag->start_pos + frag->size) {
             int ret;
             AVDictionary *opts = NULL;
             os->tail_out = os->out;
             av_dict_set(&opts, "truncate", "0", 0);
             ret = ffurl_open(&os->out, frag->file, AVIO_FLAG_READ_WRITE, &os->ctx->interrupt_callback, &opts);
             av_dict_free(&opts);
             if (ret < 0) {
                 os->out = os->tail_out;
                 os->tail_out = NULL;
                 return ret;
             }
             av_dict_set(&opts, "truncate", "0", 0);
             ffurl_open(&os->out2, frag->infofile, AVIO_FLAG_READ_WRITE, &os->ctx->interrupt_callback, &opts);
             av_dict_free(&opts);
             ffurl_seek(os->out, offset - frag->start_pos, SEEK_SET);
             if (os->out2)
                 ffurl_seek(os->out2, offset - frag->start_pos, SEEK_SET);
             os->cur_pos = offset;
             return offset;
         }
     }
     return AVERROR(EIO);
 }
 
 static void get_private_data(OutputStream *os)
 {
     AVCodecContext *codec = os->ctx->streams[0]->codec;
     uint8_t *ptr = codec->extradata;
     int size = codec->extradata_size;
     int i;
     if (codec->codec_id == AV_CODEC_ID_H264) {
         ff_avc_write_annexb_extradata(ptr, &ptr, &size);
         if (!ptr)
             ptr = codec->extradata;
     }
     if (!ptr)
         return;
     os->private_str = av_mallocz(2*size + 1);
     for (i = 0; i < size; i++)
         snprintf(&os->private_str[2*i], 3, "%02x", ptr[i]);
     if (ptr != codec->extradata)
         av_free(ptr);
 }
 
 static void ism_free(AVFormatContext *s)
 {
     SmoothStreamingContext *c = s->priv_data;
     int i, j;
     if (!c->streams)
         return;
     for (i = 0; i < s->nb_streams; i++) {
         OutputStream *os = &c->streams[i];
         ffurl_close(os->out);
         ffurl_close(os->out2);
         ffurl_close(os->tail_out);
         os->out = os->out2 = os->tail_out = NULL;
         if (os->ctx && os->ctx_inited)
             av_write_trailer(os->ctx);
         if (os->ctx && os->ctx->pb)
             av_free(os->ctx->pb);
         if (os->ctx)
             avformat_free_context(os->ctx);
         av_free(os->private_str);
         for (j = 0; j < os->nb_fragments; j++)
             av_free(os->fragments[j]);
         av_free(os->fragments);
     }
     av_freep(&c->streams);
 }
 

 static void output_chunk_list(OutputStream *os, AVIOContext *out, int final, int skip, int window_size)
 {
     int removed = 0, i, start = 0;
     if (os->nb_fragments <= 0)
         return;
     if (os->fragments[0]->n > 0)
         removed = 1;
     if (final)
         skip = 0;
     if (window_size)
         start = FFMAX(os->nb_fragments - skip - window_size, 0);
     for (i = start; i < os->nb_fragments - skip; i++) {
         Fragment *frag = os->fragments[i];
         if (!final || removed)
             avio_printf(out, "<c t=\"%"PRIu64"\" d=\"%"PRIu64"\" />\n", frag->start_time, frag->duration);
         else
             avio_printf(out, "<c n=\"%d\" d=\"%"PRIu64"\" />\n", frag->n, frag->duration);
     }
 }
 
 static int write_manifest(AVFormatContext *s, int final)
 {
     SmoothStreamingContext *c = s->priv_data;
     AVIOContext *out;
     char filename[1024];
     int ret, i, video_chunks = 0, audio_chunks = 0, video_streams = 0, audio_streams = 0;
     int64_t duration = 0;
 
     snprintf(filename, sizeof(filename), "%s/Manifest", s->filename);
     ret = avio_open2(&out, filename, AVIO_FLAG_WRITE, &s->interrupt_callback, NULL);

     if (ret < 0) {
         av_log(s, AV_LOG_ERROR, "Unable to open %s for writing\n", filename);

         return ret;

     }

     avio_printf(out, "<?xml version=\"1.0\" encoding=\"utf-8\"?>\n");
     for (i = 0; i < s->nb_streams; i++) {
         OutputStream *os = &c->streams[i];
         if (os->nb_fragments > 0) {
             Fragment *last = os->fragments[os->nb_fragments - 1];
             duration = last->start_time + last->duration;
         }
         if (s->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO) {
             video_chunks = os->nb_fragments;
             video_streams++;
         } else {
             audio_chunks = os->nb_fragments;
             audio_streams++;
         }
     }
     if (!final) {
         duration = 0;
         video_chunks = audio_chunks = 0;
     }
     if (c->window_size) {
         video_chunks = FFMIN(video_chunks, c->window_size);
         audio_chunks = FFMIN(audio_chunks, c->window_size);
     }
     avio_printf(out, "<SmoothStreamingMedia MajorVersion=\"2\" MinorVersion=\"0\" Duration=\"%"PRIu64"\"", duration);
     if (!final)
         avio_printf(out, " IsLive=\"true\" LookAheadFragmentCount=\"%d\" DVRWindowLength=\"0\"", c->lookahead_count);
     avio_printf(out, ">\n");
     if (c->has_video) {
         int last = -1, index = 0;
         avio_printf(out, "<StreamIndex Type=\"video\" QualityLevels=\"%d\" Chunks=\"%d\" Url=\"QualityLevels({bitrate})/Fragments(video={start time})\">\n", video_streams, video_chunks);
         for (i = 0; i < s->nb_streams; i++) {
             OutputStream *os = &c->streams[i];
             if (s->streams[i]->codec->codec_type != AVMEDIA_TYPE_VIDEO)
                 continue;
             last = i;
             avio_printf(out, "<QualityLevel Index=\"%d\" Bitrate=\"%d\" FourCC=\"%s\" MaxWidth=\"%d\" MaxHeight=\"%d\" CodecPrivateData=\"%s\" />\n", index, s->streams[i]->codec->bit_rate, os->fourcc, s->streams[i]->codec->width, s->streams[i]->codec->height, os->private_str);
             index++;
         }
         output_chunk_list(&c->streams[last], out, final, c->lookahead_count, c->window_size);
         avio_printf(out, "</StreamIndex>\n");
     }
     if (c->has_audio) {
         int last = -1, index = 0;
         avio_printf(out, "<StreamIndex Type=\"audio\" QualityLevels=\"%d\" Chunks=\"%d\" Url=\"QualityLevels({bitrate})/Fragments(audio={start time})\">\n", audio_streams, audio_chunks);
         for (i = 0; i < s->nb_streams; i++) {
             OutputStream *os = &c->streams[i];
             if (s->streams[i]->codec->codec_type != AVMEDIA_TYPE_AUDIO)
                 continue;
             last = i;
             avio_printf(out, "<QualityLevel Index=\"%d\" Bitrate=\"%d\" FourCC=\"%s\" SamplingRate=\"%d\" Channels=\"%d\" BitsPerSample=\"16\" PacketSize=\"%d\" AudioTag=\"%d\" CodecPrivateData=\"%s\" />\n", index, s->streams[i]->codec->bit_rate, os->fourcc, s->streams[i]->codec->sample_rate, s->streams[i]->codec->channels, os->packet_size, os->audio_tag, os->private_str);
             index++;
         }
         output_chunk_list(&c->streams[last], out, final, c->lookahead_count, c->window_size);
         avio_printf(out, "</StreamIndex>\n");
     }
     avio_printf(out, "</SmoothStreamingMedia>\n");
     avio_flush(out);
     avio_close(out);
     return 0;
 }
 

 static int ism_write_header(AVFormatContext *s)
 {
     SmoothStreamingContext *c = s->priv_data;
     int ret = 0, i;
     AVOutputFormat *oformat;
 

     if (mkdir(s->filename, 0777) < 0) {
         av_log(s, AV_LOG_ERROR, "mkdir failed\n");
         ret = AVERROR(errno);
         goto fail;
     }

 
     oformat = av_guess_format("ismv", NULL, NULL);
     if (!oformat) {
         ret = AVERROR_MUXER_NOT_FOUND;
         goto fail;
     }
 
     c->streams = av_mallocz(sizeof(*c->streams) * s->nb_streams);
     if (!c->streams) {
         ret = AVERROR(ENOMEM);
         goto fail;
     }
 
     for (i = 0; i < s->nb_streams; i++) {
         OutputStream *os = &c->streams[i];
         AVFormatContext *ctx;
         AVStream *st;
         AVDictionary *opts = NULL;
         char buf[10];
 
         if (!s->streams[i]->codec->bit_rate) {
             av_log(s, AV_LOG_ERROR, "No bit rate set for stream %d\n", i);
             ret = AVERROR(EINVAL);
             goto fail;
         }
         snprintf(os->dirname, sizeof(os->dirname), "%s/QualityLevels(%d)", s->filename, s->streams[i]->codec->bit_rate);

         if (mkdir(os->dirname, 0777) < 0) {
             ret = AVERROR(errno);
             av_log(s, AV_LOG_ERROR, "mkdir failed\n");
             goto fail;
         }

 
         ctx = avformat_alloc_context();
         if (!ctx) {
             ret = AVERROR(ENOMEM);
             goto fail;
         }
         os->ctx = ctx;
         ctx->oformat = oformat;
         ctx->interrupt_callback = s->interrupt_callback;
 
         if (!(st = avformat_new_stream(ctx, NULL))) {
             ret = AVERROR(ENOMEM);
             goto fail;
         }
         avcodec_copy_context(st->codec, s->streams[i]->codec);

         st->sample_aspect_ratio = s->streams[i]->sample_aspect_ratio;

 
         ctx->pb = avio_alloc_context(os->iobuf, sizeof(os->iobuf), AVIO_FLAG_WRITE, os, NULL, ism_write, ism_seek);
         if (!ctx->pb) {
             ret = AVERROR(ENOMEM);
             goto fail;
         }
 
         snprintf(buf, sizeof(buf), "%d", c->lookahead_count);
         av_dict_set(&opts, "ism_lookahead", buf, 0);
         av_dict_set(&opts, "movflags", "frag_custom", 0);
         if ((ret = avformat_write_header(ctx, &opts)) < 0) {
              goto fail;
         }
         os->ctx_inited = 1;
         avio_flush(ctx->pb);
         av_dict_free(&opts);
         s->streams[i]->time_base = st->time_base;
         if (st->codec->codec_type == AVMEDIA_TYPE_VIDEO) {
             c->has_video = 1;
             os->stream_type_tag = "video";
             if (st->codec->codec_id == AV_CODEC_ID_H264) {
                 os->fourcc = "H264";
             } else if (st->codec->codec_id == AV_CODEC_ID_VC1) {
                 os->fourcc = "WVC1";
             } else {
                 av_log(s, AV_LOG_ERROR, "Unsupported video codec\n");
                 ret = AVERROR(EINVAL);
                 goto fail;
             }
         } else {
             c->has_audio = 1;
             os->stream_type_tag = "audio";
             if (st->codec->codec_id == AV_CODEC_ID_AAC) {
                 os->fourcc = "AACL";
                 os->audio_tag = 0xff;
             } else if (st->codec->codec_id == AV_CODEC_ID_WMAPRO) {
                 os->fourcc = "WMAP";
                 os->audio_tag = 0x0162;
             } else {
                 av_log(s, AV_LOG_ERROR, "Unsupported audio codec\n");
                 ret = AVERROR(EINVAL);
                 goto fail;
             }
             os->packet_size = st->codec->block_align ? st->codec->block_align : 4;
         }
         get_private_data(os);
     }
 
     if (!c->has_video && c->min_frag_duration <= 0) {
         av_log(s, AV_LOG_WARNING, "no video stream and no min frag duration set\n");
         ret = AVERROR(EINVAL);
     }

     ret = write_manifest(s, 0);

 
 fail:
     if (ret)
         ism_free(s);
     return ret;
 }
 
 static int parse_fragment(AVFormatContext *s, const char *filename, int64_t *start_ts, int64_t *duration, int64_t *moof_size, int64_t size)
 {
     AVIOContext *in;
     int ret;
     uint32_t len;
     if ((ret = avio_open2(&in, filename, AVIO_FLAG_READ, &s->interrupt_callback, NULL)) < 0)
         return ret;
     ret = AVERROR(EIO);
     *moof_size = avio_rb32(in);
     if (*moof_size < 8 || *moof_size > size)
         goto fail;
     if (avio_rl32(in) != MKTAG('m','o','o','f'))
         goto fail;
     len = avio_rb32(in);
     if (len > *moof_size)
         goto fail;
     if (avio_rl32(in) != MKTAG('m','f','h','d'))
         goto fail;
     avio_seek(in, len - 8, SEEK_CUR);
     avio_rb32(in); /* traf size */
     if (avio_rl32(in) != MKTAG('t','r','a','f'))
         goto fail;
     while (avio_tell(in) < *moof_size) {
         uint32_t len = avio_rb32(in);
         uint32_t tag = avio_rl32(in);
         int64_t end = avio_tell(in) + len - 8;
         if (len < 8 || len >= *moof_size)
             goto fail;
         if (tag == MKTAG('u','u','i','d')) {
             const uint8_t tfxd[] = {
                 0x6d, 0x1d, 0x9b, 0x05, 0x42, 0xd5, 0x44, 0xe6,
                 0x80, 0xe2, 0x14, 0x1d, 0xaf, 0xf7, 0x57, 0xb2
             };
             uint8_t uuid[16];
             avio_read(in, uuid, 16);
             if (!memcmp(uuid, tfxd, 16) && len >= 8 + 16 + 4 + 16) {
                 avio_seek(in, 4, SEEK_CUR);
                 *start_ts = avio_rb64(in);
                 *duration = avio_rb64(in);
                 ret = 0;
                 break;
             }
         }
         avio_seek(in, end, SEEK_SET);
     }
 fail:
     avio_close(in);
     return ret;
 }
 
 static int add_fragment(OutputStream *os, const char *file, const char *infofile, int64_t start_time, int64_t duration, int64_t start_pos, int64_t size)
 {
     Fragment *frag;
     if (os->nb_fragments >= os->fragments_size) {
         os->fragments_size = (os->fragments_size + 1) * 2;
         os->fragments = av_realloc(os->fragments, sizeof(*os->fragments)*os->fragments_size);
         if (!os->fragments)
             return AVERROR(ENOMEM);
     }
     frag = av_mallocz(sizeof(*frag));
     if (!frag)
         return AVERROR(ENOMEM);
     av_strlcpy(frag->file, file, sizeof(frag->file));
     av_strlcpy(frag->infofile, infofile, sizeof(frag->infofile));
     frag->start_time = start_time;
     frag->duration = duration;
     frag->start_pos = start_pos;
     frag->size = size;
     frag->n = os->fragment_index;
     os->fragments[os->nb_fragments++] = frag;
     os->fragment_index++;
     return 0;
 }
 
 static int copy_moof(AVFormatContext *s, const char* infile, const char *outfile, int64_t size)
 {
     AVIOContext *in, *out;
     int ret = 0;
     if ((ret = avio_open2(&in, infile, AVIO_FLAG_READ, &s->interrupt_callback, NULL)) < 0)
         return ret;
     if ((ret = avio_open2(&out, outfile, AVIO_FLAG_WRITE, &s->interrupt_callback, NULL)) < 0) {
         avio_close(in);
         return ret;
     }
     while (size > 0) {
         uint8_t buf[8192];
         int n = FFMIN(size, sizeof(buf));
         n = avio_read(in, buf, n);
         if (n <= 0) {
             ret = AVERROR(EIO);
             break;
         }
         avio_write(out, buf, n);
         size -= n;
     }
     avio_flush(out);
     avio_close(out);
     avio_close(in);
     return ret;
 }
 
 static int ism_flush(AVFormatContext *s, int final)
 {
     SmoothStreamingContext *c = s->priv_data;
     int i, ret = 0;
 
     for (i = 0; i < s->nb_streams; i++) {
         OutputStream *os = &c->streams[i];
         char filename[1024], target_filename[1024], header_filename[1024];
         int64_t start_pos = os->tail_pos, size;
         int64_t start_ts, duration, moof_size;
         if (!os->packets_written)
             continue;
 
         snprintf(filename, sizeof(filename), "%s/temp", os->dirname);
         ret = ffurl_open(&os->out, filename, AVIO_FLAG_WRITE, &s->interrupt_callback, NULL);
         if (ret < 0)
             break;
         os->cur_start_pos = os->tail_pos;
         av_write_frame(os->ctx, NULL);
         avio_flush(os->ctx->pb);
         os->packets_written = 0;
         if (!os->out || os->tail_out)
             return AVERROR(EIO);
 
         ffurl_close(os->out);
         os->out = NULL;
         size = os->tail_pos - start_pos;
         if ((ret = parse_fragment(s, filename, &start_ts, &duration, &moof_size, size)) < 0)
             break;
         snprintf(header_filename, sizeof(header_filename), "%s/FragmentInfo(%s=%"PRIu64")", os->dirname, os->stream_type_tag, start_ts);
         snprintf(target_filename, sizeof(target_filename), "%s/Fragments(%s=%"PRIu64")", os->dirname, os->stream_type_tag, start_ts);
         copy_moof(s, filename, header_filename, moof_size);
         rename(filename, target_filename);
         add_fragment(os, target_filename, header_filename, start_ts, duration, start_pos, size);
     }
 
     if (c->window_size || (final && c->remove_at_exit)) {
         for (i = 0; i < s->nb_streams; i++) {
             OutputStream *os = &c->streams[i];
             int j;
             int remove = os->nb_fragments - c->window_size - c->extra_window_size - c->lookahead_count;
             if (final && c->remove_at_exit)
                 remove = os->nb_fragments;
             if (remove > 0) {
                 for (j = 0; j < remove; j++) {
                     unlink(os->fragments[j]->file);
                     unlink(os->fragments[j]->infofile);
                     av_free(os->fragments[j]);
                 }
                 os->nb_fragments -= remove;
                 memmove(os->fragments, os->fragments + remove, os->nb_fragments * sizeof(*os->fragments));
             }
             if (final && c->remove_at_exit)
                 rmdir(os->dirname);
         }
     }
 

     if (ret >= 0)
         ret = write_manifest(s, final);

     return ret;
 }
 
 static int ism_write_packet(AVFormatContext *s, AVPacket *pkt)
 {
     SmoothStreamingContext *c = s->priv_data;
     AVStream *st = s->streams[pkt->stream_index];
     OutputStream *os = &c->streams[pkt->stream_index];

     int64_t end_dts = (c->nb_fragments + 1LL) * c->min_frag_duration;

     int ret;

     if (st->first_dts == AV_NOPTS_VALUE)
         st->first_dts = pkt->dts;
 

     if ((!c->has_video || st->codec->codec_type == AVMEDIA_TYPE_VIDEO) &&

         av_compare_ts(pkt->dts - st->first_dts, st->time_base,
                       end_dts, AV_TIME_BASE_Q) >= 0 &&

         pkt->flags & AV_PKT_FLAG_KEY && os->packets_written) {
 

         if ((ret = ism_flush(s, 0)) < 0)
             return ret;

         c->nb_fragments++;
     }
 
     os->packets_written++;
     return ff_write_chained(os->ctx, 0, pkt, s);
 }
 
 static int ism_write_trailer(AVFormatContext *s)
 {
     SmoothStreamingContext *c = s->priv_data;
     ism_flush(s, 1);
 
     if (c->remove_at_exit) {
         char filename[1024];
         snprintf(filename, sizeof(filename), "%s/Manifest", s->filename);
         unlink(filename);
         rmdir(s->filename);
     }
 
     ism_free(s);
     return 0;
 }
 
 #define OFFSET(x) offsetof(SmoothStreamingContext, x)
 #define E AV_OPT_FLAG_ENCODING_PARAM
 static const AVOption options[] = {
     { "window_size", "number of fragments kept in the manifest", OFFSET(window_size), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, INT_MAX, E },
     { "extra_window_size", "number of fragments kept outside of the manifest before removing from disk", OFFSET(extra_window_size), AV_OPT_TYPE_INT, { .i64 = 5 }, 0, INT_MAX, E },
     { "lookahead_count", "number of lookahead fragments", OFFSET(lookahead_count), AV_OPT_TYPE_INT, { .i64 = 2 }, 0, INT_MAX, E },
     { "min_frag_duration", "minimum fragment duration (in microseconds)", OFFSET(min_frag_duration), AV_OPT_TYPE_INT64, { .i64 = 5000000 }, 0, INT_MAX, E },
     { "remove_at_exit", "remove all fragments when finished", OFFSET(remove_at_exit), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, 1, E },
     { NULL },
 };
 
 static const AVClass ism_class = {
     .class_name = "smooth streaming muxer",
     .item_name  = av_default_item_name,
     .option     = options,
     .version    = LIBAVUTIL_VERSION_INT,
 };
 
 
 AVOutputFormat ff_smoothstreaming_muxer = {
     .name           = "smoothstreaming",
     .long_name      = NULL_IF_CONFIG_SMALL("Smooth Streaming Muxer"),
     .priv_data_size = sizeof(SmoothStreamingContext),
     .audio_codec    = AV_CODEC_ID_AAC,
     .video_codec    = AV_CODEC_ID_H264,
     .flags          = AVFMT_GLOBALHEADER | AVFMT_NOFILE,
     .write_header   = ism_write_header,
     .write_packet   = ism_write_packet,
     .write_trailer  = ism_write_trailer,

     .codec_tag      = (const AVCodecTag* const []){ ff_mp4_obj_type, 0 },

     .priv_class     = &ism_class,
 };