[FFmpeg-devel] [PATCH 3/4] concatdec: add support for specifying outpoint of files

[Nicolas George]

L'octidi 18 messidor, an CCXXIII, Marton Balint a écrit :
> Signed-off-by: Marton Balint <cus at passwd.hu>
> ---
>  doc/demuxers.texi       | 13 +++++++++++++
>  libavformat/concatdec.c | 22 ++++++++++++++++++++--
>  2 files changed, 33 insertions(+), 2 deletions(-)
> 
> diff --git a/doc/demuxers.texi b/doc/demuxers.texi
> index 4bad1c8..4ba797e 100644
> --- a/doc/demuxers.texi
> +++ b/doc/demuxers.texi
> @@ -129,6 +129,19 @@ directive) will be reduced based on their specified In point.
>  Because of potential packets before the specified In point, packet timestamps
>  may overlap between two concatenated files.
>  
> + at item @code{out @var{timestamp}}
> +Out point of the file. When the demuxer reaches the specified timestamp in any
> +of the streams, it handles it as an end of file condition. Out point is
> +exclusive, which means that the demuxer will not output packets which has a
> +timestamp greater or equal to Out point.
> +
> +This directive works best with intra frame codecs, because for non-intra frame
> +ones you will usually not get enough packets to decode the last few frames
> +before the specified Out point.
> +
> +The duration of the files (if not specified by the @code{duration}
> +directive) will be reduced based on their specified Out point.
> +
>  @item @code{stream}
>  Introduce a stream in the virtual file.
>  All subsequent stream-related directives apply to the last introduced
> diff --git a/libavformat/concatdec.c b/libavformat/concatdec.c
> index 11e6759..eaf34b0 100644
> --- a/libavformat/concatdec.c
> +++ b/libavformat/concatdec.c
> @@ -44,6 +44,7 @@ typedef struct {
>      int64_t duration;
>      ConcatStream *streams;
>      int64_t inpoint;
> +    int64_t outpoint;
>      int nb_streams;
>  } ConcatFile;
>  
> @@ -145,6 +146,7 @@ static int add_file(AVFormatContext *avf, char *filename, ConcatFile **rfile,
>      file->start_time = AV_NOPTS_VALUE;
>      file->duration   = AV_NOPTS_VALUE;
>      file->inpoint    = AV_NOPTS_VALUE;
> +    file->outpoint   = AV_NOPTS_VALUE;
>  
>      return 0;
>  
> @@ -360,7 +362,7 @@ static int concat_read_header(AVFormatContext *avf)
>              }
>              if ((ret = add_file(avf, filename, &file, &nb_files_alloc)) < 0)
>                  goto fail;
> -        } else if (!strcmp(keyword, "duration") || !strcmp(keyword, "in")) {
> +        } else if (!strcmp(keyword, "duration") || !strcmp(keyword, "in") || !strcmp(keyword, "out")) {
>              char *dur_str = get_keyword(&cursor);
>              int64_t dur;
>              if (!file) {
> @@ -377,6 +379,8 @@ static int concat_read_header(AVFormatContext *avf)
>                  file->duration = dur;
>              else if (!strcmp(keyword, "in"))
>                  file->inpoint = dur;
> +            else if (!strcmp(keyword, "out"))
> +                file->outpoint = dur;
>          } else if (!strcmp(keyword, "stream")) {
>              if (!avformat_new_stream(avf, NULL))
>                  FAIL(AVERROR(ENOMEM));
> @@ -443,6 +447,8 @@ static int open_next_file(AVFormatContext *avf)
>          cat->cur_file->duration = cat->avf->duration;
>          if (cat->cur_file->inpoint != AV_NOPTS_VALUE)
>              cat->cur_file->duration -= (cat->cur_file->inpoint - file_start_time);
> +        if (cat->cur_file->outpoint != AV_NOPTS_VALUE)
> +            cat->cur_file->duration -= cat->avf->duration - (cat->cur_file->outpoint - file_start_time);
>      }
>  
>      if (++fileno >= cat->nb_files) {
> @@ -504,6 +510,16 @@ static int64_t get_cur_file_inpoint(ConcatContext *cat)
>      return file_inpoint;
>  }
>  
> +/* Returns true if the packet pts 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->pts != AV_NOPTS_VALUE) {
> +        return av_compare_ts(pkt->pts, 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;
> @@ -520,7 +536,9 @@ static int concat_read_packet(AVFormatContext *avf, AVPacket *pkt)
>  
>      while (1) {
>          ret = av_read_frame(cat->avf, pkt);
> -        if (ret == AVERROR_EOF) {

> +        if (ret == AVERROR_EOF || packet_after_outpoint(cat, pkt)) {
> +            if (ret == 0)
> +                av_packet_unref(pkt);

This will not work if the streams in the file are not exactly interleaved.
Some formats store subtitles, and even audio, a few frames early, that will
trigger EOF even though there may be frames below the outpoint still coming.

At least, the documentation should have a warning about it.

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

No other objection, but if you change the name of the inpoint option, maybe
outpoint is no longer the best choice.

Regards,

-- 
  Nicolas George
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