[FFmpeg-devel] [PATCH v3] avformat/mov: add interleaved_read option

[Steven Liu]

Zhao Zhili <quinkblack at foxmail.com> 于2023年9月12日周二 01:10写道：
>
> From: Zhao Zhili <zhilizhao at tencent.com>
>
> For bad interleaved files, manually interleave multiple tracks at the
> demuxer level can trigger seeking back and forth, which can be
> dramatically slow depending on the protocol. Demuxer level interleave
> can be useless sometimes, e.g., reading mp4 via http and then
> transcoding/remux to DASH. Disable this option when you don't need the
> demuxer level interleave, and want to avoid the IO penalizes.
>
> Co-authored-by: Derek Buitenhuis <derek.buitenhuis at gmail.com>
> Signed-off-by: Zhao Zhili <zhilizhao at tencent.com>
> ---
> v3: update doc
> v2: rename option
>
> This issue is well known. Two samples can be found at here
> http://ffmpeg.org/pipermail/ffmpeg-devel/2022-December/304951.html
>
>  doc/demuxers.texi     | 7 +++++++
>  libavformat/isom.h    | 1 +
>  libavformat/mov.c     | 5 ++++-
>  libavformat/version.h | 2 +-
>  4 files changed, 13 insertions(+), 2 deletions(-)
>
> diff --git a/doc/demuxers.texi b/doc/demuxers.texi
> index 2d33b47a56..ca1563abb0 100644
> --- a/doc/demuxers.texi
> +++ b/doc/demuxers.texi
> @@ -779,6 +779,13 @@ cast to int32 are used to adjust onward dts.
>
>  Unit is the track time scale. Range is 0 to UINT_MAX. Default is @code{UINT_MAX - 48000*10} which allows upto
>  a 10 second dts correction for 48 kHz audio streams while accommodating 99.9% of @code{uint32} range.
> +
> + at item interleaved_read
> +Interleave packets from multiple tracks at demuxer level. For badly interleaved files, this prevents playback issues
> +caused by large gaps between packets in different tracks, as MOV/MP4 do not have packet placement requirements.
> +However, this can cause excessive seeking on very badly interleaved files, due to seeking between tracks, so disabling
> +it may prevent I/O issues, at the expense of playback.
> +
>  @end table
>
>  @subsection Audible AAX
> diff --git a/libavformat/isom.h b/libavformat/isom.h
> index 4b1cd42f0f..3d375d7a46 100644
> --- a/libavformat/isom.h
> +++ b/libavformat/isom.h
> @@ -327,6 +327,7 @@ typedef struct MOVContext {
>          int64_t extent_offset;
>      } *avif_info;
>      int avif_info_size;
> +    int interleaved_read;
>  } MOVContext;
>
>  int ff_mp4_read_descr_len(AVIOContext *pb);
> diff --git a/libavformat/mov.c b/libavformat/mov.c
> index aa1d9e4ccc..8ad5f0b646 100644
> --- a/libavformat/mov.c
> +++ b/libavformat/mov.c
> @@ -8780,6 +8780,8 @@ static AVIndexEntry *mov_find_next_sample(AVFormatContext *s, AVStream **st)
>      AVIndexEntry *sample = NULL;
>      int64_t best_dts = INT64_MAX;
>      int i;
> +    MOVContext *mov = s->priv_data;
> +    int no_interleave = !mov->interleaved_read || !(s->pb->seekable & AVIO_SEEKABLE_NORMAL);
>      for (i = 0; i < s->nb_streams; i++) {
>          AVStream *avst = s->streams[i];
>          FFStream *const avsti = ffstream(avst);
> @@ -8788,7 +8790,7 @@ static AVIndexEntry *mov_find_next_sample(AVFormatContext *s, AVStream **st)
>              AVIndexEntry *current_sample = &avsti->index_entries[msc->current_sample];
>              int64_t dts = av_rescale(current_sample->timestamp, AV_TIME_BASE, msc->time_scale);
>              av_log(s, AV_LOG_TRACE, "stream %d, sample %d, dts %"PRId64"\n", i, msc->current_sample, dts);
> -            if (!sample || (!(s->pb->seekable & AVIO_SEEKABLE_NORMAL) && current_sample->pos < sample->pos) ||
> +            if (!sample || (no_interleave && current_sample->pos < sample->pos) ||
>                  ((s->pb->seekable & AVIO_SEEKABLE_NORMAL) &&
>                   ((msc->pb != s->pb && dts < best_dts) || (msc->pb == s->pb && dts != AV_NOPTS_VALUE &&
>                   ((FFABS(best_dts - dts) <= AV_TIME_BASE && current_sample->pos < sample->pos) ||
> @@ -9282,6 +9284,7 @@ static const AVOption mov_options[] = {
>      { "enable_drefs", "Enable external track support.", OFFSET(enable_drefs), AV_OPT_TYPE_BOOL,
>          {.i64 = 0}, 0, 1, FLAGS },
>      { "max_stts_delta", "treat offsets above this value as invalid", OFFSET(max_stts_delta), AV_OPT_TYPE_INT, {.i64 = UINT_MAX-48000*10 }, 0, UINT_MAX, .flags = AV_OPT_FLAG_DECODING_PARAM },
> +    { "interleaved_read", "Manually interleave between multiple tracks", OFFSET(interleaved_read), AV_OPT_TYPE_BOOL, {.i64 = 1 }, 0, 1, .flags = AV_OPT_FLAG_DECODING_PARAM },
>
>      { NULL },
>  };
> diff --git a/libavformat/version.h b/libavformat/version.h
> index cb67e0a1f8..e41362ac9d 100644
> --- a/libavformat/version.h
> +++ b/libavformat/version.h
> @@ -32,7 +32,7 @@
>  #include "version_major.h"
>
>  #define LIBAVFORMAT_VERSION_MINOR  12
> -#define LIBAVFORMAT_VERSION_MICRO 100
> +#define LIBAVFORMAT_VERSION_MICRO 101
>
>  #define LIBAVFORMAT_VERSION_INT AV_VERSION_INT(LIBAVFORMAT_VERSION_MAJOR, \
>                                                 LIBAVFORMAT_VERSION_MINOR, \
> --
> 2.34.1
>
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel at ffmpeg.org
> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>
> To unsubscribe, visit link above, or email
> ffmpeg-devel-request at ffmpeg.org with subject "unsubscribe".


lgtm

Thanks
Steven