[FFmpeg-devel] [PATCH v5] avformat/mov: Memory optimization with QuickTime/MP4

[Jörg Beckmann]

Is there still something wrong with this patch?

Cheers,
Jörg

> -----Ursprüngliche Nachricht-----
> Von: ffmpeg-devel <ffmpeg-devel-bounces at ffmpeg.org> Im Auftrag von Jörg
> Beckmann
> Gesendet: Montag, 9. Dezember 2019 16:05
> An: ffmpeg-devel at ffmpeg.org
> Betreff: [FFmpeg-devel] [PATCH v5] avformat/mov: Memory optimization with
> QuickTime/MP4
> 
> Invents a new option "discard_fragments" for the MP4/Quicktime/MOV decoder.
> 
> If the option is not set, nothing changes at all. If it is set, old fragments are
> discarded as far as possible on each call to switch_root. For pure audio streams,
> the memory usage is now constant. For video streams, the memory usage is
> reduced. It's tested with audio streams received from a professional DAB+
> receiver and with video streams created on my own with "ffmpeg -i <video>.m4v -
> c:a:0 copy -c:v copy -c:s copy -f ismv -movflags \ frag_keyframe -movflags
> faststart tcp://localhost:1234?listen" and "ffmpeg -i tcp://localhost:1234 -c:a copy -
> c:v copy -c:s copy -y <output>".
> 
> Signed-off-by: Jörg Beckmann <joerg.beckmann at scisys.com>
> ---
> libavformat/isom.h |  1 +
>  libavformat/mov.c  | 49
> ++++++++++++++++++++++++++++++++++++++++++++++++-
>  2 files changed, 49 insertions(+), 1 deletion(-)
> 
> diff --git a/libavformat/isom.h b/libavformat/isom.h index 4943b80ccf..9b4753f4d7
> 100644
> --- a/libavformat/isom.h
> +++ b/libavformat/isom.h
> @@ -268,6 +268,7 @@ typedef struct MOVContext {
>      int advanced_editlist;
>      int ignore_chapters;
>      int seek_individually;
> +    int discard_fragments;
>      int64_t next_root_atom; ///< offset of the next root atom
>      int export_all;
>      int export_xmp;
> diff --git a/libavformat/mov.c b/libavformat/mov.c index 7553a7fdfc..deb3ff5508
> 100644
> --- a/libavformat/mov.c
> +++ b/libavformat/mov.c
> @@ -7698,8 +7698,11 @@ static int should_retry(AVIOContext *pb, int error_code)
> {
> 
>  static int mov_switch_root(AVFormatContext *s, int64_t target, int index)  {
> -    int ret;
> +    int ret, i;
>      MOVContext *mov = s->priv_data;
> +    AVStream *st = NULL;
> +    MOVStreamContext *sc;
> +    MOVFragment *frag;
> 
>      if (index >= 0 && index < mov->frag_index.nb_items)
>          target = mov->frag_index.item[index].moof_offset;
> @@ -7721,6 +7724,43 @@ static int mov_switch_root(AVFormatContext *s, int64_t
> target, int index)
> 
>      mov->found_mdat = 0;
> 
> +    if (mov->discard_fragments) {
> +        frag = &mov->fragment;
> +
> +        for (i = 0; i < mov->fc->nb_streams; i++) {
> +            if (mov->fc->streams[i]->id == frag->track_id) {
> +                st = mov->fc->streams[i];
> +                break;
> +            }
> +        }
> +
> +        av_assert0(st);
> +
> +        sc = st->priv_data;
> +
> +        switch (st->codecpar->codec_type) {
> +            case AVMEDIA_TYPE_AUDIO:
> +            case AVMEDIA_TYPE_SUBTITLE:
> +                /* Freeing VIDEO tables leads to corrupted video when writing to eg.
> MKV */
> +                av_freep(&st->index_entries);
> +                st->nb_index_entries = 0;
> +                st->index_entries_allocated_size = 0;
> +
> +                sc->current_index = 0;
> +                sc->current_sample = 0;
> +
> +                av_freep(&sc->ctts_data);
> +                sc->ctts_allocated_size = 0;
> +                sc->ctts_count = 0;
> +                break;
> +        }
> +
> +        av_free(mov->frag_index.item->stream_info);
> +        av_freep(&mov->frag_index.item);
> +        mov->frag_index.allocated_size = 0;
> +        mov->frag_index.nb_items = 0;
> +    }
> +
>      ret = mov_read_default(mov, s->pb, (MOVAtom){ AV_RL32("root"), INT64_MAX
> });
>      if (ret < 0)
>          return ret;
> @@ -7975,6 +8015,9 @@ static int mov_read_seek(AVFormatContext *s, int
> stream_index, int64_t sample_ti
>      int sample;
>      int i;
> 
> +    if (mc->discard_fragments)  // Seeking is not possible if fragments are
> discarded.
> +        return AVERROR(ENOTSUP);
> +
>      if (stream_index >= s->nb_streams)
>          return AVERROR_INVALIDDATA;
> 
> @@ -8063,6 +8106,10 @@ static const AVOption mov_options[] = {
>      { "decryption_key", "The media decryption key (hex)",
> OFFSET(decryption_key), AV_OPT_TYPE_BINARY, .flags =
> AV_OPT_FLAG_DECODING_PARAM },
>      { "enable_drefs", "Enable external track support.", OFFSET(enable_drefs),
> AV_OPT_TYPE_BOOL,
>          {.i64 = 0}, 0, 1, FLAGS },
> +    {"discard_fragments",
> +            "Discard fragments after they have been read to support live streams.",
> +            OFFSET(discard_fragments), AV_OPT_TYPE_BOOL, { .i64 = 0 },
> +            0, 1, FLAGS },
> 
>      { NULL },
>  };
> 
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