Re: [FFmpeg-devel] [PATCH 2/2] avformat/movenc: Add loop parameter to animated AVIF

["\"zhilizhao(赵志立)\"" <quinkblack@foxmail.com>]

> On Jan 13, 2023, at 04:45, Vignesh Venkatasubramanian <vigneshv-at-google.com@ffmpeg.org> wrote:
> 
> The HEIF specification permits specifying the looping behavior of
> animated sequences by using the EditList (elst) box. The track
> duration will be set to the total duration of all the loops (or
> infinite) and the duration of a single loop will be set in the edit
> list box.
> 
> The default behavior is to loop infinitely.
> 
> Compliance verification:
> * This was added in libavif recently [1] and the files produced by
>  ffmpeg after this change have EditList boxes similar to the ones
>  produced by libavif (and avifdec is able to parse the loop count as
>  intended).
> * ComplianceWarden is ok with the produced files.
> * Chrome is able to play back the produced files.
> 
> [1] https://github.com/AOMediaCodec/libavif/commit/4d2776a3af53ae1aefdaed463b75ba12fd9cf8c2

Pushed.

Please use [PATCH v2] next time. It isn’t clear whether it’s the same
version as another patch or not, until diffed manually.

> 
> Signed-off-by: Vignesh Venkatasubramanian <vigneshv@google.com>
> ---
> libavformat/movenc.c | 35 +++++++++++++++++++++++++++++++----
> libavformat/movenc.h |  1 +
> 2 files changed, 32 insertions(+), 4 deletions(-)
> 
> diff --git a/libavformat/movenc.c b/libavformat/movenc.c
> index 36c76f7f60..8d31317838 100644
> --- a/libavformat/movenc.c
> +++ b/libavformat/movenc.c
> @@ -3287,7 +3287,7 @@ static int mov_write_tkhd_tag(AVIOContext *pb, MOVMuxContext *mov,
>     int64_t duration = av_rescale_rnd(calc_pts_duration(mov, track),
>                                       mov->movie_timescale, track->timescale,
>                                       AV_ROUND_UP);
> -    int version = duration < INT32_MAX ? 0 : 1;
> +    int version;
>     int flags   = MOV_TKHD_FLAG_IN_MOVIE;
>     int group   = 0;
> 
> @@ -3295,6 +3295,14 @@ static int mov_write_tkhd_tag(AVIOContext *pb, MOVMuxContext *mov,
>     size_t display_matrix_size;
>     int       i;
> 
> +    if (mov->mode == MODE_AVIF)
> +        if (!mov->avif_loop_count)
> +            duration = INT64_MAX;
> +        else
> +            duration *= mov->avif_loop_count;
> +
> +     version = duration < INT32_MAX ? 0 : 1;
> +
>     if (st) {
>         if (mov->per_stream_grouping)
>             group = st->index;
> @@ -3414,7 +3422,10 @@ static int mov_write_tapt_tag(AVIOContext *pb, MOVTrack *track)
>     return update_size(pb, pos);
> }
> 
> -// This box seems important for the psp playback ... without it the movie seems to hang
> +// This box is written in the following cases:
> +//   * Seems important for the psp playback. Without it the movie seems to hang.
> +//   * Used for specifying the looping behavior of animated AVIF (as specified
> +//   in Section 9.6 of the HEIF specification ISO/IEC 23008-12).
> static int mov_write_edts_tag(AVIOContext *pb, MOVMuxContext *mov,
>                               MOVTrack *track)
> {
> @@ -3425,6 +3436,7 @@ static int mov_write_edts_tag(AVIOContext *pb, MOVMuxContext *mov,
>     int entry_size, entry_count, size;
>     int64_t delay, start_ct = track->start_cts;
>     int64_t start_dts = track->start_dts;
> +    int flags = 0;
> 
>     if (track->entry) {
>         if (start_dts != track->cluster[0].dts || start_ct != track->cluster[0].cts) {
> @@ -3440,6 +3452,17 @@ static int mov_write_edts_tag(AVIOContext *pb, MOVMuxContext *mov,
> 
>     delay = av_rescale_rnd(start_dts + start_ct, mov->movie_timescale,
>                            track->timescale, AV_ROUND_DOWN);
> +
> +    if (mov->mode == MODE_AVIF) {
> +        delay = 0;
> +        // Section 9.6.3 of ISO/IEC 23008-12: flags specifies repetition of the
> +        // edit list as follows: (flags & 1) equal to 0 specifies that the edit
> +        // list is not repeated, while (flags & 1) equal to 1 specifies that the
> +        // edit list is repeated.
> +        flags = mov->avif_loop_count != 1;
> +        start_ct = 0;
> +    }
> +
>     version |= delay < INT32_MAX ? 0 : 1;
> 
>     entry_size = (version == 1) ? 20 : 12;
> @@ -3452,7 +3475,7 @@ static int mov_write_edts_tag(AVIOContext *pb, MOVMuxContext *mov,
>     avio_wb32(pb, size - 8);
>     ffio_wfourcc(pb, "elst");
>     avio_w8(pb, version);
> -    avio_wb24(pb, 0); /* flags */
> +    avio_wb24(pb, flags); /* flags */
> 
>     avio_wb32(pb, entry_count);
>     if (delay > 0) { /* add an empty edit to delay presentation */
> @@ -3469,7 +3492,7 @@ static int mov_write_edts_tag(AVIOContext *pb, MOVMuxContext *mov,
>             avio_wb32(pb, -1);
>         }
>         avio_wb32(pb, 0x00010000);
> -    } else {
> +    } else if (mov->mode != MODE_AVIF) {
>         /* Avoid accidentally ending up with start_ct = -1 which has got a
>          * special meaning. Normally start_ct should end up positive or zero
>          * here, but use FFMIN in case dts is a small positive integer
> @@ -3670,6 +3693,9 @@ static int mov_write_trak_tag(AVFormatContext *s, AVIOContext *pb, MOVMuxContext
>                    "Not writing any edit list even though one would have been required\n");
>     }
> 
> +    if (mov->is_animated_avif)
> +        mov_write_edts_tag(pb, mov, track);
> +
>     if (track->tref_tag)
>         mov_write_tref_tag(pb, track);
> 
> @@ -7761,6 +7787,7 @@ static const AVCodecTag codec_f4v_tags[] = {
> 
> static const AVOption avif_options[] = {
>     { "movie_timescale", "set movie timescale", offsetof(MOVMuxContext, movie_timescale), AV_OPT_TYPE_INT, {.i64 = MOV_TIMESCALE}, 1, INT_MAX, AV_OPT_FLAG_ENCODING_PARAM},
> +    { "loop", "Number of times to loop animated AVIF: 0 - infinite loop", offsetof(MOVMuxContext, avif_loop_count), AV_OPT_TYPE_INT, {.i64 = 0}, 0, INT_MAX, AV_OPT_FLAG_ENCODING_PARAM, 0 },
>     { NULL },
> };
> static const AVCodecTag codec_avif_tags[] = {
> diff --git a/libavformat/movenc.h b/libavformat/movenc.h
> index c6b3313deb..e85d83abdb 100644
> --- a/libavformat/movenc.h
> +++ b/libavformat/movenc.h
> @@ -249,6 +249,7 @@ typedef struct MOVMuxContext {
>     int64_t avif_extent_pos[2];  // index 0 is YUV and 1 is Alpha.
>     int avif_extent_length[2];   // index 0 is YUV and 1 is Alpha.
>     int is_animated_avif;
> +    int avif_loop_count;
> } MOVMuxContext;
> 
> #define FF_MOV_FLAG_RTP_HINT              (1 <<  0)
> -- 
> 2.39.0.314.g84b9a713c41-goog
> 
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