[FFmpeg-devel] [PATCH 2/2] avformat/movenc: Add loop parameter to animated AVIF
"zhilizhao(赵志立)"
quinkblack at foxmail.com
Fri Jan 13 06:40:44 EET 2023
> On Jan 13, 2023, at 04:45, Vignesh Venkatasubramanian <vigneshv-at-google.com at 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 at 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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