[FFmpeg-devel] [PATCH 2/2] avformat/movenc: Add loop parameter to animated AVIF
Vignesh Venkatasubramanian
vigneshv at google.com
Thu Jan 12 21:30:48 EET 2023
On Fri, Jan 6, 2023 at 1:45 AM "zhilizhao(赵志立)" <quinkblack at foxmail.com> wrote:
>
>
>
> > On Jan 6, 2023, at 01:34, Vignesh Venkatasubramanian <vigneshv-at-google.com at ffmpeg.org> wrote:
> >
> > On Thu, Jan 5, 2023 at 1:45 AM "zhilizhao(赵志立)" <quinkblack at foxmail.com> wrote:
> >>
> >>
> >>
> >>> On Jan 5, 2023, at 06:16, 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.
> >>>
> >>> 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 },
> >>
> >> The code treat -loop 1 means playback 1 time. It can be misleading
> >> to mean 2 times, playback 1 time then repeat/loop 1 time. That’s
> >> how ‘-stream_loop’ option works. I’m not English native speaker,
> >> I don’t know which one is correct. Better make the offset by 1
> >> clear.
> >>
> >
> > libavif uses the term "repetitionCount" instead of "loop" to not have
> > this ambiguity.
> >
> > The behavior of the "loop" parameter in this implementation is similar
> > to WebP's "loop" parameter in ffmpeg (i.e.) loop means the number of
> > times it will be played back (loop == 1 => 1 playback, loop == 2 => 2
> > playbacks and so on).
>
> LGTM then.
>
> >
> >>> { 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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> >>> ffmpeg-devel at ffmpeg.org
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> >>>
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> >>
> >
> >
> > --
> > Vignesh
> > _______________________________________________
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> >
> > To unsubscribe, visit link above, or email
> > ffmpeg-devel-request at ffmpeg.org with subject "unsubscribe".
>
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If there are no further comments, can this series of patches be merged please?
--
Vignesh
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