On Wed, Jun 1, 2022 at 10:52 AM James Zern <jz...@google.com> wrote: > > On Wed, May 18, 2022 at 2:56 PM Vignesh Venkatasubramanian > <vigneshv-at-google....@ffmpeg.org> wrote: > > > > AVIF specification allows for alpha channel as an auxillary item (in > > auxiliary >
Done. > > case of still images) or as an auxillary track (in case of animated > > images). Add support for both of these. The AVIF muxer will take > > exactly two streams (when alpha is present) as input (first one being > > the YUV planes and the second one being the alpha plane). > > > > The input has to come from two different images (one of it color and > > the other one being alpha), or it can come from a single file > > source with the alpha channel extracted using the "alphaextract" > > filter. > > > > Example using alphaextract: > > ffmpeg -i rgba.png -filter_complex "[0:v]alphaextract[a]" -map 0 -map "[a]" > > -still-picture 1 avif_with_alpha.avif > > > > Example using two sources (first source can be in any pixel format and > > the second source has to be in monochrome grey pixel format): > > ffmpeg -i color.avif -i grey.avif -map 0 -map 1 -c copy avif_with_alpha.avif > > > > The generated files pass the compliance checks in Compliance Warden: > > https://github.com/gpac/ComplianceWarden > > > > libavif (the reference avif library) is able to decode the files > > generated using this patch. > > > > They also play back properly (with transparent background) in: > > 1) Chrome > > 2) Firefox (only still AVIF, no animation support) > > > > Signed-off-by: Vignesh Venkatasubramanian <vigne...@google.com> > > --- > > libavformat/movenc.c | 185 +++++++++++++++++++++++++++++-------------- > > libavformat/movenc.h | 4 +- > > 2 files changed, 128 insertions(+), 61 deletions(-) > > > > diff --git a/libavformat/movenc.c b/libavformat/movenc.c > > index de971f94e8..00e42b7abb 100644 > > --- a/libavformat/movenc.c > > +++ b/libavformat/movenc.c > > @@ -2852,7 +2852,7 @@ static int mov_write_hdlr_tag(AVFormatContext *s, > > AVIOContext *pb, MOVTrack *tra > > hdlr = (track->mode == MODE_MOV) ? "mhlr" : "\0\0\0\0"; > > if (track->par->codec_type == AVMEDIA_TYPE_VIDEO) { > > if (track->mode == MODE_AVIF) { > > - hdlr_type = "pict"; > > + hdlr_type = (track == &mov->tracks[0]) ? "pict" : "auxv"; > > descr = "PictureHandler"; > > } else { > > hdlr_type = "vide"; > > @@ -2940,57 +2940,83 @@ static int mov_write_iloc_tag(AVIOContext *pb, > > MOVMuxContext *mov, AVFormatConte > > avio_wb32(pb, 0); /* Version & flags */ > > avio_w8(pb, (4 << 4) + 4); /* offset_size(4) and length_size(4) */ > > avio_w8(pb, 0); /* base_offset_size(4) and reserved(4) */ > > - avio_wb16(pb, 1); /* item_count */ > > + avio_wb16(pb, s->nb_streams); /* item_count */ > > This assumes at most 2 streams for AVIF, the use of nb_streams here and > elsewhere carry any risk for other formats? > For AVIF, we check and ensure we only have at most 2 streams in mov_init. iloc box is written only for AVIF as of now. So there is no risk for other formats. > > [...] > > > > @@ -6874,14 +6920,23 @@ static int mov_init(AVFormatContext *s) > > > > /* AVIF output must have exactly one video stream */ > > This is no longer true. > Updated. > > if (mov->mode == MODE_AVIF) { > > - if (s->nb_streams > 1) { > > - av_log(s, AV_LOG_ERROR, "AVIF output requires exactly one > > stream\n"); > > + if (s->nb_streams > 2) { > > + av_log(s, AV_LOG_ERROR, "AVIF output requires exactly one or > > two streams\n"); > > return AVERROR(EINVAL); > > } > > - if (s->streams[0]->codecpar->codec_type != AVMEDIA_TYPE_VIDEO) { > > - av_log(s, AV_LOG_ERROR, "AVIF output requires one video > > stream\n"); > > + if (s->streams[0]->codecpar->codec_type != AVMEDIA_TYPE_VIDEO && > > + (s->nb_streams > 1 && s->streams[1]->codecpar->codec_type != > > AVMEDIA_TYPE_VIDEO)) { > > + av_log(s, AV_LOG_ERROR, "AVIF output supports only video > > streams\n"); > > return AVERROR(EINVAL); > > } > > + if (s->nb_streams > 1) { > > + const AVPixFmtDescriptor *pixdesc = > > + av_pix_fmt_desc_get(s->streams[1]->codecpar->format); > > + if (pixdesc->nb_components != 1) { > > + av_log(s, AV_LOG_ERROR, "Second stream for AVIF (alpha) > > output must have exactly one plane\n"); > > + return AVERROR(EINVAL); > > + } > > + } > > s->streams[0]->disposition |= AV_DISPOSITION_DEFAULT; > > } > > > > @@ -7543,18 +7598,25 @@ static int avif_write_trailer(AVFormatContext *s) > > { > > AVIOContext *pb = s->pb; > > MOVMuxContext *mov = s->priv_data; > > - int64_t pos_backup, mdat_pos; > > + int64_t pos_backup, extent_offsets[2]; > > uint8_t *buf; > > - int buf_size, moov_size; > > + int buf_size, moov_size, i; > > > > if (mov->moov_written) return 0; > > > > mov->is_animated_avif = s->streams[0]->nb_frames > 1; > > + if (mov->is_animated_avif && s->nb_streams > 1) { > > + // For animated avif with alpha channel, we need to write a the > > tref > > ...write a tref... Done. -- Vignesh _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
