[FFmpeg-devel] [PATCH] avformat/movenc: Support alpha channel for AVIF
Vignesh Venkatasubramanian
vigneshv at google.com
Thu May 19 19:08:15 EEST 2022
On Wed, May 18, 2022 at 7:36 PM Bang He <hezhanbang at gmail.com> wrote:
>
> error happened:
>
> ./ffmpeg -i alpha.png -filter_complex [0:v]alphaextract[a] -map 0 -map [a]
> -still-picture 1 avif_with_alpha.avif
> ffmpeg version N-106936-gff5ea89da2 Copyright (c) 2000-2022 the FFmpeg
> developers
> built with gcc 11 (Ubuntu 11.2.0-19ubuntu1)
> configuration: --disable-ffplay --disable-ffprobe --enable-gpl
> --enable-nonfree --prefix=/home/bang/Desktop/out
> libavutil 57. 24.101 / 57. 24.101
> libavcodec 59. 28.100 / 59. 28.100
> libavformat 59. 24.100 / 59. 24.100
> libavdevice 59. 6.100 / 59. 6.100
> libavfilter 8. 38.100 / 8. 38.100
> libswscale 6. 6.100 / 6. 6.100
> libswresample 4. 6.100 / 4. 6.100
> libpostproc 56. 5.100 / 56. 5.100
> Unrecognized option 'still-picture'.
> Error splitting the argument list: Option not found
>
You would have to build ffmpeg with libaom enabled for AVIF encoding
to work (since AVIF is backed by an AV1 encoder). From the logs you
posted, it seems like you don't have an AV1 encoder available in your
ffmpeg build.
The "-still-picture" flag was added in ab05e9a7f2. Please make sure
that you are sync'ed past that to pick up that option.
> On Thu, May 19, 2022 at 5:56 AM Vignesh Venkatasubramanian <
> vigneshv-at-google.com at ffmpeg.org> wrote:
>
> > AVIF specification allows for alpha channel as an auxillary item (in
> > 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 <vigneshv at 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 */
> >
> > - avio_wb16(pb, 1); /* item_id */
> > - avio_wb16(pb, 0); /* data_reference_index */
> > - avio_wb16(pb, 1); /* extent_count */
> > - mov->avif_extent_pos = avio_tell(pb);
> > - avio_wb32(pb, 0); /* extent_offset (written later) */
> > - // For animated AVIF, we simply write the first packet's size.
> > - avio_wb32(pb, mov->avif_extent_length); /* extent_length */
> > + for (int i = 0; i < s->nb_streams; i++) {
> > + avio_wb16(pb, i + 1); /* item_id */
> > + avio_wb16(pb, 0); /* data_reference_index */
> > + avio_wb16(pb, 1); /* extent_count */
> > + mov->avif_extent_pos[i] = avio_tell(pb);
> > + avio_wb32(pb, 0); /* extent_offset (written later) */
> > + // For animated AVIF, we simply write the first packet's size.
> > + avio_wb32(pb, mov->avif_extent_length[i]); /* extent_length */
> > + }
> >
> > return update_size(pb, pos);
> > }
> >
> > static int mov_write_iinf_tag(AVIOContext *pb, MOVMuxContext *mov,
> > AVFormatContext *s)
> > {
> > - int64_t infe_pos;
> > int64_t iinf_pos = avio_tell(pb);
> > avio_wb32(pb, 0); /* size */
> > ffio_wfourcc(pb, "iinf");
> > avio_wb32(pb, 0); /* Version & flags */
> > - avio_wb16(pb, 1); /* entry_count */
> > + avio_wb16(pb, s->nb_streams); /* entry_count */
> >
> > - infe_pos = avio_tell(pb);
> > - avio_wb32(pb, 0); /* size */
> > - ffio_wfourcc(pb, "infe");
> > - avio_w8(pb, 0x2); /* Version */
> > - avio_wb24(pb, 0); /* flags */
> > - avio_wb16(pb, 1); /* item_id */
> > - avio_wb16(pb, 0); /* item_protection_index */
> > - avio_write(pb, "av01", 4); /* item_type */
> > - avio_write(pb, "Color\0", 6); /* item_name */
> > - update_size(pb, infe_pos);
> > + for (int i = 0; i < s->nb_streams; i++) {
> > + int64_t infe_pos = avio_tell(pb);
> > + avio_wb32(pb, 0); /* size */
> > + ffio_wfourcc(pb, "infe");
> > + avio_w8(pb, 0x2); /* Version */
> > + avio_wb24(pb, 0); /* flags */
> > + avio_wb16(pb, i + 1); /* item_id */
> > + avio_wb16(pb, 0); /* item_protection_index */
> > + avio_write(pb, "av01", 4); /* item_type */
> > + avio_write(pb, !i ? "Color\0" : "Alpha\0", 6); /* item_name */
> > + update_size(pb, infe_pos);
> > + }
> >
> > return update_size(pb, iinf_pos);
> > }
> >
> > -static int mov_write_ispe_tag(AVIOContext *pb, MOVMuxContext *mov,
> > AVFormatContext *s)
> > +
> > +static int mov_write_iref_tag(AVIOContext *pb, MOVMuxContext *mov,
> > AVFormatContext *s)
> > +{
> > + int64_t auxl_pos;
> > + int64_t iref_pos = avio_tell(pb);
> > + avio_wb32(pb, 0); /* size */
> > + ffio_wfourcc(pb, "iref");
> > + avio_wb32(pb, 0); /* Version & flags */
> > +
> > + auxl_pos = avio_tell(pb);
> > + avio_wb32(pb, 0); /* size */
> > + ffio_wfourcc(pb, "auxl");
> > + avio_wb16(pb, 2); /* from_item_ID */
> > + avio_wb16(pb, 1); /* reference_count */
> > + avio_wb16(pb, 1); /* to_item_ID */
> > + update_size(pb, auxl_pos);
> > +
> > + return update_size(pb, iref_pos);
> > +}
> > +
> > +static int mov_write_ispe_tag(AVIOContext *pb, MOVMuxContext *mov,
> > AVFormatContext *s,
> > + int stream_index)
> > {
> > int64_t pos = avio_tell(pb);
> > avio_wb32(pb, 0); /* size */
> > ffio_wfourcc(pb, "ispe");
> > avio_wb32(pb, 0); /* Version & flags */
> > - avio_wb32(pb, s->streams[0]->codecpar->width); /* image_width */
> > - avio_wb32(pb, s->streams[0]->codecpar->height); /* image_height */
> > + avio_wb32(pb, s->streams[stream_index]->codecpar->width); /*
> > image_width */
> > + avio_wb32(pb, s->streams[stream_index]->codecpar->height); /*
> > image_height */
> > return update_size(pb, pos);
> > }
> >
> > -static int mov_write_pixi_tag(AVIOContext *pb, MOVMuxContext *mov,
> > AVFormatContext *s)
> > +static int mov_write_pixi_tag(AVIOContext *pb, MOVMuxContext *mov,
> > AVFormatContext *s,
> > + int stream_index)
> > {
> > int64_t pos = avio_tell(pb);
> > - const AVPixFmtDescriptor *pixdesc =
> > av_pix_fmt_desc_get(s->streams[0]->codecpar->format);
> > + const AVPixFmtDescriptor *pixdesc =
> > + av_pix_fmt_desc_get(s->streams[stream_index]->codecpar->format);
> > avio_wb32(pb, 0); /* size */
> > ffio_wfourcc(pb, "pixi");
> > avio_wb32(pb, 0); /* Version & flags */
> > @@ -3001,15 +3027,30 @@ static int mov_write_pixi_tag(AVIOContext *pb,
> > MOVMuxContext *mov, AVFormatConte
> > return update_size(pb, pos);
> > }
> >
> > +static int mov_write_auxC_tag(AVIOContext *pb)
> > +{
> > + int64_t pos = avio_tell(pb);
> > + avio_wb32(pb, 0); /* size */
> > + ffio_wfourcc(pb, "auxC");
> > + avio_wb32(pb, 0); /* Version & flags */
> > + avio_write(pb, "urn:mpeg:mpegB:cicp:systems:auxiliary:alpha\0", 44);
> > + return update_size(pb, pos);
> > +}
> > +
> > static int mov_write_ipco_tag(AVIOContext *pb, MOVMuxContext *mov,
> > AVFormatContext *s)
> > {
> > int64_t pos = avio_tell(pb);
> > avio_wb32(pb, 0); /* size */
> > ffio_wfourcc(pb, "ipco");
> > - mov_write_ispe_tag(pb, mov, s);
> > - mov_write_pixi_tag(pb, mov, s);
> > - mov_write_av1c_tag(pb, &mov->tracks[0]);
> > - mov_write_colr_tag(pb, &mov->tracks[0], 0);
> > + for (int i = 0; i < s->nb_streams; i++) {
> > + mov_write_ispe_tag(pb, mov, s, i);
> > + mov_write_pixi_tag(pb, mov, s, i);
> > + mov_write_av1c_tag(pb, &mov->tracks[i]);
> > + if (!i)
> > + mov_write_colr_tag(pb, &mov->tracks[0], 0);
> > + else
> > + mov_write_auxC_tag(pb);
> > + }
> > return update_size(pb, pos);
> > }
> >
> > @@ -3019,18 +3060,21 @@ static int mov_write_ipma_tag(AVIOContext *pb,
> > MOVMuxContext *mov, AVFormatConte
> > avio_wb32(pb, 0); /* size */
> > ffio_wfourcc(pb, "ipma");
> > avio_wb32(pb, 0); /* Version & flags */
> > - avio_wb32(pb, 1); /* entry_count */
> > - avio_wb16(pb, 1); /* item_ID */
> > - avio_w8(pb, 4); /* association_count */
> > -
> > - // ispe association.
> > - avio_w8(pb, 1); /* essential and property_index */
> > - // pixi association.
> > - avio_w8(pb, 2); /* essential and property_index */
> > - // av1C association.
> > - avio_w8(pb, 0x80 | 3); /* essential and property_index */
> > - // colr association.
> > - avio_w8(pb, 4); /* essential and property_index */
> > + avio_wb32(pb, s->nb_streams); /* entry_count */
> > +
> > + for (int i = 0, index = 1; i < s->nb_streams; i++) {
> > + avio_wb16(pb, i + 1); /* item_ID */
> > + avio_w8(pb, 4); /* association_count */
> > +
> > + // ispe association.
> > + avio_w8(pb, index++); /* essential and property_index */
> > + // pixi association.
> > + avio_w8(pb, index++); /* essential and property_index */
> > + // av1C association.
> > + avio_w8(pb, 0x80 | index++); /* essential and property_index */
> > + // colr/auxC association.
> > + avio_w8(pb, index++); /* essential and property_index */
> > + }
> > return update_size(pb, pos);
> > }
> >
> > @@ -4112,6 +4156,8 @@ static int mov_write_meta_tag(AVIOContext *pb,
> > MOVMuxContext *mov,
> > mov_write_pitm_tag(pb, 1);
> > mov_write_iloc_tag(pb, mov, s);
> > mov_write_iinf_tag(pb, mov, s);
> > + if (s->nb_streams > 1)
> > + mov_write_iref_tag(pb, mov, s);
> > mov_write_iprp_tag(pb, mov, s);
> > } else {
> > /* iTunes metadata tag */
> > @@ -6040,8 +6086,8 @@ int ff_mov_write_packet(AVFormatContext *s, AVPacket
> > *pkt)
> > avio_write(pb, reformatted_data, size);
> > } else {
> > size = ff_av1_filter_obus(pb, pkt->data, pkt->size);
> > - if (trk->mode == MODE_AVIF && !mov->avif_extent_length) {
> > - mov->avif_extent_length = size;
> > + if (trk->mode == MODE_AVIF &&
> > !mov->avif_extent_length[pkt->stream_index]) {
> > + mov->avif_extent_length[pkt->stream_index] = size;
> > }
> > }
> >
> > @@ -6874,14 +6920,23 @@ static int mov_init(AVFormatContext *s)
> >
> > /* AVIF output must have exactly one video stream */
> > 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
> > + // tag with type "auxl".
> > + mov->tracks[1].tref_tag = MKTAG('a', 'u', 'x', 'l');
> > + mov->tracks[1].tref_id = 1;
> > + }
> > mov_write_identification(pb, s);
> > mov_write_meta_tag(pb, mov, s);
> >
> > moov_size = get_moov_size(s);
> > - mov->tracks[0].data_offset = avio_tell(pb) + moov_size + 8;
> > + for (i = 0; i < s->nb_streams; i++)
> > + mov->tracks[i].data_offset = avio_tell(pb) + moov_size + 8;
> >
> > if (mov->is_animated_avif) {
> > int ret;
> > @@ -7565,19 +7627,24 @@ static int avif_write_trailer(AVFormatContext *s)
> > buf_size = avio_get_dyn_buf(mov->mdat_buf, &buf);
> > avio_wb32(pb, buf_size + 8);
> > ffio_wfourcc(pb, "mdat");
> > - mdat_pos = avio_tell(pb);
> >
> > - if (mdat_pos != (uint32_t)mdat_pos) {
> > - av_log(s, AV_LOG_ERROR, "mdat offset does not fit in 32 bits\n");
> > - return AVERROR_INVALIDDATA;
> > - }
> > + // The offset for the YUV planes is the starting position of mdat.
> > + extent_offsets[0] = avio_tell(pb);
> > + // The offset for alpha plane is YUV offset + YUV size.
> > + extent_offsets[1] = extent_offsets[0] + mov->avif_extent_length[0];
> >
> > avio_write(pb, buf, buf_size);
> >
> > - // write extent offset.
> > + // write extent offsets.
> > pos_backup = avio_tell(pb);
> > - avio_seek(pb, mov->avif_extent_pos, SEEK_SET);
> > - avio_wb32(pb, mdat_pos); /* rewrite offset */
> > + for (i = 0; i < s->nb_streams; i++) {
> > + if (extent_offsets[i] != (uint32_t)extent_offsets[i]) {
> > + av_log(s, AV_LOG_ERROR, "extent offset does not fit in 32
> > bits\n");
> > + return AVERROR_INVALIDDATA;
> > + }
> > + avio_seek(pb, mov->avif_extent_pos[i], SEEK_SET);
> > + avio_wb32(pb, extent_offsets[i]); /* rewrite offset */
> > + }
> > avio_seek(pb, pos_backup, SEEK_SET);
> >
> > return 0;
> > diff --git a/libavformat/movenc.h b/libavformat/movenc.h
> > index 281576cc66..e4550f7900 100644
> > --- a/libavformat/movenc.h
> > +++ b/libavformat/movenc.h
> > @@ -246,8 +246,8 @@ typedef struct MOVMuxContext {
> > int empty_hdlr_name;
> > int movie_timescale;
> >
> > - int64_t avif_extent_pos;
> > - int avif_extent_length;
> > + 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;
> > } MOVMuxContext;
> >
> > --
> > 2.36.1.124.g0e6072fb45-goog
> >
> > _______________________________________________
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> > ffmpeg-devel at ffmpeg.org
> > https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
> >
> > To unsubscribe, visit link above, or email
> > ffmpeg-devel-request at ffmpeg.org with subject "unsubscribe".
> >
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>
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--
Vignesh
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