On Wed, Mar 16, 2022 at 10:02 AM Vignesh Venkatasubramanian
<vigne...@google.com> wrote:
>
> Add support for parsing AVIF still images. This patches supports
> AVIF still images that have exactly 1 item (i.e.) no alpha channel.
> Essentially, we will have to parse the "iloc" box and populate
> the mov index.
>
> With this patch, we can decode still AVIF images like so:
> ffmpeg -i image.avif image.png
>
> Partially fixes trac ticket #7621
>
> Signed-off-by: Vignesh Venkatasubramanian <vigne...@google.com>
> ---
> libavformat/isom.h | 1 +
> libavformat/mov.c | 142 +++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 143 insertions(+)
>
> diff --git a/libavformat/isom.h b/libavformat/isom.h
> index 5caf42b15d..02d681e3ae 100644
> --- a/libavformat/isom.h
> +++ b/libavformat/isom.h
> @@ -315,6 +315,7 @@ typedef struct MOVContext {
> int have_read_mfra_size;
> uint32_t mfra_size;
> uint32_t max_stts_delta;
> + int is_still_picture_avif;
> } MOVContext;
>
> int ff_mp4_read_descr_len(AVIOContext *pb);
> diff --git a/libavformat/mov.c b/libavformat/mov.c
> index 6c847de164..3af49427b9 100644
> --- a/libavformat/mov.c
> +++ b/libavformat/mov.c
> @@ -1136,6 +1136,7 @@ static int mov_read_ftyp(MOVContext *c, AVIOContext
> *pb, MOVAtom atom)
> c->isom = 1;
> av_log(c->fc, AV_LOG_DEBUG, "ISO: File Type Major Brand: %.4s\n",(char
> *)&type);
> av_dict_set(&c->fc->metadata, "major_brand", type, 0);
> + c->is_still_picture_avif = !strncmp(type, "avif", 4);
> minor_ver = avio_rb32(pb); /* minor version */
> av_dict_set_int(&c->fc->metadata, "minor_version", minor_ver, 0);
>
> @@ -7430,6 +7431,146 @@ static int mov_read_SAND(MOVContext *c, AVIOContext
> *pb, MOVAtom atom)
> return 0;
> }
>
> +static int rb_size(AVIOContext *pb, uint64_t* value, int size)
> +{
> + if (size == 0) {
> + *value = 0;
> + } else if (size == 1) {
> + *value = avio_r8(pb);
> + } else if (size == 2) {
> + *value = avio_rb16(pb);
> + } else if (size == 4) {
> + *value = avio_rb32(pb);
> + } else if (size == 8) {
> + *value = avio_rb64(pb);
> + } else {
> + return -1;
> + }
> + return size;
> +}
> +
> +static int mov_read_iloc(MOVContext *c, AVIOContext *pb, MOVAtom atom)
> +{
> + int version, offset_size, length_size, base_offset_size, index_size;
> + int item_count, extent_count;
> + uint64_t base_offset, extent_offset, extent_length;
> + int i, j;
> + uint8_t value;
> + AVStream *st;
> + MOVStreamContext *sc;
> +
> + if (!c->is_still_picture_avif) {
> + // * For non-avif, we simply ignore the iloc box.
> + // * For animated avif, we don't care about the iloc box as all the
> + // necessary information can be found in the moov box.
> + return 0;
> + }
> +
> + if (c->fc->nb_streams) {
> + av_log(c->fc, AV_LOG_INFO, "Duplicate iloc box found\n");
> + return 0;
> + }
> +
> + st = avformat_new_stream(c->fc, NULL);
> + if (!st) return AVERROR(ENOMEM);
> + st->id = c->fc->nb_streams;
> + sc = av_mallocz(sizeof(MOVStreamContext));
> + if (!sc) return AVERROR(ENOMEM);
> +
> + st->priv_data = sc;
> + st->codecpar->codec_type = AVMEDIA_TYPE_VIDEO;
> + st->codecpar->codec_id = AV_CODEC_ID_AV1;
> + sc->ffindex = st->index;
> + c->trak_index = st->index;
> + st->avg_frame_rate.num = st->avg_frame_rate.den = 1;
> + st->time_base.num = st->time_base.den = 1;
> + st->nb_frames = 1;
> + sc->time_scale = 1;
> + sc = st->priv_data;
> + sc->pb = c->fc->pb;
> + sc->pb_is_copied = 1;
> +
> + version = avio_r8(pb);
> + avio_rb24(pb); // flags.
> +
> + value = avio_r8(pb);
> + offset_size = (value >> 4) & 0xF;
> + length_size = value & 0xF;
> + value = avio_r8(pb);
> + base_offset_size = (value >> 4) & 0xF;
> + index_size = (version == 0) ? 0 : (value & 0xF);
> + if (index_size != 0) {
> + return AVERROR_PATCHWELCOME;
> + }
> + item_count = (version < 2) ? avio_rb16(pb) : avio_rb32(pb);
> + if (item_count > 1) {
> + // For still AVIF images, we only support one item. Second item will
> + // generally be found for AVIF images with alpha channel. We don't
> + // support them as of now.
> + return AVERROR_PATCHWELCOME;
> + }
> +
> + // Populate the necessary fields used by mov_build_index.
> + sc->stsc_count = item_count;
> + sc->stsc_data = av_malloc_array(item_count, sizeof(*sc->stsc_data));
> + if (!sc->stsc_data) {
> + return AVERROR(ENOMEM);
> + }
> + sc->stsc_data[0].first = 1;
> + sc->stsc_data[0].count = 1;
> + sc->stsc_data[0].id = 1;
> + sc->chunk_count = item_count;
> + sc->chunk_offsets = av_malloc_array(item_count,
> sizeof(*sc->chunk_offsets));
> + if (!sc->chunk_offsets) {
> + return AVERROR(ENOMEM);
> + }
> + sc->sample_count = item_count;
> + sc->sample_sizes = av_malloc_array(item_count,
> sizeof(*sc->sample_sizes));
> + if (!sc->sample_sizes) {
> + return AVERROR(ENOMEM);
> + }
> + sc->stts_count = item_count;
> + sc->stts_data = av_malloc_array(item_count, sizeof(*sc->stts_data));
> + if (!sc->stts_data) {
> + return AVERROR(ENOMEM);
> + }
> + sc->stts_data[0].count = 1;
> + sc->stts_data[0].duration = 0; // Not used for still images. But needed
> by mov_build_index.
> +
> + for (i = 0; i < item_count; ++i) {
> + (version < 2) ? avio_rb16(pb) : avio_rb32(pb); // item_id;
> + if (version > 0) {
> + avio_rb16(pb); // construction_method.
> + }
> + avio_rb16(pb); // data_reference_index.
> + if (rb_size(pb, &base_offset, base_offset_size) < 0) {
> + return AVERROR_INVALIDDATA;
> + }
> + extent_count = avio_rb16(pb);
> + if (extent_count > 1) {
> + // For still AVIF images, we only support one extent item.
> + return AVERROR_PATCHWELCOME;
> + }
> + for (j = 0; j < extent_count; ++j) {
> + if (rb_size(pb, &extent_offset, offset_size) < 0 ||
> + rb_size(pb, &extent_length, length_size) < 0) {
> + return AVERROR_INVALIDDATA;
> + }
> + sc->sample_sizes[0] = extent_length;
> + sc->chunk_offsets[0] = base_offset + extent_offset;
> + }
> + }
> +
> + mov_build_index(c, st);
> +
> + // For still AVIF images, the iloc box contains all the necessary
> + // information that would generally be provided by the moov box. So
> simply
> + // mark that we have found the moov box so that parsing can continue.
> + c->found_moov = 1;
> +
> + return atom.size;
> +}
> +
> static const MOVParseTableEntry mov_default_parse_table[] = {
> { MKTAG('A','C','L','R'), mov_read_aclr },
> { MKTAG('A','P','R','G'), mov_read_avid },
> @@ -7532,6 +7673,7 @@ static const MOVParseTableEntry
> mov_default_parse_table[] = {
> { MKTAG('k','i','n','d'), mov_read_kind },
> { MKTAG('S','A','3','D'), mov_read_SA3D }, /* ambisonic audio box */
> { MKTAG('S','A','N','D'), mov_read_SAND }, /* non diegetic audio box */
> +{ MKTAG('i','l','o','c'), mov_read_iloc },
> { 0, NULL }
> };
>
> --
> 2.35.1.723.g4982287a31-goog
>
Another ping on this?
--
Vignesh
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