15 Mar 2022, 22:38 by vigneshv-at-google....@ffmpeg.org:
> On Thu, Mar 3, 2022 at 3:58 PM 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 625dea8421..cc0a8e1ca9 100644
>> --- a/libavformat/isom.h
>> +++ b/libavformat/isom.h
>> @@ -306,6 +306,7 @@ 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 68b6d7f075..d260024e47 100644
>> --- a/libavformat/mov.c
>> +++ b/libavformat/mov.c
>> @@ -1126,6 +1126,7 @@ 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);
>>
>> @@ -7173,6 +7174,146 @@ cleanup:
>> return ret;
>> }
>>
>> +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 != 0) {
>> + 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 },
>> @@ -7272,6 +7413,7 @@ static const MOVParseTableEntry
>> mov_default_parse_table[] = {
>> { MKTAG('d','v','v','C'), mov_read_dvcc_dvvc },
>> { MKTAG('d','v','w','C'), mov_read_dvcc_dvvc },
>> { MKTAG('k','i','n','d'), mov_read_kind },
>> +{ MKTAG('i','l','o','c'), mov_read_iloc },
>> { 0, NULL }
>> };
>>
>> --
>> 2.35.1.616.g0bdcbb4464-goog
>>
>
> Ping on this patch please.
>
Fix the coding style, please.
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