Function writeCodecConfig

src/write.c:3872–3901

Implementation of section 2.3.3 of AV1 Codec ISO Media File Format Binding specification v1.2.0. See https://aomediacodec.github.io/av1-isobmff/v1.2.0.html#av1codecconfigurationbox-syntax.

// Implementation of section 2.3.3 of AV1 Codec ISO Media File Format Binding specification v1.2.0.
// See https://aomediacodec.github.io/av1-isobmff/v1.2.0.html#av1codecconfigurationbox-syntax.
static avifResult writeCodecConfig(avifRWStream * s, const avifCodecConfigurationBox * cfg)
{
    const size_t av1COffset = s->offset;

    AVIF_CHECKRES(avifRWStreamWriteBits(s, 1, /*bitCount=*/1)); // unsigned int (1) marker = 1;
    AVIF_CHECKRES(avifRWStreamWriteBits(s, 1, /*bitCount=*/7)); // unsigned int (7) version = 1;

    AVIF_CHECKRES(avifRWStreamWriteBits(s, cfg->seqProfile, /*bitCount=*/3));   // unsigned int (3) seq_profile;
    AVIF_CHECKRES(avifRWStreamWriteBits(s, cfg->seqLevelIdx0, /*bitCount=*/5)); // unsigned int (5) seq_level_idx_0;

    AVIF_CHECKRES(avifRWStreamWriteBits(s, cfg->seqTier0, /*bitCount=*/1));             // unsigned int (1) seq_tier_0;
    AVIF_CHECKRES(avifRWStreamWriteBits(s, cfg->highBitdepth, /*bitCount=*/1));         // unsigned int (1) high_bitdepth;
    AVIF_CHECKRES(avifRWStreamWriteBits(s, cfg->twelveBit, /*bitCount=*/1));            // unsigned int (1) twelve_bit;
    AVIF_CHECKRES(avifRWStreamWriteBits(s, cfg->monochrome, /*bitCount=*/1));           // unsigned int (1) monochrome;
    AVIF_CHECKRES(avifRWStreamWriteBits(s, cfg->chromaSubsamplingX, /*bitCount=*/1));   // unsigned int (1) chroma_subsampling_x;
    AVIF_CHECKRES(avifRWStreamWriteBits(s, cfg->chromaSubsamplingY, /*bitCount=*/1));   // unsigned int (1) chroma_subsampling_y;
    AVIF_CHECKRES(avifRWStreamWriteBits(s, cfg->chromaSamplePosition, /*bitCount=*/2)); // unsigned int (2) chroma_sample_position;

    AVIF_CHECKRES(avifRWStreamWriteBits(s, 0, /*bitCount=*/3)); // unsigned int (3) reserved = 0;
    AVIF_CHECKRES(avifRWStreamWriteBits(s, 0, /*bitCount=*/1)); // unsigned int (1) initial_presentation_delay_present;
    AVIF_CHECKRES(avifRWStreamWriteBits(s, 0, /*bitCount=*/4)); // unsigned int (4) reserved = 0;

    // According to section 2.2.1 of AV1 Image File Format specification v1.1.0,
    // there is no need to write any OBU here.
    // See https://aomediacodec.github.io/av1-avif/v1.1.0.html#av1-configuration-item-property.
    // unsigned int (8) configOBUs[];

    AVIF_ASSERT_OR_RETURN(s->offset - av1COffset == 4); // Make sure writeCodecConfig() writes exactly 4 bytes.
    return AVIF_RESULT_OK;
}

static avifResult writeConfigBox(avifRWStream * s, const avifCodecConfigurationBox * cfg, const char * configPropName)
{