Function avifDecoderCreateCodecs

src/read.c:5424–5468

}

static avifResult avifDecoderCreateCodecs(avifDecoder * decoder)
{
    avifDecoderData * data = decoder->data;
    avifDecoderDataResetCodec(data);

    if (data->source == AVIF_DECODER_SOURCE_TRACKS) {
        // In this case, we will use at most two codec instances (one for the color planes and one for the alpha plane).
        // Gain maps are not supported.
        AVIF_CHECKRES(avifCodecCreateInternal(decoder->codecChoice, &decoder->data->tiles.tile[0], &decoder->diag, &data->codec));
        data->tiles.tile[0].codec = data->codec;
        if (data->tiles.count > 1) {
            AVIF_CHECKRES(avifCodecCreateInternal(decoder->codecChoice, &decoder->data->tiles.tile[1], &decoder->diag, &data->codecAlpha));
            data->tiles.tile[1].codec = data->codecAlpha;
        }
    } else {
        // In this case, we will use one codec instance when there is only one tile or when all of the following conditions are
        // met:
        //   - The image must have exactly one layer (i.e. decoder->imageCount == 1).
        //   - All the tiles must have the same operating point (because the codecs take operating point once at initialization
        //     and do not allow it to be changed later).
        //   - All the tiles must have the same value for allLayers (because the codecs take allLayers once at initialization
        //     and do not allow it to be changed later).
        //   - If the image has a single tile, it must not have a single tile alpha plane (in this case we will steal the planes
        //     from the decoder, so we cannot use the same decoder for both the color and the alpha planes).
        //   - All tiles have the same type (AV1 or AV2).
        //   - No tile buffer access after another tile was decoded (i.e. no Sample Transform compositing because it happens
        //     after decoding all tiles).
        // Otherwise, we will use |tiles.count| decoder instances (one instance for each tile).
        const avifBool canUseSingleCodecInstance =
            ((data->tiles.count == 1) || (decoder->imageCount == 1 && avifTilesCanBeDecodedWithSameCodecInstance(data))) &&
            data->sampleTransformNumInputImageItems == 0;
        if (canUseSingleCodecInstance) {
            AVIF_CHECKRES(avifCodecCreateInternal(decoder->codecChoice, &decoder->data->tiles.tile[0], &decoder->diag, &data->codec));
            for (unsigned int i = 0; i < decoder->data->tiles.count; ++i) {
                decoder->data->tiles.tile[i].codec = data->codec;
            }
        } else {
            for (unsigned int i = 0; i < decoder->data->tiles.count; ++i) {
                avifTile * tile = &decoder->data->tiles.tile[i];
                AVIF_CHECKRES(avifCodecCreateInternal(decoder->codecChoice, tile, &decoder->diag, &tile->codec));
            }
        }
    }
    return AVIF_RESULT_OK;
}

// Returns the primary color item if found, or NULL.
static avifDecoderItem * avifMetaFindColorItem(avifMeta * meta)