Enforce MIAF grid constraints at decoding
diff --git a/src/read.c b/src/read.c
index 89b6dd4..8a4a590 100644
--- a/src/read.c
+++ b/src/read.c
@@ -1048,6 +1048,49 @@
return AVIF_RESULT_BMFF_PARSE_FAILED;
}
+ if (!memcmp(item->type, "grid", 4)) {
+ // MIAF (ISO 23000-22:2019), Section 7.3.11.4.1:
+ // All input images of a grid image item shall use the same coding format, chroma sampling format, and the
+ // same decoder configuration (see 7.3.6.2).
+ for (uint32_t i = 0; i < item->meta->items.count; ++i) {
+ const avifDecoderItem * tile = &item->meta->items.item[i];
+ if (tile->dimgForID == item->id) {
+ // The coding format is defined by the item type.
+ // avifDecoderGenerateImageGridTiles() skipped any non-AV1 tile.
+ if (memcmp(tile->type, "av01", 4)) {
+ continue;
+ }
+
+ // The chroma sampling format is part of the decoder configuration.
+ const avifProperty * tileAv1CProp = avifPropertyArrayFind(&tile->properties, "av1C");
+ if (!tileAv1CProp) {
+ avifDiagnosticsPrintf(diag,
+ "Tile item ID %u of type '%.4s' is missing mandatory av1C property",
+ tile->id,
+ (const char *)tile->type);
+ return AVIF_RESULT_BMFF_PARSE_FAILED;
+ }
+ // av1CProp was copied from a tile item to the grid item. Comparing tileAv1CProp with it
+ // is equivalent to comparing tileAv1CProp with the av1C property from the first tile.
+ if ((tileAv1CProp->u.av1C.seqProfile != av1CProp->u.av1C.seqProfile) ||
+ (tileAv1CProp->u.av1C.seqLevelIdx0 != av1CProp->u.av1C.seqLevelIdx0) ||
+ (tileAv1CProp->u.av1C.seqTier0 != av1CProp->u.av1C.seqTier0) ||
+ (tileAv1CProp->u.av1C.highBitdepth != av1CProp->u.av1C.highBitdepth) ||
+ (tileAv1CProp->u.av1C.twelveBit != av1CProp->u.av1C.twelveBit) ||
+ (tileAv1CProp->u.av1C.monochrome != av1CProp->u.av1C.monochrome) ||
+ (tileAv1CProp->u.av1C.chromaSubsamplingX != av1CProp->u.av1C.chromaSubsamplingX) ||
+ (tileAv1CProp->u.av1C.chromaSubsamplingY != av1CProp->u.av1C.chromaSubsamplingY) ||
+ (tileAv1CProp->u.av1C.chromaSamplePosition != av1CProp->u.av1C.chromaSamplePosition)) {
+ avifDiagnosticsPrintf(diag,
+ "The fields of the av1C property of tile item ID %u of type '%.4s' differs from other tiles",
+ tile->id,
+ (const char *)tile->type);
+ return AVIF_RESULT_BMFF_PARSE_FAILED;
+ }
+ }
+ }
+ }
+
const avifProperty * pixiProp = avifPropertyArrayFind(&item->properties, "pixi");
if (!pixiProp && (strictFlags & AVIF_STRICT_PIXI_REQUIRED)) {
// A pixi box is mandatory in all valid AVIF configurations. Bail out.
