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MPEGGroup / FileFormat

MPEG file format discussions
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On ItemReferenceBox version 1 in HEIF #87

Closed podborski closed 3 months ago

podborski commented 8 months ago

In HEIF we have this text in clause 6.6.1:

The number of SingleItemTypeReferenceBoxes with the box type 'dimg' and with the same value of from_item_ID shall not be greater than 1.

SingleItemTypeReferenceBoxes is also mentioned in a bunch of derived image items.

However, in ISOBMFF the ItemReferenceBox is defined as:

aligned(8) class ItemReferenceBox extends FullBox('iref', version, 0) {
    if (version==0) {
        SingleItemTypeReferenceBox              references[];
    } else if (version==1) {
        SingleItemTypeReferenceBoxLarge references[];
    }
}

Allowing also item references to be specified using the SingleItemTypeReferenceBoxLarge. To me this seems to be a little bit ambiguous because I don't see a clear restriction of ItemReferenceBox to be version 0 only in the HEIF spec. I see that the mif1 brand actually mentions the iref versions 0 and 1.

Table 3 — Boxes to be supported under the mif1 brand Hierarchy of boxes Version Box description
... ... ...
iref 0, 1 item reference box
... ... ...
leo-barnes commented 3 months ago

This has been fixed in the 3ed amd2 draft. All mentions of SingleItemTypeReferenceBox were changed to SingleItemTypeReferenceBox or SingleItemTypeReferenceBoxLarge.