Support variable length sgpd boxes in fMPEG#3243
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dimitry-unified-streaming wants to merge 1 commit into
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Support variable length sgpd boxes in fMPEG#3243dimitry-unified-streaming wants to merge 1 commit into
sgpd boxes in fMPEG#3243dimitry-unified-streaming wants to merge 1 commit into
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For `sgpd` boxes with version >= 1, `the default_length` field is zero if the length of the following sample group entries is variable. Since the `FragmentedMp4Extractor` only supports one entry, skip the `description_length` field if applicable (e.g. when version >= 1 and `default_length` == 0), instead of throwing an error. For parsing the following CencSampleEncryptionInformationGroupEntry, this should make no difference. Issue: androidx#3177
icbaker
reviewed
May 29, 2026
| "Variable length description in sgpd found (unsupported)"); | ||
| } | ||
| } else if (sgpdVersion >= 2) { | ||
| long default_length = sgpdVersion >= 1 ? sgpd.readUnsignedInt() : 0; |
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i don't think the >= 1 check here is correct - I think it should be == 1.
Looking at section 8.9.3.2 of ISO 14496-12:2015 it seems default_length is present at v1 only, and the same 4 bytes are default_sample_description_index on v2+:
if (version==1) { unsigned int(32) default_length; }
if (version>=2) {
unsigned int(32) default_sample_description_index;
}
This also matches the previous code.
Same below on the condition gating the description_length skip.
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For
sgpdboxes with version >= 1,the default_lengthfield is zero if the length of the following sample group entries is variable.Since the
FragmentedMp4Extractoronly supports one entry, skip thedescription_lengthfield if applicable (e.g. when version >= 1 anddefault_length== 0), instead of throwing an error.For parsing the following CencSampleEncryptionInformationGroupEntry, this should make no difference.
Issue: #3177