fix upmix object number for AC4 level 4. #978
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barbibulle
reviewed
Sep 9, 2024
| @@ -664,11 +664,12 @@ AP4_Dac4Atom::Ac4Dsi::SubStream::ParseSubStreamInfoAjoc(AP4_BitReader &bits, | |||
| // oamd_common_data() | |||
| ParseOamdCommonData(bits); | |||
| } | |||
| n_umx_objects_minus1 = bits.ReadBits(4); | |||
| int nFullbandUpmixSignals = n_umx_objects_minus1 + 1; | |||
| int nFullbandUpmixSignalsMinus = bits.ReadBits(4); | |||
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Can you explain what the intent of this change is? It seems that it does exactly the same as before, just with a new local variable.
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AC-4 level 4 supports up to 20.1 indicating the n_umx_objects_minus1 could be 21. the old calculation only read 4 bits, didn't add 3 variable bits to n_umx_objects_minus1, the max number of n_umx_objects_minus1 is 15. New calculation adds the additional 3 bits.
barbibulle
approved these changes
Sep 16, 2024
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The calculation of n_umx_objects_minus1 has been updated due to AC4 level 4 with AJOC. n_umx_objects_minus1 may contains additional 3 bits of value.