Description of the issue

numOutChannels is (value), it is not recommended that the usacElementType sequence contains (value) channels, especially when only one channel of a CPE is included in numOutChannels


General compliance
Best practice


ISO IEC 23003-3 (USAC):
numOutChannels: Not forbidden but it may leads to playback issues with some players due to uncommon value for this usacElementType sequence, especially when the last element is a CPE so only one of the channels of this CPE must be taken

Possible solution/action

ISO IEC 23003-3:
Fix the encoder to fill numOutChannels with the correct count of channels computed from the usacElementType sequence of use a SCE for the last element rather that a CPE, then reencode the content.



QC.EBU.IO Test Items

Audio Coding Syntax