There are two audio source mapping modes possible:
- "Track Mode" - when you work on a per-audio track mode, and each track of the source has its Source ID.
- "Channel Mode" - in this case, mediaEngine considers all the available source audio channels enumerated as if they come from a single audio track.
Consider multiple input sources with a variety of channels, e.g. like this:
Source 0: 2 Channels
Source 1: 8 Channels
Source 2: 4 Channels
All the channels from Source 0 will have Source ID = 0, all the channels from Source 1 will have Source ID = 1, and the channels from Source 2 will have Source ID = 2.
So if you set e.g."SourceID=0" under [AudioEncoderSettings] and the audio output in "Track mode" it will result in an 8-channel output but since the source 0 has only two channels, these two channels will be copied and the remaining 6 channels will be filled with zeros.
To avoid this e.g for IMX30, consider using the "Channel Mode" where you can output the first 8 channels not depending on the number of input sources:
ChannelMap=0,1,2,3,4,5,6,7