Undocumented: Audio PCM Sample Format

The format of the data samples - signed or unsigned - for the ADL Audio Service is not documented.

To make matters worse, the sample code misleadingly uses u8* where, I think, void* would be more appropriate.

See https://forum.sierrawireless.com/t/play-generated-voice-stream-in-a-call/3225/50 and following.

The sample code also seems to be misleading in treating “bytes” and “samples” as synonymous - which is, obviously, not true for 16-bit samples!

unsigned 16bit mono little endian
usually can be u8

No, that is not supported by my experience: https://forum.sierrawireless.com/t/play-generated-voice-stream-in-a-call/3225/50 - the data is signed.

Again, this is something that should be properly documented: https://forum.sierrawireless.com/t/endian-ness-undocumented/534/5

That is an obsolete idiom.

For ANSI ‘C’, void* should be used for a “generic” pointer to arbitrary data.

I mean:
by using GlodWave (a famous sound tool for Windows)
select “PCM unsigned 16bit mono little endian” can handle its data very easy
use .WAV file built by this option, can be replayed by module correctly
if use signed 16b, sound replay error

i trust Glodwave

But my data is clearly signed - and it “works fine”! :confused:

Which all goes to show how important it is that Sierra Wireless get this documented properly!!