Audio codecs of HLS streams are different for different streamers

I have noticed the audio codec for some streamers is mpga(version 1 layer 3) but for the majority of streamers it is LC-AAC.

This is causing me some problems as it means the client I am using is unable to play some streams.

Is this working how it should? What is causing this? is it the original encoding of the streamer or is it twitch transcoding?

Example streams: and



Source would be whatever the broadcaster is sending via their broadcasting program. I’m not sure what codec the transcoders (Hight/Medium/Low/Mobile) use.

We do not transcode audio