Uncompressed audio possible? Least CPU taxing audio codec settings?

[Piper984]

Hello: I have an application where I'd like to use Mumble with some embedded computers on a private network.  Mumble works very well, but the Opus compression is very taxing on the embedded CPU.  Before I go too far messing with Opus or Speex settings, I figured I'd ask the forum if someone knew of the least CPU intensive audio codec settings for Mumble?  It is possible to just use uncompressed audio?  The application environment is gigabit wired ethernet on a private LAN, so network traffic isn't a huge concern. The maximum number of clients would be under 8.

 

Thanks for any insights or advice here!

[Krzmbrzl]

Mumble always uses Opus (modern versions anyways) and afaik Opus does not support uncompressed audio. I could be wrong though.

I would expect however that uncompressed audio would be very demanding in terms of bandwidth requirements...

[Piper984]

Ok.  I did read that Opus has a 'complexity' setting, with the lower that value apparently the lower the CPU load.  So I think I'll test lowering that number and also increasing the bitrate and see what the CPU overhead ends up being. I might have to go into the source and see if the Opus library that the code is using supports.

 

https://wiki.xiph.org/Opus_Recommended_Settings

 

Would appreciate hearing any comments from anyone that has had a similar situation to address.

 

Thx!

[ZeroAbility]

Are there other things using the embedded CPU that lose performance due to the audio compression?

[Piper984]

Hi ZeroAbility: I am using a single core ARM processor, and yes there are other tasks running on CPU.  So I'd like to find a way to reduce the audio compression overhead as much as I can.  I have located the OPUS_SET_COMPLEXITY in the source.  Not sure if there is a quick way to set this lower then the default just yet.  If anyone has done this I'd appreciate hearing about it!  🙂

[ZeroAbility]

Perhaps these might help:

 

https://hydrogenaud.io/index.php?topic=104916.0

https://wiki.xiph.org/OpusFAQ#Opus_is_using_too_much_CPU_for_my_application._What_can_I_do.3F

[Piper984]

That is helpful information, thanks.  I did find in the source where the complexity setting is set:

opus-1.1.2/src/opus_encoder.c:    st->silk_mode.complexity                = 9;

 

I will try adjusting that down, recompile, and try see if that helps w/ CPU usage or not.

 

[Piper984]

Just wanted to capture for folks in future, I was able to lower CPU quite a bit by lowering complexity settings and also lowering encoding rate.  It's still not enough for my application, so I'm going to continue to look for a solution but I did want to capture that moving complexity to 0 did indeed lower CPU, and audio quality as as well.