AAC SBR (audio/aacp) - Sample rate and 'Using channel_format: I2SChannelSelect::Left for mono'

[pete-789]

It is great that CodecAACHelix can play AAC SBR (audio/aacp) encoded audio (as well as standard AAC).

I have come across something a bit strange though. I have two urls of AAC SBR audio.

The first gives a warning through the AudioToolsLogger

[W] CodecAACHelix.h : 154 - sample_rate: 44100

but plays fine in stereo.

The second throws two warnings in the logger

[W] CodecAACHelix.h : 154 - sample_rate: 48000
[W] I2SESP32V1.h : 239 - Using channel_format: I2SChannelSelect::Left for mono

and plays (as the warning suggests) in mono.

VLC Player on my desktop PC says both streams are stereo, and plays them both in stereo.

Is there something I can do to get the second stream to play in stereo? The hardware is a LyraT 4.3 in the Arduino IDE.

Many thanks!

[pschatzmann]

If you want to play a mono signal on both channels, you will need to convert it to 2 channels.
See the chapter Converting the Data Format...

[pete-789]

But I think that it is a stereo feed that is for some reason being played in mono (one channel).

Is that possible?

[pschatzmann]

Check the format e.g. with ffprobe.

I rather think that the VLC Player is doing this conversion automatically

[pete-789]

I've just listened to the feed with VLC Player using headphones, it's definitely stereo - it's Jazz FM -

http://stream-al.hellorayo.co.uk/jazz.aac?direct=true&aw_0_1st.skey=1602676850&rp_source=1&=&&___cb=351158590363417

[pschatzmann]

I confirm that libhelix consistently reports 1 channel for this stream: I guess this is because it is HE-AACv2!
I suggest you try anthother codec...

[pete-789]

Ah, thanks Phil... Do you have a codec in the library that will play it?

[pschatzmann]

Not sure since I have never seen this before. Just try the available alternatives:

https://github.com/pschatzmann/arduino-audio-tools/wiki/Encoding-and-Decoding-of-Audio

[pete-789]

I'll have a look.

Apparently:

HE-AAC v2 is optimized for even more aggressive compression than HE-AAC by adding Parametric Stereo (PS) to HE-AAC.

As always, many thanks for your help and for providing such wonderful libraries,