liblc3 open source codec 32kbps test

[Tommy_Li]

Hi Nordic Team,

I know that nrf5340 Audio DK uses T2 Softeware's lc3 codec, it is provided by lib.

I want to test the open source codec liblc3 which was developed by google.

Because the BAP Profile depicts that the 32kbps is mandate for the Broadcast Audio, I mainly test 32kbps.

When i did the test on pc using the command "elc3 -b 32000 haikuotiankong_16k.wav | dlc3 | aplay",

I found that the sound quality is not very good.

While the nrf5340 Audio DK's Broadcast audio demo is also 32kbps, and the sound quality is very good.

I want to know whether you have tested other open source lc3 codec?

The reason why I want to ask this question is that i want to compress the audio on pc, and store the compressed audio into sdcard,

When i want to start brodacast audio, i just read the compressed audio from sdcard,  and then start transmission.

Sincerely Regards.

Tommy.

[Amanda Hsieh]

Hi, 

Have you already broadcasted the packets that used liblc3 to encode, and not satisfied the quality? Or are you using liblc3 to enc and dec on PC, and not satisfied with the quality? If it is the last, there could be a chance that the bitrate that liblc3 is using is for stereo channel:

e.g., if we use liblc3 for enc wav with 32kbps, that means 16kbps for L and 16kbps for right channel.

So probably you can make a trial by doubling the bitrate, and also check if the encoded frame size for each channel is 40 bytes.

Regards,
Amanda H. 

[Tommy_Li]

Hi Amanda,

You are right, When i doubled the bitrate to 64kbps for stereo audio, the sound quality sounded better.

Thank you for helping me clarify this issue.

 

Sincerely Regards.

Tommy.