LC3 encoding compression issue of stereo mode

RE: LC3 encoding compression issue of stereo mode

Amanda Hsieh — Mon, 02 Dec 2024 16:03:22 GMT

Please create a new support case for your own issue.

RE: LC3 encoding compression issue of stereo mode

Rana Roy — Mon, 02 Dec 2024 14:46:48 GMT

Hi team,

I am working on a custom development board with nRF5340 MCU. I have used two mics and integrated the LC3 codec library. I have assigned the following spaces in the prj.conf:

CONFIG_MAIN_STACK_SIZE=15480
CONFIG_HEAP_MEM_POOL_SIZE=16384

I also have assigned the stack size of 24576 for the associated thread. I also tried following all the above steps. When I compile the code for a single mic, the RAM utilization reaches to 93% and works fine. But, when I use two mics simultaneously, the RAM utilization goes to almost 100% as follows:
Memory region Used Size Region Size %age Used
FLASH: 567800 B 876032 B 64.81%
RAM: 450404 B 440 KB 99.97%
IDT_LIST: 0 GB 32 KB 0.00%

Hence, the mics are not working as expected. So, it would be great if I could get a reference.

RE: LC3 encoding compression issue of stereo mode

Amanda Hsieh — Thu, 08 Aug 2024 16:15:54 GMT

Hi,

Please check the following test sample, since we cannot guarantee your code:

https://github.com/nrfconnect/sdk-nrf/tree/main/tests/nrf5340_audio/sw_codec_lc3

-Amanda H.

RE: LC3 encoding compression issue of stereo mode

Dhruv@1997 — Thu, 08 Aug 2024 12:06:33 GMT

Hi Amanda H,

I read the documentation and looks like if LC3EncodeSessionOpen API is not able to allocate required memory then it will trigger LC3_RESULT_INSUFFICIENT_RESOURCES issue.

As of now in SDK we are calling LC3EncodeSessionOpen API based on channel number and in my case number of channels are 2.

So I have modified the logic of sw_codec_lc3_enc_init API to temporary allocate the static memory for second channel in this manner.

uint8_t data[2][4096];
int sw_codec_lc3_enc_init(uint16_t pcm_sample_rate, uint8_t pcm_bit_depth, uint16_t framesize_us,
 uint32_t enc_bitrate, uint8_t num_channels, uint16_t *const pcm_bytes_req)
{
 int ret;
 uint16_t data_size = 4096;
 LC3FrameSize_t framesize;
 uint16_t size = 0;

 switch (framesize_us) {
 case 7500:
 framesize = LC3FrameSize7_5Ms;
 break;
 case 10000:
 framesize = LC3FrameSize10Ms;
 break;
 default:
 LOG_ERR("Unsupported framesize: %d", framesize_us);
 return -EINVAL;
 }

 if (enc_bitrate == 0) {
 LOG_ERR("LC3 enc_bitrate is 0");
 return -EINVAL;
 } else if (enc_bitrate <= ENC_BITRATE_WRN_LVL_LOW) {
 LOG_ERR("LC3 enc_bitrate: %d : likely too low", enc_bitrate);
 } else if (enc_bitrate >= ENC_BITRATE_WRN_LVL_HIGH) {
 LOG_ERR("LC3 enc_bitrate: %d : likely too high", enc_bitrate);
 }

 enc_pcm_bytes_req = LC3PCMBuffersize(pcm_sample_rate, pcm_bit_depth, framesize, &ret);
 *pcm_bytes_req = enc_pcm_bytes_req;

 LOG_ERR("**lC3 buffer size error: %d and size: %d***", ret, *pcm_bytes_req);

 if (enc_pcm_bytes_req == 0) {
 LOG_ERR("Required PCM bytes to encode LC3 is zero.");
 return -EPERM;
 }

 for (uint8_t i = 0; i < num_channels; i++) {
 if (enc_handle_ch[i]) {
 LOG_ERR("LC3 enc ch: %d already initialized", i);
 return -EALREADY;
 }
 LOG_ERR("****Channel count: %d***", i);
 if(i == 0)
 {
 enc_handle_ch[i] = LC3EncodeSessionOpen(pcm_sample_rate, pcm_bit_depth, framesize,
 data[i], &data_size, &ret);
 if (ret) {
 LOG_ERR("**lC3 open session API error: %d***", ret);
 return ret;
 }
 }
 else if(i == 1)
 {
 enc_handle_ch[i] = LC3EncodeSessionOpen(pcm_sample_rate, pcm_bit_depth, framesize,
 data[i], &data_size, &ret);
 if (ret) {
 LOG_ERR("**lC3 open session API error: %d***", ret);
 LOG_ERR("***Buffer size is : %d*****", size);
 return ret;
 }
 }
 
 }

 m_enc_bitrate = enc_bitrate;

 enc_num_instances = num_channels;

 return ret;
}

And after this change I am able to encode the stereo channel data. Now I will validate the data. I am getting proper length of stereo data.

Can you please check the changes which I have made. Because I don't know how it impact the overall library.

RE: LC3 encoding compression issue of stereo mode

Dhruv@1997 — Wed, 07 Aug 2024 14:51:40 GMT

Hi Amanda H,

I have a custom PCBA, and I have used nrf5340 MCU. I am using NCS in Zephyr. NCS version is 2.6.1

RE: LC3 encoding compression issue of stereo mode

Amanda Hsieh — Wed, 07 Aug 2024 13:48:59 GMT

Hi,

Are you using nRF5340DK or nRF53 Audio DK?
Are you using NCS or vanilla Zephyr? What is the version number?

Regards,
Amanda H.