CC2564C: Using PLC (packet loss concealment) for NBS

Hi Li,

You mention that PLC works for WBS correctly but that the sample rate and audio speed are incorrect at 16 kHz PCM clock. Do you mean that PLC works correctly for NBS (8 kHz)? 

Can you take firmware logs to see if you are able to view messages like "PLC initialize"?

Thanks,
Jacob

Jacob,

For clarify my first post

case 1- WBS, 16 K PCM, audio speed is OK, PLC (AVPR) working on packet loss

case 2 - NBS, 8 K PCM, audio speed is OK, PLC (AVPR) NOT working on packet loss

case 3 -  NBS, 16 K PCM, audio speed is increased, PLC (AVPR) NOT working on packet loss

According to cc2564c datasheet, "PLC support added for NBS (8 kHz) when working at 16-kHz PCM clock" but i can't active PLC for NBS by changing MCU PCM clock and config AVPR using "HCI_VS_Write_CODEC_Config (0xFD06)" command 

I can't find example or document about this feature 

thanks

Hi Li,

We do not offer documentation on this feature. Are you able to share firmware and HCI logs so that we can see if PLC is initialized for NBS?

Best,
Jacob 

Hi Jacob

Thanks but I check TX_DBG pin firmware log and seem PLC not initialized i try to follow Michael Reymond's method 

https://e2e.ti.com/support/wireless-connectivity/bluetooth-group/bluetooth/f/bluetooth-forum/879289/cc2564c-phone-audio-pops-heard-from-headset/3301619#3301619

but 16K bandwidth refused by phone. according to HFP spec 8K bandwidth is maximum for WBS and NBS (consider compression ratio)

I continue testing. please let me know if you or Michael have suggestion

Thanks

Hi Li,

I'll respond here tomorrow.

Thanks,
Jacob

Hi Li,

Can you let me know the steps you have tried to enable PLC on NBS so far? Are you using HCI_VS_WBS_Associate (0xFD78) for WBS?

Thanks,
Jacob

Hi Jacob,

Thanks for your reply

For NBS:

1 - Set MCU PCM (master) config to 16K 

2 - set voice and air coding setting: HCI_Write_Voice_Setting(BluetoothStackID, (HCI_VOICE_SETTING_INPUT_DATA_FORMAT_2_COMPLEMENT | HCI_VOICE_SETTING_INPUT_SAMPLE_SIZE_16_BIT | HCI_VOICE_SETTING_AIR_CODING_FORMAT_CVSD), &Status);

3 - disable WBS by WBS_DISASSOCIATE_COMMAND (0xFD79)

4 - CC2564c (slave) codec config to 16K by VS_WRITE_CODEC_CONFIG_COMMAND

PLC not initialized and audio speed changed wrongly 

For WBS:

1 - Set MCU PCM (master) config to 16K 

2 - set voice and air coding setting: HCI_Write_Voice_Setting(BluetoothStackID, (HCI_VOICE_SETTING_INPUT_DATA_FORMAT_2_COMPLEMENT | HCI_VOICE_SETTING_INPUT_SAMPLE_SIZE_16_BIT | HCI_VOICE_SETTING_AIR_CODING_FORMAT_NONE), &Status)

3 - enable WBS by WBS_ASSOCIATE_COMMAND (0xFD78)

4 - CC2564c (slave) codec config to 16K by VS_WRITE_CODEC_CONFIG_COMMAND

attached file related to NBS

NBS_4.rar

Best regards

Hi Li,

For your WBS case, do you see PLC initialized in the logs?

How did you enable AVPR in your NBS case?

Thanks,
Jacob

Hi Jacob,

Jacob B. said:

For your WBS case, do you see PLC initialized in the logs?

Yes

For WBS, PLC initialized and "use plc" for packet loss reported on log 

Jacob B. said:

How did you enable AVPR in your NBS case?

Yes

After start up, download AVPR patch and enable AVPR. below screenshot related to attached log on previous post and indicate AVPR enabled successfully 

I think routing NBS to AVPR for sample rate conversion and PLC not related to remote device SCO config but according to Michael's post, SCO setup must changed.

below screenshot is show SCO config for NBS

Thanks

Hi Li,

Li Ho said:

but 16K bandwidth refused by phone. according to HFP spec 8K bandwidth is maximum for WBS and NBS (consider compression ratio)

In your WBS case, does the phone accept the 16K bandwidth?

Another idea I had is to change the codec. The mSBC codec seems to support 16K based on the HFP spec:

Can you try to set the codec to be mSBC with HCI_Write_Voice_Setting?

Thanks,
Jacob

Hi Jacob,

Jacob B. said:

Another idea I had is to change the codec. The mSBC codec seems to support 16K based on the HFP spec

CVSD is mandatory and can't force remote device to use mSBC instead of CVSD. 

mSBC sample rate is 16K but bandwidth is 8K (audio sampled by 16K and compressed before transmit by 8K bandwidth on SCO)

Jacob B. said:

Can you try to set the codec to be mSBC with HCI_Write_Voice_Setting?

I try to change voice setting and update this post, but from remote device side CVSD codec must be used

please let me know if any suggestion

thanks

Hey Li,

I'll reach out to another team member who may be able to help us enable PLC for NBS.

Thanks,
Jacob

Jacob,

Thanks for your support

Hi Jacob,

I still working on issue and also check this post

Thanks

Hi Li,

Li Ho said:

For WBS:

1 - Set MCU PCM (master) config to 16K 

2 - set voice and air coding setting: HCI_Write_Voice_Setting(BluetoothStackID, (HCI_VOICE_SETTING_INPUT_DATA_FORMAT_2_COMPLEMENT | HCI_VOICE_SETTING_INPUT_SAMPLE_SIZE_16_BIT | HCI_VOICE_SETTING_AIR_CODING_FORMAT_NONE), &Status)

3 - enable WBS by WBS_ASSOCIATE_COMMAND (0xFD78)

4 - CC2564c (slave) codec config to 16K by VS_WRITE_CODEC_CONFIG_COMMAND

attached file related to NBS

Can you take firmware and HCI logs for the WBS case like you did for the NBS case? I want to compare messages to see where the PLC initialization is failing.

Thanks,
Jacob

Hi Jacob,

full log related to WBS attached

WBS_4.rar

Thanks

Hi Li,

Thanks, I'll follow up here soon.

Best,
Jacob

Hi Li,

I will be out on vacation next week, but will ask another team member to take a look at this while I am out.

Best,
Jacob

Hi Jacob,

Thanks for your support 

Hi Li,

When working with NBS at 8kHz, are you: 

- Enabling AVPR via the patch described by Michael's post?

- Changing the sampling rate of the eSCO to 16kHz? Or is it left at 8kHz?

- Setting the PCM interface to be at 16kHz audio?

Thanks,

-Ryan 

Hi Ryan,

Ryan T said:

Enabling AVPR via the patch described by Michael's post?

Yes

After start up, download AVPR patch and enable AVPR. below screenshot related to attached log on previous post (NBS_4.rar) and indicate AVPR enabled successfully 

Ryan T said:

Changing the sampling rate of the eSCO to 16kHz? Or is it left at 8kHz?

eSCO bandwidth left at 8KHz (sample rate change to 16kHz) 

I try to change eSCO bandwidth to 16K according to Michael's post by "HCI_Setup_Synchronous_Connection" command after eSCO connection complete 

but 16k refused by phone. I check HFP spec and see bandwidth is 8K for NBS and WBS (consider compression)

Ryan T said:

Setting the PCM interface to be at 16kHz audio?

Yes 

PCM change to 16KHz for MCU side and CC256x

Thanks

Hey Li,

I am back from vacation and will answer your latest query in a day or two.

Thanks,
Jacob

Hi Jacob,

Thanks for update state

I test HCI_VS_Set_Narrow_Band_Voice_Path ("0xFD94") command but received error (invalid HCI command)

Best regards

Ok thanks for the update, I should have more information soon.

Best,
Jacob

Hi Li,

I'm continuing to look into this issue to see if there is another command you need to call to enable PLC on NBS. 

Can you share any errors or warnings you receive when you say "connection refused by phone"? 

Li Ho said:

but 16k refused by phone

Thanks,
Jacob

As another test, can you try executing these commands without step 3 to enable NBS from before without running the WBS_Dissassociate command?

Li Ho said:

For NBS:

1 - Set MCU PCM (master) config to 16K 

2 - set voice and air coding setting: HCI_Write_Voice_Setting(BluetoothStackID, (HCI_VOICE_SETTING_INPUT_DATA_FORMAT_2_COMPLEMENT | HCI_VOICE_SETTING_INPUT_SAMPLE_SIZE_16_BIT | HCI_VOICE_SETTING_AIR_CODING_FORMAT_CVSD), &Status);

3 - disable WBS by WBS_DISASSOCIATE_COMMAND (0xFD79)

4 - CC2564c (slave) codec config to 16K by VS_WRITE_CODEC_CONFIG_COMMAND

When you run the above commands (without step 3) do you see these messages?

Thanks,
Jacob

Hi Jacob,

Jacob B. said:

Can you share any errors or warnings you receive when you say "connection refused by phone"?

need to check again but in the response to HCI_Setup_Synchronous_Connection (16k bandwidth) commands, phone return "Insufficient Resources" or "invalid parameter". after receiving this return value i'm worry about using custom eSCO/SCO config because of compatibility issue for phones with different OS, Bluetooth stack and Bluetooth chip

Jacob B. said:

As another test, can you try executing these commands without step 3 to enable NBS from before without running the WBS_Dissassociate command?

I'm out of office, I'll test two scenario without running the WBS_Dissassociate command and update this post

0 - power up 

1 - Set MCU PCM (master) config to 16K 

2 - set voice and air coding setting: HCI_Write_Voice_Setting(BluetoothStackID, (HCI_VOICE_SETTING_INPUT_DATA_FORMAT_2_COMPLEMENT | HCI_VOICE_SETTING_INPUT_SAMPLE_SIZE_16_BIT | HCI_VOICE_SETTING_AIR_CODING_FORMAT_CVSD), &Status);

3 - CC2564c (slave) codec config to 16K by VS_WRITE_CODEC_CONFIG_COMMAND

and

0 - enable WBS by WBS_ASSOCIATE_COMMAND (0xFD78) from last WBS SCO connection

1 - Set MCU PCM (master) config to 16K 

2 - set voice and air coding setting: HCI_Write_Voice_Setting(BluetoothStackID, (HCI_VOICE_SETTING_INPUT_DATA_FORMAT_2_COMPLEMENT | HCI_VOICE_SETTING_INPUT_SAMPLE_SIZE_16_BIT | HCI_VOICE_SETTING_AIR_CODING_FORMAT_CVSD), &Status);

3 - CC2564c (slave) codec config to 16K by VS_WRITE_CODEC_CONFIG_COMMAND

Thanks for your time

Hi Li,

If you can take firmware logs just as before when sending these commands, that will help me further identify the issue.

Thanks,
Jacob

Hi Jacob,

Jacob B. said:

Can you share any errors or warnings you receive when you say "connection refused by phone"? 

Try to change TX/RX bandwidth to 16000 (0x3e80)

Invalid LMP parameter returned

full log attached

NBS_5_16000Bandwidth.rar

Best regards

Jacob, 

full log attached but on both case plc not work and audio speed is wrong

Li Ho said:

0 - power up 

1 - Set MCU PCM (master) config to 16K 

2 - set voice and air coding setting: HCI_Write_Voice_Setting(BluetoothStackID, (HCI_VOICE_SETTING_INPUT_DATA_FORMAT_2_COMPLEMENT | HCI_VOICE_SETTING_INPUT_SAMPLE_SIZE_16_BIT | HCI_VOICE_SETTING_AIR_CODING_FORMAT_CVSD), &Status);

3 - CC2564c (slave) codec config to 16K by VS_WRITE_CODEC_CONFIG_COMMAND

NBS_withoutDisableWBS.rar

Li Ho said:

0 - enable WBS by WBS_ASSOCIATE_COMMAND (0xFD78) from last WBS SCO connection

1 - Set MCU PCM (master) config to 16K 

2 - set voice and air coding setting: HCI_Write_Voice_Setting(BluetoothStackID, (HCI_VOICE_SETTING_INPUT_DATA_FORMAT_2_COMPLEMENT | HCI_VOICE_SETTING_INPUT_SAMPLE_SIZE_16_BIT | HCI_VOICE_SETTING_AIR_CODING_FORMAT_CVSD), &Status);

3 - CC2564c (slave) codec config to 16K by VS_WRITE_CODEC_CONFIG_COMMAND

(PLC initialize related to first WBS connection)

2021.LMP_Power_test_2.rar

Thanks

Thanks Li I will review these logs.

Best,
Jacob

OK Jacob,

Thanks

Hi Li,

Sorry for the delay on this thread. I will follow up by tomorrow early next week.

Best,
Jacob

Edit: updated follow-up date

Hi Jacob,

Thanks for update state

Best regards

Hi Li,

I've reviewed your logs and I see that you are still not able to initialize PLC using NBS. It looks like the AVPR is enabled successfully, but the upsampling of 8 kHz to 16 kHz is unsuccessful.

I will try to reproduce this. In the meantime, can you test your working WBS case (with "PLC initialized" message) and then run the WBS_dissassociate command while taking logs? I'm hoping this will get us closer to the functionality you are looking for.

Best,
Jacob

Hi Jacob,

Jacob B. said:

I will try to reproduce this. In the meantime

Thanks for your time

Jacob B. said:

can you test your working WBS case (with "PLC initialized" message) and then run the WBS_dissassociate command while taking logs?

I test and update this post

Best regards

Hi Li,

I was able to reproduce your issue and also am unable to initialize PLC. I tried using HFPDemo_HF on the MSP432, what platform are you using? 

https://e2e.ti.com/cfs-file/__key/communityserver-discussions-components-files/538/my_5F00_attempt_5F00_HFP_5F00_NBS.lgr

Here are the steps I know you need to take:

1. Enable AVPR patch download

2. Configure 16 kHz audio to be used on the codec

3. Comment out / remove the HFRE_HF_CODEC_NEGOTIATION_SUPPORTED_BIT on the HFRE_SUPPORTED_FEATURES

There may still be an additional SCO audio configuration needed. Can you try these steps for now?

Best,
Jacob

Hi Jacob,

Thanks for your support

Jacob B. said:

1. Enable AVPR patch download

2. Configure 16 kHz audio to be used on the codec

This steps is OK

Jacob B. said:

3. Comment out / remove the HFRE_HF_CODEC_NEGOTIATION_SUPPORTED_BIT on the HFRE_SUPPORTED_FEATURES

Good idea for force remote device to use CVSD for testing

According to Michael post and CC2564C datasheet PLC is working if sample rate conversion (16K <=> 8K) is occurred

But I'm not sure about correct MCU PCM clock (I2S peripheral) ! 

[Q1] Need to set 16K on PCM (I2S peripheral) of MCU or only set HCI_VS_Write_Codec_Config() and MCU remain on 8K?

(if PCM clock is 16K and also SCO bandwidth is 16K, sample rate conversion is meaningless)

Jacob B. said:

I tried using HFPDemo_HF on the MSP432, what platform are you using? 

I'm using STM32F7 and CC2564C

[Q2] Can you please confirm you are using MSP432 and CC2564C?

Jacob B. said:

There may still be an additional SCO audio configuration needed. Can you try these steps for now?

I try to using SCO API to configure and also need to working on my other application level tasks

Thanks

Hi Li,

Li Ho said:

[Q1] Need to set 16K on PCM (I2S peripheral) of MCU or only set HCI_VS_Write_Codec_Config() and MCU remain on 8K?

I was under the assumption that the HCI_VS_Write_Codec_Config command set the MCU I²S line to be 8 kHz as well. Is PLC initialized if you also specify the STM32 I2S line to be 8 kHz?

Li Ho said:

[Q2] Can you please confirm you are using MSP432 and CC2564C?

Yes, I am using the MSP432 and CC2564C. But I can also test with the STM32.

Thanks,
Jacob

Hi Jacob, 

Jacob B. said:

I was under the assumption that the HCI_VS_Write_Codec_Config command set the MCU I²S line to be 8 kHz as well

On stm32 code, VS_PCM_Codec_Config_Slave_I2S() function set cc2564x and set MCU I2S peripheral by change "register_rcc_plli2scfgr"

/* The following function is used to initailize the I2S interface. */
int initializeAudio(unsigned int BluetoothStackID, unsigned long Frequency)
{
    /* some code */
	switch(Frequency)
	{
		/* The I2S clock frequency = 16bits x 2ch x Frequency, in KHz, Frequency in Hz */
		case 8000:
			ret_val = VS_PCM_Codec_Config_Slave_I2S(BluetoothStackID, 
				I2S_CLK_FREQ_IN_FS_8KHZ, Frequency);
			register_rcc_plli2scfgr = (2 << 28) | (192 << 6);
			register_spi_i2spr = (1 << 8) | 187;
			break;
		case 16000:
			ret_val = VS_PCM_Codec_Config_Slave_I2S(BluetoothStackID, 
				I2S_CLK_FREQ_IN_FS_16KHZ, Frequency);
			register_rcc_plli2scfgr = (3 << 28) | (192 << 6);
			register_spi_i2spr = (1 << 8) | 62;
			break;
		case 48000:
			ret_val = VS_PCM_Codec_Config_Slave_I2S(BluetoothStackID, 
				I2S_CLK_FREQ_IN_FS_48KHZ, Frequency);
			register_rcc_plli2scfgr = (3 << 28) | (258 << 6);
			register_spi_i2spr = SPI_I2SPR_MCKOE | (1 << 8) | 3;
			break;
		case 44100:
			ret_val = VS_PCM_Codec_Config_Slave_I2S(BluetoothStackID, 
				I2S_CLK_FREQ_IN_FS_44_1KHZ, Frequency);
			register_rcc_plli2scfgr = (2 << 28) | (271 << 6);
			register_spi_i2spr = SPI_I2SPR_MCKOE | (0 << 8) | 6;
			break;
		default:
			Display(("\r\n Unsupported I2S Frequency !!! \r\n"));
			ret_val = -1; 
			return ret_val;
	}
	
	if(ret_val)
	{
		Display(("\r\n Failed to configure the BT PCM Interface !!! \r\n"));
		return ret_val;
	}
	
	/* some code */
	
}

Jacob B. said:

Is PLC initialized if you also specify the STM32 I2S line to be 8 kHz?

PLC not initialized on both MCU I2S case (16/8) but speech speed is OK on 8K and NOT OK on 16K

Jacob B. said:

But I can also test with the STM32

If you can using STM32 we can share code for testing

Thanks