How to mix multiple pcm capture stream into one and save to wav file as if it's from one single multi channel alsa card device

How to mix multiple pcm capture stream into one and save to wav file as if it's from one single multi channel alsa card device

[semiydsemiyd]

Hi

I have 8 alsa capture devices for one card.
Each capture device support 1 channel only:

root@light-a-val:~# arecord -l
**** List of CAPTURE Hardware Devices ****
card 0: LightSoundCard [Light-Sound-Card], device 0: light-tdm-dai-slot1-ES7210 ADC 0 es7210.5-0042-1 [light-tdm-dai-slot1-ES7210 ADC 0 es7210.5-0042-1]
  Subdevices: 1/8
  Subdevice #0: subdevice #0
card 0: LightSoundCard [Light-Sound-Card], device 1: light-tdm-dai-slot2-ES7210 ADC 0 es7210.5-0042-1 [light-tdm-dai-slot1-ES7210 ADC 0 es7210.5-0042-1]
  Subdevices: 2/8
  Subdevice #1: subdevice #1
...
card 0: LightSoundCard [Light-Sound-Card], device 7: light-tdm-dai-slot8-ES7210 ADC 1 es7210.5-0042-1 [light-tdm-dai-slot1-ES7210 ADC 0 es7210.5-0042-1]
  Subdevices: 8/8
  Subdevice #7: subdevice #7

the signal comes in TDM format from external codec ES7210 to my soc's TDM controller.
each capture device has 1 channel that correspond to one of the slot in TDM. i have 8 TDM slots in configuration. so i have 8 devices in total.


the reason that i have so many capture devices with 1 channel each is that, our tdm IC design decides that each tdm slot data_register would be assigned a 
dedicated dma channel. this is quite uncommon. thus i have 8 dma channels for 8 tdm slots.
since i can only register one rx dma channel and one tx using devm_snd_dmaengine_pcm_register().
like:
struct dmaengine_pcm {
	struct dma_chan *chan[SNDRV_PCM_STREAM_LAST + 1];    // there can be only one tx + one rx dma for struct dmaengine_pcm
	...
};
i have to register like 8 times to create 8 devices.
the dts for the cpu dai driver for tdm slot1 would look like:
		tdm: audio_tdm@0xffcb000000 {
			#sound-dai-cells = <0>;
...
			dmas = <&dmac2 31>;
			dma-names = "rx";
...
		};

now...i want to open all the devices at the same time. and have them save to one single wav file. As if i'm opening one single alsa capture device with  8 channels.
the saved wav file should look something like this (take this 8 channel wav file for example)

 First Multichannel Sample 
 --------------------------
{BB FF FF}  3 bytes slot1
{A1 FF FF}  3 bytes slot2
{00 00 00}  3 bytes slot3
{00 00 00}  3 bytes slot4
{00 00 00}  3 bytes slot5
{00 00 00}  3 bytes slot6
{00 00 00}  3 bytes slot7
{00 00 00}  3 bytes slot8

Second Multichannel Sample
 --------------------------
{E6 FF FF}  3 bytes slot1
 .,.. etc ....


Is this possible and if yes how can i do that?

thank you guys


semiyd

Re: How to mix multiple pcm capture stream into one and save to wav file as if it's from one single multi channel alsa card device

[Geraldo Nascimento]

Hi Semyid,

On Thu, Apr 27, 2023 at 05:53:17AM -0000, semiydsemiyd@163.com wrote:
> now...i want to open all the devices at the same time. and have them save to one single wav file. As if i'm opening one single alsa capture device with  8 channels.
> the saved wav file should look something like this (take this 8 channel wav file for example)
> 
>  First Multichannel Sample 
>  --------------------------
> {BB FF FF}  3 bytes slot1
> {A1 FF FF}  3 bytes slot2
> {00 00 00}  3 bytes slot3
> {00 00 00}  3 bytes slot4
> {00 00 00}  3 bytes slot5
> {00 00 00}  3 bytes slot6
> {00 00 00}  3 bytes slot7
> {00 00 00}  3 bytes slot8
> 
> Second Multichannel Sample
>  --------------------------
> {E6 FF FF}  3 bytes slot1
>  .,.. etc ....
> 
> 
> Is this possible and if yes how can i do that?
>

For such a task usually I'd use JACK on top of ALSA with the
alsa_in/alsa_out scripts or the Zita tools.

Good luck,
Geraldo Nascimento

> thank you guys
> 
> 
> semiyd

Re: How to mix multiple pcm capture stream into one and save to wav file as if it's from one single multi channel alsa card device

[semiydsemiyd]

thank you Geraldo !  i'll look into these tools.

Re: How to mix multiple pcm capture stream into one and save to wav file as if it's from one single multi channel alsa card device

[Jaroslav Kysela]

On 27. 04. 23 7:53, semiydsemiyd@163.com wrote:
> Hi
> 
> I have 8 alsa capture devices for one card.
> Each capture device support 1 channel only:
> 
> root@light-a-val:~# arecord -l
> **** List of CAPTURE Hardware Devices ****
> card 0: LightSoundCard [Light-Sound-Card], device 0: light-tdm-dai-slot1-ES7210 ADC 0 es7210.5-0042-1 [light-tdm-dai-slot1-ES7210 ADC 0 es7210.5-0042-1]
>    Subdevices: 1/8
>    Subdevice #0: subdevice #0
> card 0: LightSoundCard [Light-Sound-Card], device 1: light-tdm-dai-slot2-ES7210 ADC 0 es7210.5-0042-1 [light-tdm-dai-slot1-ES7210 ADC 0 es7210.5-0042-1]
>    Subdevices: 2/8
>    Subdevice #1: subdevice #1
> ...
> card 0: LightSoundCard [Light-Sound-Card], device 7: light-tdm-dai-slot8-ES7210 ADC 1 es7210.5-0042-1 [light-tdm-dai-slot1-ES7210 ADC 0 es7210.5-0042-1]
>    Subdevices: 8/8
>    Subdevice #7: subdevice #7
> 
> the signal comes in TDM format from external codec ES7210 to my soc's TDM controller.
> each capture device has 1 channel that correspond to one of the slot in TDM. i have 8 TDM slots in configuration. so i have 8 devices in total.
> 
> 
> the reason that i have so many capture devices with 1 channel each is that, our tdm IC design decides that each tdm slot data_register would be assigned a
> dedicated dma channel. this is quite uncommon. thus i have 8 dma channels for 8 tdm slots.
> since i can only register one rx dma channel and one tx using devm_snd_dmaengine_pcm_register().
> like:
> struct dmaengine_pcm {
> 	struct dma_chan *chan[SNDRV_PCM_STREAM_LAST + 1];    // there can be only one tx + one rx dma for struct dmaengine_pcm
> 	...
> };
> i have to register like 8 times to create 8 devices.
> the dts for the cpu dai driver for tdm slot1 would look like:
> 		tdm: audio_tdm@0xffcb000000 {
> 			#sound-dai-cells = <0>;
> ...
> 			dmas = <&dmac2 31>;
> 			dma-names = "rx";
> ...
> 		};
> 
> now...i want to open all the devices at the same time. and have them save to one single wav file. As if i'm opening one single alsa capture device with  8 channels.
> the saved wav file should look something like this (take this 8 channel wav file for example)

You may use the multi plugin from alsa-lib, just google "alsa multi plugin" 
for details.

				Jaroslav

-- 
Jaroslav Kysela <perex@perex.cz>
Linux Sound Maintainer; ALSA Project; Red Hat, Inc.