> >Hi. I'm developping a signal processing program which needs to compute data
>
> >from each channel of soundcards separately.
> >After searches I found that I must open the soundcard with the
> >SND_PCM_ACCESS_RW_NONINTERLEAVED flag but it doesn't works well : for each
>
> >readn operation i get the -32 error code . Meanwhile, I tested capture in
> >interleaved mode and it works well.
> >I had to use hw:x,y for the interleaved capture and plughw:x,y for the
> non-
> >interleaved capture, I don't know if non-interleaved capture works with
> hw:x,y.
>
> [ We need a FAQ ... ]
>
> ALSA's "hw" devices can only be used with parameters that match
> capabilities offered by the underlying hardware. There's not much
> hardware out there that supports non-interleaved I/O, so as a result,
> most "hw" devices can't do this. The Hammerfall and ice1712 series are
> notable exceptions. But there is a corollary: if you were using a
> hammerfall, the "hw" device cannot do interleaved I/O either.
>
> as to your error, its probably a bug in your code. JACK uses
> non-interleaved mode by default, and it works with both plughw and hw
> models of many different kinds. if you posted the relevant parts of it
> here, somebody can probably help you.
>
>
I join the relevant parts of the source (without error handlers) :
#define BUF_SIZE 128
struct snd_card
{
snd_pcm_t *handle;
snd_pcm_hw_params_t *params;
short inputBuffer[BUF_SIZE*2];
void *buffer[2];
};
typedef struct snd_card snd_card_t;
int
main (....)
{
char card_id[32];
int err;
itn card = 0;
snd_card_t *card1;
card1 = calloc(1,sizeof(snd_card_t));
card1->buffer[0] = card1->inputBuffer;
card1->buffer[1] = &card1->inputBuffer[BUF_SIZE];
snprintf (card_id, 32, "plughw:%d", card);
snd_pcm_open (&card1->handle, card_id, SND_PCM_STREAM_CAPTURE, 0);
snd_pcm_hw_params_malloc (&card1->params);
snd_pcm_hw_params_any (card1->handle, card1->params);
snd_pcm_hw_params_set_channels (card1->handle, card1->params, 2);
snd_pcm_hw_params_set_access (card1->handle, card1->params,
SND_PCM_ACCESS_RW_NONINTERLEAVED);
snd_pcm_hw_params_set_format (card1->handle, card1->params,
SND_PCM_FORMAT_S16_LE);
snd_pcm_hw_params_set_rate_near (card1->handle, card1->params, ECHANT, 0);
snd_pcm_hw_params (card1->handle, card1->params);
snd_pcm_hw_params_free (card1->params);
snd_pcm_prepare (card1->handle);
while (...)
{
err = snd_pcm_readn (card1->handle, card1->buffer, BUF_SIZE);
printf("err=%d, buff=%d\n", err, card1->buffer[0]);
...
}
...
}
And here is the result of printf
err=-32, buff=-1
err=-32, buff=-1
err=-32, buff=-1
err=-32, buff=-1
err=-32, buff=-1
If you see the problem...
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