Re: Couple of questions

[Lee Revell <rlrevell@joe-job.com>]

On Fri, 2006-03-17 at 23:51 +0000, Adrian McMenamin wrote:
> On Fri, 2006-03-17 at 18:46 -0500, Lee Revell wrote:
> > On Fri, 2006-03-17 at 23:29 +0000, Adrian McMenamin wrote:
> > > 
> > > So, just to be clear. When I am transferring a "period" I should
> > > actually stream half a period's worth of bytes into the channel
> > > playing
> > > the left and half a period into the right - and can advance each dma
> > > transfer through the buffer by half a period length on both the left
> > > and
> > > the right side of the buffer 
> > 
> > No, one period.
> > 
> 
> 
> How does that work? That would imply that there were half as many
> periods in the DMA buffer as specified here...
> 
> static snd_pcm_hardware_t snd_pcm_aica_playback_hw = {
> 
> 	.info = (SNDRV_PCM_INFO_NONINTERLEAVED),
> 	.formats =
> 	    (SNDRV_PCM_FMTBIT_S8 | SNDRV_PCM_FMTBIT_S16_LE |
> 	     SNDRV_PCM_FMTBIT_IMA_ADPCM),
> 	.rates = SNDRV_PCM_RATE_8000_48000,
> 	.rate_min = 8000,
> 	.rate_max = 48000,
> 	.channels_min = 2,
> 	.channels_max = 2,
> 	.buffer_bytes_max = AICA_BUFFER_SIZE,
> 	.period_bytes_min = AICA_PERIOD_SIZE,
> 	.period_bytes_max = AICA_PERIOD_SIZE,
> 	.periods_min = AICA_PERIOD_NUMBER,
> 	.periods_max = AICA_PERIOD_NUMBER,
> };
> 
> 
> As the buffer and period (in bytes) size is constant. 
> 
> 

That's why the maximum buffer and period is in bytes not frames.  Stereo
has twice as many bytes per frame than mono.

Lee



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