Re: emu10k1 latency / capture period

[Takashi Iwai <tiwai@suse.de>]

At Mon, 21 Jun 2004 17:35:18 +0200,
I wrote:
> 
> At Sun, 20 Jun 2004 00:06:23 -0400,
> Lee Revell wrote:
> > 
> > On Wed, 2004-06-16 at 16:14, Lee Revell wrote:
> > > Hey,
> > > 
> > > I am having a problem with the emu10k1 driver where I am unable to set
> > > the capture period lower than 512.  The result is that the lowest
> > > achievable input to output latency is in the neighborhood of 40ms.
> > > 
> > 
> > I think I may have solved this problem.  Here is a patch against
> > alsa-driver-1.0.5a.
> > 
> > --- alsa-driver-1.0.5a/alsa-kernel/pci/emu10k1/emupcm.c.orig   
> > 2004-06-19 23:21:09.000000000 -0400
> > +++ alsa-driver-1.0.5a/alsa-kernel/pci/emu10k1/emupcm.c 2004-06-19
> > 23:21:12.000000000 -0400
> > @@ -932,7 +932,7 @@
> >         spin_unlock_irqrestore(&emu->reg_lock, flags);
> >         emu->capture_efx_interrupt = snd_emu10k1_pcm_efx_interrupt;
> >         emu->pcm_capture_efx_substream = substream;
> > -       snd_pcm_hw_constraint_list(runtime, 0,
> > SNDRV_PCM_HW_PARAM_PERIOD_SIZE, &hw_constraints_capture_period_sizes);
> > +       // snd_pcm_hw_constraint_list(runtime, 0,
> > SNDRV_PCM_HW_PARAM_PERIOD_SIZE, &hw_constraints_capture_period_sizes);
> >         return 0;
> >  }
> > 
> > I do not think that the FX8010 capture device is constrained by the 
> > period size limitations on the standard emu10k1 capture device.
> 
> Right, this constraint is invalid.

Well, after checking the code again, I'm not convinced any more...
Are you sure that it works without this constraint on half-duplex
capture?


Takashi


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