2010/2/2 Jaroslav Kysela <perex@xxxxxxxx> > On Mon, 1 Feb 2010, pl bossart wrote: > > > All, > > I'd like to reopen a thread on concerns with the current > > implementation of rewind in ALSA. This was already discussed on the > > mailing list last year without any progress. > > I don't think that there have been no progress. The queued samples can be > stored to runtime->delay now, so snd_pcm_delay() returns a correct > value. > > The snd_pcm_rewind() and snd_pcm_forward() functions should operate in the > ring buffer and it's ok. See the USB driver for an example. Just add > support for runtime->delay to the lowlevel drivers and use snd_pcm_delay() > correctly in the user space and everything will work as expected. > > In other words - for hardware with large FIFOs, the runtime->delay should > be used for queued samples and the hw_ptr in the ring buffer should be > increased as soon as the FIFO is filled with samples from the ring buffer. > > Jaroslav > > Are there any demo program using snd_pcm_rewind()/snd_pcm_forward() to verify the driver meet your proposal ? For the interrupt driven model, the application fill the period while the driver playing the other period on two periods per buffer , the drivers don't need to provide accuracy up to a few sample derivation. However It seem to me that your proposal give an impression to the application developer that all ALSA drivers can provide accuracy up to sample accuracy _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
