On Mon, Jun 08, 2009 at 05:58:54PM +0200, pHilipp Zabel wrote: > On Mon, Jun 8, 2009 at 2:40 PM, Mark > > OOI which MUA are you using? I've noticed several people with this very > > odd word wrapping the past day. > This mail was sent with the Google Mail web interface. Ah. Why am I not surprised. :/ > > I'm inclined to go with sample here since it seems harder for the > > machine drivers to get wrong but I've not really thought it through yet? > I thought sample width is determined by the snd_pcm_hw_params. But > maybe I'm mixing up alsa sample width vs sample width on the wire? Essentially what we're doing here is providing a mechanism to specify a separate wire format. > I'm leaning towards set_frame_width because that's directly what I > want to do: override pxa_ssp_hw_params' standard decision to use > 32-bit frames for S16_LE stereo and set 16-bit frames instead. Hrm. Now I remember what you're doing - you're trying to essentially send your stereo stream as mono data due to your hardware either having a flip flop or an entertainingly non-standard CODEC which needs a frame sync per sample rather than per frame. > > OTOH I don't really see much difference between the two cases - it's > > just an extra couple of parameters on the end of the call. > Technically there isn't. It just seems much more obvious to me to > write something like: > /* nonstandard: 16-bit frames, even for 2x 16-bit stereo */ > if (params_format(params) == ..._S16_LE) > set_frame_size(16); Thing is, I'd expect this would be just as likely to cause the CPU to discard every other sample since it doesn't have enough clocks to clock out a stereo sample in the frame. It occurs to me that this is something that it might be better to work around this with a user space plugin which rewrites the sample formats on the way down to the driver so that it claims the stream is configured as mono even if it's stereo :/ Not sure how practical that is or if there's a sensible way to do that in kernel space. > in the machine driver instead of: > /* nonstandard: 16-bit frames, even for 2x 16-bit stereo > * pxa_ssp_hw_params will check for TTSA==1 > * and then set the frame size accordingly > */ > set_tdm_slot(1,1); > especially as I don't really need network mode at all. Same issue with "it's a surprise it works" applies here. That TDM configuration ought to disable network mode if the driver doesn't need it. _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
