[alsa-devel] USB asynchronous mode feedback format

[Julian Scheel]

Am Samstag, 16. Oktober 2010, 03:52:54 schrieb Alex Lee:
> On Fri, 2010-10-15 at 19:19 +0200, Julian Scheel wrote:
> > Correcting myself. It detects the card, but playback is not possible
> > anymore:
> > 
> > LC_ALL=en speaker-test -Dusb -c 2 -t sine -f 1000
> > 
> > speaker-test 1.0.23
> > 
> > Playback device is usb
> > Stream parameters are 48000Hz, S16_LE, 2 channels
> > Sine wave rate is 1000.0000Hz
> > Rate set to 48000Hz (requested 48000Hz)
> > Buffer size range from 96 to 262144
> > Period size range from 48 to 131072
> > Using max buffer size 262144
> > Periods = 4
> > Unable to set hw params for playback: Broken pipe
> > Setting of hwparams failed: Broken pipe
> 
> > Is this a hint to not-working feedback? (c:
> You may need to respond to the specific requests for get and set of the
> sampling rate of the audio stream, once you have the Sample Rate
> Attribute set.  See my sdr-widget code to process these requests:

Thanks, I implemented them the way same you did. So for get_min/max/cur I 
always return 48kHz and set_cur simply does nothing.
Now playback in general works again. But still the rate feedback seems to have 
no impact on the data-rate. Also the frequency value shown in proc-interface 
is unchanged. When rate feedback works, it would probably be slightly 
different than 48.000kHz?!

Regards,
Julian