[alsa-devel] Channel swapping issue on TI OMAP3/TWL4030

Peter Ujfalusi peter.ujfalusi at nokia.com
Wed Feb 16 08:20:21 CET 2011

On 02/15/11 18:23, ext ylin at mail.com wrote:
>> I forgot to ask:
>> what mode you are using the McBSP?
>> Is it in element, or threshold mode?
>> You can check/change the McBSP mode in:
>> /sys/devices/platform/omap-mcbsp.2/dma_op_mode
> It is in threshold mode, with max threshold 1023.  I will try other 
> modes.

This sounds safe, give the fact that the McBSP2 FIFO is 1280 word long.
The McBSP FIFO configuration has been corrected in newer kernels.

One thing that I would try is to synchronize the McBSP2 FIFO
configuration with the period size you use:
48KHz/stereo/16bit 10ms = 480 samples,
so configure the McBSP2 FIFO to 960 (for both tx, and rx threshold).
Might not help, but it worth a try...

>>> For playing, the left and right are the same data, we could not 
> tell if
>>> the channel switch happens to playback as well.
>> I see. Is there a way for you to run your application to capture only,
>> and from a separate app (aplay?) play a sample, which has audio only 
> on
>> one channel?
> I can fill zero to one of the play channel in our app to test it.

Let's see, if the swap also happens in the playback path as well.


More information about the Alsa-devel mailing list