>> I have some trouble with stereo audio through the atmal ssc interface >> based on at91-ssc.c. > (Merged into atmel_ssc_dai.c since about one year ago.) >> Unfortunately left and right channels were swapped periodically. >> >> In my environment the codec supplies the BLCK and LRC clocks and >> the SSC is configured to transmit one sample on both edges of the LRC clock. >> But I guess the audio frames will always start with a frame of the left channel >> while the LRC clock is in an undefined state. > Indeed. > >> How does normally the audio driver detect when a left and when a right channel >> frame should be send and with which it should start ? > The driver cannot do anything about this; the hardware must be told > to start transmitting at the falling edge. > > If possible. If there is only one channel to transfer, I set the start of transmission on the rising edge (left justified format). But if I do this for two channels, both channels will be transmit on the left channel, this is what I would expect. Is there way to tell the hardware (Atmel SSC on at91rm9200) that 2 Frames shall be send after a rising edge with an indication that the second frame shall be send after the falling edge ? This is the way it should work, but of course I don't know if it's even possible. > Is there a reason why the codec supplies LRC? > The SSC is connected to a FPGA that assigns the bus to different devices depending on the application. And for all applications the FPGA generates the clocks. Maybe this is not the best solution but I will try to deal with this limitation first before I try to persuade other people to change it. _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
