Hi,

Earlier this year I wrote to this list:

I am trying to write an alsa driver for my audiowerk8 soundcard. The aw8 uses a Philips saa7146 chipset. There are 2 capture and 8 playback channels mapped on the saa7146's DMA as follows:

DMA1: 2xcapture DMA2: 4xplayback DMA3: 4xplayback

Sample format is 16bit.

Frame format is as follows: (A number corresponds to a channel, a stereo channel-pair is embraced by [] and 1 digit corresponds to one sample byte)

capture channels [0,1] on DMA1: 00--11-- playback channels [2,3],[4,5] on DMA2: 22443355 playback channels [6,7],[8,9] on DMA3: 66887799

I tried to find a way to handle this in the card, but this special interleaving for the playback channels is by hardware restriction and can't be worked around in the soundcard itself. AFAIK alsa provides the samples interleaved like 22334455 (66778899). To avoid channel switching I guess some special processing in the alsa driver is required. Where is this done best? Do I have to move around the samples in the interrupt handler or does alsa provide some (possibly better) means to achive the correct (for the soundcard) interleaving?

Regards, Matthias