Ben Stanley wrote: > Dear List, > > Hello. I'm new here. This is my first attempt to hack an alsa driver. > > I recently purchased a "Sound Blaster Audigy Value!" card for use in a > MythTV box. As I have a digital receiver, I was mainly concerned with > getting a working S/PDIF output (coax or optical) and not too much more. > > Summary: I can make 44.1kHz digital output work, but I think that the > driver model of the card having 3 or 4 digital output channels is > incorrect. I believe the card only has 1 digital output channel. > The ca0106 chip has 3 or 4 digital outputs. These outputs may or may not be present on the output connectors of the card. I know that one of the SB cards does in fact work with 3 digital outputs using the 4 pin jacks because I have tested it myself. I GPIO is programmed to switch it between 3 digital outputs and 1 in, 1 out. > Details: > > The card I have is characterised by the following: > http://www.soundblaster.com/products/product.asp?category=1&subcategory=205&product=14189 > Model: SB0570 > serial: 100a1102 > Also known as: Sound Blaster Audigy SE > > During initial testing, I noticed that 44.1kHz playback was not > implemented. Subsequent testing shows that speaker-test works fine with > 48kHz, 96kHz and 192kHz. (I only tested 16bit output so far.) > > I noticed in the source code that 44.1k was explicitly disabled. I added > code in snd_ca0106_pcm_prepare_playback to set up this rate for S/PDIF > output as per the comments in ca0106.h . Initial tests using hw:0,0 at > 44.1kHz produced recognisable signals with some noisy corruption. Later > I accidentally discovered that serially opening hw:0,2 , hw:0,1 and > hw:0,0 at 44.1kHz then produces perfectly good 44.1kHz sampled digital > audio output. Removing hw:0,1 or hw:0,2 from this sequence causes noisy > corruption. It seems that channels 0-2 in reg40 must all be set to the > same sampling frequency for S/PDIF to work where 44.1kHz is concerned. > Conversely, to sucessfully output 48kHz again, I have to open hw:0,2 , > hw:0,1 and hw:0,0 at 48kHz to restore proper output. I do not have such > troubles with 96kHz and 192kHz, for which it suffices to just open > hw:0,0 at the relevant sampling rate. > The ca0106 can do 44.1kHz for digital output ONLY. The ca0106 cannot output 44.1kHz to the DACs so it will only work in Digital mode. It is a hardware restriction. You are correct, all the inputs and outputs have to be at the same rate. > Anyway, this is speculation. I'd love to have the docs. I haven't tried > to get them. Is it likely/unlikely that I would get them? > > You can sign an open-source NDA and get the datasheets. It lets me write drivers like the current ca0106 and E-Mu drivers. If you are interested in a NDA, priv-email me. Kind Regards James _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
