I did some more digging on the mixer setup of the C400 using usbmon+tcpdump+wireshark. I'm happy to provide binary captures if it helps.
I adjusted volume on each channel under and arrived at the following. Best to consult the C400 manual for screenshots of the interface.
The values listed correspond to the wValue in the URB block. The wIndex for all is 16385. Looks like two bytes for values.
Treat this as CSV in any editor and you'll see my table. Omitted numbers are sequential based on the other numbers in the row. Out 1-6 are the software returns, In 1-4 being the hardware inputs. The top row are the 6 outputs. For each output it would appears that the routed signal is always manipulated in (stereo) pairs - ex. Adjusting volume on software return 1 (Out 1) for Analog1/2 will adjust volume on 0x0100 AND 0x0101.
,A1-2 (1),A1-2 (2),A3-4 (3),A3-4 (4),SP (L),SP (R) Out 1,0x0100,0x0101,,,,0x0105 Out 2,0x0106,0x0107,,,,0x010b Out 3,0x010c,0x010d,,,, Out 4,0x0112,0x0113,,,,0x0117 Out 5,0x0118,0x0119,,,,0x011d Out 6,0x011e,0x011f,,,,0x0123 In 1,0x0124,0x0125,0x0126,0x0127,0x0128,0x0129 In 2,0x012a,0x12b,0x012c,0x012d,0x012e,0x012f In 3,0x0130,0x0131,,,,0x0135 In 4,0x0136,0x0137,,,,0x013b
Also captured some sample rate adjustment values
wValue = 0x0100 (always) wIndex = 33025
values in the data for the sample rates 0x00770100 => 96000 0x44ac0000 => 44100 0x80bb0000 => 48000 0x88580100 => 88200
On 4/21/2012 5:19 AM, Grant Diffey wrote:
>(channels = 2, ifnum = 2). Why do you use channels=2. As fas as I can tell the device has 6 channels. Try that. > Except I can't get it to play anything (figure it would all be too good > to be true) > > $ speaker-test -Dfront:C400 > speaker-test 1.0.25 > > Playback device is front:C400 > Stream parameters are 48000Hz, S16_LE, 1 channels > Using 16 octaves of pink noise > Sample format not available for playback: Invalid argument > Setting of hwparams failed: Invalid argument > The device probably supports only S24_3LE audio. At least that's what you tell Alsa with the FTU quirk. Try to play something through the corresponding hw device or use Jack or convert some audio file to S24_3LE and play through aplay etc...that's a good point
try speaker-test -D plughw:C400