[alsa-devel] E-MU 0404 USB - 4ch capture at > 48kHz -> corrupted data

[Pavel Hofman]

Hi,

The E-MU 0404 USB has 2ch and 4ch altsettings (first two channels are for
analog in/out, the other two channels for digital in/out).

* Stereo playback/capture works OK at all samplerates (44.1 - 192kHz).
* 4-ch playback works OK at all samplerates (at least the lower two analog
channels are OK, spdif output not tested - for reasons to follow)
* 4-ch capture works OK for fs <= 48kHz
But 4ch capture at fs > 48kHz produces incorrect samples in channels. I
have attached a picture - recorded 1kHz sine should be in channel 1 and 2.
Instead some mangled data are in channel 2 and 3.

The soundcard uses the CA0188 FPGA. I know the PCI version (and older
models) required some channel mangling in the FPGA firmware (programmed by
the driver) to support > 48kHz. This was never implemented in the alsa
driver for the PCI version (only base fs 44.1/48kHz are supported), but I
recall reading some discussions about it long time ago.

I understand the USB version has the CA0188 firmware hardcoded and the alsa
USB driver does not have to handle it. However, I think the CA0188 firmware
does not decode the 4ch samples for fs > 48kHz capture correctly to the
four USB audio channels and the vendor-supplied USB driver (windows, mac)
does it - the samples are OK on windows.

Please does anyone have any deeper knowledge of the E-MU technology so that
we could untangle the mangled samples?

Thanks a lot for any hints.

Best regards,

Pavel.
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