Takashi Iwai wrote:
Charles Eidsness wrote:
It looks like the parse_audio_format_i_type function at line 2369 of usbaudio.c (linux v2.6.23) doesn't support the case where bSubframeSize (fmt[5]) = 4 bytes and bBitResolution (fmt[6]) = 24 bits, which should correspond to a S24_LE (or BE) type. I'm developing a new USD DAC which supports this mode (24-bit sample in a 4 byte package). Right now Linux sends me S32_LE formated data, which is wrong. Would it be possible to expand this function to support S24_LE/BE? It would only require adding a few lines of code.
Yes, it's possible, of course.
BTW, is this behavior strictly defined? I fail to find in the usb-audio spec that bBitResolution specifies the lower bits, not the higher bits...
The spec assumes that 24-bit samples use S24_3LE. 24-bit samples in 32-bit words are an extension that must be handled with some device- specific code (like with the UA-1000).
(The audio 2.0 spec allows 32-bit words, and the wording seems to imply that samples are aligned to the most significant bit, i.e., that S32_LE would be used in this case.)
Regards, Clemens