I have been studying the data_ep_set_params() function in sound/usb/endpoint.c. This is the routine that calculates the number of samples and I/O requests to keep on the USB hardware queue for PCM audio, based on the ALSA parameters.
It uses the PERIOD_BYTES parameter but not BUFFER_BYTES. In simplified terms (ignoring rounding, boundary cases, and other things), the number of periods per buffer is fixed at 24 for recording and 1 for playback, completely ignoring the user's setting. If you look at the parameters copied in snd_usb_hw_params() in sound/usb/pcm.c, you'll see what I mean. Is this really the intended behavior? It doesn't seem right at all. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
