[alsa-devel] What does snd_pcm_delay() actually return?

Lennart Poettering mznyfn at 0pointer.de
Fri Jun 13 20:29:53 CEST 2008

On Fri, 13.06.08 18:26, Takashi Iwai (tiwai at suse.de) wrote:

> Wait, wait.  Please don't mix up.  The above doesn't imply anything
> about the further implementation of usb-audio driver.  What I
> suggested is, instead of hiding two pointers (hw_ptr and curr_ptr) and
> creating a complex API, simply expose them.
> Now, regarding the usb-driver.  Honestly, I don't understand what you
> want to do with an extra URB.
> As now, usb-audio driver handles as curr_ptr == hw_ptr.  But, in
> reality, curr_ptr = hw_ptr - samples_in_urbs.  So, in the case
> of USB-audio, hw_ptr is ahead of curr_ptr.  (And the granularity is
> samples_in_urbs).

BTW: what's the relation between periods and URBs on usb-audio right
now? I mean, the URBs should be exposed as periods to userspace,
right? But they are not right now, are they? I mean, I can set all
kinds of strange period settings for my USB device and I am pretty
sure that this is not reflected in the URB size, or am I wrong?


Lennart Poettering                        Red Hat, Inc.
lennart [at] poettering [dot] net         ICQ# 11060553
http://0pointer.net/lennart/           GnuPG 0x1A015CC4

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