[pulseaudio-discuss] What is corking?

[Lennart Poettering]

On Fri, 25.12.09 03:57, David Henningsson (launchpad.web at epost.diwic.se) wrote:

> Hi,
> 
> I triage some sound bugs in Ubuntu and for one user I found the
> following lines in the "pulseaudio -vvvv" log:
> 
> D: sink-input.c: Requesting rewind due to corking
> D: module-suspend-on-idle.c: Sink alsa_output.default becomes idle,
> timeout in 5 seconds.
> D: sink-input.c: Requesting rewind due to uncorking
> D: module-suspend-on-idle.c: Sink alsa_output.default becomes busy.
> D: protocol-native.c: Requesting rewind due to rewrite.
> D: sink-input.c: Requesting rewind due to corking
> D: module-suspend-on-idle.c: Sink alsa_output.default becomes idle,
> timeout in 5 seconds.
> D: sink-input.c: Requesting rewind due to uncorking
> D: module-suspend-on-idle.c: Sink alsa_output.default becomes busy.
> D: protocol-native.c: Requesting rewind due to rewrite.
> D: protocol-native.c: Requesting rewind due to rewrite.
> 
> These lines keep repeating themselves over and over again (at least 20
> times), sometimes with multiple "Requesting rewind due to rewrite" lines.
> 
> So, can someone explain a little bit what this is all about? Is it
> something to worry about? I think it happens during regular playback.
> I'm not a native English speaking person, so I don't even know what
> "corking" means in this context (and "define:corking" on Google didn't
> help much...).

Corking means that the application asked for the audio stream to be
"corked" temporarily, so that data flow stops. "uncorking" then makes
things flow again.

It's mostly synonymous to application triggered pause/unpause.

If the app corks playback we need to drop most of the playback buffer
and rerender it again, that's why you see the rewind lines there,
which "rewinds" the read index in the playback fifo buffer. 

A "rewrite" means that the application itself rewrote what it already
wrote before. I.e. an explicit rewind of the write index triggered by
the application.

In both cases this is triggered by the app explicitly.

Lennart

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