snd_pcm_avail_update() needs to be called in vm-sound-ALSA

>
> From: "Sayamindu Dasgupta (JIRA)" <[hidden email]>
> Date: 16. Dezember 2009 22:37:40 MEZ
> To: [hidden email]
> Subject: [JIRA] Created: (SQ-638) snd_pcm_avail_update() needs to be called in vm-sound-ALSA
>
> snd_pcm_avail_update() needs to be called in vm-sound-ALSA
> ----------------------------------------------------------
>
>                 Key: SQ-638
>                 URL: http://tracker.squeakland.org/browse/SQ-638
>             Project: squeakland
>          Issue Type: Bug
>          Components: etoys-sugar
>            Reporter: Sayamindu Dasgupta
>         Attachments: dlo_9375.patch
>
> In XO 1.5, the the sounds produced in Etoys and Scratch are jumpy (http://dev.laptop.org/ticket/9375). It turns out that the issue is solved by calling snd_pcm_avail_update() after calling snd_pcm_delay() in squeak/platforms/unix/vm-sound-ALSA/sqUnixSoundALSA.c
>
> This seems to be consistent with the ALSA documentation (http://www.alsa-project.org/alsa-doc/alsa-lib/group___p_c_m.html#g41ca534658076885d9b077ad674750cd) which says about snd_pcm_avail_update():
>
> "Also this function might be called after snd_pcm_delay() or snd_pcm_hwsync() functions to move private ring buffer pointers in alsa-lib (the internal plugin chain)."