On Thu, 13 Feb 2003, Takashi Iwai wrote:
> At Mon, 10 Feb 2003 18:21:12 +0100,
> Arnaud de Bossoreille de Ribou wrote:
> >
> > Hi, I discovered a bug in the emu10k1 driver which I'll explain here:
> >
> > I was developing an application which uses the timestamps given in the
> > status of the device to send S/PDIF data to it. This app worked pretty
> > well except that sometimes I heard sound discontinuities and then a
> > constant time delay between the sound and the video.
> >
> > I finally found where was the problem, my results is based on the
> > emu10k1-debug.patch file attached. The "frame" argument is equal to 0
> > when the app gets the status of the device. With this patch applied I
> > saw some output on the console exactly at the same time the bug occured.
> > Adding a "else" after the "if" to prevent sw_ready from being updated
> > fixed the problem and the output looked like
> >
> > ----------------
> > plop 0 -1536 A B
> > plop 0 1536 B A
> > ----------------
> >
> > where B == A - 1536 (1536 is the period_size). These two lines were
> > repeated a few times during playback.
> >
> > So the bug looks like a signedness problem since sw_ready is unsigned
> > and there is a while(sw_ready > 0), which explain the constant delay,
> > next in the "snd_emu10k1_fx8010_playback_transfer" function.
>
> this is because of the incorrect check of boundary-wrap.
> the comparison below must be <= instead of <.
> (or, it can be simply "diff < 0".)
> if there only two periods, the original code cannot detect the
> boundary-wrap.
>
> if (diff) {
> ==> if (diff < -(snd_pcm_sframes_t) (runtime->boundary / 2))
> diff += runtime->boundary;
> pcm->sw_ready += diff;
> }
>
> sw_ready should be unsigned safely.
> please try the change above with the unsigned sw_ready.
Not really. Note that the application can move the appl_ptr backward
(using snd_pcm_rewind()). The problem is that pcm->appl_ptr is updated
wrongly, thus calling function with frames == 0 twice or more causes
different results. I'm working on a proper fix.
Jaroslav
-----
Jaroslav Kysela <[EMAIL PROTECTED]>
Linux Kernel Sound Maintainer
ALSA Project, SuSE Labs
-------------------------------------------------------
This SF.NET email is sponsored by: FREE SSL Guide from Thawte
are you planning your Web Server Security? Click here to get a FREE
Thawte SSL guide and find the answers to all your SSL security issues.
http://ads.sourceforge.net/cgi-bin/redirect.pl?thaw0026en
_______________________________________________
Alsa-devel mailing list
[EMAIL PROTECTED]
https://lists.sourceforge.net/lists/listinfo/alsa-devel
