At Mon, 23 Feb 2009 17:28:04 +0100, I wrote: > > At Mon, 23 Feb 2009 17:24:32 +0100, > Lennart Poettering wrote: > > > > On Mon, 23.02.09 08:45, Takashi Iwai (tiwai@xxxxxxx) wrote: > > > > > > > > At Sun, 22 Feb 2009 00:45:04 +0100, > > > Lennart Poettering wrote: > > > > > > > > On Tue, 07.10.08 17:32, Takashi Iwai (tiwai@xxxxxxx) wrote: > > > > > > > > > Hi, > > > > > > > > Sorry for the overly long delay. > > > > > > > > > > the patch below (to the latest sound git tree) adds the extra delay > > > > > count for USB-audio driver. This change will appear as the return > > > > > value of snd_pcm_delay(). > > > > > > > > > > Could you check whether it's appropriate behavior you've wanted? > > > > > > > > I have now tested this patch on the current 2.6.29-rc5 kernel. The > > > > effect is that snd_pcm_delay() returns always increasing values, as if > > > > the playback never proceeds. Most movie players which need that call > > > > to synchronize video frames hence stall completely. > > > > > > OK, that's bad. However, the increased value of snd_pcm_delay() is > > > exactly the effect. The usb-audio always prefetch the buffer in > > > advance. > > > > > > That means, changing (or "fixing") snd_pcm_delay() would cause many > > > regressions with many apps -- thus basically we are not allowed to > > > change the semantics any more at this too late point. > > > > > > I feel it's better to introduce another kernel-side API to give a > > > better sync/timing information, and mark snd_pcm_delay as obsolete for > > > future (although we can never deprecate such a basic API). > > > > No, snd_pcm_delay() with this patch is clearly broken: it apparently > > increases at the same speed as the hw ptr, ignoring the app > > ptr. i.e. after 5 min of playback the delay will be reported a 5 mins! > > After 10 min of playback the delay will be reported as 10 mins! > > Ah, then it must be a buggy patch indeed. It didn't appear in my > some test cases at that time, so didn't check after that. > > Maybe some delay account in complete callback wasn't correct. Maybe a stupid typo below (or removed lines accidentally at merge/rebase)... Takashi --- diff --git a/sound/usb/usbaudio.c b/sound/usb/usbaudio.c index 03384db..7b362d1 100644 --- a/sound/usb/usbaudio.c +++ b/sound/usb/usbaudio.c @@ -651,6 +651,8 @@ static int retire_playback_urb(struct snd_usb_substream *subs, spin_lock_irqsave(&subs->lock, flags); if (processed > runtime->delay) + runtime->delay = 0; + else runtime->delay -= processed; spin_unlock_irqrestore(&subs->lock, flags); return 0; _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
