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ALSA: usb-audio: fix delay account during pause

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When a playback stream is paused, the stream isn't actually stopped,
thus we still need to take care of the in-flight data amount for the
delay calculation.  Otherwise the value of subs->last_delay is no
longer reliable and can give a bogus value after resuming from pause.
This will result in "delay: estimated XX, actual YY" error messages.

Also, during pause after all in flight data are processed
(i.e. last_delay = 0), we don't have to calculate the actual delay
from the current frame.  Give a short path in such a case.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Takashi Iwai 2012-11-23 16:00:37 +01:00
parent 3f94fad095
commit 48779a0b8f
1 changed files with 17 additions and 1 deletions
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18
sound/usb/pcm.c
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@ -46,6 +46,9 @@ snd_pcm_uframes_t snd_usb_pcm_delay(struct snd_usb_substream *subs,
int frame_diff;
int est_delay;
if (!subs->last_delay)
return 0; /* short path */
current_frame_number = usb_get_current_frame_number(subs->dev);
/*
* HCD implementations use different widths, use lower 8 bits.
@ -1195,6 +1198,9 @@ static void retire_playback_urb(struct snd_usb_substream *subs,
return;
spin_lock_irqsave(&subs->lock, flags);
if (!subs->last_delay)
goto out; /* short path */
est_delay = snd_usb_pcm_delay(subs, runtime->rate);
/* update delay with exact number of samples played */
if (processed > subs->last_delay)
@ -1212,6 +1218,15 @@ static void retire_playback_urb(struct snd_usb_substream *subs,
snd_printk(KERN_DEBUG "delay: estimated %d, actual %d\n",
est_delay, subs->last_delay);
if (!subs->running) {
/* update last_frame_number for delay counting here since
* prepare_playback_urb won't be called during pause
*/
subs->last_frame_number =
usb_get_current_frame_number(subs->dev) & 0xff;
}
out:
spin_unlock_irqrestore(&subs->lock, flags);
}
@ -1253,7 +1268,8 @@ static int snd_usb_substream_playback_trigger(struct snd_pcm_substream *substrea
return 0;
case SNDRV_PCM_TRIGGER_PAUSE_PUSH:
subs->data_endpoint->prepare_data_urb = NULL;
subs->data_endpoint->retire_data_urb = NULL;
/* keep retire_data_urb for delay calculation */
subs->data_endpoint->retire_data_urb = retire_playback_urb;
subs->running = 0;
return 0;
}