Commit 48779a0b authored by Takashi Iwai's avatar Takashi Iwai
Browse files

ALSA: usb-audio: fix delay account during pause 



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: default avatarTakashi Iwai <tiwai@suse.de>
parent 3f94fad0

sound/usb/pcm.c

+17 −1
Original line number Diff line number Diff line
@@ -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;

	}

CRA Git | Maintained and supported by SUSTech CRA and CCSE