At Fri, 30 Jan 2015 17:55:57 -0600, Pierre-Louis Bossart wrote:
The first URBs are submitted during the prepare stage. When .trigger is called, the ALSA core saves a trigger tstamp that doesn't correspond to the actual time when the samples are submitted. The trigger_tstamp is now updated when the first data are submitted to avoid any time offsets.
Signed-off-by: Pierre-Louis Bossart pierre-louis.bossart@linux.intel.com
sound/usb/pcm.c | 9 +++++++++ 1 file changed, 9 insertions(+)
diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c index 0d8aba5..7c36fc1 100644 --- a/sound/usb/pcm.c +++ b/sound/usb/pcm.c @@ -1464,6 +1464,14 @@ static void prepare_playback_urb(struct snd_usb_substream *subs, subs->last_frame_number = usb_get_current_frame_number(subs->dev); subs->last_frame_number &= 0xFF; /* keep 8 LSBs */
- if (runtime->trigger_tstamp_pending_update == 1) {
Ah I see that trigger_tstamp_pending_update is used here at first. But then I wonder whether this is specific to USB-audio, if there is no relevant code in PCM core side? If so, we don't need to add the field to snd_pcm_runtime but to snb_usb_usbstream instead.
(BTW, for boolean, avoid use of 0 and 1.)
thanks,
Takashi
/* this is the first actual URB submitted,* update trigger timestamp to reflect actual start time*/snd_pcm_gettime(runtime, &runtime->trigger_tstamp);runtime->trigger_tstamp_pending_update = 0;- }
- spin_unlock_irqrestore(&subs->lock, flags); urb->transfer_buffer_length = bytes; if (period_elapsed)
@@ -1550,6 +1558,7 @@ static int snd_usb_substream_playback_trigger(struct snd_pcm_substream *substrea
switch (cmd) { case SNDRV_PCM_TRIGGER_START:
substream->runtime->trigger_tstamp_pending_update = 1;-- 1.9.1
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