Minki/linux
1
0
Fork 1
mirror of https://github.com/torvalds/linux.git synced 2024-12-27 05:11:48 +00:00
Code Issues Packages Projects Releases Wiki Activity

ALSA: snd-aloop - improve the sample copy accurracy

Browse Source 
Maintain both streams (playback, capture) synchronized. Previous code
didn't take in account the small byte count drifts caused by the irq
position rounding.

Signed-off-by: Jaroslav Kysela <perex@perex.cz>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Jaroslav Kysela 2012-05-13 13:39:45 +02:00 committed by Takashi Iwai
parent 92b862c7d6
commit b012513c66
1 changed files with 35 additions and 27 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

62
sound/drivers/aloop.c
View File

@ -117,6 +117,7 @@ struct loopback_pcm {
/* timer stuff */
unsigned int irq_pos; /* fractional IRQ position */
unsigned int period_size_frac;
unsigned int last_drift;
unsigned long last_jiffies;
struct timer_list timer;
};
@ -264,6 +265,7 @@ static int loopback_trigger(struct snd_pcm_substream *substream, int cmd)
return err;
dpcm->last_jiffies = jiffies;
dpcm->pcm_rate_shift = 0;
dpcm->last_drift = 0;
spin_lock(&cable->lock);
cable->running |= stream;
cable->pause &= ~stream;
@ -444,34 +446,30 @@ static void copy_play_buf(struct loopback_pcm *play,
}
}
#define BYTEPOS_UPDATE_POSONLY 0
#define BYTEPOS_UPDATE_CLEAR 1
#define BYTEPOS_UPDATE_COPY 2
static void loopback_bytepos_update(struct loopback_pcm *dpcm,
unsigned int delta,
unsigned int cmd)
static inline unsigned int bytepos_delta(struct loopback_pcm *dpcm,
unsigned int jiffies_delta)
{
unsigned int count;
unsigned long last_pos;
unsigned int delta;
last_pos = byte_pos(dpcm, dpcm->irq_pos);
dpcm->irq_pos += delta * dpcm->pcm_bps;
count = byte_pos(dpcm, dpcm->irq_pos) - last_pos;
if (!count)
return;
if (cmd == BYTEPOS_UPDATE_CLEAR)
clear_capture_buf(dpcm, count);
else if (cmd == BYTEPOS_UPDATE_COPY)
copy_play_buf(dpcm->cable->streams[SNDRV_PCM_STREAM_PLAYBACK],
dpcm->cable->streams[SNDRV_PCM_STREAM_CAPTURE],
count);
dpcm->buf_pos += count;
dpcm->buf_pos %= dpcm->pcm_buffer_size;
dpcm->irq_pos += jiffies_delta * dpcm->pcm_bps;
delta = byte_pos(dpcm, dpcm->irq_pos) - last_pos;
if (delta >= dpcm->last_drift)
delta -= dpcm->last_drift;
dpcm->last_drift = 0;
if (dpcm->irq_pos >= dpcm->period_size_frac) {
dpcm->irq_pos %= dpcm->period_size_frac;
dpcm->period_update_pending = 1;
}
return delta;
}
static inline void bytepos_finish(struct loopback_pcm *dpcm,
unsigned int delta)
{
dpcm->buf_pos += delta;
dpcm->buf_pos %= dpcm->pcm_buffer_size;
}
static unsigned int loopback_pos_update(struct loopback_cable *cable)
@ -481,7 +479,7 @@ static unsigned int loopback_pos_update(struct loopback_cable *cable)
struct loopback_pcm *dpcm_capt =
cable->streams[SNDRV_PCM_STREAM_CAPTURE];
unsigned long delta_play = 0, delta_capt = 0;
unsigned int running;
unsigned int running, count1, count2;
unsigned long flags;
spin_lock_irqsave(&cable->lock, flags);
@ -500,12 +498,13 @@ static unsigned int loopback_pos_update(struct loopback_cable *cable)
goto unlock;
if (delta_play > delta_capt) {
loopback_bytepos_update(dpcm_play, delta_play - delta_capt,
BYTEPOS_UPDATE_POSONLY);
count1 = bytepos_delta(dpcm_play, delta_play - delta_capt);
bytepos_finish(dpcm_play, count1);
delta_play = delta_capt;
} else if (delta_play < delta_capt) {
loopback_bytepos_update(dpcm_capt, delta_capt - delta_play,
BYTEPOS_UPDATE_CLEAR);
count1 = bytepos_delta(dpcm_capt, delta_capt - delta_play);
clear_capture_buf(dpcm_capt, count1);
bytepos_finish(dpcm_capt, count1);
delta_capt = delta_play;
}
@ -513,8 +512,17 @@ static unsigned int loopback_pos_update(struct loopback_cable *cable)
goto unlock;
/* note delta_capt == delta_play at this moment */
loopback_bytepos_update(dpcm_capt, delta_capt, BYTEPOS_UPDATE_COPY);
loopback_bytepos_update(dpcm_play, delta_play, BYTEPOS_UPDATE_POSONLY);
count1 = bytepos_delta(dpcm_play, delta_play);
count2 = bytepos_delta(dpcm_capt, delta_capt);
if (count1 < count2) {
dpcm_capt->last_drift = count2 - count1;
count1 = count2;
} else if (count1 > count2) {
dpcm_play->last_drift = count1 - count2;
}
copy_play_buf(dpcm_play, dpcm_capt, count1);
bytepos_finish(dpcm_play, count1);
bytepos_finish(dpcm_capt, count1);
unlock:
spin_unlock_irqrestore(&cable->lock, flags);
return running;