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ALSA: snd-aloop - improve the sample copy accurracy 

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>
hifive-unleashed-5.1
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
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62
sound/drivers/aloop.c
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@ -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;