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[ALSA] cmipci: fix distortion on rear channels

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When playing multichannel data, the rear channels can get distorted if
the last sample of the last played stereo stream was not zero.  To avoid
this, add a hack to play a few silence samples after the stream is
stopped.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>
This commit is contained in:
Clemens Ladisch 2007-09-17 09:41:36 +02:00 committed by Jaroslav Kysela
parent ebe9e289d8
commit c36fd8c3cd
1 changed files with 67 additions and 1 deletions
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68
sound/pci/cmipci.c
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@ -434,6 +434,7 @@ struct cmipci_pcm {
u8 running; /* dac/adc running? */
u8 fmt; /* format bits */
u8 is_dac;
u8 needs_silencing;
unsigned int dma_size; /* in frames */
unsigned int shift;
unsigned int ch; /* channel (0/1) */
@ -903,6 +904,7 @@ static int snd_cmipci_pcm_trigger(struct cmipci *cm, struct cmipci_pcm *rec,
cm->ctrl &= ~chen;
snd_cmipci_write(cm, CM_REG_FUNCTRL0, cm->ctrl | reset);
snd_cmipci_write(cm, CM_REG_FUNCTRL0, cm->ctrl & ~reset);
rec->needs_silencing = rec->is_dac;
break;
case SNDRV_PCM_TRIGGER_PAUSE_PUSH:
case SNDRV_PCM_TRIGGER_SUSPEND:
@ -1304,11 +1306,75 @@ static int snd_cmipci_playback_spdif_prepare(struct snd_pcm_substream *substream
return snd_cmipci_pcm_prepare(cm, &cm->channel[CM_CH_PLAY], substream);
}
/*
* Apparently, the samples last played on channel A stay in some buffer, even
* after the channel is reset, and get added to the data for the rear DACs when
* playing a multichannel stream on channel B. This is likely to generate
* wraparounds and thus distortions.
* To avoid this, we play at least one zero sample after the actual stream has
* stopped.
*/
static void snd_cmipci_silence_hack(struct cmipci *cm, struct cmipci_pcm *rec)
{
struct snd_pcm_runtime *runtime = rec->substream->runtime;
unsigned int reg, val;
if (rec->needs_silencing && runtime && runtime->dma_area) {
/* set up a small silence buffer */
memset(runtime->dma_area, 0, PAGE_SIZE);
reg = rec->ch ? CM_REG_CH1_FRAME2 : CM_REG_CH0_FRAME2;
val = ((PAGE_SIZE / 4) - 1) | (((PAGE_SIZE / 4) / 2 - 1) << 16);
snd_cmipci_write(cm, reg, val);
/* configure for 16 bits, 2 channels, 8 kHz */
if (runtime->channels > 2)
set_dac_channels(cm, rec, 2);
spin_lock_irq(&cm->reg_lock);
val = snd_cmipci_read(cm, CM_REG_FUNCTRL1);
val &= ~(CM_ASFC_MASK << (rec->ch * 3));
val |= (4 << CM_ASFC_SHIFT) << (rec->ch * 3);
snd_cmipci_write(cm, CM_REG_FUNCTRL1, val);
val = snd_cmipci_read(cm, CM_REG_CHFORMAT);
val &= ~(CM_CH0FMT_MASK << (rec->ch * 2));
val |= (3 << CM_CH0FMT_SHIFT) << (rec->ch * 2);
if (cm->chip_version == 68) {
val &= ~(CM_CH0_SRATE_88K << (rec->ch * 2));
val &= ~(CM_CH0_SRATE_96K << (rec->ch * 2));
}
snd_cmipci_write(cm, CM_REG_CHFORMAT, val);
/* start stream (we don't need interrupts) */
cm->ctrl |= CM_CHEN0 << rec->ch;
snd_cmipci_write(cm, CM_REG_FUNCTRL0, cm->ctrl);
spin_unlock_irq(&cm->reg_lock);
msleep(1);
/* stop and reset stream */
spin_lock_irq(&cm->reg_lock);
cm->ctrl &= ~(CM_CHEN0 << rec->ch);
val = CM_RST_CH0 << rec->ch;
snd_cmipci_write(cm, CM_REG_FUNCTRL0, cm->ctrl | val);
snd_cmipci_write(cm, CM_REG_FUNCTRL0, cm->ctrl & ~val);
spin_unlock_irq(&cm->reg_lock);
rec->needs_silencing = 0;
}
}
static int snd_cmipci_playback_hw_free(struct snd_pcm_substream *substream)
{
struct cmipci *cm = snd_pcm_substream_chip(substream);
setup_spdif_playback(cm, substream, 0, 0);
restore_mixer_state(cm);
snd_cmipci_silence_hack(cm, &cm->channel[0]);
return snd_cmipci_hw_free(substream);
}
static int snd_cmipci_playback2_hw_free(struct snd_pcm_substream *substream)
{
struct cmipci *cm = snd_pcm_substream_chip(substream);
snd_cmipci_silence_hack(cm, &cm->channel[1]);
return snd_cmipci_hw_free(substream);
}
@ -1736,7 +1802,7 @@ static struct snd_pcm_ops snd_cmipci_playback2_ops = {
.close = snd_cmipci_playback2_close,
.ioctl = snd_pcm_lib_ioctl,
.hw_params = snd_cmipci_playback2_hw_params,
.hw_free = snd_cmipci_hw_free,
.hw_free = snd_cmipci_playback2_hw_free,
.prepare = snd_cmipci_capture_prepare, /* channel B */
.trigger = snd_cmipci_capture_trigger, /* channel B */
.pointer = snd_cmipci_capture_pointer, /* channel B */