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[ALSA] es1968: fix jitter on some maestro cards

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This patch suppresses jitter on several Maestro cards in stereo mode (ALSA of
course).

The patch is also incorporated in the *BSD drivers where I "ported" it from.

Without this patch most of the stereo audio gets out of sync and really
distorted (oss-emulation with mplayer at 48000khz worked somehow).

Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Andreas Mueller 2008-04-14 13:08:05 +02:00 committed by Takashi Iwai
parent 62cef8212f
commit f24bfa53da
1 changed files with 21 additions and 1 deletions
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22
sound/pci/es1968.c
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@ -1827,6 +1827,23 @@ snd_es1968_pcm(struct es1968 *chip, int device)
return 0;
}
/*
* suppress jitter on some maestros when playing stereo
*/
static void snd_es1968_suppress_jitter(struct es1968 *chip, struct esschan *es)
{
unsigned int cp1;
unsigned int cp2;
unsigned int diff;
cp1 = __apu_get_register(chip, 0, 5);
cp2 = __apu_get_register(chip, 1, 5);
diff = (cp1 > cp2 ? cp1 - cp2 : cp2 - cp1);
if (diff > 1) {
__maestro_write(chip, IDR0_DATA_PORT, cp1);
}
}
/*
* update pointer
@ -1948,8 +1965,11 @@ static irqreturn_t snd_es1968_interrupt(int irq, void *dev_id)
struct esschan *es;
spin_lock(&chip->substream_lock);
list_for_each_entry(es, &chip->substream_list, list) {
if (es->running)
if (es->running) {
snd_es1968_update_pcm(chip, es);
if (es->fmt & ESS_FMT_STEREO)
snd_es1968_suppress_jitter(chip, es);
}
}
spin_unlock(&chip->substream_lock);
if (chip->in_measurement) {