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Commit f24bfa53 authored by Andreas Mueller's avatar Andreas Mueller Committed by Takashi Iwai
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[ALSA] es1968: fix jitter on some maestro cards 



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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
parent 62cef821

sound/pci/es1968.c

+21 −1
Original line number Diff line number Diff line
@@ -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) {