On 03-04-08 20:54, akpm@xxxxxxxxxxxxxxxxxxxx wrote:
> The patch titled
> es1968: fix jitter on some maestro cards
> has been added to the -mm tree. Its filename is
> es1968-fix-jitter-on-some-maestro-cards.patch
[ ... ]
> Subject: es1968: fix jitter on some maestro cards
> From: Andreas Mueller <andreas@xxxxxxxxxxxxxxxxxx>
>
> 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).
>
> Cc: Rene Herman <rene.herman@xxxxxxxxxxxx>
> Cc: Jaroslav Kysela <perex@xxxxxxx>
> Cc: Takashi Iwai <tiwai@xxxxxxx>
> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> ---
Tested-By: Rene Herman <rene.herman@xxxxxxxxx>
on a TerraTec DMX (ESS Canyon3D, ES1970MS-3D) which doesn't need this but
doesn't seem to be suffering from it either. No idea about this otherwise.
> sound/pci/es1968.c | 22 +++++++++++++++++++++-
> 1 file changed, 21 insertions(+), 1 deletion(-)
>
> diff -puN sound/pci/es1968.c~es1968-fix-jitter-on-some-maestro-cards sound/pci/es1968.c
> --- a/sound/pci/es1968.c~es1968-fix-jitter-on-some-maestro-cards
> +++ a/sound/pci/es1968.c
> @@ -1815,6 +1815,23 @@ snd_es1968_pcm(struct es1968 *chip, int
>
> 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
> @@ -1936,8 +1953,11 @@ static irqreturn_t snd_es1968_interrupt(
> 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) {
Rene.
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