At Tue, 01 Apr 2008 00:24:43 +0200,
Rene Herman wrote:
>
> On 30-03-08 00:49, Andreas Mueller wrote:
>
> > 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.
> > I am barely used to driver-development so please take a look (esp. the channel
> > parameters), nevertheless it completely works for me.
> >
> > Without this patch most of the stereo audio gets out of sync and really
> > distorted (oss-emulation with mplayer at 48000khz worked somehow).
> >
> > CCed to those listed in the .c file.
>
> Added the alsa-devel list (and re-attached the patch). My TerraTec DMX (ESS
> Canyon3D, ES1970MS-3D) doesn't need this but doesn't seem to suffer from it
> either. Otherwise no idea about this.
This should depend on the sample rate you use. 48k would work without
the patch.
Anyway, I applied it to ALSA tree now. Thanks.
Takashi
>
> Rene.
> [2 es1968_jitter.patch <text/plain (7bit)>]
> --- sound/pci/es1968.c.old 2008-03-29 19:17:16.771116317 +0100
> +++ sound/pci/es1968.c 2008-03-30 00:14:35.363057160 +0100
> @@ -1816,7 +1816,24 @@
>
> 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
> */
> @@ -1937,8 +1954,11 @@
> 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) {
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