[ALSA] cmipci - utilize ADC48K44K bit
Timofei Bondarenko [Wed, 7 Nov 2007 14:49:57 +0000 (15:49 +0100)]
Setting the ADC48K44K greatly improves capture quality at 48k sampling rate.
With this bit clear ADC does ZOH interpolation of every 22th sample at 48k.
At frequencies higher than 48k there ADC performs a little better with
ADC48K44K bit set.
At 44.1k ADC performs a little better with this bit clear.
At frequencies below 44.1k there is no difference.

Signed-off-by: Timofei Bondarenko <tim@ipi.ac.ru>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>

sound/pci/cmipci.c

index 3a2d942..d1f23eb 100644 (file)
@@ -869,6 +869,13 @@ static int snd_cmipci_pcm_prepare(struct cmipci *cm, struct cmipci_pcm *rec,
        snd_cmipci_write(cm, CM_REG_CHFORMAT, val);
        //snd_printd("cmipci: chformat = %08x\n", val);
 
+       if (!rec->is_dac && cm->chip_version) {
+               if (runtime->rate > 44100)
+                       snd_cmipci_set_bit(cm, CM_REG_EXT_MISC, CM_ADC48K44K);
+               else
+                       snd_cmipci_clear_bit(cm, CM_REG_EXT_MISC, CM_ADC48K44K);
+       }
+
        rec->running = 0;
        spin_unlock_irq(&cm->reg_lock);