Intel HD Audio - Realtek ALC88x

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These particular audio chips took a lot of time to set up correctly. There is an issue with these chips that has to bypassed for it to work correctly. As of 3-19-07, ALSA still has the issues described below until you bypass them with the workaround. So far this has been confirmed on the ALC882 and the ALC883 chip. Could also be on other version of the Reltek ALC88x chipset.

  • This is for a Fedora Core 6 Installation

Modprobe.conf

These should be automatic, but if not, this is what my modprobe.conf has in it

alias snd-card-0 snd-hda-intel
options snd-card-0 index=0
options snd-hda-intel index=0
remove snd-hda-intel { /usr/sbin/alsactl store 0 >/dev/null 2>&1 || : ; }; /sbin/modprobe -r --ignore-remove snd-hda-intel

Issues with sound

After having loaded the driver snd-hda-intel, the IEC958 output is muted as it should. In this state the following result are obtained:

a1) Mplayer normal audio (mplayer dvd://): [^]
      nothing can be heard.
a2) Mplayer AC3 audio (mplayer dvd:// -ac hwac3):
      noisy clicks can be heard.
a3) aplay through analog output device (aplay some/stereo/file.wav):
      nothing can be heard.
a4) aplay through digital output device (aplay -Dspdif some/stereo/file.wav):
      correct audio but with a strange reverb/distortion in high frequencies.
   

If I unmute the IEC958 output using alsamixer just after having loaded the snd-hda-intel driver i get the following results:

 b1) Mplayer normal audio (mplayer dvd://): [^]
       good quality audio can be heard.
 b2) Mplayer AC3 audio (mplayer dvd:// -ac hwac3):
       noisy clicks can be heard.
 b3) aplay through analog output device (aplay some/stereo/file.wav):
       good quality audio.
 b4) aplay through digital output device (aplay -Dspdif some/stereo/file.wav):
       completely saturated but recognizable audio.

Workaround

Something must be played after the driver snd-hda-intel has been loaded and before unmuting the IEC958 output using alsamixer. The best way I've found to do this is to put these three lines in /etc/rc.local so they run at startup.

amixer set IEC958 mute
aplay -D spdif /usr/share/sounds/alsa/Front_Center.wav
amixer set IEC958 unmute


Doing so, the following results are obtained:

 c1) Mplayer normal audio (mplayer dvd://): [^]
       good quality audio can be heard.
 c2) Mplayer AC3 audio (mplayer dvd:// -ac hwac3):
       good quality audio can be heard.
 c3) aplay through analog output device (aplay some/stereo/file.wav):
       good quality sound.
 c4) aplay through digital output device (aplay -Dspdif some/stereo/file.wav):
       good quality sound

Myth Settings

In mythfrontend->Setup

(Worked for me)

Audio Output Device: ALSA:iec958
Passthrough device: ALSA:iec958:{AES0 0x02}
Enable AC3 to SPDIF Passthrough
Enable DTS to SPDIF Passthrough

(Did not work for me, but worked for others)

Audio Output Device: ALSA:iec958
Passthrough device: ALSA:iec958
Enable AC3 to SPDIF Passthrough
Enable DTS to SPDIF Passthrough


.asoundrc and asound.conf

no need for an .asoundrc and my asound.conf file only contains

defaults.pcm.card 0
defaults.pcm.device 0
defaults.ctl.card 0

Contributers

Thanks to mikpolniak at adelphia on the myth-users mailing list and mrd on the Alsa-bug tracking list

Remark

I just replaced everithing in /etc/asound.conf with this:

pcm.!default {
        type plug
        slave {
                rate 48000
                pcm "spdif"
                }
}