I'm sure the solution is right in front of me if only I could see it! I googled around for hours now and also searched the MythTV, ALSA and MPlayer archives as well as the excellent KnoppMyth forum and found of course a lot threads and discussions on this issue... unfortunately I still can't get it to work.

I'd "simply" like to connect my KnoppMyth box via digital out (spdif) to my receiver.

I installed R4V3 from scratch, then modified set_ivtv_params (I have a PVR350) for PAL land, configured my capture card (PVR350), sources and channels, etc. Everything - except spdif - works just fine!

I already upgraded to mplayer-1.0pre4 and alsa-1.0.5. I configured my /etc/asound.conf like discussed in http://mythtv.org/pipermail/mythtv-users/2004-April/039304.html. I checked my card and device number for spdif playback (cat /proc/asound/pcm) which tells me it is 0,2 and made sure it is in my /etc/asound.conf. I think I systematically tried all possible combinations within alsamixer (unmuted Master, PCM and set both to 74, unmuted SPDIF, muted line-in, ...).

My settings in MythTV are as follows:

In Setup -> General:
audio output device = /dev/dsp (also tried with ALSA:nforce, ALSA:spdif, ALSA:iec958).
AC3 passthrough is enabled
Mixer device = /dev/mixer
Mixer controls = PCM

In Setup -> DVD Settings -> Play Settings:
mplayer dvd:// -dvd-device %d -fs -zoom -monitoraspect 16:9 -vo xv -ao alsa9:nforce -ac hwac3, -alang de,en -srate 48000

With this my receiver detected a DTS signal (3/2) and the magic blue light went on... but: still no sound!

I also tried with:
-ao alsa9:hw:0,0
-ao alsa9:hw:0,1
-ao alsa9:hw:0,2
-ao alsa9:spdif
-ao alsa9:iec958

and the same again except that I changed it to "-ao alsa1x:..." because I found another hint in http://wopr.yi.org/mythtv.html.

Now I'm out of ideas where to look at further and what to try out next... anybody out there capable to help me out?!?

My specs:
KnoppMyth R4V3, mplayer-1.0pre4, alsa-1.0.5
Gigabyte K7 Triton GA-7N400 Pro with nforce2 chipset
AMD Athlon XP 2600 CPU
512 MB Ram
120 GB HDD (Seagate Barracuda 7200.7 8MB)
DVD Rom drive SD-M1712 (Toshiba)
Gainwards GF4 MX440 (AGP8)
WinTV PVR 350

Someone within the past month posted on how the got spdif working(if I remember correctly)...

_________________
cesman

When the source is open, the possibilities are endless!

Thanks Cesman! Did you mean http://mysettopbox.tv/phpBB2/viewtopic.php?t=1290? If yes, then I alreadey tried everything inside that thread and even followed the links inside it pointing to the alsa-project.

One thing I see now in http://mythtv.org/pipermail/mythtv-users/2004-April/040336.html: is MythTV compiled with this native ALSA support?!? How can I check it?

Master, PCM and IEC958 are unmuted, "IEC958 Playback AC97-SPSA" is set to zero. Something more to mute/unmute or to be set to zero or 100?!?

I have still the nice blue light on on my receiver, telling me (on its display) that it receives DTS signal... but no sound! Are there issues / problems with the intel8x0 driver combined with mplayer-1.0pre4 and/or alsa-1.0.5? Does my hardware cause problems / is it too exotic?

Thanks anyone for help!

I guess that is the link... Yes, the new 0.15 debs are compiled w/ native ALSA.

_________________
cesman

When the source is open, the possibilities are endless!

Do I understand this correctly, that the MythTV 0.14 in R4V3 wasn't compiled with native ALSA support? If yes, then I will of course move to R4V4 and then see if spdif works.

Another thing I'm not sure about: I understand, that MythTV doesn't need to be recompiled if MPlayer is upgraded to v1.0pre4 because it does not depend to it in any way. But what about ALSA? Do I have to recompile MythTV after having upgraded ALSA to v1.0.5 because of MythTVs compiled in native ALSA support?

Thanks anyone to clarify this to me!

no you should not need to do anything to mythtv because you upgraded alsa, even if you are using native alsa support.

Thanks for that! When running mplayer from command line with

I can see a message from mplayer saying "Sample format big endian AC3 not yet supported". After having consulted the mplayer docs I thought that maybe the "-format" option would help me out... but unfortunately it didn't. Tried with

Nothing changed something, except that with -format 128 I could hear for 1/10 of a second a "clicker" and then nothing more...

I'm out of ideas once more now... thinking about to go and buy a SB Live! sound card to see if this solves my issue... If anyone has other ideas, please let me know. Else I will post again as soon as I know more about the SB live soundcard. Until then: thank you all for any tips / hints...

I looked at that thread you linked too, and I know there is another one somewhere talking about this very thing, because on of the guys had a typo left out a comma or something. try searching these forums again.

well this post is not talking about nforce, but might help with the mplayer command lines.

Even with the newly released nforce 1.0-0274 drivers from NVidia I couldn't get it to work. Really don't know what's wrong... Tried out ALSA-1.0.5a with its intel8x0 driver, then tried nforce 1.0-0274 drivers (nvaudio module) and last but not least I had a Terratec Aureon Fun 5.1 laying around and was hoping to get sp/dif out to work with this sound card (cmipci module).
All my attempts lead to the same result: "Sample format big endian AC3 not yet supported" (output from mplayer). I even played around with different DVD's (all with DTS)... no change.

Is someone out there with nforce2 mobo having sp/dif out (optical) working? There are a lot of posts/threads saying "yes"... anyone willing to share his /etc/asound.conf (or ~/.asoundrc), /etc/asound.state, /etc/modules.conf, /etc/modules as well as the output of lsmod, cat /proc/asound/pcm.

Is there something special to configure in my BIOS? Is it the MPlayer-1.0pre4? Do you think Xine could be worth a try?

Chipset details are: nVIDIA nforce2 SPP / MCP-T

Thanks everyone!

well something certainly seem very odd because of "big endian" x86 is not big endian, unless something in ac3 also refers to big and little endian it seems like mplayer is for some reason thinking you are on different hardware, although I may be way off on all this, because I don't deal that much with audio.

For the records: I solved it by plugging in a SB live! 5.1 soundcard in my box and running ALSA with the emu10k1 driver. Because most development / testings (ALSA) around ac3 / dolby digital via spdif out were done using this card I thought with this one it should work... et voilà, it works! I have now everything working trough spdif out (coax) including ac3/dolby digital when watching a DVD!!! now I just have to make sure that alsamixer settings are restored properly after a reboot.

But it's really weird... some people seem to have a working AC3 / dolby digital passthrough (e.g. when watching a DVD) using the onboard sound (with ALSA intel8x0 or nvaudio oss driver 1.0-0274 from nvidia) of their nforce2 motherboards and some others (like me before) not.

Would really like to know, why some of us cannot get ac3 / dolby digital working via spdif out connected to spdif in of a AV receiver when using onboard sound or other soundcard than a sb live! 5.1. Is it the ALSA driver (intel8x0, cmipci, ...)? Soundcard? nForce2 chipset? ALC650F chip? AC97_codec? Bios? ... or (most probable from my point of view) a combination of all those components including the AV receiver doing dolby digital / ac3 decoding which only works properly when using a sb live! 5.1?

Before trying with a SB live! 5.1 soundcard I put in a Terratec aureon fun 5.1 using ALSA cmipci driver. With this I had the same results: spdif optical out was working for PCM 48khz but not for ac3 / dolby digital passthrough. Even trying with nvidias nvaudio oss driver 1.0-0274 didn't change something... same results, no ac3 / dolby digital.

However, if one day someone finds out what was wrong... I'd like to know!

Thanks to all for your help!

I'm apparently one of those lucky people who managed to get my onboard nForce2 optical out working with everything. I documented everything over on the wiki:

http://knoppmythwiki.homelinux.org/index.php?page=DigitalAudioHowTo

Live TV and recordings work, MythMusic works, DVDs work via xine, videos work. Haven't tried videos with AC3 soundtracks as all mine have MP3 soundtracks.

Since I barely know what I'm doing, the only thing I can recommend is to start from scratch... I've done it enough times that the pain wears off quickly now. Then again, if your Live card works, that's fine too.

Well, somehow my digital audio success has taken a step backwards somewhere. :-/

I'm still getting digital audio via SPDIF for Live TV, playing back PVR-250 recordings from within MythTV, and for Dolby Digital and DTS soundtracks via xine. Oh, and MP3 playback under MythMusic.

However, I'm not getting ANY audio when I play back videos in /myth/video/ with mplayer. This is with .mpg videos that have been transcoded using nuvexport. Soundtrack should be MP3 format. As mentioned in the thread above, I could have sworn this was working at some point.

In the mplayer command line in Setup->Videos->Playback, I've tried -ao (x):(y) where x is one of (alsa1; alsa9; alsa1x; alsa), and where y is one of (digital; hw:0,2; hw:0,3; mixed-digital; iec958). I may not have tried every combination but it sure seemed like I did.

xine is also refusing to give me any sound when playing an authored DVD with any of my PVR-250 recordings (presumably MP2 audio).

Could this be a mixer setting? If so, which one? I thought I had all the IEC 958 applicable stuff turned on.

I can live without this capability but I'd sure like to figure this one out. Any suggestions on how to troubleshoot this would be appreciated. Thanks.

did you make sure you have the trailing comma? If you are not sure what I'm talking about search for it, or I know it's on the digital audio page on the wiki.

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