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No Digital Audio???
http://forum.linhes.org/viewtopic.php?f=2&t=19334		 Page 1 of 1
Author:  Girkers [ Tue Dec 09, 2008 8:32 am ]
Post subject:  No Digital Audio???
I have just installed a new motherboard and a fresh version of R5.5. The Mainboard is a Gigabyte GA-M61PME-S2 http://www.gigabyte.com.au/Products/Motherboard/Products_Overview.aspx?ClassValue=Motherboard&ProductID=2755&ProductName=GA-M61PME-S2 which uses the Realtek ALC662 codec. Here is some information on the Mainboard:

Code:
root@mythtv:/home/garth# aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: NVidia [HDA NVidia], device 0: ALC662 Analog [ALC662 Analog]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 0: NVidia [HDA NVidia], device 1: ALC662 Digital [ALC662 Digital]
  Subdevices: 1/1
  Subdevice #0: subdevice #0


Code:
root@mythtv:/home/garth# lspci -v (only audio part listed)

00:05.0 Audio device: nVidia Corporation MCP61 High Definition Audio (rev a2)
        Subsystem: Giga-byte Technology Unknown device a002
        Flags: bus master, 66MHz, fast devsel, latency 0, IRQ 18
        Memory at ee000000 (32-bit, non-prefetchable) [size=16K]
        Capabilities: [44] Power Management version 2
        Capabilities: [50] Message Signalled Interrupts: Mask+ 64bit+ Queue=0/0 Enable-
        Capabilities: [6c] HyperTransport: MSI Mapping


I have tried using twk_audio.pl --implement digital and whilst it looks it does the right thing with alsamixer and stuff, it still didn't work. I have tried doing a speaker-test with different combinations of -Dhw:0,1 and -Dhw:0,0 and I found that with either of these the audio still comes out the analog port not the spdif.

If I run mplayer from the command line, if I specify the -ao option it runs, but returns no sound. If I run it without the -ao option it crashes with:
Code:
Selected audio codec: [hwac3] afm: hwac3 (AC3 through S/PDIF)
==========================================================================
[AO OSS] Can't set audio device /dev/dsp to ac3 output, trying s16le...
AO: [oss] 48000Hz 2ch s16le (2 bytes per sample)
[format] Sample format big-endian AC3 not yet supported
[libaf] Reinitialization did not work, audio filter 'format' returned error code -2
Couldn't find matching filter/ao format!


Now reading this your find that it is trying to use /dev/dsp, so I specify /dev/adsp on the command line and again no sound.

The only thing that I can think to do now is update ALSA to the latest version as looking through some posts that have had similar problems an update to ALSA was one of the probable solutions amongst others.

Please help :oops:
Author:  Martian [ Tue Dec 09, 2008 9:40 am ]
Post subject: 
Have you tried:
Code:
twk_audio.pl --implement digital


Taken from Human's post in this thread: http://mysettopbox.tv/phpBB2/viewtopic. ... highlight=

Good Luck,

Martian
Author:  tophee [ Tue Dec 09, 2008 9:46 am ]
Post subject: 
You may have to turn on an alternative the optical output in ALSAMIXER (?)
On my current setup, it worked automagically but for some wierd reason I had to turn another muted setting for the optical out on for it to work with other stuff like the internet sound (like apple trailers or what not)

Alternatively - have you tried changing the outputs in the setup menu? Where you can select /dev/dsp etc? I seem to recall that if I selected 5.1 sound as opposed to stereo - nothing outputed. Is the light coming on from the optical?

HTH (May not tho)

Chris
Author:  Girkers [ Tue Dec 09, 2008 2:54 pm ]
Post subject: 
Unfortunately I can't "check the light" as I am using coax.

In alsamixer I have two digital, IEC958 and IEC958 Default PCM and I just found IEC958 was Off. I turned it on and I have sound, but it is very flaky, dropping in and out.

When I tried to watch crawford I get nothing and then when I went back to Watch TV I got no sound at all. I turn my AMP off then back on I get the flaky sound back. By flaky I mean it drops in and out, although it is in more than out.

I will check my RCA lead with my DVD player and confirm that it is alright. The SPDIF connector I made myself and as sound is coming out, just not all the time. :?

Martian, if you read my post I have attempted to run twk_audio.pl --implement digital without success and I had read that post you quoted. As I now have some sound I have put n the /etc/asound.conf as suggested. I rebooted and still the same result.

I have test the coax lead from another source and it works perfectly, so all I have left is the home made connector or a configuration issue. Any more suggestions.
Author:  Martian [ Tue Dec 09, 2008 3:17 pm ]
Post subject: 
Sorry :oops: that's what I get for skimming...

Don't know if this helps but I was able to buy an (overpriced) SPDIF to RCA composite converter / adapter that worked perfectly for converting from the 3.5mm stereo mini SPDIF output jack on my sound card to the composite / RCA style coaxial digital audio input on my receiver at Radio Shack.

Martian
Author:  Girkers [ Tue Dec 09, 2008 3:41 pm ]
Post subject: 
Yeah I went down a similar path previously with my Sound Blaster Audigy, I have moved on since then. This current computer has 3 analog 3.5mm phono jacks for standard audio, the Mainboard has 3 pin SPDIF header which I have constructed a connector.

Now though even just sitting at the Menu my amp is indicating the signal is dropping in and out. Is there a way to test my connector, all I can think of is a multimeter to ensure that I can get signal through OK from the head of the connector to the RCA plug, apart from that I am lost.
Author:  Liv2Cod [ Tue Dec 09, 2008 5:27 pm ]
Post subject: 
It could be a problem with signal levels, impedance, or ground loops. This is an interesting read:

http://www.andrewkilpatrick.org/blog/?page_id=215

He says the S/PDIF connector is 75 ohms and should be 0.5V levels. If the connector outputs TTL level signals, you need at least a voltage divider and a series cap to block DC levels. Might be easier just to get the back-panel bracket from Gigabyte.
Author:  manicmike [ Tue Dec 09, 2008 7:31 pm ]
Post subject:  Re: No Digital Audio???
Hi Girkers,

According to the mobo's specs, there is no digital output on that board. Also, the ALC662 is in my experience simply a 5.1 analogue output.

Am I missing something? If not, I can tell you step by step how to activate the 5.1 channel mode for the 3 audio jacks using Knoppmyth (I have successfully done this on that chipset).

Mike.
Author:  tophee [ Wed Dec 10, 2008 7:19 am ]
Post subject: 
Appologies I read the reference to SPDIF to mean optical. My bad.
Good luck.
Author:  Girkers [ Thu Dec 11, 2008 2:52 pm ]
Post subject: 
I have contacted Gigabyte to find out what the part is that I am after, they tell me it is 12CR1-1SPOUT-02R, the problem is googling this part number reveals nothing apart from references in Gigabyte's manuals. They state to contact there suppliers, so I have checked there website and found there "suppliers" are all wholesalers, I will try than anyway.

Liv2Cod, I read through that link and whilst interesting I could not quite get how it applies in my situation. My signal is "flapping" for lack of a better word, so do I need to buffer the signal to make it work? I also found this very similar article, http://www.hardwarebook.info/S/PDIF_output. So I am thinking to make my current setup to work I need to add something like a resistor or something like that, I just don't have a clue as to what.

My circuit is currently very simple:
GND--------------- Outside of RCA connector (and back plane)
SPDIFO----------- Inside RCA connector

Funnily enough in my search I found an article on MythTV that may solve my problems, could the electronic people amongst us check the theory for me please. This is the article I am referring too: http://www.mythtv.org/wiki/index.php/How_to_build_an_optical_SPDIF_bracket and here is the connector that I can source instead of the toshiba one in the article: http://www.jaycar.com.au/productView.asp?ID=ZL3003&CATID=&keywords=toslink&SPECIAL=&form=KEYWORD&ProdCodeOnly=&Keyword1=&Keyword2=&pageNumber=&priceMin=&priceMax=&SUBCATID= Would this resistor be the one mentioned in the article: http://www.jaycar.com.au/productView.asp?ID=RR0594&CATID=&keywords=resistor+ohm&SPECIAL=&form=KEYWORD&ProdCodeOnly=&Keyword1=&Keyword2=&pageNumber=&priceMin=&priceMax=&SUBCATID=

Thanks.
Author:  Martian [ Thu Dec 11, 2008 4:02 pm ]
Post subject: 
Hey Girkers,

As an Electrical Engineer I think I can actually help with this one!

So far as I can tell the idea in the article seems sound. It appears that almost all motherboard SPDIF outputs use 5V TTL logic which will work perfectly with the Toshiba TOTX173 device linked in the article.

Unfortunately the device at Jaycar you have linked is an optical RECEIVER not and optical TRANSMITTER and will NOT work! Also, the resistor you have linked is listed as being 1/2 Watt which will probably be fairly large and hard to work with. a 1/4 or even 1/8 Watt will be much small and easier to solder. I wish I could give you some recommendations on where to buy from but being on the other side of the world I really have none.

While this looks to be a fairly simple DIY project if you've never soldered before it could prove quite frustrating as the pins on the optical transmitter will be very close together. Expect to get a couple soldering iron burns if your not careful!

One last thought: Have you tried looking for a TOSLINK adapter on EBay? They make generic ones. The manual for your motherboard clearly labels the Power (+5V), Ground, and signal pins on the SPDIF output. You might need to "re-wire" the header a little bit (can be done with a toothpick) to make the pins line up. Any TOSLINK adapter with 5V TTL input should work.

Hope this helps.

Martian
Author:  Girkers [ Sat Dec 20, 2008 5:05 pm ]
Post subject: 
To let you all know this story does have a happy ending.

On eBay I found a SPDIF IN connector (yes I know it isn't out, but that is another story) and so I ordered it and connected it up. Obviously I can't use the optical side due to it being a receiver, but connect up the coax and all good.

I have NO asound.conf file and am using ALSA:spdif in MythTV. With xine I am using passthrough, the only problem left is that xine will not pass through normal 2 channel mp3 audio in my xvid files.
Author:  Martian [ Sat Dec 20, 2008 10:21 pm ]
Post subject: 
Girkers wrote:
I have NO asound.conf file and am using ALSA:spdif in MythTV. With xine I am using passthrough, the only problem left is that xine will not pass through normal 2 channel mp3 audio in my xvid files.


I pretty certain that your lack of 2-channel audio is due to your use of "ALSA:spdif" in the settings. Try switching to ALSA:default and see if that gets 2-channel audio working.

If that doesn't work you may have no choice but to mess with an asound.conf file.

Good Luck,

Martian
Author:  Girkers [ Sat Dec 20, 2008 10:45 pm ]
Post subject: 
2 channel audio inside MythTV works fine, it is outside of Myth that is the problem, in particular xine.

I made a movie encoded in xvid and mp3 audio and to get it to play (outside of mythtv) I had to pass mplayer the -ao command to get it to work.
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