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Realtek onboad optical out to receiver - choppy sound for DD/DTS

K

KingGheedora

Diamond Member
HTPC spec:
MSI 890FXA-GD65
Sempron 140 w/ 2nd core unlocked
8GB DDR3
Sapphire Radeon HD5830 1GB
2TB Seagate
WHS 2011
XBMC/VLC
Connected to DLP 720p tv via HDMI
Connected to HK AVR-635 receiver via SPDIF

When I try to play content that has DTS or DD 5.1 audio stream, the sound stutters extremely, and is really choppy. The problem exists in both VLC and XBMC.

I thought I fixed this yesterday by re-installing the latest Realtek drivers off the Realtek site, but since then I also re-installed some ATI video card drivers. I'm now wondering if i really did fix it or if I was imagining things. I tried everything I could to fix it again but nothing is working this time. Re-installed Realtek drivers, AMD drivers, and ATI drivers.

When I set the sound device to 5.1 in VLC, it works. If i set it to analog in XBMC, it also works. But when i set it to DTS or Dolby, it gets choppy. At some point I also tested the DTS and DD output in the Sound Devices "Supported Formats" dialog, and it worked there.


Is this an audio problem, or is this somehow related to my system trying to sync the audio and video by dropping/duplicating audio frames to keep in sync with the video stream? Any other thoughts on how to fix?
 
What is the source? Are you just passing though DD/DTS from a DVD or Blu-ray or are you trying to encode it in real time?
 
The source is multiple .mkv files with DD 5.1 or DTS audio streams. I'm just trying to play the video and have the DD or DTS streamed to my receiver, and for my receiver to decode and play the audio.

I tried ffdshow and LAV and had the same problem with both of those, using MPC. Getting really frustrated with this. I'm starting to wonder if the problem is with the OS (WHS2011) or my hardware. Though I think Realtek onboard audio is pretty ubiquitous and I'm sure I've read about people getting bitstreaming to work with it before.
 
I've heard of this issue before, it seems to only affect AMD video cards. What I think is happening is that your video card is outputting sound, and your mobo is outputting sound. Audio processing fight.

My HT setup is very similar to yours, except that I use a DVI->HDMI cable instead of a regular HDMI cable. Plus I use nVidia. And I'm going to assume you have no problem with audio over the TV speakers.

First thing to try is to go into the BIOS and check graphics initialization: if it's set to HDMI, change this to DVI. As Windows boots and Catalyst loads, audio won't be initialized over HDMI, and this might clear up the issue via optical. But video via HDMI should still initialize after booting into Windows.

Next thing to consider (related) is to switch to a DVI->HDMI cable. For nVidia, this still results in sound on the TV speakers, and probably does with AMD as well...but this might clear it up since you're not specifically using HDMI-out.

Other options would be to upgrade the amp to one that does HDMI switching, or switch to a non-AMD video card.
 
Slug: spdif is the default.

I haven't checked if sound works on my tv speakers, i usually keep the tv speakers off (configured via the TV's OSD).


I changed the refresh rate in windows from 60hz to 59hz and that seemed to make the sound stuttering a little better, but it could also just be placebo effect. Tried messing with the audio/video syncing settings in xbmc but that didn't help.

I'm not inclined to get a new receiver right now, so what I might do if I can't solve this any other way is use the analog outputs on the mobo (i think this mobo has them. my old mobo had them).
 
Another possibility:

My TV has a SPDIF out. I'm thinking of trying to connect from that to the receiver to see if the TV will forward the audio signal from its HDMI input to the receiver.

I'm not sure if this will work though, because windows seems to detect the audio capabilities of the HDMI device it's connected to, and since the TV only has two speakers I'm not sure if the TV will tell windows new info when the TV's SPDIF is being used. But then again that shouldn't matter because if the DD/DTS signal is being bitstreamed windows and the TV shouldn't care what the speaker config is.
 
KingGheedora said:
My TV has a SPDIF out. I'm thinking of trying to connect from that to the receiver to see if the TV will forward the audio signal from its HDMI input to the receiver.
Click to expand...
I'm pretty sure this won't work. It's usually not a passthru: the S/PDIF on most tvs is for the tuner, meaning that you connect your antenna and receive DD over the air, and the S/PDIF-out sends that signal to your amp. Besides, HDMI is protected.

Again, check the BIOS settings and see if there is a graphics option set to HDMI that can be changed to DVI.

The analog output would work, since you have discreet channel inputs on your amp, but what a hassle...
 
KingGheedora said:
The source is multiple .mkv files with DD 5.1 or DTS audio streams. I'm just trying to play the video and have the DD or DTS streamed to my receiver, and for my receiver to decode and play the audio.

I tried ffdshow and LAV and had the same problem with both of those, using MPC. Getting really frustrated with this. I'm starting to wonder if the problem is with the OS (WHS2011) or my hardware. Though I think Realtek onboard audio is pretty ubiquitous and I'm sure I've read about people getting bitstreaming to work with it before.
Click to expand...

Yeah, you should be able to bitstream no problem. I think that Slugbait is onto something though. As an alternative way of disabling the HDMI output, try going into the Device Manager and disabling the AMD High Definition Audio Device.
 
mfenn said:
Yeah, you should be able to bitstream no problem. I think that Slugbait is onto something though. As an alternative way of disabling the HDMI output, try going into the Device Manager and disabling the AMD High Definition Audio Device.
Click to expand...

I tried this before but I will give it another shot. I know for sure I currently have the HDMI device disabled in system tray -> audio -> playback devices.

Analog outputs are a hassle especially because the cables are so long and there are so many of them. I was a bit worried about the audio quality but I don't know if the difference would actually be audible. People like pass-through because supposedly the receiver does a better job of the decoding, right?

Another thing I might try is to pop in another hard drive and install windows 7 to see if maybe the WHS install has something wrong with it.
 
Yeah, the receiver is generally going to have higher quality DACs than a sound card. It's also outside of the EMI storm that is the inside of a PC case.
 
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