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spdif output keeps cutting out...

Discussion in 'Desktop & Laptop Computers Forum' started by _Sin, Jan 10, 2004.

  1. _Sin

    _Sin
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    I've just built myself a PC to play around with digital video on my plasma. However although the picture is fine, I'm having terrible trouble getting the audio to behave.

    It's a shuttle bare-bones system with onboard audio. I'm only expecting to use the optical out to send audio directly from the DVD player to my receiver - I don't care about ordinary PC sound much, so the lack of realtime encoding shouldn't be an issue for me (and it ought to be able to cope with stereo anyway).

    The problem is that when I play DVDs on it, the sound just keeps dropping out. My receiver seems to just lose the plot after a second or so of audio and stops decoding. Then there's a second or two gap and it picks it up again.

    Doesn't matter whether I'm listening to stereo, DD5.1 or DTS.

    Sound through headphones is fine, but sort of misses the point :)

    Never had any trouble with any other device, and I've had a fair few hooked up to the receiver before...

    Has anyone experienced anything like this? Any suggestions as to what might be wrong, or how to fix it?

    FYI:
    Shuttle SB75G2 system with onboard realtek AC97 audio.
    Sony STR-DB925 receiver (ok, it's a bit old - but perfectly serviceable!)
     
  2. Chipster

    Chipster
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  3. _Sin

    _Sin
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    Yeah, I've done a fair amount of searching around without much luck. I've seen a few people with similar problems, but either their solutions don't work for me, or there weren't any...

    I've tried installing linux instead and having a play around with that too - gives exactly the same problem.

    It *seems* to be a timing thing - I suspect the PC just isn't clocking the data accurately enough and my amp is getting upset. But I don't know of a solution so I suspect my HCPC is going to get turfed out of the living room soon.
     
  4. Chipster

    Chipster
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    Dont quote me, but I'm sure I read a thread somewhere where a guy had a similar problem. Swopped his Sony for a Yamaha reciever and all was well. Easier said than done, and you wouldent really expect a compatibility problem like this.

    Can you try your shuttle through a non Sony amp?...you could then at least rule out compatibility problems.

    PS. Heres a dedicated Shuttle forum if you havent found it allready: http://forums.sudhian.com/categories.cfm?catid=43&forumid=1
     
  5. _Sin

    _Sin
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    Well, I fear the amp may indeed be partially to blame - but only because it's meticulously sticking to the spec. Sadly I don't have access to anything else right now to test with and I'm not really planning an upgrade any time soon (having just bought a plasma, various bits of PC hardware, a new hifi rack, a dvd recorder, a cd/hdd player... )

    If only early(ish) digital amps experience problems, it might explain why most people haven't run into this though. I guess I might have to move "new amp" up the list of priorities.

    However I have had some partial success in sorting the problem out. I followed a thread over on the avsforum site, and one problem mentioned was that IRQ sharing caused audio to become slightly unstable. It's a real pain to fix, but changing the windows kernel to a non ACPI enabled one, I've gotten it into a state where it seems much much happier. I still get the occasional drop-out on stereo stuff (i.e. PC generated sound), but the DTS / DD passthrough appears to be stutter-free, at least in my initial test. I've yet to try watching whole DVDs through it, but I'll see how it goes.

    I must say I'm fairly disappointed that a PC of reasonable spec can't do a simply thing like output digital data at a relatively low bit-rate in a stable way...
     
  6. saggio

    saggio
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    _sin
    would you mind posting a few tips (or a tread) on how to do it?
    Although with totally complete hardware I have the same problem: the audio signal keeps getting in and out of Dolby Digital (or DTS) and my amp stutters.

    I have the following:
    Gigabyte Mo.Bo with a P4 1.5Mhz
    768MB ram
    Hitachi DVD Rom
    Asus V9180 Video Suite graphic card (Nvidia GF4, 4xAGP)
    play DVDs with Nvidia NVDVD or Sonic Cineplayer
    Audio card: MAudio DIO2496, Optical SPDIF out
    Windows XP home
    Denon 1802 Amp

    It is possible that the MAudio clashes with the built-in Soundblaster PCI of the Motherboard: they both share IRQ 9, but there are no clashes reported by windows. And I have all the possible latest drivers.

    thanks
     
  7. _Sin

    _Sin
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    Well I'm not sure how useful this will be (I tried a whole bunch of different solutions until I stumbled across the combination that seemed to work for me), but the things I found most effective were:

    reclock - on it's own this only had partial success. It was still completely unusable, but it was stable for considerably longer than without.

    refresh rate - I don't know what buffoon wrote a sound driver that assumes things about video refresh, but it seems to make a difference if you tweak the video refresh rate. I've aimed to get mine as close to 59.94 as possible, which ought to improve video playback anyway. I'd hope this is just a random side-effect.

    disabling ACPI - this was the thing that finally swung it for me. supposedly the easiest solution is to disable plug'n'play in the BIOS (find the "plug and play OS" option) and install from clean. However I didn't want to reinstall and that option doesn't even exist in my bios from what I can see. So I went into the windows device manager and "updated" driver on the "Computer" entry to be a non ACPI type.

    here's more info on the ACPI thing

    Having done all that, it seems stable enough - but I still haven't given it a full test. Hopefully it'll prove ok, or I'll be able to fine-tune it now that it's mostly good.
     
  8. saggio

    saggio
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    Thanks for reply. two questions about above:

    A) do you refer to the refresh rate of the Monitor in the Display Adaptor Settings? if so, It cannot be fixed to 59.94, but to 60Hz (or 65, 70, etc)

    B) for the ACPI thing: did you do the above "update" and then re-install any hardware or driver?

    thanks
     
  9. _Sin

    _Sin
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    Yes, I mean the vertical refresh rate. The standard options don't give you much choice there - and I'm assuming the standard 60Hz option really is 60 and not 59.94 rounded up.

    However I use power-strip to customise my resolution in order to drive a panasonic plasma at it's native resolution on DVI. So I was able to tweak the settings.

    And yes, I had to reinstall drivers after removing ACPI - my PC started up in a pretty sorry looking state and required me to kick most of the drivers to get it happy again. Everything seems to be working just fine after this though.
     
  10. saggio

    saggio
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    have you had any other problem due to the absence of APCI? like installing new devices? (how does windows recognises them without ACPI?)
     
  11. _Sin

    _Sin
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    No, I've had no real problems with it in this state - but then I've only played with it for a few days.

    In theory at least it shouldn't make much difference, except for the way things get configured.

    I guess if you're worried about configuration problems with changing the ACPI settings, you could create a backup "hardware profile" in XP. Then you ought to be able to flip back to your current setup should anything go wrong (the only settings you need to do manually are the ones in the bios - and you can usually restore these to sane defaults automatically).
     

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