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SPDIF in Vista

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  • Sven Groot

    I'm hoping Larry Osterman or someone else closely involved with audio in Vista can chime in here... but SPDIF in Vista still confuses me to no end.

    If you don't know what SPDIF is, see here. In my case, I use to get an AC3 or DTS signal to an external decoder, providing better sound than letting the software or soundcard do the decoding and using an analog speaker connection.

    In XP, this is really simple. There is only one "entry" for each audio device (I have two, an onboard Realtek AC'97 and a Creative Sound Blaster X-Fi), and it takes care of everything: analog sound, PCM digital out, and SPDIF passthrough digital out. In an app such as PowerDVD, I simply select "SPDIF" as the output option and it uses my external decoder no problem.

    On Vista, I get two audio devices (or "end-points" I suppose). One is called "Speakers", the other is "Spdif-output" (for the X-Fi) or "Digital output" (for the Realtek). The Speakers one is the default audio device by default.

    When I open the properties of the "Spdif-output" device, I can select the supported formats and sample rates, and this works fine. If I choose to test Dolby Digital, I hear sound and my decoder says its receiving a Dolby Digital signal. Note that the "Digital output" device for the realtek has the configuration option grayed out, has barely any properties, and cannot be tested. I can't make the PC make any sound at all with that device.

    So far, regardless of whether I set "Speakers" or the specific "SPDIF" option as the default, no app can successfully use SPDIF. Applications like PowerDVD and Media Player Classic simply produce no sound at all when SPDIF is selected. In Windows Media Player I can't explicitly choose to use SPDIF, but if the "Spdif-output" device is the default WMP produces no sound with DVDs.

    Windows Media Center comes closest. It can be set up to use digital output in the setup screen (which changes the system default audio device to "Spdif-output") and it does indeed give sound, using the external decoder. So that sounds good, right? Unfortunately, after about a minute of playback, the sound either gets very choppy or goes away completely (with the decoder showing "No digital data").

    So what's the deal here? Am I supposed to set "Spdif-output" as the default if I want to use SPDIF? Why can't WMP use SPDIF? What're third-party apps such as PowerDVD supposed to do to use SPDIF since obviously the old way with a DirectSound stream doesn't work anymore?

    If only this would work, then I could watch DVDs in Vista and I wouldn't need XP at all anymore. Having to reboot everytime I want to watch a DVD is driving me nuts. Sad

  • Matthew van Eerde

    What driver versions are you using for the Realtek and the X-Fi?

    Are these 32-bit or 64-bit machines?

    This is the RC1 build, I assume?

  • Sven Groot

    Matthew van Eerde wrote:
    What driver versions are you using for the Realtek and the X-Fi?

    Are these 32-bit or 64-bit machines?

    This is the RC1 build, I assume?

    Sorry, I should have mentioned. Yes, it is RC1, and it's x64 (although the same thing happened on 5536 x86).

    I'm using the latest Vista beta drivers for both the Realtek and the X-Fi. I just discovered I actually wasn't using the latest drivers for the Realtek, so I installed those, and now Realtek's "Digital output" endput has the same type of options as the X-Fi's "Spdif-output" (although it supports considerably less sample rates).

    Using this now functional Realtek option, Media Center performs much better; there's still the occasional glitch but it doesn't lapse into silence or continuous glitches anymore. So it seems that part at least is to blame on the X-Fi driver.

    WMP, PowerDVD and Media Player Classic show no change. No sound whatsoever when using SPDIF out. It's also interesting to note that they all have regular playback stutters (about every 5 seconds or so) when configured to use SPDIF, which don't occur using normal analog sound.

  • Matthew van Eerde

    The "no sound" could be a protected media path failure; I assume the DVD you're trying to play is copyrighted.  If there's an unsigned driver that handles the audio, digital outputs will be disabled for protected media.

    Could you try playing some non-protected .wav file in WMP?

  • Sven Groot

    Matthew van Eerde wrote:
    Could you try playing some non-protected .wav file in WMP?

    Anything that doesn't require actual passthrough (but would use PCM output), such as MP3 or WMA works fine in WMP even with the SPDIF device selected. Only DVD has a problem. The Creative driver is not signed, but the Realtek driver is, but as I said the problem occurs on both.

    Plus, if it was that, why would Media Center be able to do it but not WMP?

    One thing that does have to do with copyright protection is that both WMP and Media Center refuse to let me use my main DVD drive (which is RPC-1, i.e. region-free) so I have to use my DVD writer (which is RPC-2). But in this case, both tell me that there is a problem with copyright protection preventing playback.

  • W3bbo

    Sven Groot wrote:
    One thing that does have to do with copyright protection is that both WMP and Media Center refuse to let me use my main DVD drive (which is RPC-1, i.e. region-free) so I have to use my DVD writer (which is RPC-2).


    ...!?

    Windows Vista won't let you use region-free DVD drives?

  • Sven Groot

    W3bbo wrote:
    Windows Vista won't let you use region-free DVD drives?

    WMP and Media Center won't, apparently. PowerDVD has no trouble with them, even on Vista.

    That's not the topic of this discussion either, please keep this thread about SPDIF.

  • Matthew van Eerde

    Can you hear system alerts when S/PDIF is the default?

  • Larry​Osterman

    Matthew van Eerde wrote:
    Can you hear system alerts when S/PDIF is the default?


    Hold on Matt - you're Maurits?  Why didn't you tell me?

  • Sven Groot

    Matthew van Eerde wrote:
    Can you hear system alerts when S/PDIF is the default?

    Yes.

    Although with the X-Fi, the global format for the "Spdif-output" is set to "16 bit, 44100kHz" by default which my decoder apparently doesn't support since the sound gets sped up. Setting the format to "16 bit, 48000kHz" fixes it.

    EDIT: Just to be clear, everything works normally with the SPDIF output, except actual AC3 or DTS passthrough, which only works in the audio control panel (by using the test option) and in Media Center, but not anywhere else.

  • Matthew van Eerde

    Are you using this driver for the Creative?
    http://tinyurl.com/kca2r

    There's this intriguing caveat...

    * AC-3/DTS decoding (only in Windows Vista 32-bit)

    AFAICT, the X-Fi isn't HD audio compliant, so it won't work with the generic "HD Audio" inbox driver.

  • Sven Groot

    Matthew van Eerde wrote:
    Are you using this driver for the Creative?
    http://tinyurl.com/kca2r

    There's this intriguing caveat...

    * AC-3/DTS decoding (only in Windows Vista 32-bit)

    I am using that driver, but that isn't relevant here. That remark means that the driver isn't capable of doing AC3/DTS decoding in Vista x64. However, I don't need the driver to do it; I need it to output the undecoded signal to my external decoder, which it is perfectly capable of doing (as I said, using the "test" option in control panel and playing DVDs with media center works correctly, just everything else doesn't).

  • Matthew van Eerde

    It would be interesting to see whether WMP worked if you installed a 32-bit version of Vista, though.  Maybe for some reason WMP is decoding the digital audio and then re-encoding it.

  • eloekset

    I have a Media Center PC with an onboard sound controller, called C-Media AC97 Audio Device. I see a Digital Output device in Control Panel -> Sound. But when I choose that output device in the volume mixer, it says that there is no device.

    Does anyone know what I need to do to get the digital output device work for this sound controller? I run Vista RC1, and don't even have Windows XP Media Center installed anymore, so now I'm stuck with the poor analog sound quality. [C]

  • JasonOlson

    eloekset, can you open another thread for this? I would also prefer for this thread to stay concentrated on SPDIF pass-through as well (since I use it when doing music composition and have contemplated upgrading to vista on my composition computer (but haven't because of support issues from the composition software company)).

  • Sven Groot

    Just an update: according to MS, both the "SPDIF doesn't work in WMP" and the "stutters in media center using SPDIF" issues are supposed to be fixed in future builds. We will see. Smiley

  • eddwo

    According to Raymond, any genuine original RPC1 DVD-Drives will have ceased to function by now, so the fact that Vista will not support them will have minimal impact in the real world!

  • Lee_Nover

    waiting for the fixed SPDIF passthrough Smiley in the meantime I've setup AC3 Filter to encode into Dolby Prologic II works great!

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