EAX question again

Discussion in '3-D Audio' started by Dogbreath, Mar 26, 2004.

  1. Dogbreath

    Dogbreath New Member

    Joined:
    Mar 22, 2004
    Messages:
    5
    Likes Received:
    0
    Trophy Points:
    0
    Ok,

    Quick questioonnay...

    With the proposed EAX support will it work through the AC3 output and resolve surround issues that inspire digital 5500 mugs are getting?

    Cheers once again

    I promise, no more EAX questions :x
     
  2. HunterZ

    HunterZ New Member

    Joined:
    May 14, 2003
    Messages:
    257
    Likes Received:
    0
    Trophy Points:
    0
    Umm, there is no AC3 output on any 10kX cards that I'm aware of. Also, the encoding on the SPDIF outputs is probably done outside of the DSP, so I'd be surprised if it's even possible to write DSP code to output AC3-encoded data to the SPDIF outputs of 10kX cards.
     
  3. nervsjuk

    nervsjuk New Member

    Joined:
    Aug 18, 2003
    Messages:
    5
    Likes Received:
    0
    Trophy Points:
    0
    Uuuuummm... of course there is a AC3 output.. I´ve used it a lot of times when I watch movies. Works with both digital out and analog 5.1... Or does he mean that the kX drivers should convert the EAX sound to Dolby Digital (AC3) and output it digitally as Dolby Digital ??
     
  4. nervsjuk

    nervsjuk New Member

    Joined:
    Aug 18, 2003
    Messages:
    5
    Likes Received:
    0
    Trophy Points:
    0
    I´ve got a Audigy Platinum..
     
  5. dj_stick

    dj_stick Apple Fanboy?

    Joined:
    Jun 3, 2003
    Messages:
    17,575
    Likes Received:
    204
    Trophy Points:
    88
    EAX has nothing to do with 3D audio… all it is is a series or reverb (or more accurately, delay) settings, it is the D3D part that turns EAX to 3D audio
     
  6. isdochegal

    isdochegal New Member

    Joined:
    May 21, 2004
    Messages:
    12
    Likes Received:
    0
    Trophy Points:
    0
    Yes. EAX doesn't have anything to do with audio, at all.
    It's merely like giving programmers an additional compiler-feature,
    lowering development-costs a bit. Nothing to take serious, from what I've seen.

    Gruss

    Jan Bruns
     
  7. dj_stick

    dj_stick Apple Fanboy?

    Joined:
    Jun 3, 2003
    Messages:
    17,575
    Likes Received:
    204
    Trophy Points:
    88
    re-reading this thread i have two things to say
    1. no soundblaster card can create an ac-3 stream, but it can allow passthrough from another device, or direct output from the hdd (*.ac3 files).
    2. EAX is a series of reverbs and preset triggers that allow game developers to add an aspect of environmental sound (hence the Environmental Audio eXtensions name) by simulating rooms and area types on a real time basis with out a built in reverb engine in the game
     
  8. isdochegal

    isdochegal New Member

    Joined:
    May 21, 2004
    Messages:
    12
    Likes Received:
    0
    Trophy Points:
    0
    So there's no (SPDIF) AC3-out from the DSP, but a SPDIF route around DSP, on some cards (those providing "HQ-wavedevice")?
     
  9. dj_stick

    dj_stick Apple Fanboy?

    Joined:
    Jun 3, 2003
    Messages:
    17,575
    Likes Received:
    204
    Trophy Points:
    88
    no the wavehq device is the 24/96 output on the audigy 2 cards, it has nothing to do with AC-3… the hardware simply cannot encode AC-3… but using AC-3 passthrough bypasses the card's DSP
     
  10. isdochegal

    isdochegal New Member

    Joined:
    May 21, 2004
    Messages:
    12
    Likes Received:
    0
    Trophy Points:
    0
    >>> 1. no soundblaster card can create an ac-3 stream, but it can allow
    >>> passthrough from another device, or direct output from the
    >>> hdd (*.ac3 files).

    >> So there's no (SPDIF) AC3-out from the DSP, but a SPDIF route
    >> around DSP, on some cards (those providing "HQ-wavedevice")?

    > no the wavehq device is the 24/96 output on the audigy 2 cards,
    > it has nothing to do with AC-3… the hardware simply cannot
    > encode AC-3… but using AC-3 passthrough bypasses the card's DSP

    Just to make this clear (I don't have a HQ-device, nor any AC3 amp):

    Not having focussed much AC3 (that is, 6 ch Audio over SPDIF) ,
    I expect it to rely on bitwise correctness of the SPDIF-signal.

    So one should enable "AC3-output on SPDIF-x" to get a bitwise correct
    SPDIF from Wave0/1?
    If so:
    Does the player-application need to assign it's stream as AC3 (how?)
    for this, and so could one use this trick to get bitwise correct
    SPDIF 16/48 out of the card?
     
  11. dj_stick

    dj_stick Apple Fanboy?

    Joined:
    Jun 3, 2003
    Messages:
    17,575
    Likes Received:
    204
    Trophy Points:
    88
    so you want an un-modified S/PDIF stream from an input of the card to the output of the card, if so there is the "S/PDIF Bypass" mode (i can't remember if is on 10k1 boards but definately on 10k2 boards)
    if that is what you want you are confusing me by using the "AC-3" term. If you have no AC-3 decoder and simply want a bit for bit accurate s/pdif stream use the method i described. It should work
     
  12. isdochegal

    isdochegal New Member

    Joined:
    May 21, 2004
    Messages:
    12
    Likes Received:
    0
    Trophy Points:
    0
    Ok, let's first clear up these terms.

    S/P-DIF (Sony/Philips Digital InterFace) more or less consits of 2 parts, one of which is the physcal transmission of digital signals over some media (may it be cable or optical). It's further a transmission-protocol, describing the fpormat, in which digital data has to be sent.
    Basically, 32bit per sample and channel are transmitted, where up to 24 bits may be used for audio data, 4 special purpose bits (1 parity for error detection, 2 bit subcode data, carrying format decription and manufactor specific data).
    S/P-DIF can easily be used to transmit more than 2 channels, but this capability was never really used, as it seems to me.

    AC3 in contrast is neither a physical transport layer, nor is it substantly a transmission protocol. AC3 in substance is a compression-sheme for audio data, just like mp3 is. It is designed to carry more than 2 channels of audio data. In the very common case of 5.1 channels, it's datarate normally fits into that 2*24 bits per stereo-sample sheme of the established S/P-DIF. So someone (Dolby?) designed a protocol, providing an AC3 layer over (de-facto limited) S/P-DIF layer, completly ignoring multichannel capabilities of S/P-DIF, I believe. That is, it seems to transmit the (compressed multichannel) AC3-data inside the 2*24=48 bits per doublesample layer of S/P-DIF.

    Now, If some device acting as a S/P-DIF forwarder (one that is between a S/P-DIF sender and another S/P-DIF receiver) takes the interprets the S/P-DIF stream as carrying Stereo-data and (based on this assumption somewhat legally) modifies the S/P-DIF cotained audio data (resampling, scaling volume,....) I'd expect this to lead in a nearby complete destruction of a possibly encapsulated AC3-stream.


    (feel free to include above in corrected form to your docu).


    Ok, having an Audigy (SB090), the mixer shows:

    So you seem to mean, "SPDIF Bypass" is to bypass DSP,... and let digital samples sent to wave0/1 directly be forwarded to (which? all?) SPDIF out? Wave0/1 is normally assigned to more than one application, so one needs exclusive access to wave0/1 for bitwise correct SPDIF out?
     
  13. dj_stick

    dj_stick Apple Fanboy?

    Joined:
    Jun 3, 2003
    Messages:
    17,575
    Likes Received:
    204
    Trophy Points:
    88
    SPDIF bypass is used to output SPDIF signals from an input to the SPDIF output(s) directly *i think*
     
  14. Eugene Gavrilov

    Eugene Gavrilov kX Project Lead Programmer and Coordinator

    Joined:
    Dec 7, 2002
    Messages:
    3,146
    Likes Received:
    9
    Trophy Points:
    48
    spdif bypass:
    the hardware bypasses SPDIF-In (coaxial in) --> SPDIF-Out (coaxial out) without any interaction
    (unrelated to any other software settings)

    spdif decode:
    the software captures SPDIF-In signal (in 'bit-accurate mode') and decodes it into 5.1 stream

    spdif passthru:
    user-level application sends AC-3 encoded signal in 16/48000/stereo format (marked as 'Not Audio') and the driver tries to pass it thru the DSP unaltered (to SPDIF-Out -- coaxial out) -- currently supported for audigy & audigy2 only -- although certain people experience issues with audigy2 passthru
    the player should be set in 'SPDIF' mode

    ac-3 decode:
    user-level application sends AC-3 encoded signal in 16/48000/stereo format (marked as 'Not Audio') and the driver decodes it (in software) and outputs 5.1 stream
    the player should be set in 'SPDIF' mode

    player-based decoding:
    a user application decodes the AC-3 streams itself and sends to the driver 5.1 streams (multichannel output). no driver-based processing is applied

    any '5.1' stream can be up/downmixed by the DSP algorithms
    in 'passthru' mode the DSP is passed thru :)

    that's it :)

    /E

    p.s.
    dj_stick: please add this to your guide
     
  15. dj_stick

    dj_stick Apple Fanboy?

    Joined:
    Jun 3, 2003
    Messages:
    17,575
    Likes Received:
    204
    Trophy Points:
    88
    alright i shall do
     

Share This Page

visited