Dolby TrueHD

Discussion in 'Home Entertainment Computers' started by vadim45, Feb 6, 2009.

  1. vadim45

    vadim45
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    Hi everyone,

    Hoping somebody can help me with my problem.
    I've just bought a new sound card (Creative SoundBlaster X-Fi Xtreme Audio PCI-Express - OEM - Ebuyer) and am trying to connect it up to my Onkyo 605 amp to get TrueHD from Blurays.
    A friend said that i couldn't do it over the optical out, cause it doesn't carry data fast enough?? is this true? If so, could i do it the old fashioned way with the phono leads?

    tried looking all over the net, but have come back more confused then from when i started!:rolleyes:

    cheers
    ed
     
  2. andy1249

    andy1249
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    Yes

    No you cant do it that way ,this article explains why,

    http://www.tweaktown.com/articles/1306/dts_hd_and_dolby_truehd_on_your_pc/

    The only way to get the equivalent of Tru Hd out of a soundcard at the moment is with the Asus Xonar card , there was also supposed to a card from Auzentech at the end of January but this is now delayed till march.

    http://www.auzentech.com/site/company/announce.php?switch=39#39
     
    Last edited: Feb 6, 2009
  3. jameson_uk

    jameson_uk
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    This is not right. These solutions are the only way to get a truHD bitstream to your amp. You can get HD audio decoded to LPCM and output over HDMI using many graphics cards and motherboards.

    The issues with decoding to LPCM does mean that it is limited to 16 bit 48Khz but as this is what most TruHD soundtracks are recorded at it should not make any difference. I am yet to experiment with this but even if there is a slight loss in quality over a bitstream you are still going to get a huge improvment over lossy DD or DTS
     
  4. vadim45

    vadim45
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    cheers andy,

    real shame.....but i suppose it gives me something to look forward to dipping into the wallet again for!:devil:

    Could it not be possible to run the audio straight through a HDMI equiped MB and let the amp do the decoding?

    EDIT: sorry just read your reply jameson
    As above really, with a MB allowing a pass through and the amp doing the hardwork?
     
  5. vadim45

    vadim45
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    At the moment, my amp is saying that its receiving PCM (which i thought was a lossless stream like TrueHD), which was why i was confused why i couldn't get TrueHD as well.
     
  6. andy1249

    andy1249
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    The question was can you get Dolby tru Hd , DTS HD over a pc card , in that respect the answer is correct , there may well be a slight improvement in the downmixed version you get off current HDMI enabled graphics cards and motherboards , but it is not Dolby tru HD or DTS HD.

    With the new formats , the real benefit is movies or music with tracks done at 48KHz/24 bit and higher , such as 96Khz/24bit and so on , these cannot be passed over the majority of current HDMI enabled PC cards.

    Technically the analog outs could do it , but due to content restrictions this is not possible either.

    Theres just the Xonar and the upcoming Auzentech.
     
    Last edited: Feb 6, 2009
  7. jameson_uk

    jameson_uk
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    In theory it is Tru-HD or DTS-MA. LPCM is uncompressed audio and the HD audio codecs are compressed lossless audio. If you uncompress the audio to LPCM it should be exactly the same audio signal as the Tru HD signal. yes the Tru-HD audio light will not come up on your amp but it is still the same audio as the Tru-HD audio.

    It is the same as a zip file. If the actual file is LPCM you can put this into a zip file and reduce the file size. If you wanted to then send someone the data you could either send an email with the original LPCM file or the zip file. Once the user has unzipped the file at the other end the net result will be no different whether you sent them then original LPCM or the zip file.

    The conversion of a HD bitstream to LPCM is a conversion of digital data so there should be difference in quality between doing this on your PC or your amp (the difference is when you convert these digital bits to an analog signal)

    As you point out there is one slight issue with this; Protected Audio Path (PAP). The standards say that without PAP a player should only output a maxium quality signal (this seems to universally be 16 bit 48Khz)

    I have yet to find a definitive answer to what powerDVD is doing with a 16bit 48Khz signal but I am lead to believe that it is just outputting as is. My research so far, it is possible to get a bitperfect output from a 16but 48Khz Tru-HD signal.

    I am going to do some more digging once my new amp arrives so I will update what I find but assuming you can get bitperfect output of 16 bit 48Khz Tru-HD audio track in Power DVD then the output in your amp will be identical to feeding it a Tru-HD bitstream.

    True but I am struggling to find many titles which have audio tracks above 16 bit 48Khz anyway (bar music discs anyway). Does anyone have info on what (non-music) discs have audio tracks any higher than 16 bit / 48Khz ??
     
  8. Blu4KHD

    Blu4KHD
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    Wrong again sorry to say Dolby TrueHD and DTS-HD MA are infact just containers for LPCM, Once the Container is unzipped so to speak then LPCM is what you hear. It does not matter if your Amp does the Unzipping of the container or the Player or in this case HTPC software in the forms of Powerdvd and Arcsoft TMT both are identical bit for bit. Apart from the software that only downsamples the 24bit part to 16bit. Of course there is also the argument about HDMI jitter and does the software apply correct bass management and so forth that is another case in point.

    Most high end Graphics cards ATI 4XXX series and mGPU's 8200/8300 9300/9400 and most high end souncards can do up to 192khz sample rates and if the software limitation to downsample was removed 48bit too.

    andy1249 you are correct in that the only non downsampling hardware available to buy at this moment is of course the Asus Xonar HDAV 1.3 and soon the Auzentech as well, They do in fact transport bitstream straight to your amp for the decode to take place there as well as also doing LPCM from a HTPC.

    Now and i will not go into great detail as there are guides available if you do a search, But there is only one way at the moment i know that you can get NON-Downsampled HD audio from a PC without buying the HDAV 1.3 and that is to convert your Blu rays to MKV format with Flac Audio, To keep this short Flac audio does not get downsampled if played through say MPC-HC or KMplayer, Zoom Player ...etc, So infact you do get the full 48kz/24bit soundtrack sent to your amp and can be played back by the Cards i mentioned above.


    Forgot to add jameson uk is quite correct that most Blu Rays i would say a good 80% do infact only have a 48kz/16bit HD track.
     
    Last edited: Feb 6, 2009
  9. andy1249

    andy1249
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    All pointless semantics ,
    Can you get Blu rays to output Dolby tru HD or DTS HD from a PC at the moment ?
    The answer is no ? ( besides the illegal way you mentioned )

    Usually 48khz/16bit on blu rays is advertised as PCM , not Dolby tru HD of DTS HD as these usually imply higher than 48khz/16bit , and if its downsampled its not the same quality.

    Regardless of the capabilites of the hardware , if you cannot get it to play the content due to software / firmware restrictions it is in the same boat as the analog connections and useless for the task.

    Yes you can get any HDMI to output PCM at 48KHz/16bit , but this is not the format of the majority of Dolby tru HD or DTS HD tracks. In the case where it is the format of a Dolby Tru HD track or DTS track , then it is no better than the standard audio anyway other than being lossless.

    ( L) PCM in itself does not imply the higher quality soundtracks.
     
    Last edited: Feb 6, 2009
  10. andyUK101

    andyUK101
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    FFdshow decodes all the latest HD codecs and since August the SVN builds support 16bit+ output

    What i do is remux the video and TrueHD/DTSMA track to M2TS and playback via FFDshow (LPCM via HDMI on ATI4670) - Which i thought would give me non downsampled playback

    The OSD for FFDshow certainly suggest it is decoding and outputting at 24bit
    when required
     
  11. Blu4KHD

    Blu4KHD
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    I suggest you do some reading on the different formats i have included some examples that contradict what you say above

    I could go on but the list of Dolby TrueHD and DTS-HD titles masterd with a 48khz/16bit soundtrack is endless.
     
  12. Blu4KHD

    Blu4KHD
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    Hi andyUK101,

    If you want the Full 24bit ouput .flac is the only way to do it at the moment and it is only supported from inside the MKV container and nothing else as far as i am aware anyway.

    Regards
     
  13. andy1249

    andy1249
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    I
    Nice list , and point taken , my small collection is made up of music titles for the most part , and in all those cases the sample rates are at least 48khz/24bit and the of the few that dont have these bitrates or higher they are just advertised as PCM , not tru HD or DTS HD.

    With music titles these bitrates are clearly labelled on the box.
     
  14. andyUK101

    andyUK101
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    Hi,

    A post on AVSforum suggest otherwise

    [Mod Comment by graham.myers: link removed - please do not link to competing forums, thanks]

    Ill have a play round tonight with some films and see what FFdshow is actually decoding

    Im sure ive seen FFdshow outputting 24bit audio from a m2ts file before - will check and confirm

    Regards

    <EDIT> unless its windows that has the problem with >16bit output?
     
    Last edited by a moderator: Feb 6, 2009
  15. jameson_uk

    jameson_uk
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    As above some soundcards are capable of 24 bit 92Khz. The thread is about Tru-HD and I guess I am really talking about playing back BD media. (which generally means PowerDVD or TMT)

    The limiting to 16 bit / 48Khz is part of the AACS specs rather than anything to do with sound cards, windows or audio players. PowerDVD and TMT correctly stick to this.

    I am guessing that if FFDShow now decodes Tru-HD and DTS-MA then in theory you should be able to extract various streams from BD media and remux them in a fashion which would bypass all the AACS specs (ie. by not using PowerDVD or TMT). This however is illegal so I guess is not a topic to be discussed on these forums :)
     
  16. jameson_uk

    jameson_uk
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    I guess music discs have far less need for all the extra rubbish you seem to get with films now. Also I guess the video is actually not as big. This all leaves lots of room on the disc. My understanding is that LPCM does not require and licensing so if you have the space then having a LPCM soundtrack makes sense as to save your pennies going to Dolby.

    Films tend to use Tru-HD and DTS-MA purely for their compression meaning they can give you lots of useless extras you will most likely never even open ;)
     
  17. andy1249

    andy1249
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    Heres some movies with 48khz/24bit by the way ,

    Master and Commander,
    Wanted,
    Pulp Fiction,
    Pearl Harbor,
    PotC: Dead Man's Chest,
    Kill Bill Vol. 2,
    Transformers,
    Resident Evil,
    Godfather Part 1,
    and Iron Man

    They are out there. I got this list here ,

    http://www.hydrogenaudio.org/forums/index.php?showtopic=68122

    Which has an interesting point of view from the OP in that particular thread.
     
    Last edited: Feb 6, 2009

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