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PCM vs. Bitstream (Denon 3808 and Panasonic BD30)

Discussion in 'AV Receivers' started by DrRoebuck, Jun 18, 2008.

  1. DrRoebuck

    DrRoebuck Member

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    I just got my Denon 3808, and am using the Panasonic BD30K to play BDs.

    The Panasonic has the option to output in PCM or Bitstream. I've searched the Internets high and dry and can't seem to find a concrete answer as to which is better. Most say PCM is better. Some say only PCM can output lossless audio.

    My Panasonic manual, however, seems to say otherwise. Its says to choose Bitstream to play the "original format," and that choosing PCM will cause the audio to be downmixed.

    And while we're at it, what Surround setting should I employ on the 3808 to make sure I'm listening to the lossless audio signal from the Panasonic?

    Thanks.
     
  2. David Willow

    David Willow Babbling Idiot
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    The BD30 will not decode the newer formats internally. The only way to get them is to bitstream to a capable receiver (one that decodes them).

    BTW - Choosing bitstream will not prevent the BD30 from passing actual PCM to your receiver.
     
  3. DrRoebuck

    DrRoebuck Member

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    So that means the BD30 does indeed decode those signals, but I need to choose Bitstream. Right? (Just trying to sort this all out.)

    The good news is that with Bitstream selected, and Surround Mode on the Denon set to Standard (DD or DTS), the display finally shows Dolby TrueHD or DTS Master HD. So I guess at that point all is well. Um, right?
     
  4. David Willow

    David Willow Babbling Idiot
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    Not sure what that quote means (could it be for the new BD50 or the old BD10?). I'm am positive that the BD30 DOES NOT decode the new formats. As long as you have a receiver that does, you will not miss anything. When setup correctly, your receiver will read TrueHD or DTS Master HD. It sounds like you got it.
     
  5. Jack Gilvey

    Jack Gilvey Well-Known Member

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    Yeah, you don't need to worry about internal decoding, it's being done in your AVR.
     
  6. DrRoebuck

    DrRoebuck Member

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    Thanks for the help, guys.

    Btw, David: That quote was from Panasonic's page on the BD30.
     
  7. Jeff_CusBlues

    Jeff_CusBlues Well-Known Member

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    I'm as perplexed as you Jack. I goggled UniPhier and it appears to be a hardware/software design architecture that makes it easier for customers to integrate different equipment (probably Panasonic equipment) by using similar/common design architectures. UniPhier doesn't appear to be related to decoding (as this forum and most engineers refer). BD30 outputs bitstream. Obviously, Marketing wrote the paragraph.
     
  8. DrRoebuck

    DrRoebuck Member

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    Well, it's nice to know I'm not a total moron for getting confused by their literature.

    So is there any validity to what so many others have said, regarding PCM being better than Bitstream?
     
  9. hodedofome

    hodedofome Well-Known Member

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  10. Paul Kemp

    Paul Kemp Well-Known Member

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    Yes and no.

    LPCM signals allow you to use an 'old' HDMI receiver that doesn't incorporate its own decoding for HD audio streams. This saves people with older kit from replacing their receiver (something which can be very expensive) and it helps keep prices of HDMI kit in the second hand market at a reasonable level.

    The quid pro quo with this is that you need a player which is itself capable of decoding all of the relevant audio formats and streaming them as LPCM across an HDMI interface - this means the PS3 and not much else.

    But in strict quality terms, the issue goes deeper. Audio signals transmitted across an HDMI interface do not have their own clock signal to regulate the data flow. As a result of this, audio sent across HDMI is suceptible to high levels of transmission jitter. Ordinarily, transmission jitter can easily be filtered out with a Phase Locked Loop (although this does not solve all problems), but with HDMI the cost of doing this gets expensive.

    Where does this leave us? Audio signals across HDMI are open to both transmission and conversion jitter, and there are a wealth of lab tests on the web to illustrate what this means for signal fidelity. As any Acoustician will tell you - just as this one is - broadband jitter spectra equates to a reduction in SNR whereas periodic jitter equates to frequency depenent distortions. Audio signals transmitted across an HDMI interface are thus inherently proned to reduction in total Signal to Noise ratio as a consequence of high levels of broadband jitter.

    What does this mean for HD Audio? LPCM is arguably more subjectively open to 'corruption' of the audio signal when transmitted across an HDMI signal since it is not 'packed' data and any conversion errors introduced will impact directly upon signal fidelity. 'Packed' data, that is to say, bitstream of Dolby True HD or DTS HD Master Audio, could be said to be less vulnerable to direct signal corruption because it is yet to be decoded when it reaches the receiver.

    Is there any real world difference, however? That's where subjectivity comes into play. The worst that could happen to an LPCM signal sent over HDMI would be a lessening of the SNR - is that a deal breaker? For me it is not, at least, not in multichannel. Receiver/Processor manufacturers will of course be happy to support the rumour that the quality of the decoding matters - which is a fallacy. As with all things in this wonderful hobby, only the individual can decide.
     
  11. Jack Gilvey

    Jack Gilvey Well-Known Member

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    Decoding is not D/A conversion, it's the process by which a bitstream is "unzipped" into its original PCM...but it's still digital. Even if the player decodes, only the DACs in the AVR are used. Very common misconception, and often the basis for a preference for AVR decoding.
     
  12. Robert G

    Robert G Well-Known Member

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    Just wanted to say thanks to Paul and Jack. Very simply put and informative posts.
     
  13. DrRoebuck

    DrRoebuck Member

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    +1
     
  14. Jack Gilvey

    Jack Gilvey Well-Known Member

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    Glad it helped! [​IMG]
     

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