Bitstream vs. PCM

Discussion in 'Playback Devices' started by EricRWem, Sep 21, 2004.

  1. EricRWem

    EricRWem Screenwriter

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    Great confusion seems to be surrounding these two things...and now its made me confused. I've tried searching other forums and all, but I just really want two very straightforward, blunt, and simple definitions for these two terms and the appropriate use. If this has already been done, then please link me to it and sorry for the redundant thread.
     
  2. Tony Kwong

    Tony Kwong Supporting Actor

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    I'm confused... Are you refering the a DVD player and the DTS setting?
     
  3. EricRWem

    EricRWem Screenwriter

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    Yes, it's usually an option you select in a DVD player.
    PCM or Bitstream. I just want to double check my facts...
     
  4. greg_t

    greg_t Screenwriter

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    The bitstream setting is used when you want to pass the digital audio bitstream to your reciever for decoding. PCM will use either the decoder in your DVD player (if it has a built in DD/DTS decoder) or will downconvert to 2 channel if that is the output you are using.
     
  5. John Garcia

    John Garcia Executive Producer

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    This is not correct. PCM is a digital stream also, and it is not a decoded signal (analog is a decoded signal). PCM is, for all intents and purposes, STEREO ONLY, and is designed to be the lowest common denominator; basically every digital processor should be able to handle it. Dolby is not passed via PCM. DTS can be passed via PCM by "tricking" the processor and sneaking the extra channels into the stream somehow - this is how DTS CDs work.
     
  6. Jon W.

    Jon W. Stunt Coordinator

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    Now for the short answer:

    PCM = Pro Logic/Stereo [​IMG]

    Bitstream = DD/DTS [​IMG]
     
  7. EricRWem

    EricRWem Screenwriter

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    ^^ THERE we go! Good! Nice to know I set my equipment properly after all!

    I have the Zenith 318 set to Bitstream and it's connected to the HK 630 via a coax cable.

    When the time comes for me to get a niceer audio player, say some universal player, would I still keep it all thrown to bitstream then? (Example: Denon 3910?)
     
  8. John S

    John S Producer

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    Yes, you will be mostly bitstream.

    On the PCM side of things.. Laserdisc players typically only use PCM out the Optical output. (AC-3 / DD is usually passed only by a very specialized circuit via coax)...

    PCM will pass real DTS Multichannel, I never realized this until I played a disc with DTS after I upgraded to my Denon 4802, it comes right up with the real DTS multichannel decoding.

    Just an additional FYI on it is all, more than anything.
     
  9. EricRWem

    EricRWem Screenwriter

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    So if I get a universal player, for SACD and DVD-A do I stick with Bitstream or go to PCM for those two things?
     
  10. John S

    John S Producer

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    DVD-A = Bitstream

    SACD, requires you to hook up the analog out from the player into, the multi-channel analog in of the AVR/Pre-Pro.....
     
  11. John Garcia

    John Garcia Executive Producer

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    DVD-A cannot be passed via digital unless you are using components (both player and processor) that have firewire or proprietary digital connection such as Denon link. DVD-A hires is analog only right now, just like SACD. If you pop in a DVD-A and get sound via digital, it is DD/DTS, and you are not listening to the hires content. Many SACDs have a CD layer that can be read by any CD player.

    Which means, you will not use either bitstream or PCM for DVD-A/SACD.
     
  12. John S

    John S Producer

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    Dang, I was pretty sure, DVD-A could be passed by the digital connection.. See you live and learn if this is not so......

    I also know some people, that are not really getting their full potential on their DVD-A then too. Interesting.
     
  13. Brian L

    Brian L Cinematographer

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    I think this is true with 99.999% of the DVD-A discs out there.

    But per my player's manual (Pio 45a), DVD-A discs COULD allow for 96K output via a standard digital connection. It further goes on to say that 176K or 192K content (which would be 2CH by definition) would be downsampled to 96K.

    Lastly, it does say that whether or not I turn off the downsample option, some 96K DVD-A will automatically be down converted to 48K.

    But thats all academic, in that it would require a DVD-A disc that is not copy protected, of which I know of none at the present time.

    BGL
     
  14. Tony Kwong

    Tony Kwong Supporting Actor

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    Are there not 2 different encodings for DTS on a DVD? I think I had to change the settings on some older disc to PCM instead of bitstream.
     
  15. LanceJ

    LanceJ Producer

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    Just for clarity's sake:

    When the PCM option is chosen instead of bitstream for Dolby, you won't get a Dolby Surround-encoded signal. This will just result in a downmixed version of the 5.1 track & when this new 2.0 channel signal is processed by a Dolby Surround or Dolby Pro-Logic decoder, you'll hear.....well to be honest I'm not sure! A true Dolby Surround encoded stereo track contains information specifically designed for the mono rear channel generated by a Dolby Surround/Dolby Pro-Logic playback processor. This information is in the form of an out-of-phase signal placed in the left & right channels of a stereo mix (when using a stereo-only system, you can't hear this channel because the out-of-phase signals cancel each other out by the time they reach your ears). But a downmixed mix will not contain this type of data and I'm pretty sure any rear channel action will occur simply by random chance which is not exactly the way I like to listen to my movies.

    So if you're using an older receiver or one of those mini-systems equipped only with Dolby Surround/Pro-Logic, look for a 2.0 track on your dvd (though most don't seem to have this) & select that instead of the 5.1 mix.

    FYI: quite a bit of music has naturally-ocurring out of phase sounds in it and routing it through a Dolby Surround processor can result in some pretty good sound sometimes.

    BTW: if someone wants the best sonic fidelity & doesn't care about 5.1 surround effects, if it's present choose the disc's PCM 2.0 track. Because don't forget that while Dolby/DTS can sound very good, these are both lossy formats (sort of like Super Ultra MP3 formats [​IMG] ) and so don't contain all the information from the original recording. And just like an analog format, PCM can still contain Dolby Surround data since (again) you just need an out-of-phase signal for the Dolby Surround/Pro-Logic decoder system to work. This is also how we get a rear effects channel out of VHS tapes that have a stereo track (taken either from the linear tape track [which sounded like crap] or the Hi-Fi format [which can sound very good; in fact I've made a few personal-use 2 hour mix tapes this way & they are nearly indistinguishable from the CD versions]).

    If anyone is interested & also likes classical music, the first CDs I heard of using the Dolby Surround process are from this artist. I have his album Kosmos in vinyl form (non-surround) & it's a novel/fun way to listen to this type of music.

    Dvd-audio pimping section [​IMG] : Tomita's The Planets 2003 album is available in dvd-audio surround form and has received good reviews for its sometimes wacky surround mix. But I don't think it is available here in the States yet. EDIT: here's a review of this by an HTF member.
     
  16. EricRWem

    EricRWem Screenwriter

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    Much appreciated. Bitstream seems to be the answer of what I should stick to. [​IMG]
     

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