Bitstream vs. PCM

Discussion in 'CD/DVD/Blu-ray & Misc Hardware' started by Tomorrow, Jun 25, 2006.

  1. Tomorrow Audioholic Ninja

    Tomorrow
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    Will one or more of you digital whizkids give me a clue...puhleeze.

    I recently upgraded my receiver from a Panasonic SA-HE200 (decent Mosfet amp'ed Rx) to a new Yamaha RX-V2500. I set everything up and settings were checked, double checked, triple checked, had AverageJoe quadruple check...and we knocked our heads around trying to discover why the digital signal (via coax) from the trusty Panasonic F87 DVD player was much inferior to the analog signal. I couldn't seem to get a discrete surround process going unless it was in Pure Direct or Multi-channel. I must have tried all the PLII+, DD-EX, etc formats 10 times each. Still no soap. I almost figured I had a defective Rx.

    THEN!!...we decided it had something to do with the DVD digital output of either Bitstream or Pulse Code Modulation...which is DVD player selectable. I checked and it was set to PCM with warnings against using Bitstream on some receivers (could damage speakers). Well, that turned out to be the big problem. The Yammie would not process the PCM data into surround formats (as did the Panasonic Rx). But it now sounds great with the DVD set to output with Bitstream.

    Can someone describe in simple English for my simple mind why this is so and why some receivers are functional in one mode only? Or, is there an Rx setting I missed that would have properly engaged the PCM data?

    Thanks in advance for your wisdom.
  2. MACCA350 Audioholic Chief

    MACCA350
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    Basically,

    Bitstream - will send the raw digital audio without processing out of the DVD player so your receiver can process

    PCM - the player will convert everything to and output as 2 channel PCM

    So if you want your receiver to process DD and DTS multichannel tracks then you must set the player to Bitstream

    This PCM/Bitstream option doesn't effect the players analogue outputs. This is the reason why your analogue outs sounded better than your digital out when its set to PCM.

    cheers:)
  3. MDS Audioholic Spartan

    MDS
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    The probability that the RXV-2600 cannot take a 2 channel PCM signal and apply any one of the many matrix surround decoders to it is zero. Pure Direct should not touch it, so if you had the receiver set to pure direct that is likely why you could not engage any of the matrix decoders.
    MDS,
  4. Tomorrow Audioholic Ninja

    Tomorrow
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    MDS.... No. The Yammie will not switch to digital modes while in Pure Direct or Multi-channel.

    MACCA350... what then is the purpose of PCM? Digital stereo only?
  5. MDS Audioholic Spartan

    MDS
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    Exactly...that is what I said.
    MDS,
  6. Tomorrow Audioholic Ninja

    Tomorrow
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    I thought you meant it wouldn't WHILE the unit was in Multi-channel or Pure Direct mode. (It won't in any mode.)

    So the bottom line is PCM is a 2 channel signal, not meant for DD or DTS 5.1 discrete + one or two (6.1-7.1) rear surround production. I didn't realize that only bitstream provided that function.

    Nowhere on any of my manuals has this been said. Thus my confusion. Thanks for the info!
  7. MDS Audioholic Spartan

    MDS
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    If you set the player to PCM it will decode DD and/or DTS 5.1 and then downmix it to 2 channel PCM. Matrix surround decoders like PLII and DTS:Neo6 can take that 2 channel PCM signal and turn it into 5.1.

    If you cannot use PLII or any other matrix decoder it is because the receiver is in Pure Direct mode; change it to Stereo and those modes should be available. If you connect the dvd player to the receiver using the 5.1 analog inputs on the receiver, then it won't work because receivers do no processing on those inputs.

    So...if the player is set to PCM and you make a digital connection from the player to the receiver's DVD input OR you make an analog connection from the player to the receiver's DVD input and put the receiver in any mode other than pure direct, you will be able to choose any of the matrix decoders to turn the 2 channel PCM into surround.
    MDS,
  8. Tomorrow Audioholic Ninja

    Tomorrow
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    Thanks guys.

    Whodathunk 30 years ago in the golden age of stereo one would have to understand bitstreaming and pulse code modulation in order to be able to hook up one's system. What ever happened to PnP?! :mad:
  9. avliner Audioholic Chief

    avliner
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    Could someone elaborate on that matter? Really never heard about such a possibility...

    Cheers / Avliner.
  10. MACCA350 Audioholic Chief

    MACCA350
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    OK I'll elaborate, If you want your receiver to decode DD or DTS then you need your player set to BITSTREAM, simple;)

    I think the possibility they refer to is if the receiver doesn't support DTS and If set to BITSTREAM the receiver will play something similar to 'pink noise' which if played at high volume has the possibility to damage speakers.

    cheers:)
    BTW, anyone tried the Elijah Craig bourbon? quite a nice drop at 47%:D
    Last edited: Jun 30, 2006
  11. billy p Audioholic Ninja

    billy p
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    What I found out when my dvd was set in PCM and not BITSTREAM (RAW) was with dts movies I got no sound or poor quailty sound.Can this be possible or am I out to lunch?:eek:
  12. j_garcia Audioholic Jedi

    j_garcia
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    You can get dts from PCM, but only from dts CDs. DVDs use a different method for passing the digital signal so you will get pink noise only if you try to playback a dts track from a DVD. You should not hear "sound" at all, only pink noise with it set to PCM with a DVD.
  13. hearrean Audiophyte

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    clarification?

    Hopefully this is not a ridiculous question, so here goes. I assume these settings will also apply if you are using HDMI for both audio & video? I ask because this particular topic is being beaten to death over on another forum and no one consensus has been reached yet. Everyone has their own opinion including Toshiba (the DVD player mfg.) & they're all different!
    So let me try & make sure I've got this. If I am running a HD DVD player and a HDMI capable a/v receiver and playing back either SD DVD's or HD DVD's, then in the HD DVD player's set-up menu, I would set the SPDIF to "Bitstream" & the HDMI to "Auto" or should the HDMI setting be on "PCM?"....This setting recommendation at least seems to be the most popular one on the other forum.

    Ken
    Last edited: Sep 19, 2007
  14. sarod@comcast.n Audiophyte

    sarod@comcast.n
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    PCM/Bitstream

    I have the same ? The only dif is I have the onkyo tx- sr705 and all I see on the display is pcm on the reciever when I have my hd dvd player going.
  15. GlocksRock Audioholic Spartan

    GlocksRock
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    That is what you want, that means that your receiver is getting the TrueHD or Dolby Digital +
  16. Harrison476 Junior Audioholic

    Harrison476
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    displaying TrueHD and DTS HD

    The way I understand it is only when players have the abililty to send HD bitstream, then and only then will recievers decode the signal and display it on the panel as TrueHD,dobly plus, and DTS HD.

    Very Confusing
  17. mtrycrafts Audioholic Slumlord

    mtrycrafts
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    Yes, and it is not getting simpler but more complex.
  18. mr-ben Audioholic

    mr-ben
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    The SPDIF connection (the single optical or digital coax connection) can only carry so much data over it. PCM is uncompressed data, like what's on a CD, and the cable can only carry two channels worth of it. Dolby Digital or DTS are both compressed audio, like MP3, so by compressing the data they can send more channels through than with PCM. The receiver decompresses the signal if it understands DD/DTS by turning it into PCM internally, but some equipment doesn't understand DD/DTS, so that's why PCM may be the default or recommended method in the manual. With SPDIF, the cable is the bottleneck.

    HDMI is a different story. The HDMI cable can carry a lot more data than the SPDIF cable can, including more audio data. If you use HDMI to connect your player to the receiver, then you don't need to use the SPDIF cable at all. The HDMI cable has the bandwith to transmit PCM for all the channels on the disc if you want it to. The audio on the disc can be decoded by the player and sent over HDMI as PCM, or it can be sent as a raw signal over HDMI and get decoded by the receiver, assuming the receiver is capable of decoding that format. You'll hear the same thing either way.

    The choice is needed because there are so many formats for the audio. PCM, DD, DD+, TrueHD, bla bla bla. If the disc contains some format that the player can decode but the receiver can't, then you need to send it to the receiver as PCM, because it will understand that. The opposite may also happen - the disc contains TrueHD that the receiver can decode, but the player can't. This needs to be sent in bitstream format to the receiver so it can be decoded there. Happily you have an "auto" setting which probably figures all this out for you.
    Last edited: Nov 8, 2007
  19. MACCA350 Audioholic Chief

    MACCA350
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    Not sure if you guy's noticed this, but this thread is over a year old and originally about SD DVD players

    cheers:)
  20. Lenin Audiophyte

    Lenin
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    Bitstream Vs PCM

    My name is Lenin,... and recently I have realized my BD/ DVD player is able to output bitstream or PCM audio signals? What selection do you recommed to get the best sound quality in stereo & 7.1 multichannel? Why? My receiver is able to take both...via HDMI or optical digital...

    Appreciate any help you can provide...

    Regards

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