Receiver DSP question

Discussion in 'AV Receivers' started by MattWel, Feb 20, 2006.

  1. MattWel

    MattWel Stunt Coordinator

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    Hi guys, I'm hoping someone can help me with this. I recently was watching and listening to Rush's R30 concert dvd on my small 2 channel setup. My receiver is a Panny XR10. The dvd has a DD 5.1 track and a PCM Stereo track. The PCM track sounded great on my setup and the 5.1 was really, really low and almost muffled by comparison. The 5.1 track sounded like it was at about half of the volume of the PCM track. I know a 5.1 track downmixed to 2 channel will not sound ideal but the difference was unbelievable. The movies I watch with DD and DTS tracks usually sound fine on my setup.

    Out of curiosity I pulled out my old cheap Sony DE595 receiver and the results were the exact same until I applied the Digital Cinema Sound movie sound fields while listening to the DD 5.1 track. This made the 5.1 track louder than the PCM Stereo track and all of the individual instruments were more defined. The Music sound fields (Hall, Jazz, Concert, etc) did nothing to improve the 5.1 track at all but the Cinema Studio EX A,B, and C all made a world of difference to the 5.1 track. Do these type of DSP's often make this big of a difference?
     
  2. Shane Harg

    Shane Harg Second Unit

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    I'm not sure of the whole reason, but the same thing is true on my Eagles' Hell Freezes Over DVD. Although the DTS soundtrack is terrific, it lacks the punch of the PCM stereo track. I do know this. The PCM track is not a downmix of the 5.1, but a separate uncompressed track of CD quality.

    The part I am unsure of is why the 5.1 mix lacks the luster of the PCM track. I always attributed it to compression, but I could be wrong on that. I know that some SACDs don't have as much gain as the CD versions, but they do have more accuracy and detail.

    Applying a DSP mode to it is just a matter of equalization (depending on the quality of the DSP circuit), so that doesn't really surprise me. Perhaps somebody else has a better answer for you. Good luck.

    Shane
    Yamanashi prefecture, Japan
     
  3. Shane Harg

    Shane Harg Second Unit

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    I think I found the answer to your question in the FAQ section of this sight. I can't post links yet (since I haven't racked up 15 posts), so I'll go ahead an quote it to you to save you the time in locating it.

    "Explaining this actually means a basic trip into the technical world of digital audio. Are you ready? Here we go...

    Digital audio has a hard maximum ceiling for audio. This level is known as "0". All sound in the digital realm is then measured in a scale using ZERO as maximum and working downward (-10, -20, -30 etc). Sound cannot be written to a digital audio format that exceeds this 0 maximum. So think of 0 as the absolute speed limit in the digital audio world.


    Now- movie soundtracks are designed to be dynamic. They want to give you all those big loud booms and hushed whispers....

    The idea of "dynamic" is simply that there is a big difference between the loudest sound and the quietest sound. But, like we said before- no matter what we're encoding- digital has a very hard limit of the maximum level something can be... So, in order to have room for dynamics- you can't make the loud louder- so what do you do? Well, you have to make everything else softer!

    So- movies are created to have their average overall sound level be low. If the average level is kinda low then this gives them plenty of room to get loud before they hit that digital maximum level (they call this headroom-- its the amount of room you have to go up before you hit your head on the ceiling- cute huh?).

    Movies are designed to have their average dialog level be about 25 or 30 steps below the maximum level available. That way, when they want to have some big dynamic special effect- they have room to go louder... So between the dialog (average level) and the loudest sound (max level) they have 30 steps of dynamics to use.


    Video games and CDs are often designed in a different way. Instead of being dynamic- they are squashed. Almost the entire signal is squashed down into a tight package- and the whole thing is just "loud" all the time. The average CD uses just the top 3-6 steps of available volume all the time. In other words- where movies have the ability of having 30 steps of dynamics to use-- CDs only use about 1/10th that much! They push the entire signal all the way up to those top 3 levels below the max- and thus it seems significantly louder than a DVD.

    The same audio "squashing" process is used for TV broadcasts, Radio Broadcasts and VHS (although for slightly different reasons)-- you'll find they will also be "louder" on your system. The case isn't really that one is louder than the others (like I said above, they all have relatively the same maximum level)-- it just appears "louder" because all the signal is squished as close to the top as possible... while others set the average level lower to have room for dynamics.

    In closing, there is nothing wrong with your receiver or equipment. The difference in volume is normal and exactly how it should be given the nature of the different audio types."

    Hope this sort of answers your question. It kind of did for me.

    Shane
    Yamanashi prefecture, Japan
     
  4. MattWel

    MattWel Stunt Coordinator

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    Very nice. Thanks Shane!
     
  5. Shane Harg

    Shane Harg Second Unit

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    Not a problem. I hope that answered your question.

    Shane
    Yamanashi prefecture, Japan
     
  6. John Titan

    John Titan Stunt Coordinator

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    Another thing to look at is making sure your dvd player is set to bitstream when listening to 5.1 track.
     

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