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PCM vs. Bitstream (Denon 3808 and Panasonic BD30)


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13 replies to this topic

#1 of 14 OFFLINE   DrRoebuck

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Posted June 18 2008 - 01:27 PM

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 of 14 OFFLINE   David Willow

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Posted June 18 2008 - 01:55 PM

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 of 14 OFFLINE   DrRoebuck

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Posted June 18 2008 - 02:01 PM

Quote:
Originally Posted by David Willow
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.
Thanks for the reply.

I was surprised by what you said about the BD30 not decoding the formats internally, so I went to Panasonic's site. Guess I could have started there, since this what they say:

Quote:
With Precise Digital Audio, Blu-ray's beautiful images are complemented by exceptionally pure, accurate sound thanks to Dolby® TrueHD and DTS-HD™. UniPhier®'s advanced processing capability decodes these audio signals with high precision and outputs them in bitstream form with no degradation. It also brings re-mastering to Blu-ray for the first time, which compensates for data lost during the compression process creating a fuller, richer sound.

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 of 14 OFFLINE   David Willow

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Posted June 18 2008 - 04:27 PM

Quote:
Originally Posted by DrRoebuck
Thanks for the reply.

I was surprised by what you said about the BD30 not decoding the formats internally, so I went to Panasonic's site. Guess I could have started there, since this what they say:



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?

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 of 14 OFFLINE   Jack Gilvey

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Posted June 19 2008 - 12:36 AM

Quote:
So that means the BD30 does indeed decode those signals, but I need to choose Bitstream. Right? (Just trying to sort this all out.)
Seems to be some contradiction in terms here, some semantic confusion. "Decoding", as used on these forums, is the process of "unzipping" the TrueHD/DTS-HD MA data from a disc into its native PCM form to be sent over HDMI. This the BD30 does not do.
Panasonic's statement that the BD30 "decodes these audio signals with high precision and outputs them in bitstream form" makes little sense in that once a stream is decoded (again, in the accepted use) it's not bitstream anymore. They're using "decoding" in another sense.

Quote:
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?
Yeah, you don't need to worry about internal decoding, it's being done in your AVR.
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#6 of 14 OFFLINE   DrRoebuck

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Posted June 19 2008 - 03:37 AM

Thanks for the help, guys.

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

#7 of 14 OFFLINE   Jeff_CusBlues

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Posted June 19 2008 - 03:51 AM

Quote:
Originally Posted by Jack Gilvey
Seems to be some contradiction in terms here, some semantic confusion. "Decoding", as used on these forums, is the process of "unzipping" the TrueHD/DTS-HD MA data from a disc into its native PCM form to be sent over HDMI. This the BD30 does not do.
Panasonic's statement that the BD30 "decodes these audio signals with high precision and outputs them in bitstream form" makes little sense in that once a stream is decoded (again, in the accepted use) it's not bitstream anymore. They're using "decoding" in another sense.


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

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 of 14 OFFLINE   DrRoebuck

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Posted June 19 2008 - 03:56 AM

Quote:
Originally Posted by Jeff_CusBlues
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.
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 of 14 OFFLINE   hodedofome

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Posted June 19 2008 - 07:53 AM

Quote:
Originally Posted by DrRoebuck
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?

No, it is the same information just being decoded in either your player or receiver. If the D/A converters in the player are superior to the D/A converters in the receiver I could see having it decoded in the player and output via PCM, otherwise just send it via bitstream and have your avr do the decoding.

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#10 of 14 OFFLINE   Paul Kemp

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Posted June 27 2008 - 06:07 AM

Quote:
Originally Posted by DrRoebuck
So is there any validity to what so many others have said, regarding PCM being better than Bitstream?

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 of 14 OFFLINE   Jack Gilvey

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Posted June 27 2008 - 02:01 PM

Quote:
If the D/A converters in the player are superior to the D/A converters in the receiver I could see having it decoded in the player and output via PCM, otherwise just send it via bitstream and have your avr do the decoding.
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.
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#12 of 14 OFFLINE   Robert G

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Posted July 01 2008 - 12:16 AM

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

#13 of 14 OFFLINE   DrRoebuck

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Posted July 01 2008 - 04:37 AM

Quote:
Originally Posted by Robert G
Just wanted to say thanks to Paul and Jack. Very simply put and informative posts.
+1

#14 of 14 OFFLINE   Jack Gilvey

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Posted July 03 2008 - 10:14 PM

Quote:
Originally Posted by Robert G
Just wanted to say thanks to Paul and Jack. Very simply put and informative posts.

Glad it helped! Posted Image
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