# Multi Ch PCM



## I=V/R (May 25, 2011)

I have done some reading, but don't feel that my query has been definitively answered. What I want to know is whether I need to buy new features or if what I have does the same thing. I have a HK avr347 which plays multi ch PCM, a fat ps3 which outputs Dolby true hd and DTS HD-MA as multi ch PCM. From what I gather PCM is uncompressed audio, and the hd formats are compressed but decoded and played at the same bit rates as uncompressed. So does my setup play the same audio as if I had a slim ps3 that did the hd audio via bitstream and a receiver that was hd audio enabled? Would the difference be audible enough to justify a new receiver and console or Blu-Ray player?


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## I=V/R (May 25, 2011)

Does anyone have any insight on this matter?


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## Kal Rubinson (Aug 3, 2006)

Inconsequential.


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## Ares (Nov 23, 2009)

The only difference is one will make the HD symbol light up on the receiver and one won't.


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## gdstupak (Jul 13, 2010)

This is what I have read, please correct me if I'm wrong:

Both bitstream and PCM will put out the exact same audio signal.

But I understand that there are 'flags'(?) in the original signal that can tell your AVR to change certain settings (such as level controls for speakers (these can increase/decrease volume levels of the center channel or LFE channel)). This is what you see flashed in your AVR display when it first receives a signal (such as "Dialog...").
Your receiver will act on these 'flags' only when it converts the PCM signal to bitstream. But if the PCM signal was converted to bitstream before the AVR (converted inside the Bluray player), then these 'flags' are not activated.

Because of this some people say they hear a difference.

EDIT: I may have written that process backwards earlier...
Maybe the 'flag' can only be activated when the signal is converted in the Bluray player, and then the bitstream is sent to the AVR???
...I think this is the proper process because this is how my system is set up and I do get the messages flashed on the AVR display.


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## Owen Bartley (Oct 18, 2006)

I have been a little confused by this topic too, and did some reading around this and other sites. I think a big part of it is that it comes down to where the decoding is done? If I understand correctly, the receiver's "language" is PCM. It gets converted to this for output at some point in the chain regardless of what happens, and the main difference is that if your player converts and passes PCM, the receiver isn't sure what to call it, but it will output the proper sound. If your receiver is doing the decoding, it will know what to call it, and can display the format (DD 7.1, DTS 5.1, whatever it is).

This post HERE was the most concise explanation I read on the subject, and I think it helped me the most.


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## Kal Rubinson (Aug 3, 2006)

As I said, the difference is inconsequential. No reason to spend money for this.


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## Jeebee (Jan 13, 2011)

Even running direct or Pure direct, the receiver will convert the signal to PCM? What's the point then, just less circuits to pass through?


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## Kal Rubinson (Aug 3, 2006)

Jeebee said:


> Even running direct or Pure direct, the receiver will convert the signal to PCM? What's the point then, just less circuits to pass through?


There is no generic answer as different AVRs mean different things by these terms.


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## Mark Techer (Jan 17, 2008)

gdstupak said:


> EDIT: I may have written that process backwards earlier...
> Maybe the 'flag' can only be activated when the signal is converted in the Bluray player, and then the bitstream is sent to the AVR???
> ...I think this is the proper process because this is how my system is set up and I do get the messages flashed on the AVR display.


Are you referring to "Dialogue Normalization"? If the level on the soundtrack is recorded correctly (-31dBFS) no flag will be seen regardless of the format used to encode. Many of my DTS HDMA soundtracks seem to be encoded at DN-27dBFS which displays a DN+4 message on the AVRs front panel. I queried THX about this and their replay suggested that THX certifed AVRs boost all program from -31dB to -27dB and therefor when playing a soundtrack that displays a DN+4dB reading, the actual level is now 8dB too loud. 

I have heard reports from people with non THX gear claiming their AVRs will show this is a -4dB, but I've never checked out the discs they were discussing to know if I get a + or - DN reading.


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## gdstupak (Jul 13, 2010)

Yes, Dialogue Normalization is a feature I was referring to, I don't know if there are other changes that are made.
Thanks for your info on dialogue normalization. As far as I know this is simply boosting the volume of the center channel, or is there more to it to focus on the dialogue specifically? It irks me that I spend hours equalizing my system and then the system does something to unequalize it. It also irks me when people speak of the center channel as mainly the dialogue channel, the center channel does so much more than dialogue and boosting it throws the whole front soundstage out-of-whack. If dialogue is unintelligible then a better center speaker is needed, or maybe better sound treatment in the room, or maybe the DVD sound engineer sucks at his job.


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## Mark Techer (Jan 17, 2008)

gdstupak said:


> Yes, Dialogue Normalization is a feature I was referring to, I don't know if there are other changes that are made.
> Thanks for your info on dialogue normalization. As far as I know this is simply boosting the volume of the center channel, or is there more to it to focus on the dialogue specifically? It irks me that I spend hours equalizing my system and then the system does something to unequalize it. It also irks me when people speak of the center channel as mainly the dialogue channel, the center channel does so much more than dialogue and boosting it throws the whole front soundstage out-of-whack. If dialogue is unintelligible then a better center speaker is needed, or maybe better sound treatment in the room, or maybe the DVD sound engineer sucks at his job.


The system as a whole should be boosted, not just the centre speaker. The -31dBFS DN figure means that the average level of dialogue (assuming normal conversation and no shouting or whispering) will be recorded at -31dB below the level of Full Scale (being 105dB per channel). They use dialogue because pretty much every movie has it and it is something that is fairly consistent. Music or Score has too many variables. 

So when you see a DN+4, it means that the level of the soundtrack has been raised from -31dB to -27dB so you can turn the master volume down by 4dB. You only really need to compensate when listening at 00dB or reference levels which is only useful if you have set your system up to play back at +75dB/CH using C and SLOW response. Many auto calibration systems (whilst good) are not 100% and I've seen some that set levels too low at 71dB and others that set the levels as high as 79dB. I recommend checking the levels after auto cal just to make sure that the main channels are playing at the correct level of 75dB. 

Your right about the centre channel containing more then just dialogue. It is said that it can contain as much as 90% of a soundtrack including music, sound effects and of course, dialogue. 

Yeah there was this really bad habit in the early days of surround where people would crank the centre and or the surrounds. Many still do it for their subs today. When an average film takes about 2 or 3 weeks to finalize the mix, it is no wonder they (the pro's) don't like HT enthusiasts. They do all this work to get everything sounding perfect only to have the end user think it is OK to mess with that. It is not OK at all :rant:


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## gdstupak (Jul 13, 2010)

Thank you for all that info Mark, I like hearing the details of the whys & hows. So DN actually raises or lowers everything. It's good to finally get the real scoop.


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## Mark Techer (Jan 17, 2008)

gdstupak said:


> Thank you for all that info Mark, I like hearing the details of the whys & hows. So DN actually raises or lowers everything. It's good to finally get the real scoop.


Yes, according to the contact I have at THX. When I emailed him about this, he took about three days to respond but he gave a very technical answer and it was good to hear this "from the horses mouth" so to speak..


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