What are the pros and cons of bitstream TrueHD/DTS-HD(MA) vs LPCM of the same?  

well, bitstreaming is sending the undecoded audio from the blu-ray player to the receiver, and LPCM is sending the decoded audio from the blu-ray to the player. if you use HDMI, the DACs in the player are never used (still just sending digital info. to the receiver).

the only time the DAC comparison would come into play would be if you were decoding to analog in the blu-ray player, not with bitstreaming or LPCM over HDMI.

as for where it is better, it shouldn't matter quality wise, it is just an unzipping process and should be lossless either way. but if you want secondary audio and certain other disc audio features, it has to be decoded in the player and then sent out via LPCM. you lose the ability to access these features if you bitstream.

There is no difference in the PCM produced from lossless encoding, regardless of where the decoding takes place. There simply cannot be a difference if the decoders work properly since lossless means every bit taken out is restored exactly as it was originally.

However, once the data is back to its original PCM format, other variables get introduced which may affect audio output. For example, PCM gets run through a mixer in the player in order to add the secondary audio. And, some players have improperly handled LFE for PCM over HDMI. So, I think you really need to try it both ways on your equipment, after properly setting up everything on the player and receiver.

From Jimj Peterson (Lumagen) re: LPCM (decoded audio)

The main advantage is for the new uncompressed formats for audio. HDMI 1.1 can support these if the sources decodes them to LPCM. Looks like some players will support them only in bit-stream. So HDMI 1.3 would be needed.

For a number of reasons the Blu Ray player should decode (to LPCM): 1) Decoded you don't need HDMI 1.3. 2) Decoded the PrePro has more compute cycles for audio enhancements. 3) Decoded the source can mix in audio commentary and other features. This is not possible if the source does not decode these formats.

All things being equal, LPCM has a small advantage..

As I understood the OP, this discussion relates to qualitative advantage of bitstreaming audio data out of a player vs. decoding to PCM internal to the player. Referencing the quotes thebland lifted above...


Not germane to this discussion. HDMI 1.1 or 1.3 have no affect on audio quality. The point being made by Mr. Peterson is merely that someone with HDMI 1.1 hardware doesn't have to change hardware. This could only be construed as an "advantage" for in-player decoding assuming one, a) does not already have HDMI 1.3 hardware or, b) is not disposed to updating hardware.


This would require more detailed input from an engineer. There is more likely to be greater computational resources, particularly hardware resources, dedicated to both audio decoding and processing in a, say, $1500 to $5000 AV receiver or pre/pro than a Blu-ray player.


See above. This is a convenience feature and has nothing to do with the quality of the decoded audio, except to possibly add a step where degradation could occur.


If you are saying in-player decoding and sending PCM to the receiver/processor has a small advantage over bitstreaming, then I disagree. And, unlike you, bland, I have both capabilities in my system and have been able to actually compare both configurations as the basis for my opinion.

Saying that the decoded output of a TrueHD or DTS Master audio track is the same no matter if that decoding is done in a player and sent out as PCM or done in a receiver completely ignores the simple fact that the decoded PCM data in a player then has to be sent out of that player using a less than perfect physical medium that covers inches/feet of copper and connectors rather than nanometers of circuitry on a chip and into a receiver where is still has to follow a digital processing path that may well be different from the path taken by the raw bitstream data. Sure, digital is digital, but how that digital data is handled up to and through the analog conversion is not the same.

If any digital processing is done by the receiver it's done on the decoded pcm stream. So regardless where the decoding is executed any further processing (level matching, delay, eq, surround field pocessing etc. etc.) in the receiver is the same for both.

Jim Peterson is an engineer working the field.. Are you?

Robert, that's a lot of hot air. A small advantage doesn't translate into an audible advantage. Your verbose theories as to why LPCM is less perfect compared to bitstream undermine your own argument that they are equal. Make up your mind! Jim Peterson is a smart guy, and I go with his statement on this one. No offense..

True. But, the PCM being processed may not be the same. The PCM produced by decoding in the player and the receiver start out identical. But, player decoded PCM may go through changes on its way from the player to the receiver that don't happen when the decoding is done in the AVR.

Assuming that any processing of decoded audio stream is switched off or bypassed (a minimum requirement of any decent player) there are no changes from the player to the receiver happening. Perhaps jitter could be an issue but if that's the case it's a matter of poorly designed equipment.

I just don't see how decoding in the player could be better than decoding in the reciever.

I would think that bitstreaming to the receiver and having the reciever decode the signal and then send it through a DAC would reduce possible signal loss or degredation.

I guess the question is, where during the process of pickup from the disc to the analog conversion can bits be affected?

The answer just might be they can't be effected at all in either scenerio.

Build a reference system and then this question might become pertinent.

Correct me if I am wrong, but PCM decoded in the player must go through a mixer on its way to the AVR. I don't believe there's a path out of the player that bypasses the mixer. And, why do some players improperly reduce LFE by an additional 5db when sending PCM over HDMI? There is certainly no way for an end user to bypass whatever player circuitry/software is responsible for that processing.

So what happens in a digital mixer if I add a secondairy audio stream?
It just adds the pcm words.
If the secondairy audiostream is not used then nothing happens.
10 + 00 = still 10.


Software bug in the firmware or poor design choice. Get them to fix it or buy a good player.

If you leave the levels at 0dB nothing happens to the signal. 10 x 1 = still 10

Now in analog mixers and gain stages you will get noise and distortion added from the resistors and the buffer and summing amplifier stages.

{QUOTE]Build a reference system and then this question might become pertinent.[/quote]

Out of curiosity, what exactly would you consider a reference system?

Excuse my naivety in this area as I am just getting more into the audio side of things.

If I understand correctly the audio is compressed on the disk, the choice is where is the decompression done?

Bitstream is compressed and PCM is uncompressed?

Sorry if they are basics I should already know.

I think you misunderstand my point here. Player decoding and receiver decoding necessarily put the audio stream through different processing, which introduces real world variables. You are describing how things ought to work and you are absolutely correct. But, that doesn't mean I can actually buy a player that presents the same PCM to the AVR that the receiver produces when it does the decoding. I'd love to buy a "good" player. But, sadly, even the $2,000 Denon 3800BDCI has lots of issues. What "good" players have you found?

Out of curiosity, what exactly would you consider a reference system?[/quote]

State of the art equipment in a properly designed, EQ'd and treated room. One that meets the metrics of freq response, output, and dialog intelligibility.... and even with that, there may be no way to audibly tell a difference. The fact here is this debate is more theoretical than practical. Not even worth a debate.

The biggest plus for LPCM is mixing secondary audio and related stuff, compatibility with today's high end and legacy pre pros so as to use their DACs and post processing. There are no high end HDMI 1.3 pre/pros yet so LPCM has its place. In terms of Jim's (Lumagen) assertion of more audio computing cycles, he's the engineer so I believe him (likely due to the fact that DSPs are working with LPCM only and not decoding a bitstream track concomitantly. A more ideal situation.. divide and conquer the decoding rather than doing it all in one place.. An audible difference? Doubtful.

I have been thinking a bit regarding secondary audio. Wouldn't this audio be mainly DD 5.1 rather than PCM or lossless? Wouldn't it then be possible to choose one of the discs DD 5.1 tracks at the same time as you would listen to the commentary track of a 1.1 PIP feature? That would mean that you could bitstream this combined track to a normal receiver using coax or optical.

I personally do not own a 1.1 player so I can't try this out, but I DO sincerely doubt that even the most trained audiophile ear could hear the difference from a lossy track when simultaneously trying to make any sense from the overlaid commentary track!

Any thoughts?

Wow, imagine that. Someone on AVS that actually seems to understand the difference between real world variables and textbook theory.

Too bad there aren't more here that do.

Yes, you should bow out, Robert.

Right now it seems the cons to LPCM are waiting for a stand alone player that will decode all the formats. Bitstream seems easier to implement so the fully functional players are longer in coming and those who have HDMI 1.3 receivers/prepros which decode everything are at an advantage (although it's temporary).

I'll be waiting, I guess, but I have to admit I'm a little impatient that my HDMI 1.1 "high end" processor can't decode anything.

I'm going out to CEDIA in the next few months to see the new HDMI pre/pros. I imagine Lexicon, Meridian, Halcro, and Theta will have their models. It will have to be good sales job to get many to move to HDMI 1.3 for audio simply because theoretically, it seems 'easier'. I want to know about what else will be offered in these pre/pros.

LPCM makes a lot of sense. You lose nothing with LPCM vs bitstream. I don't see any reason yet to give up my pre/pro for a 1.3 model (as their is little on the market worth owning). If something looks significantly better at CEDIA, I'll buy it... but I am not holding my breath.

Please explain how and on what equipment you have compared bitstream audio decoding to internal audio decoding?