A question to all you audiophiles on DVD Sound (1 Viewer)

[Adam Barratt]

The PCM signal is never compressed. You are performing the same tasks either way, but the DACs in your receiver may well be better than the DACs in your DVD player (then again, the opposite may be true. The only way to be sure is to experiment).
I always use my receiver to process digital audio, even though the DACs in my player are pretty good.
Adam

 

[Richard Cooper]

Sean;
This is what I *believe* happens with PCM. Anyone feel free to correct me if I'm worng. PCM is Audio encoded (in a lossless way, as opposed to DD/DTS, which loses some information) digitally. When a PCM source is extractedf rom a disc (be it CD, DVD or whatever), it has to be passed through a DAC at some point. If you use the analogue outputs from your player, then the DAC in the pplayer has been used, and the output is analogue. i.e it is not PCM anymore, but an analogue signal.
If you pass the signal throught your digital connection to your reciever (be it coax or fibre optic) then the PCM data is extracted from the source and put straight onto that connection without any modification (except to turn it into light pulses rather than electrical with fibre optic connections). This PCM signal is then picked up by your reciever which then passes it through its DAC. From then on, it is an analogue signal.
At no point in either method is any compression taking place. Source direct removes from the signal path any form of tone/effect/etc. processing. Even if the processing is set to do nothing, it still has to pass throught the circuitry. Source direct bypasses this.
Hope that makes sense!
[Edited last by Richard Cooper on October 30, 2001 at 03:12 PM]

 

[Ken_McAlinden]

My opinion would probably vary by title, and I hesitate to provide a hard and fast rule. In general, the films that benefit from a LPCM track are those whose mix is much more reliant on fidelity and clarity than precise location of sounds in a 360 degree field. For instance, given the choice, I probably would prefer a well-mastered LPCM track on the new Funny Girl disc than the full-bitrate DTS track that would take up the same amount of space. I know that I prefer the LPCM sound of The Little Mermaid laserdisc to the DD5.1 track on it or the DVD. The Lion King DD5.1 versus PCM pro-logic is less of a clear cut choice for me as each has its strengths and weaknesses.
By the way, the "L" in Linear Pulse Code Modulation distinguishes it from other schemes like Delta Pulse Code Modulation (DPCM). In LPCM, the digitally sampled value corresponds to the magnitude of the sample curve. In DPCM, the digitally sampled value represents the incremental change from the previous value of the sampled curve.
BTW, does anyone know what the native word size is for Dolby Digital? Is it 16 bit? 20 bit? Can it vary?
Regards,
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Ken McAlinden
Livonia, MI USA

 

[Sean Conklin]

Richard, Adam,and Patrick,
It makes perfect sense, and now that I think about it, you guys are right!!
Thanks!
Ken: Nice breakdown of LPCM! I for one don't know the answer to your quiz, but I'm sure you will tell us!
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Sean
"I was thinking of the immortal words of Socrates who said.......I drank what?"
[Edited last by Sean Conklin on October 30, 2001 at 03:18 PM]