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-   -   PCM vs. HD audio codecs (http://www.avrev.com/forum/blu-ray-players/3235-pcm-vs-hd-audio-codecs.html)

RRF743 03-22-2009 06:59 AM

PCM vs. HD audio codecs
 
I've finally given up on LG being able to come up with a firmware update to allow for their bh100 to play the new hd codecs in 5.1 or 7.1. They had an update in Feb. '09. that didn't do anything. So I took the plunge and picked up a BDP-S350. I wanted the panny 35k but they are hard to find without overpaying. My problem is I have a 7.1 theater (room is 14'x24') and love to use 7.1 all the time. The Dolby True hd 5.1 movies are not a problem getting 7.1 beause of the Dolby Prologic IIx feature that will send sound to my surround backs. But when it comes to DTS MA 5.1 movies, the receiver can't send sound to my surround backs. The setting in the Sony player is set to Direct, wich says Straight on my Yammy receiver and the DTS MA indicator is lit but will not let me use the Prollogic IIx feature. So I set the player to Mix instead of Direct and no hd codec indicators are lit. The Yammy reads "PCM + PrologicIIx", which is good because I'm getting the 7.1. The problem is I notice the difference in sound between the Hd codecs vs. the PCM. The hd audio sounds better, more explosive, and easier to hear at lower volumes. Isn't PCM an uncompressed format just as hd audio? Or is the quality of PCM as good as hd audio and I'm only hearing a difference in volume level when the player decodes the hd audio to PCM? If that is the case I would be very happy knowing I'm getting the best audio and 7.1.

bad_fish 03-24-2009 11:53 AM

Re: PCM vs. HD audio codecs
 
You are putting processing on the stream that was not there before. Anytime the stream has to go through processing you are talking about adding DACs and loss. It bothers me as well to know that I have two speakers not getting use during a lot of material, but the quality degradation far out weighs any benefits I feel I get from hearing those two speakers get some exercise. I NEVER EVER EVER EVER EVER EVER process any TrueHD or DTS-MA. They are lossless and you are hearing the best quality, most accurate representation of what you were SUPPOSED to hear. I suggest no one else ever put any processing on them either. DSP, IIx, Neo:6, and the like are all meant for turning crap into acceptable, not quality signal to crap...

my two cents.

meatyb0y 03-24-2009 12:05 PM

Re: PCM vs. HD audio codecs
 
RR -

In theory, there should be no difference between PCM and the DTHD or DTSMA. I wonder if the problem is the ProLogic processing that the receiver is doing? I'm not 100% but isn't ProLogic (even IIx) a matrixed, derived surround mode? I am wondering if your receiver is taking the discrete 5.1 channel sound and matrixing it, likely downsampling it, to process and derive the extra 2 channels. If I am correct (a big "if"), then you are getting 7 channels now, but lower resolution (maybe 16 bit, 48Khz or so), and NOT discrete channels.

If that's the case, then I would stick with straight PCM 5.1 channel or DTHD/DTSMA without engaging ProLogic IIx - you will maintain the higher resolution that way and also maintain discrete surround rather than matrixed. Your earlier post made it pretty clear that you like the sound of the lossless codecs - I would postulate that the vast majority of time, 5 discrete channels are better than 7 matrixed channels. Besides, if you use PCM without Pro Logic, then when you DO run across a disc encoded for 7 channels, you will get all 7 channels. Right now, you may be trying to force usage of those extra 2 channels to your detriment.

And that's really the answer - the reason you don't have 7.1 channels active all the time w/ Blu-Ray is because most of them are currently encoded for 5.1, and forcing ProLogic processing kills the discrete channels and *may* downsample the higher resolution bitrate from PCM.

RRF743 03-25-2009 05:08 PM

Re: PCM vs. HD audio codecs
 
Thanks a lot for the reply guys. What you all say makes sense. There is a huge difference between the dts-ma and the pcm-mix. If I sit in the front row of the theater I may not notice the surround backs not in use as much vs. sitting in the rear row. But Bluray needs to get on the ball with the 7.1 audio. There was a lot of advertisement in the big box stores and on dvd (pre-movie) about 7.1 lossless. The only disc I know of is Narnia. Do you know of any others?

meatyb0y 03-26-2009 04:31 AM

Re: PCM vs. HD audio codecs
 
Quote:

Originally Posted by RRF743 (Post 20157)
Thanks a lot for the reply guys. What you all say makes sense. There is a huge difference between the dts-ma and the pcm-mix. If I sit in the front row of the theater I may not notice the surround backs not in use as much vs. sitting in the rear row. But Bluray needs to get on the ball with the 7.1 audio. There was a lot of advertisement in the big box stores and on dvd (pre-movie) about 7.1 lossless. The only disc I know of is Narnia. Do you know of any others?

Googled it, found this list - don't know how accurate it is:
http://forum.blu-ray.com/showthread.php?t=91824

It's actually quite a bit longer than I expected, if it's correct. Sounds like you have a real theater type setup that can benefit from the extra 2 channels. I'd still rather have lossless high resolution than the extra 2 channels (and PCM is lossless, high resolution, just like DTSMA and DTHD), but if you can get it all, then that's great, so motor on, friend!


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