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Dolby Prologic IIz vs DolbyTrueHD / DTS Master Audio

post #1 of 7
Thread Starter 
My current old 2004 Pioneer receiver can do Prologic IIx but I am upgrading to a Pioneer SC-67 and had a few questions.

On my old receiver soundwise, I noticed a BIG difference between Prologic II and Dolby Digital or DTS. There was just a much more open lush sound with DD/DTS.

So I am looking forward to experiencing the lossless TrueHD and DTS Master Audio sound. My new receiver will also be able to do ProLogic IIz which I am intrigued about, particularly with Front Height speakers.

My BIG question is, by using IIz and gaining those Height Speakers, am I foregoing the lossless audio for TrueHD or DTSMA?

Does IIz matrix from the DD/DTS 5.1/7.1 audio stream? Or matrix from the 2 channel stereo audio like ProLogic IIx? I might be making incorrect assumptions here with how it works so I would welcome some clarification.

I am trying to decide if I want to buy some speakers for front height ability. I would love to have those presence, but wouldn't want to forego that great lush sound from lossless DD/DTS.
post #2 of 7
No, not forgoing the lossless audio and AFAIK the DD PLIIz audio is derived from the SL/SR speakers.
post #3 of 7
Thread Starter 
So it is applied to the DD track and not the 2 channel stereo track?
post #4 of 7
You're conflating two different technologies: data compression/packing vs surround processing.

Dolby Digital and DTS are lossy compression technologies, like MP3 and AAC. The goal is to reduce the amount of data with minimal loss of sound quality. They can be any number of channels, from 1.0 to 5.1 (6.1 for DTS). Dolby TrueHD and DTS-HD Master Audio are lossless packing algorithms, like zipping a computer file to take up less storage space. The goal here is to pack all the data more efficiently while keeping it bit-for-bit identical to the original. They can be any number of channels, though the Blu-ray spec only allows for up to 8 (7.1) discrete audio channels.

By comparison, Dolby PLIIx and PLIIz are surround processing technologies, which scale the number of channels in the source material to the number of speakers in your set-up. For example, PLIIx can scale 2-channel and 5.1-channel sources to 7.1 outputs. PLIIz can scale sources to 9.1 outputs (7.1 plus heights). Doesn't matter if your source is lossy or lossless, stereo or surround, Dolby or DTS (or even uncompressed PCM). The surround processing algorithms from both companies are format agnostic, so you can use them on any source.

So it's not a question of choosing between PLIIz and DTS-HD MA, since one can be used with the other (just as you don't have to choose between a frying pan and a raw egg, since they are typically used together). Applying surround processing to a lossless source doesn't stop it from being lossless (any more than frying an egg stops it from being an egg).
post #5 of 7
Quote:
Originally Posted by sdurani View Post

You're conflating two different technologies: data compression/packing vs surround processing.
Dolby Digital and DTS are lossy compression technologies, like MP3 and AAC. The goal is to reduce the amount of data with minimal loss of sound quality. They can be any number of channels, from 1.0 to 5.1 (6.1 for DTS). Dolby TrueHD and DTS-HD Master Audio are lossless packing algorithms, like zipping a computer file to take up less storage space. The goal here is to pack all the data more efficiently while keeping it bit-for-bit identical to the original. They can be any number of channels, though the Blu-ray spec only allows for up to 8 (7.1) discrete audio channels.
By comparison, Dolby PLIIx and PLIIz are surround processing technologies, which scale the number of channels in the source material to the number of speakers in your set-up. For example, PLIIx can scale 2-channel and 5.1-channel sources to 7.1 outputs. PLIIz can scale sources to 9.1 outputs (7.1 plus heights). Doesn't matter if your source is lossy or lossless, stereo or surround, Dolby or DTS (or even uncompressed PCM). The surround processing algorithms from both companies are format agnostic, so you can use them on any source.
So it's not a question of choosing between PLIIz and DTS-HD MA, since one can be used with the other (just as you don't have to choose between a frying pan and a raw egg, since they are typically used together). Applying surround processing to a lossless source doesn't stop it from being lossless (any more than frying an egg stops it from being an egg).

I don't know if I'm tired but it took me awhile to get your egg analogy lol
post #6 of 7
PLIIz should work with 2CH source but it must engage PLII(x); you can't just have the front mains and FH. If FH really only uses surround info then I don't know if it applies PLII first, then uses the surround info in the new channels for the FH or does it directly from the the original 2CH. For music it doesn't make sense using surround info in front, OK for rain drops and helicopters in movies. It's also unsatisfactory because there are only three levels you can adjust and that's too crude generally.

One should also lower the expectation for the audible difference (if any) between lossless and lossy. This has been covered many times.
post #7 of 7
Thread Starter 
Thanks sdurani and others for your explanations. Very big help in me understanding the differences! smile.gif
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