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 Post subject: Re: Dolby Surround vs Pro Logic IIx?
PostPosted: 13 Jan 2014, 00:41 
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signofzeta wrote:
If your listening furniture (sofa, chair, whatever) has its back up against a wall then 7.1 is pointless. If you can't get the speakers several feet behind you the system isn't going to work as designed.


Funny you should say when rear seat rows in cinemas are so close right up to the back wall. You'd think they'd remove at least 4 rows to get some benefits it use of 7.1 or even Atmos but they cram as many seats in as they can.

Also depends on how good a listen you are and how well you can remember what some scenes sounded like in say 3 locations front and centre row middle centre row and rear back centre row. That would cost you on an average at cinema of around $42.00 or more. They don't allow you to stay in the cinema all-day long for the same price like did maybe up until upper early 80's, least in the UK.

But at home you have the scene playing on A & B repeat and sit in several rows at the cost of $14.99 average for a bluray 7.1.

I can hear fair decent pans around the room in back row even with pink noise circling around and around. The close to the back surrounds the tone will sound slightly different with matched speakers and little small EQ adjustments to get the tone close.

Plus the rear back on some films often ether carries effects only or music and effects. STAR TREK INTO DARKNESS only carries sound effects on the rear stereo surrounds while the side wall surrounds carries sound effects and music.

TRON LEGACY carries music and effects on the rear stereo surrounds same with the side wall surrounds.
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 Post subject: Re: Dolby Surround vs Pro Logic IIx?
PostPosted: 04 Jul 2015, 17:28 
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elieb wrote:
okay, 4 questions:
1) when playing back a DTS/AC-3 ld, how improved will it sound when it's upmixed to 7.1?


The same as when you play a DVD or BluRay that's Dolby Digital/DTS 5.1 in up mixed 7.1 mode.

Quote:
2) some ld's have NO lfe on lfe, is this normal?


Yes. Not all LD are encoded with Dolby Surround or have information to be sent to the LFE channel.

Quote:
3) some ld's have mono surround on AC-3, is there a list of mono surround ac-3 encoded movies
and finally.


If there is - I'd love to see it ;)

Quote:
4) how improved will PL2 be on stereo/PL encoded movies, if you selected either 5.1, with lfe as a lowpass or 7.1, simulated back surrounds?


Most often, Pro Logic II will send the frequencies below the crossover to the sub on stereo films. As to whether that sounds better than an up mixed 7.1 (which would also do the same with the low frequencies) - that's up to your own personal taste.

Quote:
i realize you can't play back an AC-3 movie in PL mode, with the lfe. such as die hard 1.

You could play the stereo track in Pro Logic mode. But why would you want to play a discrete surround track as a matrixed one?
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 Post subject: Re: Dolby Surround vs Pro Logic IIx?
PostPosted: 04 Jul 2015, 19:06 
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Old thread but here again,

Both Dolby Stereo (aka Dolby Surround) encoding and decoding was designed keeping the hardware limitations (of late 70s to mind 90s) in mind. Decoding needs to be done in real time. Until late 90s digital decoding is not feasible so it had to be a system which could be done in analog domain.

4 separate tracks namely L R C S matrixed into L R.

L and R are recorded onto L R untouched.

C is reduced in volume by -3db and recorded on both L R. This makes it compatible if it played back on a stereo system. Idential C info played on both L and R combined will have 3db gain and -3db will compensate this.

S is recorded on both L R in out of phase form. L will get -90 degree (advanced in time) and R will get 90 degree (delayed in time) versions of S recorded on them. If played back through stereo system since they are 180 degree out of phase they will cancel each other. S info is also band limited to 8kHz so if any leak occurs to mains, high frequencies won't pinch your ears.


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 Post subject: Re: Dolby Surround vs Pro Logic IIx?
PostPosted: 04 Jul 2015, 19:09 
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Decoding:

Two analog comperators are used.

1- compare L R and idential info is directed to C. Also boost by 3db.

2- compare L R for delay. Out of phase S info is extracted and send to S.

Now since 90s this is done in digital. Entire L R tracks are digitized and digital comperators are used in software.

If the track is dolby encoded the limitations are already applied in encoding so it doesn't matter if you used pl or pl2. Pl decoder should be able to decode dolby surround just as good as pl2. The advantage of pl2 is it can also work with none dolby encoded (plain stereo) soundtracks.
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 Post subject: Re: Dolby Surround vs Pro Logic IIx?
PostPosted: 04 Jul 2015, 19:26 
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Ac-3 is compressed and its fidelity is equal to or less than 192kbps mp3. L R C S LFE are encoded as separate digital streams so no comparing or phase delays like pro logic. its actually a container which houses all streams.

On laserdisc dolby surround is on digital pcm tracks which have fidelity of 1.4mbps( similar to cd). On DVDs dolby surround is on compressed container in 192kbps fidelity.

So you pick your poison here. If you want better channel separation then ac-3 for you. If you want higher fidelity dolby surround will beat ac-3 by a margin.
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 Post subject: Re: Dolby Surround vs Pro Logic IIx?
PostPosted: 04 Jul 2015, 20:41 
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It also depends on the mix, or if there were separate ones done for the formats. With the advent of multichannel mixing they could finally have full stereo separation in the rears and not mono. True four channel mixes will sound fine to outstanding, whereas the folds from a 5.1 track will sound a touch mushy and restrained in comparison. In PCM they can still sound stellar and phenomenal on headphones, but cranked up they will not have the range or separation clarity of discrete 5.1.

For example:

The best PCM matrixed 4 channel mix I've found is on the WS LD of TEMPLE OF DOOM.
A good example of the same mix being used for both PCM matrixed 4.0 and the 5.1 is on the Star Wars Trilogy SE, or the well loved MISSION IMPOSSIBLE LD. On both of these the PCM is great but as soon as you try out that ac3 track...it gets louuuud and in your face!

The big one that bucks the trend is BATMAN FORVER. The 5.1 is great but it does accentuate all the heavy ADR in the center channel, so for this one film the extremely well done Dolby matrixed PCM is not only preferred but essential. Better bass extension, great range, good sense of overall warmth.

Of course this is only discussing LD. As soon as you go into DVD this goes out the window due to that format's heavy re-compression and filtering of all audio for crappy consumer products. Despite the LD 5.1 being limited to 384 kbp/s these are practically theatrical audio tracks with full integrity so that they can not only keep up with their lossless PCM counterparts but usually best them.
Best example of this is for the Burton Batmans. Their LDs featured 2 ch PCM matrix tracks which are awesome. They didn't make it onto LD again and instead wound up as very early DVDs (which from WB were all LD sourced) and has what I can only assume are LD prepped DD 5.1 mixes in 384 kbp/s. On the first film, the LD PCM obliterates the DVD and all successive versions, presumably because they just remixed the PCM track into DD 5.1 without using the source 4ch master.
RETURNS premiered 5.1 in theaters, and I think the DVD track is indeed that milestone audio--but the prints I have seen are all Dolby Stereo and the LD PCM knocks it out of the park.

In short, just remember the PCM 2.0-4.0 version will largely keep the action centered and have a nice meatiness to it at the cost of some of the higher end range. Discrete audio will give better clarity and of course stereo separation.
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 Post subject: Re: Dolby Surround vs Pro Logic IIx?
PostPosted: 04 Jul 2015, 21:56 
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Dolby surround can and does create the front L C R just as good as AC-3. Matrixing C into L R is a very simple process and almost no leaks. Clarity goes to Dolby Surround as well. 1.4mbps pcm will always beat 384kbps compressed. Only thing going for AC-3 is totally discrete rears which human hearing is least sensitive to directions from behind.

Early days of ac-3 they cooked up effect channels to promote the systems. On my system the lossy nature of ac-3 is very obvious. The sound is very dull and boring. Dts is better and fine for films but if there is any musical score on the film pcm is the way
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 Post subject: Re: Dolby Surround vs Pro Logic IIx?
PostPosted: 03 Jun 2016, 22:14 
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substance wrote:
Dolby surround can and does create the front L C R just as good as AC-3. Matrixing C into L R is a very simple process and almost no leaks. Clarity goes to Dolby Surround as well. 1.4mbps pcm will always beat 384kbps compressed. Only thing going for AC-3 is totally discrete rears which human hearing is least sensitive to directions from behind.

Early days of ac-3 they cooked up effect channels to promote the systems. On my system the lossy nature of ac-3 is very obvious. The sound is very dull and boring. Dts is better and fine for films but if there is any musical score on the film pcm is the way


Interesting read this thread. I've observed that ac-3 tracks can be quite "different" and was wondering how much more effort I should into fixing my setup with my demodulator (see other thread). But I should try out some other titles like Batman that I have in my shelf 8-) And maybe just settle with that..
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