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LtRt to LR question
#1
If I have a FLAC or WAV file encoded as LtRt and it gets converted to LR/L0R0, will that affect the matrix decoding for Dolby Surround playback. In other words will the LR/L0R0 no longer be able to properly play back as LRCS?
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#2
Dolby Surround isn't something that's digitally encoded into the audio stream. Unless you did something to change the audio itself the DS decoder should see it the same.
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#3
(2023-04-13, 02:00 PM)stwd4nder2 Wrote: Dolby Surround isn't something that's digitally encoded into the audio stream. Unless you did something to change the audio itself the DS decoder should see it the same.

Thanks for the reply. So its doesn't matter what MediaInfo reports the channel layout as since the phasing for Dolby Surround is baked into the audio mix already, correct? To give you an example of what I am talking about, here is what MediaInfo reports for the Dolby track on the Scarface UHD disc. Notice the channel layout.



ID :
4
Format :
DTS
Format/Info :
Digital Theater Systems
Codec ID :
A_DTS
Duration :
2 h 49 min
Bit rate mode :
Constant
Bit rate :
768 kb/s
Channel(s) :
2 channels
Channel layout :
Lt Rt
Sampling rate :
48.0 kHz
Frame rate :
93.750 FPS (512 SPF)
Bit depth :
24 bits
Compression mode :
Lossy
Stream size :
933 MiB (1%)
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#4
Bitstream formats like DTS might have a flag for matrixed surround, which might affect how it's upmixed. I'm not 100% sure there.
But any PCM format will be treated the same by the upmixer.
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Thanks given by: uVSthem
#5
I've read a few threads around these parts, but I'm still a bit confused on how to play a 2.0 track with modern AVRs.

Here's what I've read so far:
- What the hell is "2.0 Surround" anyway?
- List of releases using Dolby Pro Logic and other matrixed surround stereo tracks? (this thread contains 2 pdfs from Dolby listing all(?) Dolby Stereo films)
How was matrixed audio mixed?

A few questions:

- I understand that the "Dolby Surround" upmixer on modern AVRs is not "authentic" in the way it de-matrixes Dolby Stereo. But absent an SDU4 or old AVR with ProLogic, is it generally more "authentic" to listen to a Dolby Stereo track in LR only, or still engage Dolby Surround? I have a 5.1 setup.

- I have my Yamaha AVR (RX-V6A) set to the "straight" mode and my players all bitstream to it, and I've never seen it automatically engage Dolby Surround on any soundtrack (1.0, 2.0, 5.1, etc). I thought I read that at least older AVRs would engage ProLogic automatically. Is there a flag in PCM/DTS/TrueHD that signals Dolby Stereo content? Should I manually set my AVR to "surround decode" mode when I know I'm listening to a Dolby Stereo track?

- The other day I was watching Kino's The Usual Suspect (1995) UHD. Someone on the B-R.com forum mentioned that the DTS HD-MA 2.0 there is nearly identical to the LaserDisc's 2.0, and that the poster says Dolby Stereo SR (4.0). So, I tried manually engaging Dolby Surround on the 2.0 track. The result was really a mess. Dialog wasn't anchored to the center channel at all—a lot of it was leaking to the surrounds. The entire mix just sounded weird, for the lack of a better word. It was almost nauseating. Switching back to LR only was much better. Is that just how bad the Dolby Surround upmixer is? Was The Usual Suspect's 2.0 track actually matrixed?

Thanks in advance!
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#6
TBH I just leave my AVR in Neural-X mode all the time. I think it handles old Dolby Surround tracks better then DSU and handles regular stereo tracks/music and 5.1 sources pretty well.
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#7
I believe the main issue with Dolby Surround and the DTS equivalent on modern AVRs is that the decoder isn't trying to spread the stereo signal out to 4 channels. It's trying to spread the signal to out all the channel so you're get 5.1 or 7.1 instead of 4.0.

Someone please correct me if I am wrong.
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Thanks given by: axeyou
#8
(2023-05-13, 04:16 PM)uVSthem Wrote: I believe the main issue with Dolby Surround and the DTS equivalent on modern AVRs is that the decoder isn't trying to spread the stereo signal out to 4 channels. It's trying to spread the signal to out all the channel so you're get 5.1 or 7.1 instead of 4.0.

Someone please correct me if I am wrong.

As far as I know, there's no way to get just the 4.0 mix using just a modern avr. If you really care about this (i dont think it's worth the time), there are free tools you can use to separate the 2.0 mix into a separate 4 channel mix that should then play properly on a modern avr. This would give you the choice between the 4.0 mix or upmixed to w/e your setup is. There is at least one group online that separates 2.0 mixes into 4.0.

Both dolby surround and neural-x do a fine job on matrixed surround tracks. If you switch one of these on and you don't get speech from the center channel on a 2.0 mix, it's not matrixed surround.
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Thanks given by: axeyou
#9
I'm not saying dolby surround and neural-x do not work, I'm saying that they are not reliable for reproducing the original 4.0 as intended. Even if you end up getting nice sounding split surround channels, that's not how it was originally presented. I wish modern AVRs gave a choice between Dolby Surround, Pro Logic IIz and Atmos.
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#10
(2023-05-14, 08:36 PM)uVSthem Wrote: I'm not saying dolby surround and neural-x do not work, I'm saying that they are not reliable for reproducing the original 4.0 as intended. Even if you end up getting nice sounding split surround channels, that's now how it was originally presented. I was modern AVRs gave a choice between Dolby Surround, Pro Logic IIz and Atmos.

of course they aren't 1:1 exactly the same, but imo the difference between the raw 4.0 mix, from prologic iiz, and what my avr adds via upmixing isn't enough to drastically change the experience. these upmixers are so good these days, i'd argue it probably improves it, especially if the 4.0 mix is great to start with.

you could always pick up a $20 avr at the thrift store and test it out though.
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