A little help for a noob regarding DTS, DTS HD, and downmixing

[neelshiv]

Hey guys. My parents have a bit of a home theater setup in their basement (most of it came with the house), and they received a blu ray player as a gift for last christmas. Up until about a month ago, the only dvd's that they had were The Dark Knight and Transformers, but they then bought Marley and Me. They called me and asked me why the sound wasn't working, but I was over 500 miles away, and couldn't really help.

I just got home a few days ago, and tried it out. I found that the non-english tracks were working, and I assumed that the disc was defective. They then bought Slumdog Millionaire, and it had the same problem. It was then that I put one and one together (or perhaps some more complex equation, like two and two) and realized that audio tracks labeled "DTS HD" were not working. Batman and Transformers did not have these, which explained why they worked.

I then looked into the blu ray players settings (a sony BDP-BX1), and messed around a bit. I know relatively little, but there were also very few options for most of the dialogs, so I worked something out.

Our receiver is an older yamaha rx-v992, and it is capable of dolby digital. The player is connected to it via an optical cable, and it is connected to the projector via an hdmi cable.
Our player has the options of "downmix pcm" and "dolby digital" for dolby digital output, and it is set to dolby digital. It sounds great. When watching a movie, the player displays "Dlby Digital" on the front and everything is in order.

The DTS output setting used to be DTS, but it is now set to Downmix PCM. We now get sound when watching these movies, but the receiver displays "Pro Logic", with the letters text "PCM Digital" under that. Sound certainly comes out of all speakers, but I don't really know much about whether or not it is the same rear speaker sound that DTS output would get.

Another setting that may be relevant is the "Downmix" field, which has the options Dolby Surround (selected) and Normal.

*Does this seem like the best setup we can achieve for DTS audio tracks? How does it differ from an actual DTS output? I believe somebody has told me it is lossy, but that is not our greatest concern. We mostly care about getting actual 5.1 sound (which the previous owners had not set up correctly for the several years they lived here).


Sorry for the lengthy post. It really boils down to one question (precluded by an asterisk), but I felt that it required a bit of setup and back story.

[callas01]

It sounds as if the receiver cannot process DTS surround sound at all whether the core DTS or DTS HD(lossless), so if the Blu-ray player downmixes to PCM (I think its stereo basically) which is 2 channel then the receiver is creating a virtual surround sound, like its matrixing, but matrixing is outputting unique sounds from seperate speakers, but then if all the speakers are outputting the same sound then you are not getting matrixing, you are getting virtual speakers, which is not surround sound. If you are not getting unique sound from each speaker, then you need to get a new reciever capable of outputting DTS or DTS HD.

[J6P]

Hello, and welcome! It looks right to me.

The BDP-BX1 is a Costco-specific version of the BDP-S350, I believe. So they should have exactly the same capabilities.

The S350 does have a Dolby TrueHD decoder (the "lossless", highest bitrate version of Dolby Digital) onboard, but not a decoder for DTS HD Master Audio (the DTS equivalent). It can, however, stream both codecs over HDMI. So, if your parents were able to connect this player via HDMI to a receiver that did the decoding (which the Yamaha doesn't do, as you state) they would be able to hear uncompressed Dolby and DTS.

But in the here and now, since even decoded Dolby TrueHD and DTS HD MA cannot be sent over an optical connection (only HDMI), you've made the right choice by having DTS decoded and downmixed by the player. The Yamaha can decode the Dolby lossless track down to its lossy core (still 5.1), but it can't decode the lossy DTS core. By downmixing the lossy DTS core in the player, and outputting it as PCM, you should be all set. That's giving you true, discrete 5.1 sound, just not full bitrate, lossless 5.1 sound.

I'm pretty sure, anyway!

If your parents wanted to upgrade someday, an A/V receiver that decodes both HD codecs and receives the signal via HDMI can be had for 2 or 3 bills nowadays. It's getting much more affordable. I'm sure they'll like the sound now, but they have room to grow down the road.

[neelshiv]

Thanks for the info, everybody. The audio coming out of each speaker is certainly unique (or at least I can say that about the front three), but the rear speakers do not seem to do a lot (may be the movie). I had the feeling that their sound was just being computed by some sort of process, and if I understand what you said correctly, that's what is happening.

BIslander, you mentioned that optical connections can not transfer surround pcm. Would this work any better if I used the coaxial output? We have one of those connected to our cable box, and I'm sure the cable box would be just fine if we switched the two.

Speaking of which, is coaxial superior to optical in any way? I feel like we might want to connect the better of the two to the blu ray player. They probably watch more tv than they do movies, though, so perhaps the better of the two should be on cable. Honestly, I dont know that any of us would notice the difference.

Thanks for the help.

[BIslander]

Originally Posted by neelshiv

Thanks for the info, everybody. The audio coming out of each speaker is certainly unique (or at least I can say that about the front three), but the rear speakers do not seem to do a lot (may be the movie). I had the feeling that their sound was just being computed by some sort of process, and if I understand what you said correctly, that's what is happening.

With Dolby Surround encoding as part of the downmix process in the player, the surround information is not being matrixed. It's actually a discrete channel taken from the original 5.1 mix. But, it's sent as mono and fed to both surround speakers by your receiver. So, it will never sound as good as two discrete surrounds.

BIslander, you mentioned that optical connections can not transfer surround pcm. Would this work any better if I used the coaxial output? We have one of those connected to our cable box, and I'm sure the cable box would be just fine if we switched the two.

No. Optical and coax both use the S/PDIF protocol when transmitting audio. S/PDIF is limited to two channels of PCM.

Speaking of which, is coaxial superior to optical in any way? I feel like we might want to connect the better of the two to the blu ray player. They probably watch more tv than they do movies, though, so perhaps the better of the two should be on cable. Honestly, I dont know that any of us would notice the difference.

No. There's no difference that would matter.

[neelshiv]

Gotcha. I suppose that this current setup is pretty much reaching its full potential, then. Thanks for the help.

They are considering upgrading, but they are not in any hurry. I don't think that an upgrade would serve them in any real noticeable way, and I think they feel the same way.

Thanks for the help. It will certainly make it easier for me to understand what I am getting when I start buying a system in the next year or so.

[BIslander]

Since your AVR can't decode DTS, you have to do the decoding in the player and send it PCM instead. The PCM setting tells the player to decode DTS into 5.1 PCM.

And, since you are using an optical connection, which doesn't support multichannel PCM, the player downmixes to stereo for a 2.0 output.

But, by selecting Dolby Surround when downmixing, the player actually takes four channels (L,R,C, and one mixed surround) and folds them into the stereo signal. The ProLogic decoder in your receiver then pulls the center and surround out of the stereo mix, giving you four discrete channels. Dolby Surround is the technique that was used on VHS.

Congratulations on finding the best possible set-up for playing back a DTS track with your receiver. You have real left, center, and right channels. The receiver sends the mono surround audio to both surround speakers. There's no separate subwoofer channel for LFE, although bass management may still send low frequencies from the main channels to the sub.

Originally Posted by J6P

The Yamaha can decode the Dolby lossless track down to its lossy core (still 5.1), but it can't decode the lossy DTS core. By downmixing the lossy DTS core in the player, and outputting it as PCM, you should be all set. That's giving you true, discrete 5.1 sound, just not full bitrate, lossless 5.1 sound.

A couple of corrections:

With TrueHD, the player is not sending the lossless version to the receiver over optical. Rather, it is sending a DD 5.1 track. That's what the AVR is decoding. The Yamaha would be unable to do anything with a TrueHD track if it were sent by the player.

With DTS, the player is not sending out discrete 5.1 over optical, as described above in my post. It's a stereo signal, but with two extra channels embedded in the stereo information.

[got rice]

BI,
Does his AVR and BDP have analog outs? If so, you can explain better than me.

I just looked up his receiver on yamaha and it does offer 5.1 preouts and the Sony350 has 7.1 pre outs. So I'm thinkning this may be his best solution. What do you think?

[BIslander]

Originally Posted by got rice

BI,
Does his AVR and BDP have analog outs? If so, you can explain better than me.

The AVR might. But, the player doesn't. The S350's analog output is just stereo.

[got rice]

Originally Posted by BIslander

The AVR might. But, the player doesn't. The S350's analog output is just stereo.

OK just a thought.

Edit: his avr has pre-outs not multichannel in. my mistake.

[v_squared123]

Originally Posted by BIslander

Since your AVR can't decode DTS, you have to do the decoding in the player and send it PCM instead. The PCM setting tells the player to decode DTS into 5.1 PCM.

And, since you are using an optical connection, which doesn't support multichannel PCM, the player downmixes to stereo for a 2.0 output.

But, by selecting Dolby Surround when downmixing, the player actually takes four channels (L,R,C, and one mixed surround) and folds them into the stereo signal. The ProLogic decoder in your receiver then pulls the center and surround out of the stereo mix, giving you four discrete channels. Dolby Surround is the technique that was used on VHS.

Congratulations on finding the best possible set-up for playing back a DTS track with your receiver. You have real left, center, and right channels. The receiver sends the mono surround audio to both surround speakers. There's no separate subwoofer channel for LFE, although bass management may still send low frequencies from the main channels to the sub.

A couple of corrections:

With TrueHD, the player is not sending the lossless version to the receiver over optical. Rather, it is sending a DD 5.1 track. That's what the AVR is decoding. The Yamaha would be unable to do anything with a TrueHD track if it were sent by the player.

With DTS, the player is not sending out discrete 5.1 over optical, as described above in my post. It's a stereo signal, but with two extra channels embedded in the stereo information.

Um so I have the same bluray player and a old receiver that can do dts and dd and has Dolby pro logic 2. I'm trying to get two channel PCM which is lossless right? So I set the dts mix to downmix PCM in the Sony player and then down mix PCM i choose Dolby surround but there is also normal which is for receivers that don't decode Dolby right? But when I play thmovie and press display I see it's says 48hz 3/2.1 dts and on the receiver the linear PCM is lit up and the prologue 2 is lit up. I only want sound that is lossless PCM sound for two channel not all 5. So why is it showing me 3/2.1 dts then? The coaxial cable is able to do this right? I'm confused. My receiver is broken

[v_squared123]

In the Sony manual it's say the downmix method can be Dolby surround for receivers who have it and normal for avrs who don't have Dolby surround. Here I choose Dolby surround right? Because it should downmix it all into two channels only? If I choose normal should it not still do the same thing and downmix it all to two lossless channels?

[BIslander]

I am a bit confused by what you want to accomplish. If you have a 5.1 system that lacks HDMI and/or lossless decoders, you will be best served by using an optical connection to feed DD 5.1 and DTS to the receiver for decoding. They aren't lossless. But, the high bitrate lossy codecs on BD rival lossless in quality. Stereo PCM, regardless of resolution, will never compare favorably with a genuine 5.1 mix.

Meanwhile, since your player lacks a dts-MA decoder, it will have to decode the lossy DTS core to produce a stereo PCM output. Since the source is the same lossy core either way, you're much better off having your AVR do the decoding to produce 5.1 instead of stereo.

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