Automatic signal selection

[vanbladi]

Hi,
I want an A/V receiver that automatically changes to the right signal type i.e. stereo / 5.1 / dolby surround / ... when my TV channel broadcasts a movie in dolby surround, when before the same channel that I was watching was broadcasting the news in simple stereo.

On my Yamaha it is me that currently has to push the right mode button to switch between modes, and I find this annoying.

What A/V receiver does support this feature ?

Many thanks,
Ivan.

 

[j_garcia]

How old is your reciever? There are very few receivers on the market that don't do this. Also, the Yamahas I've seen have a setting to remember the last method used or auto; if it isn't set to auto, it uses whatever was last used no matter what the signal type is on that input. Most other receivers will also use the last method chosen if you manually selected or "forced" that mode by a button push last time.

 

[Adam]

Ivan, welcome to the forum.

JG is right. A lot of receivers will have an automatic setting that will pick the appropriate sound mode. If you specifically select a certain mode (stereo, pro-logic, etc.), though, the ones I know of will stay with that until you select something else.

I've come across what you're talking about quite a few times, though, and I'm frankly unsure if what JG mentioned (and I parrotted) is the issue. When watching television and listening through two different models of Sony receiver in automatic mode (both at my brother's house and a friend's house), the Sony's never switched out of stereo playback. Even when I was pretty sure that the broadcast was in dolby surround, it still read as stereo. I never tracked down if the receivers weren't recognizing the surround signal or if the television broadcast was actually just stereo. I'm wondering if someone here can enlighten us both on this, because that makes me wonder if the automatic mode is the solution to your problem or not.

 

[darien87]

On my old Denon 2805, you could have it either way. You could set it to always output a certain type of audio, or you could set it so that the receiver selected for you. Perhaps your Yamaha is the same way and you just need to set it to "Automatic".

Give that a shot.

 

[j_garcia]

I am pretty sure all recent Yamahas have the same setting in the receiver setup, even the 5840 I setup for my girlfriend's parents had this feature.

One more question - how do you have the sound connected to the receiver? Is there a cable box? Digital? (optical, coaxial, HDMI?)

 

[AcuDefTechGuy]

The Harman Kardon AVR-247, which I just sold to my brother for $200, can automatically detect the surround sound signal (HDMI, Optical, Coaxial Digital) and play it accordingly, which was nice.

 

[j_garcia]

The Harman Kardon AVR-247, which I just sold to my brother for $200, can automatically detect the surround sound signal (HDMI, Optical, Coaxial Digital) and play it accordingly, which was nice.

Like I said before, it would be quite rare to find a receiver that DIDN'T do this....

 

[vanbladi]

Hi Adam,
Tha's exactly it: my satellite channel broadcasts a movie in 5.1 but commercials are in stereo. I want my AV receiver to switch also to adapt to the 5.1 or stereo signal when there are commercials. can someone try this please as this is the only reason why I would change from my Yamaha who doesn't do this.
Thanks,
Ivan.

 

[Adam]

Ivan,

Quick question: do you have your satellite receiver hooked up to the Yammy using a digital (i.e. coax or optical) connection?

 

[Pyrrho]

I think several people in this thread are mistaken. There is NO WAY a receiver can tell the difference between a 2 channel stereo original signal and a Dolby Pro Logic encoded signal. This is because a Dolby Pro Logic encoded signal is only two channels, which your decoder separates out in a particular manner. If you want to read about this in detail, see:

http://www.dolby.com/consumer/technology/surround.html

http://www.dolby.com/assets/pdf/tech_library/208_Dolby_Surround_Pro_Logic_Decoder.pdf

As you can see from the information at the above links, Dolby Pro Logic starts as a 4 channel signal that is mixed in a particular manner into two channels only. So Dolby Pro Logic encoded material is only two channels, just like 2 channel stereo recordings. A Dolby Pro Logic decoder reverses the encoding process (without, of course, adding back the frequencies that were filtered out for the surround channel, as they are not in the recording to be decoded). You can apply this "decoding" circuitry to any 2 channel source, but if it was not originally encoded for Dolby Pro Logic, you are altering the original to something that was not intended by the engineers who produced the recording.

What a receiver can do is select between Dolby Digital (DD) 5.1, dts and Dolby Pro Logic (DPL) automatically. And many receivers can be set to different settings on different inputs (e.g., stereo for CD input, DD/DPL for DVD input, etc.). But it cannot know whether a 2 channel signal was encoded with DPL or not.

Edited to add:

See also:

http://www.dolby.com/assets/pdf/tech_library/42_DDFAQ.pdf

 

[Adam]

Thanks for the links and the info, Pyrrho. I knew that Pro-Logic was a two-channel mix, but I wasn't aware that a receiver couldn't detect it. Thanks.

 

[darien87]

I didn't know we were discussing Pro Logic. When someone says 5.1, I assume they're talking about Dolby Digital. Pro Logic is ANCIENT history.

 

[Adam]

I didn't know we were discussing Pro Logic. When someone says 5.1, I assume they're talking about Dolby Digital. Pro Logic is ANCIENT history.

Your correct in that the OP is talking about 5.1. That's the actual thing that we're trying to fix. However, I mentioned Pro-Logic earlier on, and the OP responded to that...so I think that Pyrrho was just clearing something up for us.

 

[Pyrrho]

I didn't know we were discussing Pro Logic. When someone says 5.1, I assume they're talking about Dolby Digital. Pro Logic is ANCIENT history.

Reread the opening post:

Hi,
I want an A/V receiver that automatically changes to the right signal type i.e. stereo [emphasis added] / 5.1 / dolby surround / ... when my TV channel broadcasts a movie in dolby surround, when before the same channel that I was watching was broadcasting the news in simple stereo [emphasis added].

On my Yamaha it is me that currently has to push the right mode button to switch between modes, and I find this annoying.

What A/V receiver does support this feature ?

Many thanks,
Ivan.

He is talking about DD 5.1, DPL, and 2 channel stereo. Normally, when one selects Dolby, if there is no DD multichannel signal, the receiver will automatically go with DPL (or DPL II, which is not simply a decoder, but adds additional processing which redirects [misdirects] some of the front channel information to the rear [as the encoded rear channel is NOT full frequency--see links above--and DPL II is full frequency in all channels], and also alters the surround so that the left and right rear are not identical [which is unlike the encoded signal; again, see links above]).

So, as for his problem with preferred modes, most receivers partially solve his problem, but cannot distinguish between DPL and 2 channel stereo. DPL was a clever way to get 4 channels of sound with using only 2 discrete channels.

He should read his owner's manual to see what is possible with his receiver. Unless it is very old, it should allow him to do all that is possible automatically. My Yamaha does the automatic switching that is possible.

 

[Buckeye_Nut]

Hi,
I want an A/V receiver that automatically changes to the right signal type i.e. stereo / 5.1 / dolby surround / ... when my TV channel broadcasts a movie in dolby surround, when before the same channel that I was watching was broadcasting the news in simple stereo.

On my Yamaha it is me that currently has to push the right mode button to switch between modes, and I find this annoying.

What A/V receiver does support this feature ?

Many thanks,
Ivan.

Your Yammi should pass through whatever signal is sent through it providing you have it set to "auto" mode, and have the cabling connected properly. So if you're channel surfing between 2.0 & 5.1 sources.......you shouldnt have to hit any buttons.

 

[j_garcia]

So, as for his problem with preferred modes, most receivers partially solve his problem, but cannot distinguish between DPL and 2 channel stereo. DPL was a clever way to get 4 channels of sound with using only 2 discrete channels.

You are mistaken. ANY DPL/PLII/PLIIx decoding system DOES know the difference between stereo and Dolby Surround encoded signal regardless of whether it is an analog or digital signal and if set to auto, should pick it up. My first receiver could do this over 10 years ago and every receiver I've owned since then does also.

 

[Buckeye_Nut]

The only caveat being.... with my Yammi (because I run 7.1)..... I do sometimes have to manually activate PLIIx. It will always automatically distinguish between 2channel PCM, 5.1, etc, etc, etc.... It's just that sometimes I need to manually activate the matrixed back channels.

 

[Pyrrho]

You are mistaken. ANY DPL/PLII/PLIIx decoding system DOES know the difference between stereo and Dolby Surround encoded signal regardless of whether it is an analog or digital signal and if set to auto, should pick it up. My first receiver could do this over 10 years ago and every receiver I've owned since then does also.

There is no way it could possibly tell the difference, as the whole point of DPL was to put 4 channels onto a standard 2 channel playback system.

Anyone who wishes to test this matter for themselves may do so easily. They may take a DVD that has a DPL soundtrack (not a DD 5.1 soundtrack), load it into their DVD player, and see what their receiver does with it during playback of the movie. Then, they may load a stereo CD into their DVD player, and, without making any adjustments to their receiver, see what their receiver does with it. If you are right, one should be treated as DPL and the other as stereo, and if I am right, both will be treated the same (which one will depend upon the settings of the receiver).

If you are comparing your CD player with your DVD player, most receivers can be set differently for different inputs, so that will not be relevant to the discussion. Both must be played through the same inputs to test the ability of the receiver to distinguish between the different material.

So, I invite everyone to test the matter for themselves, and feel free to post their results.

 

[j_garcia]

The whole point of Dolby Surround encoding is so that the receiver can tell the difference and appropriately choose the decoding option. If I put in a CD, it does not automatically choose DPLII, it chooses stereo. If I put in a DVD and choose a Dolby Surround track, it will choose DPLII.

 

[MDS]

An analog signal that is Dolby Surround encoded, say a TV show, cannot be distinguished from a regular 2 channel analog signal. If you engage the ProLogic or PLII decoder it will follow the steps to extract the surround info - if the signal was surround encoded then doing so will extract exactly what was intended to be extracted; if it was not surround encoded the result is a simulation.

If the signal is digital, like DD 2.0 that was Dolby Surround encoded then it can be identified BUT whether the receiver uses straight stereo or PLII depends on its settings. For example on Onkyo receivers you can specify that for any D.F 2 ch (digital format 2 ch - that's what the menu option is named) you can set it to automatically use stereo or PLII or any other decoder that can operate on a 2 channel digital format. You can manually choose any decoder too after it automatically chooses one.