Hi
I have yamaha rxv657 reciever. i would like to know which mode do i put on to decode surround sound which is fed in. like if its a dts movie dvd. my mate usually uses surround decode mode to do this on his rxv861 but i dont have this option.
thanks in advance.
I don't mean to sound rude, but have you read your owner's manual? If you have lost it, you can download one from Yamaha's web site (though you may have to register to do that; registration is free).
I believe that your receiver has a mode for automatically selecting dts or Dolby Digital or another mode (your choice, to a degree) depending on the input signal. But to know the setting on your particular model, I would need to look at the manual.
As for what surround mode to select for 2 channel dvd sound, I would use Dolby Pro Logic (DPL), but you may use whatever DSP (Digital Signal Processing) mode you want that your unit will do.
What follows may be more technical than you care to read at the moment, so feel free to stop reading now. The reason I would select DPL, and not another mode, is that with DPL encoded material (that will be broadcast as 2 channel, or put on a DVD as 2 channel), the original mix in the studio is 4 channels, and DPL will decode it as the original 4 channels. The 4 channels are the front right, front left, front center, and rear (also called "surround", which is why it is "S" in the quote below). These four channels are then mixed together down to two channels in a special way:
The L and R inputs go straight to the Lt and Rt outputs without modification. The C input is divided equally to Lt and Rt with a 3 dB level reduction (to maintain constant acoustic power in the mix). The S input is also divided equally between Lt and Rt, but it first undergoes three additional processing steps:
• Frequency bandlimiting from 100 Hz to 7 kHz.
• Encoding with a modified form of Dolby B-type noise reduction.
• Plus and minus 90-degree phase shifts are applied to create a 180 degree phase differential between the signal components feeding Lt and Rt.
From:
http://www.dolby.com/assets/pdf/tech_library/208_Dolby_Surround_Pro_Logic_Decoder.pdf
Your DPL decoder at home reverses this process to give you 4 channel sound from a two channel source. This whole scheme was developed for theaters to use, so that there would only need to be two channels of sound on the film. There was not room on the film to easily add more channels, and also, this way, they could use existing projectors with two channel readers, which then feed the signal to a special decoder. But it also is perfect for two channel VCRs and 2 channel sound on analog TV.
Now, of course, they can do sound differently than when DPL was invented, and they can keep the channels totally separate from each other. Dolby Digital and dts (in their 5.1 versions) do just that.
Now, other surround modes enable one to make up channels that never existed in the original recording studio. This is what happens, for example, when you apply DPL IIx to an ordinary two channel CD. The recording studio did not have a mix for 7.1 sound; they had a two channel mix. The processing that is done at home in this case moves sound that was intended for the front right and left speakers to other places. Hence, it re-directs, or mis-directs, the sound to other places. Now, whether this creation of previously non-existing channels is a good thing or a bad one is a matter of preference. But it simply is not what was originally mixed, whereas the result of using DPL on a DPL encoded movie soundtrack is not creating any new channels that did not previously exist, but is only recreating what was in the mixing studio before it was forced onto only two channels.
