>> Monday, October 22, 2007
DOn a demo disc there's a demo of Chaos Control with Dolby surround on CD-i and also The 7th Guest features Dolby Surround. But is it real Dolby surround, or false (surround in stereo)? The 7th Guest on CD-i is displayed in widescreen, as are more CD-i games. There are several demonstration discs with widescreen and there are players with a widescreen option built into ROM. Although the CD-i could not output 480p seeing as it lacks the necessary outputs (Composite/SVideo cant transfer 480p video). But does CD-i support the 16:9 signal or does it just stretch the 4:3 format?
I have asked myself the same question, because on 'modest' cd-i players the only audio output is analogue in two channels. But some also have digital output, but I thought this was only for audio cd's. Terratron explains the CD-i Surround Sound issue: "All dolby surround is based on stereo or 2 channel input only if you got an amplifier supporting Dolby Surround you will able to hear all input in a false simulated (by the amp) surround sound. I will show you how it works: Dolby surround is based upon the (semi)quadrophonic technique. The left and right channel are divided with each other so the back speaker will only give a sound that's harder on one of the channels. So in my opinion all the games if played on a Dolby Amp will (if they have some kind of stereo effects) give the full Dolby Surround sound.
Maybe the CD-i titles that have the Dolby Surround logo on it were specially designed for use with a Dolby system so the effects are more realistic. Example of a special Dolby Surround effect: when you quickly switch a sound from the left to the right and back repeating you get the idea the sound is on top of you!"
Also ICDIA has some info about this: "Dolby Surround is an analogue encoding technique that allows for the storage or center and rear audio in addition to the normal left and right stereo signal. Every stereo audio carrier that provides for a high frequency audio reproduction can use Dolby Surround encoding. In CD-i, Dolby Surround can only be used for MPEG audio, since ADPCM does not offer the dynamic range that is necesary for the encoding of the additional channels. Most movies use Dolby Surround, as do several games such as Seventh Guest. Please be aware of the fact that Dolby Surround is an analogue matrixing technique, which does not add extra discrete audio channels. Dolby Digital and MPEG Multichannel are audio encoding techniques that allow for discrete surround channels to be encoded individually. Ususally, this includes two front signals, two back signals, a center signal and a low-frequency subwoofer signal. Both techniques are widely used in DVD-Video. CD-i does not support either of them."
Cdifan explains the CD-i widescreen issue: "On CD-i, "wide screen" means "able to drive the 16x9 signal on the SCART (euroconnector) output". This signal causes widescreen TV's to switch into 16x9 display mode, stretching the incoming 4x3 signal horizontally so that it fills the entire screen. The actual video signal never changes, it remains 768x560 interlaced (PAL); due to restrictions on color resolution and vertical filtering this is really just 384x280 with some resolution enhancement in horizontal and vertical direction. It's no better then plugging a CD-i into a modern TV and using the stretch feature to stretch "full screen". But note that the SCART connector provides (analog) component video so it's a better quality then just composite video!"
Thanks to Terratron and cdifan