Originally posted by: El Lono
So, to recap:
The 2 channel PCM, actually contains further channels, that can be read and divided by a Dolby decoder/reciever, so you have split these channels and recombined them to 5.1?
It's called Dolby surrond is teally a MATRIXED stereo track...
Dolby Surround 101 - The Matrix
Clearly, the concept is to store additional audio channels on two conventional stereo channels. The technique is to "matrix" the audio channels, a concept originally conceived and patented by Peter Scheiber and subsequently applied by Dolby Laboratories. Simply stated, if the sound mixer wants to place a sound in the front center speaker, he would add that signal at equal amplitude and equal phase to both the left and right stereo channels. If the sound mixer wants to place a sound in the surround speakers, he would add that signal to the left stereo channel shifted by 90 degrees, and add the same signal to the right channel shifted by -90 degrees (so the surround information is of equal amplitude and 180 degrees apart - inverted - on the stereo channels). When such a matrixed stereo program is passed through a Dolby decoder, the sum of the left and right becomes the center. (The center is needed to position certain sounds at the center of the screen for off-center viewers, dialog in particular.) The difference between the left and right channels becomes the rear. I'll remind you that Dolby Surround channels are indeed monaural. The disadvantage of this passive decoding system is that separation between adjacent channels (L-C, R-C, R-S, or L-S) is only 3 dB.
Dolby Surround 102 - Pro Logic
Dolby Pro Logic enhances Dolby Surround by using a number of techniques to increase the separation between adjacent channels. Cancellation subtracts the left channel from the right and subtracts the right channel from the left. This has the effect of greatly reducing sounds intended to be directed to the center speaker in the left and right channels; signals that are common to both left and right are removed. Pro Logic controls this process by detecting sound dominance and its direction. If a sound is found to be significantly louder in any one direction such that it exceeds a predefined threshold, a fast acting voltage controlled amplifier enhances the dominant signal. These techniques may yield adjacent channel separations in excess of 30 dB for static test signals, but may exhibit problems for dynamic program material. (For the sake of this discussion, I'll omit descriptions of such manipulations as phase and pitch shifts to diffuse the surround sound, rear channel bandwidth limitations, and noise reduction - these processes are not relevant to front channel processing of Dolby Digital surround channel information.)
So, to recap:
The 2 channel PCM, actually contains further channels, that can be read and divided by a Dolby decoder/reciever, so you have split these channels and recombined them to 5.1?
It's called Dolby surrond is teally a MATRIXED stereo track...
Dolby Surround 101 - The Matrix
Clearly, the concept is to store additional audio channels on two conventional stereo channels. The technique is to "matrix" the audio channels, a concept originally conceived and patented by Peter Scheiber and subsequently applied by Dolby Laboratories. Simply stated, if the sound mixer wants to place a sound in the front center speaker, he would add that signal at equal amplitude and equal phase to both the left and right stereo channels. If the sound mixer wants to place a sound in the surround speakers, he would add that signal to the left stereo channel shifted by 90 degrees, and add the same signal to the right channel shifted by -90 degrees (so the surround information is of equal amplitude and 180 degrees apart - inverted - on the stereo channels). When such a matrixed stereo program is passed through a Dolby decoder, the sum of the left and right becomes the center. (The center is needed to position certain sounds at the center of the screen for off-center viewers, dialog in particular.) The difference between the left and right channels becomes the rear. I'll remind you that Dolby Surround channels are indeed monaural. The disadvantage of this passive decoding system is that separation between adjacent channels (L-C, R-C, R-S, or L-S) is only 3 dB.
Dolby Surround 102 - Pro Logic
Dolby Pro Logic enhances Dolby Surround by using a number of techniques to increase the separation between adjacent channels. Cancellation subtracts the left channel from the right and subtracts the right channel from the left. This has the effect of greatly reducing sounds intended to be directed to the center speaker in the left and right channels; signals that are common to both left and right are removed. Pro Logic controls this process by detecting sound dominance and its direction. If a sound is found to be significantly louder in any one direction such that it exceeds a predefined threshold, a fast acting voltage controlled amplifier enhances the dominant signal. These techniques may yield adjacent channel separations in excess of 30 dB for static test signals, but may exhibit problems for dynamic program material. (For the sake of this discussion, I'll omit descriptions of such manipulations as phase and pitch shifts to diffuse the surround sound, rear channel bandwidth limitations, and noise reduction - these processes are not relevant to front channel processing of Dolby Digital surround channel information.)
Ripped from DVDFILE.com
Dig?
BONG!
Snoogins...