9/10/2023 0 Comments Reverse audio logic pro x 2017![]() So, an explosion on the right would cause the L,C and S channels to drop.Īs I recall (and we're talking decades back) there was also a number of phase inversion happening to try to isolate the center from L and R. The logic seemed to want to choose between immersion, where all channels are active, and effects, when events would take place predominantly L, C, or R for instance. What I mean by "channel steering" is that there were a number of VCAs (Voltage Controlled Amplifiers) which would, depending on a number of factors, raise and lower the gain of each channel. The first home version to incorporate the channel steering was called Dolby Pro-Logic, and AFAIK, was basically Dolby Stereo for home, and on a chip. The first home version was called Dolby Surround and if memory serves, did not steer at all. While we can mathematically make sense of adding L and R to get a center, removing the center from the L and R signals is quite tricky in an analog realm.ĭolby Stereo (as the pro version was called) steered channels aggressively. When VHS came out of course it was first stereo then Hi-Fi stereo, and they took the tracks as-is from the film versions. You got the encoding right (as far as I can tell) but since Dolby Stereo tried to encode 4 (L,C,R,S) or 5 channels (split surround) into two analog tracks that were actually on the film, the decoding was never this straight forward. What follows here specifically excludes mag-tape movies, and Dolby Digital or DTS. If you know what a CP-50 was, you'll know what I'm talking about. So I know at least the pro end as well as anyone left around. Just quickly, I worked for one of Dolby's competitors and was able to look at the reverse engineered schematics, as well as evaluated our own version. Nice info, Bill, but I don't see an important component here in the thread, which is the channel steering. # (useful for measuring the subwoofer response in REW)Ĭopy: SUB=L L=0.0 R=0.0 C=0.0 RL=0.0 RR=0.0 # the audio on the left channel while muting all other channels of a 5.1 speaker system # Real world example: Replaces the audio on the subwoofer channel with # (not to constant value 2, because no decimal point is present) # Attention: Sets the audio on channel L to the audio on the second channel # Also sets the audio on channel R to the constant value 0.5 # Replaces the audio on the first channel by the audio previously on channel R # plus the audio on channel C attenuated by 6 dB # Replaces the audio on channel L by the audio on channel R # Adds the audio on channel R multiplied by 0.5 to channel L For more information about channel identifiers, see the Channel command. To avoid ambiguity with numerical channel indices, the constant value must contain a decimal point. Instead of channel and factor, a constant value can be specified. Multiple channel assignments can be specified on a single line by separating them with spaces, therefore a single assignment must not contain spaces. ![]() ![]() The factor can also be specified in dB by appending dB. To add instead of replace the audio on the target channel, the target channel itself can also be a source channel. Replaces the audio on the target channel by the sum of the given source channels with optional factors. In particular, we need the copy function: opy (since version 0.9) So you can implement all the filters using APO, and if you're using a HTPC you can have a setup that looks really clean. I love the thing, but it sure is a mess of cables that doesn't look too good in my living room. This is the main reason that I wrote this post I wanted to ditch my MiniDSP. If you're running a home PC, APO can do nearly everything that MiniDSP can do. (Just cut the cable in half, swap the positive and negative, and put it back together.) Obviously you'll want to mark this cable because it could really make troubleshooting confusing Since MiniDSP can't invert an input, you would have to make an RCA cable that inverts it. ![]() 49% of the right channel combined, but the left portion is inverted. IE, to make the left surround channel, we need. Note that the plugin doesn't offer a way to invert the inputs, so I think you'd literally have to make a cable to create the surround with MiniDSP. To produce the rear channels you'll need another miniDSP because four outputs isn't sufficient. Then use the 'delay/gain/rms' tab to adjust the output of the center so that the output is 41% higher than the left and the right. This mono output will correspond to your center channel. Just go to the 'routing' tab of the plugin, and create a mono output. ![]() IE, you can combine a stereo input to produce a mono output, for a sub.īut there's nothing stopping you from using this plugin for Dolby ProLogic II. This plugin is intended for people that want to do sub-satellite setups. ![]()
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