Originally Posted by chros
I have been thinking about the stereo channel upmix:
1. matrix mixer only supports 5.1 channels, so who has 7.1/9.1 systems they can't use it with the rest. (I currently only have 5.1 setup, but I plan to buy 2 more to make it 7.1 as my receiver supports it)
2. maybe it's not that simple to just duplicate the 2 channels to the backs and to the rest:
- maybe some additional things has to be considered (like phase, e.g. if I'd use 2 subwoofers they should have been using different phase)
- my Yamaha RX-A830 has extra modes with 7.1 stereo: Monaural on or off (I couldn't find any info about it what it does with or without it)
The Maiko plug-in was the only Winamp plug-in I ever found that could correctly support more than 6 channels.
Multi-channel sound systems are currently best used for reproducing movie and game soundtracks. The intent is to position the sounds to provide a realistic experience. If the sound system has enough channels then sounds can come from any direction. For example in a game, you can hear something approaching from directly behind you, or behind you but off to the left or right side, or coming from beside you on the left or right, or coming from directly in front of you or in front but off to the left or right side. This positioning of sounds is used similarly in movies.
For music, the sound stage is usually in front of you (or off to the front left or right at a live performance). There is no direct sound behind you (unless you turn around). There can be reflections (echoes) from various surfaces behind you.
The ".1" in multi-channel sound systems represents the LFE (low-frequency effects) channel. This channel is intended for sound frequencies that you feel (at sufficient volume), you don't really hear them. It is not a bass channel. The LFE channel is best used connected only to a subwoofer. Bass sound frequencies should be sent to ordinary woofers or appropriate mid-range speakers.
A six channel (5.1) system has a front center, front left, front right, and LFE channel. The other 2 channels can be used as left side or left rear and right side or right rear. Some 5.1 sound cards/chips are designed to use these 2 channels as side or rear channels only. But you are free to position and connect your speakers any way you want. However when gaming, sounds coming from the wrong direction can be the difference in winning or losing.
A seven channel (6.1) system adds a rear center channel. A eight channel (7.1) system does not have a rear center channel, but adds separate left and right, side and rear channels. A nine channel (8.1) system adds a rear center channel to the 7.1 arrangement.
When listening to music with a multi-channel sound system, some people just want to hear music from all of their speakers. Some don't care if the sounds from each speaker are different and some don't want the sounds to be different. The Yamaha RX-A830 monaural mode
is used to make the sounds sent to each speaker (except for the LFE channel) be the same.
Some want to hear stereo sound from the front left and right speakers mirrored to the rear and/or side left and right speakers. Some want to hear the left and right sounds merged in the front center (and/or rear center) speaker and some don't want to hear anything from the front center (and/or rear center) speaker.
I prefer to hear different sounds from each of my speakers in my 5.1 system. This is why I use the matrix mixer plug-in. This plug-in has built-in stereo up-mixing modes or lets the up-mixing be configured manually. In manual mode, the stereo (or mono) input channels can be mirrored to any other output channel desired or carefully altered so that different portions of these input channels can be sent to any other output channel desired (simulating surround sound with slightly to substantially different sound coming from each speaker). An LFE channel can be derived from the stereo (or mono) input channels and sent to a subwoofer and/or mixed in with the other output channels. If the manual mode is not used correctly, the input sound can easily be turned into a bunch of noise. If the source (input) is already multi-channel, this plug-in can be used to direct these inputs to the intended outputs.
The matrix mixer plug-in uses a modified version of the free AC3Filter. Here is a link (http://www.ac3filter.net/wiki/AC3Filter_Help
) to some technical info on the AC3Filer, some of which can be applied to setting up the matrix mixer plug-in.
Knowing the method used to encode a stereo music file (stereo, joint stereo, or dual channel) is also useful to making a successful manual surround sound up-mix. It is not a 'one size fits all' kind of thing.