Specifications

5.1-Channel Production Guidelines Production Techniques
5-10
version when the master is not available in the 5.1 format. The question is how to deal
with this latter situation.
The most obvious and best solution is the remix. If original elements such as a multitrack
source tape or individual stems have been archived, then this could provide the source
material to create a new 5.1 version. Of course the original mix should be given due
consideration, preferably by enlisting the help of the original artist or producer.
A difficulty arises when these elements do not exist and the only source material is
the final release master. There is much debate about how best to upmix to create extra
channels from a given source. Most approaches rely on the use of phase relationships
or timing between signals, based on the simple idea that in-phase material should go
to the center channel and out-of-phase material should go to surrounds. See below for
a discussion of some of the benefits and consequences of upmixing using this method.
Two-Track Master
It is usually best to transmit two-channel material, be it matrix-encoded or
conventional stereo, to the consumer in its existing two-channel format, rather than
decoding it in the studio to derive an artificial discrete multichannel mix. The results
of upmixing will vary from the intent of the original producer/director, especially in
the case where extra processing has been added on top of surround decoding in the
studio, perhaps to generate an LFE channel or stereo surrounds. Consequently, the
sound may fail to meet listener expectations for true 5.1-channel material. Upmixing
in this way can never create a truly discrete mix and the effects of the upmixing
system will always be audible.