hi all,
some basic things about surround :
5.1 or more ?
5.1 is the universal standard in surround, this means that it is the only mode that can be played back, others exist but need some specific materials (hardware and audio)
5.1 means :
- 5 (sattelite) channels:
Left
Right
Center
Left surround (rear left)
Right surround (rear right)
- 1 LFE (Low frequency effects) Channel
How to play it :
the audio channels (5+1) are multiplexed in a digital file .
The main formats are AC3 (Dolby digital) DTS , WMA (free encoders from bill gates
) there are many others but in fact the only ones we find on medias are AC3 and DTS.
Audio is usually in 16 bits 48 Khz but you can do what you want with the encoder ...
you need a specific encoder to "mutiplex" the audio channels in a AC3 or DTS file ...
So you need a decoder to play it ...
The main media that contains surround digital files are DVD , even without video ...
in fact you can burn it on what you want, but practically, only DVD players (hardware and software) understand the files AC3 or DTS : note that some HW DVD players also contains the decoder and ouput the six channels (analog and generally on cinch)
but the multiplexed digital files is generally outputed via optical or coaxial connector and goes in a AV receiver amp that decodes the media and play it on 5+1 channels.
Note that DTS is better (soundly speaking) that AC3 while WMA is very correct, let's say better than the others ...
The reason is quite simple ... AC3 is older than DTS that is older than WMA ...
AC3 is a MP3 compression of the 6 channels before multiplexing
the bitrate of AC3 is generally around 480 while DTS is usually 1024 (i don't remember the exact values but easy to find on the net ...)
Notes about the .1 channel :
the LFE channels combines Two things :
The lower part of each 5 (sattelite) channels (below 80 Hz generally) + the specific LFE channel
This process is build with the Bassmanagement in the decoder ... it adds the lowfreq of the 5 channels and add LFE channel
the LFE channel is mainly used in movies ... for "big" effects , like bombs, guns, thunders ...
in music, it is recommended to not use it ... while the .1 channel will have the lowfreq of each channels ... mixing for example the bass or the kik drum in the LFE can be a disaster when plyaing it through a decoder ...
if you know you won't use a decoder, for example, you will play back directly your DAW (6channels) in the PA, you must use the LFE for the low freq ... but if you know that your music will be played via AC3 or DTS ... don't use it ... let the bass manager do the job !
About the "center" channel :
There are many theories for music , some don't use it at all, some love it (i do) ...
You can use it as a "real" center while a "virtual" center would be a center pan in the L/R mix ...
these possibilities give you a wild range of mixing some tracks, like vocals, solos ...real or virtual ...
for movies or TV the center channels is mainly used for the voices (the voice of the one you see on screen)
About the "surround" channels :
Here again, nobody has the same use of it ...
some only mix the reverbs and a little bit of music arguing that music comes "in front" and not "behind"
I personnally don't agree, like many others, surround channels can be a very artistic way of mixing ...
Even Live, i already have mixed some live music in 5.1 using surround channels with very amazing results ...
In fact i do think that ONLY EMOTION COUNTS ... if what the audience hear is emotional enough, it'ok !!!
about reverbs in 5.1 :
my own experience teached me that reverbs are quite unusefull in 5.1 while the space placement is already done with the 5 channels ... nothing to do with stereo ... you immediately have a sensation of space and spatialisation in 5.1 mixes and you quicly understand that reverbs are not usefull, at least , much less than in stereo ...
you can use one on the "master", 5 in/5 outs , just to give some specific effects on your mix ...
in facts reverb in 5.1 must be understood like effects and not as spacialisation ...
here are some of my thoughts ... would like to read others experiences here
cheerz
olive
