Cinema sound requires a different mix from TV for a number of reasons; there are more channels, it is carried on a different medium, it has a much greater dynamic range and runs at 24 frames per second whereas TV runs at 25 frames per second.

Elements.
A normal stereo mix of VO, music and SFX together is not useable in cinema as Dolby state that you must have some control over each of the separate mix elements when producing a 5.1 mix for use with their equipment. This is why it is important to supply all the elements separate. If you have been supplied with pre-mixed elements, please make sure that the following mix stems are made available as a bare minimum…

1. Stereo music only
2. SFX or separate sound design only
3. VO and dialogue only

If you are unsure what it is you’ve been supplied with then call us and we’ll be happy to help.

The Frame Rate Challenge.
Film runs at a slower frame rate than video so if you were to play your original 25fps TV mix in a cinema at 24fps the pitch of everything would be lower which is not good.

The Picture Stretch Solution.
Although we can mix your spot at 25 fps to the original 25 fps picture, then digitally pitch up the whole mix to compensate for the slowing down which occurs when it’s transferred to film, we feel that this system is fundamentally flawed. This is because you don’t see the pictures and hear the sound running at the actual speed they’ll be running in the cinema. You may find that, for example, you feel that the music is running too slow all of a sudden, by which time you’ve paid for a print.
What we do is digitize your 25fps picture and create a new digitally stretched picture which runs to the same length as the 24 fps film copy. We can now position all the separate elements against this 24fps picture and you’ll now hear exactly how it’ll sound when it’s printed.

Music
If your spot contains music, more often than not a separate stereo music track will suffice for your mix.  If, however, you feel the creativity of the sound track of your spot relies heavily on the music mix, perhaps it’s been especially composed, you may want to take full advantage of the 5.1 capabilities of cinema.  This will require separate elements of the music and therefore more mixing time but you may find, if the budget allows, that it’s well worth it.  Feel free to discuss with one of our cinema engineers the best options available to you.

Whilst voice and sound effects are fairly easily dealt with when you convert from 25fps to 24fps, music can occasionally be a problem in terms of pace. There are a couple of ways of dealing with this, if you suspect that your track might be adversely affected then do ask.

Mixing Time
A surround mix will always take longer than a TV mix. Even the simplest of mixes will take at least half an hour. Also remember that an analogue SR mix will be needed for each Dolby Digital mix produced.  This is to cater for non Dolby Digital cinemas and also acts as a safety mix in case the main Digital track drops out during playback so you always have sound. Finally, we produce a set of 24bit WAV files which is required by DCM and Pearl & Dean for use with their digital projection system.  Both mixes will be of correct loudness, or LEQ, for Cinema Commercial presentation with a maximum of reading of LEQ 82.

For the average commercial we normally allow the first hour or so to do the conversion from 25fps to 24fps.  Whilst you are welcome to come along at the start of the session, it is complicated work for the mixer as they convert and check sound files and boring for the client, so we normally suggest that you come in after an hour or so when the creative process really begins.