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Steps in Sound Post Production, Part 2
By Carmen Borgia

Mix Preparation
All of the above types of audio; dialogue, music and effects make up the sound elements of the project. Once all of the sound elements have been recorded and edited, they must be organized for the mix. For many projects this means that all of the elements are put in a single Pro Tools session. To fit the tracks into the available Pro Tools system, some of the elements may be premixed into fewer tracks. Premixing can narrow the options during a mix, so it should be carefully considered. Premixing is very common in the area of composed music. The composer will often deliver completed stereo, 4 channel or 5.1 mixes to be dropped into the mix session. The process of mix preparation can take anywhere from a couple of hours to several days depending upon the project.

The Mix
All prepared elements are now mixed. This means that all elements are equalized, balanced in volume and overall volume is set. Effects such as reverbs, telephone and TV futz are added. The final output format, be it mono, stereo, 5.1 or other is set. The time required for mix is highly variable, depending upon the project. Short films for screening or festival purposes can sometimes be done in a few hours to a couple of days. Features can take from a few days to a week or more. Programs for broadcast can take from a couple of days to a week or more depending upon length and complexity.

Layback and printmaster
Upon completion of mix we will have sound with the proper number of channels; mono, stereo, LCRS or 5.1, but it will not yet exist on the finished master tape or print. If you are making a video tape of some sort, be it NTSC, PAL or HD, there must be a “layback” when the sound is recorded onto the final master tape. If there are multiple versions of the project, such as with text and without text, there will have to be multiple laybacks. If you are making a 35mm print, there must be a “printmaster”, when a master audio tape or magneto optical disk is made that will be used to shoot an optical track negative. If the format is stereo or LCRS, the format can be DAT, DA88 or MO disk. If the format is Dolby digital, there will be an MO disk. If the format is DTS digital, there will be a DA88. Laybacks and printmastering can take anywhere from a few hours to a day or more, depending upon the needs of the project and are considered to be mixing time.

Other sound elements
Once the mix is completed, there are a variety of additional output options. It is frequently desirable to have the final mix in the form of sound files; two files for stereo, 4 files for LCRS, 6 files for 5.1, etc. These elements are usually either AIFF or .WAV files and can be copied to the client’s hard drive. They can be imported into an NLE if additional outputs are done outside of the mixing room.
Mix stems, also called splits, are useful in the event that there will be trailers or alternate versions of the film made on an NLE system. Stems split out the various elements of the mix (dialogue, narration, effects & music) into separate tracks so that elements of the mix can be removed at will without going back into an expensive mix room. A stereo mix will call for 6 stems (mono dialogue, mono fx, fx left, fx right, music left and music right). A 5.1 mix will call for 12 or more stems. Stems can be created after the mix is completed and usually takes 2 to 4 hours for a feature if the pre-mix elements were prepared properly.

Another output that may be needed is a Music and Effects track, also called an M&E. An M&E is needed when the original dialogue of the film is to be replaced with dubbed dialogue in another language. This may seem unusual, but many films are picked up for distribution in foreign countries first. Some M&E’s are very simple, as in a documentary with narration. In this case, the narration track is turned off and the mix is output without narration, which will be re-recorded in the new language. In a documentary, it is not customary to dub dialogue for interviews; rather they are subtitled. A feature film is more complex. The original dialogue must be removed, which also removes any non-dialogue sound recorded in the production tracks such as footsteps, movement, etc. Ambience must be edited in to smooth out the holes and foleys (sound effects recorded in sync with the picture) must be recorded to make it all sound more normal once the foreign language is dubbed in. An M&E for a feature takes a week or so of editing, foley and mixing and can add significantly to the budget of a modest project. Once the M&E is created, it must be laid back to the final format. Clients sometimes wait to do the M&E until after the film is picked up by a distributor. Access to the original Pro Tools mix elements can make the M&E go faster, alternately you could start with mix stems and go from there.

With all of these types of sound output available, it may seem a bit overwhelming. It is not necessary to generate all of these elements at once. Producers who have not yet secured distribution for their project often start with just the mix and maybe a set of stems. If you have a distributor, they should provide you with a deliverable sheet that specifies what they will need from you. Your sound mixer should see the deliverable sheet.

Picture and sound reference tapes
Throughout the audio post process, the sound engineers will need a reference tape. This is a tape that has been output from the picture editing system that contains the final cut of the picture, an output of the sound and time code. The reference tape is essential for the sound people to know what is going on in your system. Quick Time movies are not acceptable for a variety of sound editing systems; we’ve got to have the tape. For editing work, an offline output is acceptable; that is to say an output from the picture editing system. For mix, the final picture is essential. For video work this would be a master tape generated during an online session. If you are not doing a real online session, then it would be your final master tape. For a 35mm print, a telecine of the answer print is needed.

The audio post process can be complex. It is highly recommended that picture be completely finished and locked before starting the sound work. Prior to mix, have all visual elements completed; credits, titles and anything else that the audience will see. This will save you time, aggravation and money.


Carmen Borgia is the head of audio services for DuArt Film & Video in New York City. He oversees a post production sound department that provides mixing, sound design, restoration, transfer and printmastering. His department caters to independent projects in all formats from mono optical up to digital 5.1.

Editor’s note: If anyone has any questions, please submit them to cborgia@duart.com. Carmen will do his best to answer any of your queries.


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