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By Chris Munro As more and more sound mixers record production audio using multi-track digital disk recorders such as the Aaton Cantar-X, Fostex PD-6, HHB Portadrive and Zaxcom Deva III, IV and V, some picture and sound editors and assistants are concerned that the additional tracks recorded on these machines will mean more work for them. But in fact, the new technology may solve many of the problems that have long hampered those who work with sound, provided that everyone along the line fully understands the new tools and how to take advantage of them. I have been actively involved in the development of the Fostex PD-6, as well as methods for it to interface with Avid, Pro Tools and other post applications, so this article will focus on how to integrate that particular machine into the audio workflow. I will also discuss two different ways to use the audio from the PD-6, one for synching in the Avid, and the other for blind synching of magless film dailies. The Basics of Digital Disk Recording Multi-track digital disk recorders are non-linear
machines that capture sound as digital files. Rather
than laying a signal down on tape, they store their
files on a hard drive or removable disk.
Like other digital files, the recordings made on
these machines can be imported into a non-linear
editing system by dragging-and-dropping from one
drive to another.
Organizing the Production Chain At the start of a production, it is key that all the departments involved with sound develop a firm understanding of what formats will be used, how tracks will be organized, what sample rate and bit depth will be employed, and how other technical details will be addressed.
In addition to being a production mixer, I also co-own two London-based post facilities, SoundStation and EditStation, where we design custom flowcharts like those shown in Figures 1 and 2, tailored to individual productions. These are valuable for any show, but they are particularly critical for those working with new technology. On any project, you should make a flowchart, give it to everyone (including the production mixer, picture and sound editors, mixers and producers) and get them all to sign off on it. You should also do a test run for sound, going from production recording through to the final mix or online, to make sure everything works smoothly. The new multi-track recorders offer many new capabilities, so when you choose your sound facility, make sure that they’ll be able to take advantage of all those features. This means that when post production supervisors get bids on work, they need to confirm that facilities are advanced enough to handle the new technology, and not just resort to whatever they’ve always done.
The Changing Role of the Production Mixer
Many production mixers have little experience with
post production, and as they learn to use multi-track
digital disk recorders, they may need guidance
on how to organize their tracks to make them
as usable as possible in post. Recording this way
doesn’t necessarily
mean more work for the mixer, but it does mean thinking about the process
in a different way, and it is critical that the mixer thoroughly learn
how to do the various file management tasks involved.
Track two can be used for offstage lines. While picture editors generally want to edit with only one track, it can be useful for them to be able to access the offstage lines, and this is easy if they always know where those can be found. The remaining four tracks can contain the components of the mix, or backgrounds for the other tracks. For instance, imagine a police car or fire truck passing by a dialogue scene with its siren blaring. The sound might fit in the show very well, so the director may have no problem hearing it in the master; the problem is that if the editor cuts to close-ups, there will be no siren. But if a back-up microphone is placed at a distance from the dialogue microphone, the mixer can record a clean copy of the siren on a separate track, so that the sound can be cut into the close-up shots as necessary. The PD-6 requires mixers to type in information about what is being recorded. I set up my system so that every take is a separate file, the name of which is the scene and take number. This information is incorporated into the file’s metadata, which can be converted into an Avid Log Exchange (ALE) text file that can easily be printed out — this means that there is no need for the mixer to keep handwritten sound reports. Technical Information about the PD-6 While some multi-track recorders store their files on a hard drive, the PD-6 records to an 8cm DVD-RAM disk, which is about half the size of a conventional DVD. Depending on the sample rate and bit depth, each 8cm disk can hold approximately 28 minutes of six-track audio. The DVD-RAM disks that the Fostex uses are known as “Type 2” disks, which means that they come in protective plastic cartridges. They can be read in conventional DVD-ROM drives, but first the disk must be temporarily removed from its cartridge. To write to the disk, a DVD-RAM drive is needed. Disks can be single- or double-sided. Double-sided disks can record twice as much information. To use the second side, the disk must be turned over. Currently, Fostex recommends using disks from Maxell; although another company, Optodisk, now manufactures 8cm disks. Fostex is still testing them and as of this writing does not endorse them. The default PD-6 file format is Broadcast Wave Format (BWF) polyphonic files, with a .wav extension. The PD-6 can record two, four, five or six tracks in a single file, or you can use one of two special modes: 1+5 simultaneously makes two files, one with one track and the other with five, while 2+4 makes one file with two tracks and a second with four. (This is helpful because many Avids cannot take in more than four tracks at once.) When working with split files, the default PD-6 file name for both is the slate number: for example, a scene with the slate number “123A, Take 1” would be called “123A_1” for the two-track file and “123A+1” for the four-track file. Before DVD-RAM disks are used for recording, they need to be formatted in Universal Disk Format (UDF Rev 1.5), which is compatible with Avid and Pro Tools systems and is equally at home in both Windows and Mac environments. In most cases, it is sufficient to do a fast format, which takes about 14 seconds. However, bad disks or disks that have been previously recorded on may need a physical format, which takes 20 minutes. I have established some helpful recording, formatting and labeling conventions that you may want to pass along to your production mixer. Because most editors still use Avid Film Composers that are not capable of handling anything better than 16-bit audio, for the moment I still record at 48K, 16 bits. (Note that the Avid Media Composer Adrenaline will handle 24-bit files.) I generate timecode using the Record Run setting, because if one side of the 8cm DVD starts at one hour and the other starts at two hours, it’s easier for someone in post to recognize the source of the material. In the user bits (extra information embedded in the timecode), I include the reel number; the date is unnecessary since all DVD-RAM files are date stamped. On a PD-6, there is also something called event numbering, which adds a number to the user bits and increments it each time the machine goes into record. This uniquely identifies every recording made with the machine on a particular project. The Impact on the Picture Editing Room Although it might seem that production mixers would have the most interest in file-based recording, I actually get more inquiries about the process from picture editors, because it makes things work so much better for them. I know of no editor who has wanted to return to older working methods after trying this route. However, at first the idea can seem intimidating, especially for assistant editors who are told that they will have to synch in the Avid. They immediately want to know how they will have dailies ready on time. But as you’ll see, it is possible to synch in the Avid in about the same time it takes to synch on the bench. Because the slate and take information that the production mixer inputs on set is carried along as metadata, there is no need for the assistant to log the clips. Sound can be brought into the Avid much more quickly, because rather than being a real-time operation, an hour’s worth of dailies can be imported in about six minutes. All that is necessary is a DVD-RAM drive attached to the Avid. Fostex recommends LaCie drives, and they report that on Macintosh-based Avid systems, users have generally had better luck with FireWire drives than SCSI drives. After copying the audio from the production disk to an Avid drive, the assistant then needs to copy the ALE files (one per disk side) into a single folder. All the audio should be on specific partitions so it can be easily copied, in its entirety, to a removable FireWire drive and handed over to sound. Synching in the Avid If you look at the flowcharts included in this article, you will see two methods for using sound from the PD-6. Figure 1 shows an approach for synching in the Avid. In this case, the film goes to the lab for processing overnight, probably coming out at 5 or 6 a.m. An assistant assembles the selected takes into dailies rolls, which then go to telecine, where picture only is transferred to Beta tape and also digitized directly to an Avid hard drive using an Avid Media Station XL. The hard drive goes to the picture editing room, where it is attached to the Avid system. The assistants then synch the PD-6 audio, imported directly into the Avid from the DVD-RAM drive, with the picture, using the slate. Typically, it takes half an hour to 45 minutes to synch a day’s worth of footage, a process that is not sped up by using timecode. This means that the camera department doesn’t have to use a timecode slate — which generates considerable good will among the camera crew. Once all the takes are in sync, the assistant just has to output the audio to a standard, full-sized DVD-RAM disk that will run in sync with the original film dailies. A Fostex DV40 studio player/recorder is installed in the projection room and slaved to the projector via timecode for playback. Blind Synching However, if for some reason it’s impossible to telecine MOS dailies in time, Figure 2 shows a way to synch film blindly and still have magless dailies. First, the film print is put on a KEM or a bench, and the feet-and-frame number for the clap of each slate is noted. This information is given to the Avid assistant, who then makes a new composition in the Avid and places the audio sound clap for each take at exactly the point that corresponds to the same frame from the KEM list. This audio composition is exported to a DVD-RAM disk, as previously described. For safety’s sake, you can slave a Fostex DV40 to the KEM to check synch. After dailies, the film and DVD-RAM disk go to telecine, where film is transferred normally. Telecine must be equipped with its own DV40 for audio playback. After telecine, the video is digitized MOS and synched with the previously imported audio using Avid’s Autosync function. The resulting clips should then be checked for synch, and Avid’s “slip by perfs” function can be used to synch them to subframe perfection. Sound Editing When the sound editors take over, they’re provided with all the audio — not just the material used in the cut — which means that they’re able to immediately check not only the alternate takes, but also the unmixed tracks. As a result, they’ll be able to use more original material and order less ADR. I recommend exporting OMF files from the Avid without the media, then handing the OMF files and audio to the sound department on a portable FireWire drive. The sound files moved over from the Film Composer will be of the best possible quality, and all the tracks for each take will also be available, even though the picture editor may have chosen to edit with only one track of production audio. Sound editors may want to use MetaFlow from Gallery (www.metaflow.info/), which will help them connect the one- or two-track files used by the picture editor to the four- or five-track files that contains the additional tracks for each take. (For additional information on MetaFlow, see Editors Guild Magazine May/June 2003.) Talking to Producers As you set out to convince your producer that it would be advantageous to use this technology on a job, be aware that your telecine facility may argue against doing so, because if synching goes back to the editing room, it means a loss of revenue for them. Fortunately, this is one time when we’re asking for something that will not only make our lives easier, but also save producers money. For each shoot day, a production mixer will probably use only one DVD-RAM disk, which currently costs about $18 (and will only get cheaper), as opposed to around six reels of tape at $8, for a total of $48. The big savings, however, will come from not using mag. It’s not unusual for a major feature to shoot several hundred thousand feet of film, and that means an equivalent amount of mag, which at today’s prices would cost between $25,000 and $75,000 a show. Conclusion Changing over to multi-track digital disk recorders positively impacts many different departments. And while adapting to technological change is not always easy, the rewards can be great, not only for those who have the courage to be among the first to adopt a new tool, but for everyone else who uses it later on. The key is having a clear line of communication between the production mixer, the picture and sound editors and assistants and the re-recording mixers. All too often, these departments are isolated from one another, but perhaps these machines will give us an excuse to open new and helpful conversations with our colleagues.
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