The Adventures of Audio Post for Film
A quick recap for anyone who didn't get to read Part One. In the beginning of 2008, my friend, writer/director Tibor Spiegel shared with me the completed production footage of his independent film, "Overnite Shift". The thirty-plus minute movie tells the story of an older, immigrant New York City taxi driver who, on a particular evening, picks up a series of passengers. As he interacts with them, his past hauntingly resurfaces, and in the process changes his future irrevocably.
The footage looked great. Really good. However, the production sound was somewhat compromised, due to the movie having been filmed inside a moving vehicle, with none of the actors ever being together during the entire shoot. There was also very little ambient sound for use in post production. Despite these issues (or perhaps because of them), I signed on to do the audio work.
Our chosen workflow took advantage of the episodic nature of the script and I began to clean up the first passengers' dialogue. We also decided to ADR the driver's dialogue, a process that would require a lot of editing to fit it back into sync with the picture. As soon as I had finished editing the first section and fixing the ADR, some temporary ambient sound was added and we had our first test screening. While the overall process looked like it was working well, a major hurdle presented itself.
Namely, the sound and picture had slipped out of sync very noticeably by the end of the six minute section. Wow, three months of work down the drain!
For those interested, here is a link to Part One
Having recovered from the shock of this rather huge setback, we got down to trying to figure out the cause of the problem. And here is one of the many advantages of working on a relatively small scale production. The director was able to come to my studio with his MacBook Pro computer along with his edited sessions and we started to repeatedly export/import sections of the movie from/to his Final Cut Studio session and into/out of my Pro Tools rig.
We finally figured out that the problem lay with the original export from his system, and the subsequent import of the completed 2-track audio file back to his timeline. The director had shot the movie in 24p, and while preparing to export the various files for me, he was asked in Final Cut Pro what the export frame rate should be. He chose "same as source". However, Pro Tools software does not support 24p, so on import the session was stamped as 23.97fps. When the audio was exported from Pro Tools and placed back into FCP, the editing software now saw a different frame rate for the audio and tried to compensate, resulting in our audio drift. The solution was to specify 23.97 as the export frame rate and the problem was "magically" solved.
(The Digidesign User Conference "Pro Tools Post & Surround" section has a sticky here that goes much deeper into these issues between FCP and Pro Tools. I also recommend the forum as a great resource for help with other audio post problems. It is frequented by some very experienced and helpful professionals.)
At this point decisions had to be made as to how to proceed with the rest of the project. Obviously all the video sections and the audio had to be re-exported from Final Cut and new sessions created in Pro Tools. The director also decided that the work involved in editing the driver's dialogue replacement was not worth the time and effort, and we agreed to stick with his original production dialogue. So my immediate task was to finish cleaning up the rest of the dialogue.
I also started to think about the overall sound design of the movie. Obviously I needed audio associated with a traveling vehicle, like engine noise, etc. I searched most of the various on-line sound libraries and my own DVD collection for suitable material, and although these resources contained large quantities of sound effects, I could not find any that really fit the bill. I was looking for the vehicle accelerating from standstill, slowing down for corners, and also stopping for lights. While I tried to splice together various parts from numerous sound samples, the overall results were unconvincing. So I decided to re-record my own production sound.
After much research I settled on using the Sony PCM D50 as my recorder. While not in the same league as Sound Devices, Nagra, and other similar offerings often found on bigger budget movies, for my purposes it was perfect. The unit is cost effective, comes with a pair of decent microphones, is relatively small, and delivers extraordinary long operation times using 4 AA batteries. It sounds good, is well built and also includes 4GB of internal memory. However, the recorder absolutely needs a windscreen when using the internal microphones, as even the slightest breeze will cause distortion. And the VCT-PCM1 tripod stand helps with isolating the unit from handling noise, something which the recorder, and many of the similar products on the market, are susceptible to.
So one late spring evening we hailed a New York City taxi on 8th avenue and presented for the driver our rather strange request. We wanted him to drive up and down the various avenues and streets that were used in the original filming while I recorded the resulting sounds. After a certain amount of negotiations, we set out on our journey of audio acquisition. For those readers that have never been in a NY taxi, it is important to note that there is a divider separating the driver (for safety reasons) from the passengers. And after a taxi has been in service for any length of time, the divider rattles. It rattles a lot! Our taxi rattled a lot, but here I was thinking that would only lend itself to providing authenticity to the final product. After several hours of driving around, I had what I felt was enough material, including specific sounds like the meter running at the end of a trip.
When I got home and started to add the new audio to the sessions, I realized my assumption about authenticity was completely wrong. The original footage was not filmed in a real taxi, but rather in a vehicle of the same make and model used by taxi fleets. A divider would have impeded the necessary camera angles needed to shoot the movie, hence no divider. And no divider meant no rattling. So all the audio recordings ended up being totally inappropriate for the visuals.
But as I mentioned in part one, most of the dialogue could not be completely cleaned of background sound. Consequently, I still needed some "glue" that would join together the various takes and draw the ear away from hearing the background interference as exemplified in the following extract. (It should be noted that the video used in this example is from a work copy exported from Pro Tools. It is in no way representative of the final video quality, and is only included as a reference.)
Here my own car came to the rescue. It was smaller than the production car, but still quite new. Although the engine sound would have a higher frequency content (being a smaller engine), I felt that with a little judicial pitch shifting inside Celemony's Melodyne plug-in, the audience would be none the wiser. The other issue was to find a road surface that was as smooth as possible, and of sufficient length to allow for capturing a reasonably long sound sample. As luck would have it, a sizable stretch of the Southern State Parkway here in Long Island had just been resurfaced, so I set up the recorder in the front seat and went out for a first run.
|Sony recorder on front seat ready for car ambience runs|
On playback I realized that my key chain introduced far too much interference as it bounced against the steering column, so those recordings had to be discarded. On my second attempt it rained and the water hitting the windscreen was obviously unacceptable. After multiple attempts I eventually got what I wanted, along with some door closings, seat belt clicks, and other sundry noises. However, the whole process reminded me of just how much we filter out sounds that aren't necessary to our everyday survival. It is only when we capture these sounds on an outside device, that we become aware of them again. So another lesson learned - really listen with "ears wide open" to any potential recording situation, and then thoroughly analyze it.
Having acquired and assembled all the necessary sound files along with the cleaned up dialogue, I began the job of mixing. Here I had two advantages. The first was the music, and I'm happy to say that I was able to work with one of the best musicians in the business. In the story, the taxi driver loves to listen CDs of Mozart while driving. Mozart's compositional prowess hides an intricate yet highly logical compositional process, making it very easy to edit sections of his music together when needed. Luckily for me the director had already chosen the sections he wanted to use, leaving me with only one major and a couple of minor adjustments.
Of course, it goes without saying that obtaining rights to use the music is essential, since festivals (our intended primary focus) will not accept product without the rights having been secured. However, the process is relatively painless because most licensing entities will grant temporary licenses with little or no cost for use in festivals, with the understanding that any future commercial exploitation of the movie will require re-negotiation.
The second advantage was that while the filming process had inherent audio problems, the very nature of the story meant that I didn't have 100+ tracks to mix with a wide diversity of sound effects.
Mixing proceeded smoothly at this point. I also made the personal decision to place low-cut filters, at around 125Hz with a steep roll-off, on all tracks except for the special effects. Since in many cases the resulting audio is heard in conjunction with a sub-woofer, this crude but easy bass management allowed for the dialogue and other ambient sounds to cut through and not compete in the bottom end of the mix. The added advantage was that the special effects could then stand out and be more dramatic.
Here is the same video clip as presented before but with the background ambience filler and music included.
On completing the mix for each reel, the individual two-track audio files were then sent to the director for insertion into his timeline, but only for use as guides. He then re-exported the final edit from Final Cut and I imported the whole video with the audio into my Pro Tools system as a new session. Using the guides from the QuickTime import, I re-aligned my final audio files, adjusted levels and created in and out fades between each reel. The resulting audio was bounced to disc with a touch of limiting and with the appropriate bit reduction. The director then took this file, inserted it back in Final Cut and created the finished DVD.
In closing I would like to make several recommendations. A very valuable tool I discovered during this entire process was Speakerphone from Audio Ease. While a little expensive for the weekend warrior, the tool is essential for the post professional, and even for some musicians. It is obviously highly useful for creating a vast array of speaker simulations, but due to the very modular arrangement of the plug-in, it can be useful in many other situations. One of the modules utilizes Altiverb for creating room and ambience simulations, and the speaker selection provides great resources for the electric guitar or bass player. It also includes a very decent collection of sound samples for use in audio post projects.
As mentioned before, there are many places on the Internet to obtain sound samples. Many allow preview and all accept credit cards, especially useful when working in the early hours of the morning and a particular sound sample is needed. However, I found an elegant solution that is a variant on this theme. Sonomic sells a prepaid Library Card that is both cost effective and simple. Once an identifying code has been entered on Sonomic's site, samples can be downloaded up to the card's limit without the need to constantly search for the credit card.
Finally, I thoroughly recommend all the plug-in products from Steven Massey, a one-man developer who makes fabulous sounding plug-ins for Pro Tools systems. He has a very liberal demo policy and his products are priced extremely competitively. His plug-ins are only available through his website.
As to what happened to our finished movie, that will have to wait for Part Three.
Jurek Ugarow is a technical writer for B&H, creating professional audio content for the web. He brings to the task over 40 years of experience in many aspects of the music and audio industry. His early days were spent as a musician playing London's cabaret circuit and doing spots for the BBC. In the early 70s, he was a founding member of a British Arts Council funded, residential arts community, an endeavor that would eventually give birth to the renowned Foots Barn Theatre. Subsequent years were spent working in TV and film as a production sound engineer, and as a member of various English rock bands. These days he spends his time in his own studio, writing music, recording and producing other artists, and doing audio post for film. He also practices and teaches Tai Chi Chuan in New York City. His music can be found here.