|Introduction/Importance of Film Audio
Submitted by: John Moore (JohnMoore)
Part (1) - Introduction
Hello, my name is John Moore. I havenít been making films for as long as many members of various forums I attend have, but Iím writing this tutorial in the hopes that it will get you started in the long and treacherous path of digital audio.
Digital audio is a funny thing, in that unlike digital video, audio sounds very real to our ears. The better the quality of the audio, the more real it feels. Video on the other hand, looks nothing like what we really see. What does this mean? It means that achieving realistic audio is at least twice as important as achieving beautiful visuals.
Itís interesting that a lot of thought goes into different aspects of filmmaking; Storyline, cinematography, acting, editing, special effects, and in the end, the neglected part is the part that is so essential to the film: Audio.
I know Iím guilty of this, as we all are, and though I donít know as much as I would like about various elements of audio, I have discovered a few things that vastly improved the audio in my videos, and a few very hideous mistakes that can and will kill you if theyíre not caught quickly.
Part (2) - On set, marvels and mishaps, and musts
One thing we had problems with when shooting films in my house, is the tile floor, which causes a horrible echo. We overcame the problem by hanging blankets and sheets all over the room (off camera,) and lying blankets on the floor. Unfortunately, these made it into a few of the shots in the film, so they really arenít the optimum solution, but the idea behind it, which is something that can be improved, is to deaden the echoes, allowing for a less tinny audio image.
Obviously, a quality shotgun mic on a boom is a great advancement for audio, but because most of us are more concerned with other issues (food, clothing), we tend to avoid spending loads of cash on those items. One of the big advantages though, of getting an external mic, is that your camera hum is virtually eliminated.
For blocking wind, a lot of external mic rigs have a thing called a windsock, which in reality is just a fancy name for a piece of wind resistant sponge foam. On onboard mics, what Iíve found works great, is a sock. Yes, a sock. A thick sock, covering only the side of the mic that is getting hit by the wind, can greatly improve the wind resistance of the microphone. This is something that must be played with to make it work on various camera systems, based upon the placement of your particular onboard mic.
Never place your actors back to the microphone, unless you have a separate audio track from that exact location, with the camera pointed toward that same actors face. Consistency is key. Remember, ADR is only a good thing if consistency can be maintained, which means that if you have to replace a single word, you have to replace them all.
I continually had my back to the camera mic, and it continually killed the audio, since the only audio making it to the mic was a distorted bounce back. For your own sake, film the scene an extra time on set with your primary focus on audio, and forget your visuals. Then you have a usable ADR track for later purposes if you need it.
Be sure to get a backtrack; 15 seconds at least, of on set silence. Just yell, ìSHUT UPî at the top of your lungs, and hit record. People will be so stunned, it will take at least 15 seconds for everyone to recover, and ask what your exclamation was all about. Not to mention, it breaks up the dull monotony of filmmaking.
Another must, is to make sure to turn off ALL unnecessary electrical devices on set. I discovered little things like the microwave (even when not running) and the refrigerator, are horrible about making noise. Cameraís usually have batteries, so just make sure your battery is charged, kill the electricity from the breaker panel of your house, for the room that youíre filming in, and voila! If you can (hopefully nobody kills you) kill the main breaker for the entire house. That will ensure a much more dead silence. Then all you have to worry about is quiet actors, mic angles, and echoes.
As for outdoors, always block your mic from the wind. Film with the wind to your back if you can, and the actors talking up toward you. If you need a little bit of wind track for your back track, get it, but avoid it if you can.
If a car passes by on a street near you, rerecord the lines. Itíll be worth the effort in the end. Another little item, if youíre by a very busy street, you can use an old piece of cardboard covered with fabric to block sound coming from the direction of the street. Just try to keep it out of the camera! (This may mean an extra man on set, or a special mount. Use your Yankee ingenuity!)
Part (3) - Post Production Jingle Jangles
ADR is a very slow process, which can and will almost kill you. ADR is something that requires practice, time, and practice. And time.
Mostly what Iím going to focus on now, is the improving of audio already recorded. My audio program is Adobe Audition, and unlike a few of Adobes other bits of software, Audition kicks major butt. Unfortunately, Auditions price tag also kicks butt: mine. If you arenít interested in dropping a summerís worth of extra Audition, youíre not the only one. What most people tend to use is Audacity. Go onto google and search for Audacity. It should come up under audacity.sourceforge.net, but theyíve changed it in the past, so Iím not sure if thatís current.
Pretty much any software will work if it has a noise removal filter, a levels equalizer, and a volume equalizer. Hereís where you start though.
The following process must be repeated for each individual location or scene.
Edit your film to visual perfection, and export your finished track as an uncompressed .wav file. Be sure to turn off all sound effects such as explosions, richochets, music, or machinery.
From premiere, I export in the absolute highest quality possible, which means I exported it at 32 bit, 96000 khz. That created a very large file, (just like uncompressed video, very large but it has better color fidelity) so be sure to have some space, and also be sure to keep your files organized.
Open this in your audio app, and find a spot with just background noise. In audacity, thatís effects > noise removal. Then click get noise profile. Then, go back, select the entirety of the area that needs noise removal, and remove it. Youíll notice that the noise removal quality of Audacity isnít all that fantastic. It actually ends up leaving a bunch of grimy sewer noises, which would drive any self respecting filmgoer insane. That is, IF you set the noise removal level to highest. Set it down just a bit, and youíll be a little better off.
Now quite frankly, of all programs Iíve used, I would say that Audition has the most powerful noise removal filter available. The difference? Audacity takes about 2 minutes for a two minute clip on my system. Audition took me 18 hours and 36 minutes (on a stopwatch) to complete a 1 minute 58 second clip. However, the finished quality was far superior to anything Audacity could do.*
Here are the settings for noise removal in Audition.
Iíve got the FFT size set to 24000 points, which takes a minute or two to scan the audio track for noise (unlike audacity, which only takes seconds) I usually reduce audio by 95 decibals, but play with it. Precision factor is set to 1000 at least, but I can set it to 9999, which I do if itís a very difficult clip. Warning, this will take several hours per minute, even on a very high end system.
Next, play with the bass and treble levels of your audio. This can improve clarity, and deepen the feel. Once youíve completely rendered out your audio, and balanced the volume throughout, save the audio clip. Import it into your NLE, and paste it. Match it up to your visuals, and turn your sound effects and music back on, and move on to the next scene. Repeat this process until the movie is finished.
When it is, watch it through to check for consistency. Fix any major inconsistencies, and publish. Final audio compression will hide some bad mistakes. ADR the absolute worst parts if you have to. If you can, go onto your original set for your ADR. Whatever you do, donít do it at your computer, as the electrical distortion will be terrible.
Open your ADR audio into your audio app and apply a whole shebang of filters to make it match as close as you possibly can to the original audio, and then redo the ENTIRE scene, with ADR. You canít just do a few words.
Part (4) - Final Words
Thatís really pretty much it for the audio scene, but I have one last bit of advice.
When editing your film, look at the worst audio, figure out what caused it, write it down. Then, get together with your crew, and figure out how to avoid that problem next time. If you do not write it down, chances are youíll make the same exact mistake. This advice also applies to your visuals.
Thank you for reading this tutorial, I hope it helps. If you have learned anything helpful, be sure to send me an email, and Iíll try to update the tutorial quickly.