The Big Finish: A Guide to Mastering Your Video Projects5/22/2012 1:17 PM Eastern
Adobe Audition offers a range of built-in filters and support for AU and VST
plug-ins, such as this Focusrite Scarlett compressor.
The last step in commercial music production is mastering, which typically involves making a recording sound as good as it possibly can through the application of equalization and multiband compression. In the case of LPs and CDs (remember those?), mastering also includes setting up the flow from one tune to the next and balancing out levels so the entire product has a consistent sound. Video post has a similar phase, historically the responsibility of the finishing or online editor.
That Sounds So Sweet
The most direct comparison between the last video finishing steps and commercial music mastering is how filters are applied in order to properly compress the audio track and bring video levels within legal broadcast specs. When I edit projects in Apple Final Cut Pro 7 and do my own mixes, I frequently use Apple Soundtrack Pro as the place to polish the audio.
Apple Soundtrack Pro is a good mixing companion to FCP 7,
or it may be used simply for final mastering of mixed tracks.
My Soundtrack Pro mixing strategy employs tracks that route into one or more subgroup busses and then a master output bus. Four to eight tracks of content in FCP might become 20 tracks in Soundtrack Pro. Voiceover, sync sound, SFX and music elements get spread over more tracks and routed to appropriate subgroups. These subgroups then flow into the master bus. This setup gives me the flexibility to apply specific filters to a track and exercise fine control over the audio.
I’ll usually apply a compressor across the master bus to tame any peaks and beef up the mix. My settings involve a low compression ratio and a hard limit at -10dB. The objective is to keep the mix levels reasonable so as to preserve dynamic range. I don’t want to slam the meters and drive the signal hard into compression. Even when I do the complete mix in Final Cut, I will still use Soundtrack Pro simply to compress the composite mix because I prefer its filters. When you set the reference tone to -20dB, these levels will match the nominal levels for most digital VTRs. If you are laying off to an analog format, such as Betacam SP, set your reference tone to -12dB and match the input on the deck to 0VU.
Getting Ready for Broadcast
Avid’s safe color limiter can be applied to an upper track of a sequence so
all video conforms to broadcast specs.
The video equivalent is the broadcast safe limiting filter. Most NLEs have one, including Avid Media Composer and both old and new versions of Final Cut. The broadcast safe filter should normally be the last filter in the chain of effects. It’s often best to apply it to a self-contained file in FCP 7, a higher track in Media Composer or a compound clip in FCP X. Broadcast specs will vary with the network or station receiving your files or tapes, so check first. It’s worth noting that many popular effects, like glow dissolves, violate these parameters. You want the maximum luminance levels (white peaks) to be limited to 100 IRE and chrominance not to exceed 110, 115 or 120, depending on the specs of the broadcaster to whom you are delivering. In short, the chroma should stay within the outer ring of a vectorscope. I usually turn off any RGB limiting to avoid artifacts.
It’s often a good idea to reduce the overall video levels by about five percent prior to the application of a broadcast safe filter, simply so you don’t clip too harshly. That’s the same principle as I’ve applied to the audio mix. For example, I will often first apply a color correction filter to slightly lower the luminance level and reduce chroma. In addition, I’ll frequently use a desaturate highlights or lows filter. As you raise midrange or highlight levels and crush shadows during color correction, the chroma is also driven higher and/or lower accordingly. Reds, blues and yellows are most susceptible, so it’s a good idea to tone down chroma saturation above 90 IRE and below 20 IRE. Most of these filters let you feather the transition range and the percentage of desaturation, so play with the settings to get the subtlest result. This keeps the overall image vibrant but still legal.
Final Cut Pro X’s easy-to-use broadcast limiter is best applied to a compound clip.
Let me interject at this point that what you pay for when using a music mastering specialist are the “ears” (and brain) of the engineer and his premium monitoring environment. This should be equally true of a video finishing environment. Without proper audio and video monitoring, it’s impossible to tell whether the adjustments being made are correct. Accurate speakers, calibrated broadcast video monitors and video scopes are essential tools.
Having said that, though, software scopes and modern computer displays aren’t completely inaccurate. For example, the software scopes in FCP X and Apple’s ColorSync technology are quite good. Tools such as Blackmagic Design’s UltraScope, HP’s DreamColor monitor and Apple’s Cinema Display do provide accurate monitoring in lower-cost situations. I’ve compared the FCP X Viewer on an Apple iMac to the output displayed on a broadcast monitor fed by an AJA Io XT and found them to match surprisingly well. Ultimately it comes down to trusting an editor who knows how to get the best out of a given system.
Navigating the Formats
Editors work in a multi-standard world. I frequently cut HD spots that run as downconverted SD content for broadcast as well as at a higher HD resolution for the internet. The best production and post lingua franca format today is 1080p/23.976. This format fits a sweet spot for the internet, Blu-ray, DVD and modern LCD and plasma displays. It’s also readily available in just about every camera at any price range. Even if your product is intended to be displayed only as standard definition today, it’s a good idea to future-proof it by working in HD.
Avid’s software scopes can be accessed as part of the color correction mode.
If you shoot, edit and master at 1080p/23.976, then you can easily convert to NTSC, 720p/59.94 or 1080i/29.97 for broadcast. The last step for many of my projects is to create deliverables from my master file. Usually this involves creating three separate broadcast files in SD and two HD formats using either ProRes or uncompressed codecs. I will also generate an internet version (without bars, tone, countdown or slate) that’s a high-quality H.264 file in the 720p/23.976 format. Either .mov or .mp4 is fine.
Adobe After Effects is my tool of choice for these broadcast conversions because it does high-quality scaling and adds proper cadences. I follow these steps.
1. Export a self-contained 1080p/23.976 ProRes HQ file from FCP 7 or X.
2. Place that into a 720 x 486, 29.97 fps After Effects D1 composition and scale the source clip to size. Generally this will be letterboxed inside of the 4:3 frame.
3. Render an uncompressed QuickTime file, which is lower-field ordered with added 2:3 pull-down.
4. Re-import that into FCP 7 or X using a matching sequence setting, add the mixed track and format it with bars, tone, countdown and slate.
5. Export a final self-contained broadcast master file.
6. Repeat the process for each additional broadcast format.
Final Cut Pro X includes precision video scopes for an accurate display of levels.
Getting Back There
Archiving is the “$64,000 Question” for today’s digital media shops. File-based mastering and archiving introduces dilemmas that didn’t exist with videotape. I recommend always exporting a final mixed master file along with a split-track, textless submaster. QuickTime files support multichannel audio configurations, so building such a file with separate stereo stems for dialogue, sound effects and music is a very easy process in just about any NLE. Self-contained QuickTime movies with discrete audio channels can be exported from both FCP 7 and FCP X (using Roles).
Even if your NLE can’t export multichannel master files, export the individual sub-mixed elements as .wav or .aif audio files for future use. In addition to the audio track configuration, remove any titles and logos. By having these two files (master and submaster), it’s very simple to make most of the future revisions you might encounter without having to restore the original editorial project.
Naturally there’s the question of which codec to use now for reliable access to your files in the future. The preferred codec families these days are Avid DNxHD, Apple ProRes, uncompressed, OP1a MXF (XDCAM) or IMX. FCP editors will tend toward ProRes and Avid editors toward DNxHD, but uncompressed is quite viable with the low cost of storage. For feature films, another option to consider is image sequences, like a string of uncompressed TIFF or DPX files.
LTO appliance and media from Cache-A
Whichever format you standardize on, make multiple copies. LTO data tape is considered the best storage medium, but for small files like edited TV commercial masters, DVD-ROM, Blu-ray and XDCAM media are likely the most robust. This is especially true in the case of water damage.
The typical strategy for most small users who don’t want to invest in LTO drives is three-pronged:
1. Store all camera footage, elements and masters on a RAID array for near-term editing access.
2. Back up the same items onto at least two copies of raw SATA or SSD hard drives for longer-term storage.
3. Burn DVD-ROM or BD-ROM copies of edited master files, submasters, project files and elements (music, VO, graphics, etc.).
A properly polished production with audio and video levels that conform to standards is an essential aspect of delivering a professional product. Developing effective mastering and archiving procedures will protect the investment your clients have made in a production. Even better, a reliable archive routine will bring you repeat business, because it’s easy to return to the project in the future.