TUTORIAL | Cut Lines: Optimizing Compression in Apple Compressor 3
Posted Apr 1, 2008

Apple’s Compressor application has always been a workhorse for video compression and transcoding. Today Compressor 3, part of Final Cut Studio 2 (FCS 2), is easier to use with even better compression results. The layout is easier to deal with, and the presets are more organized. In this second anniversary edition of Cut Lines we’ll take a brief walk through Compressor 3 to see just how easy it is to prepare your video projects for delivery.

Step 1: Get Familiar with the Five Windows
When you open Compressor there are five windows to work with: Project, Settings, Inspector, History, and Preview (Figure 1, below). In the Window menu under the Layouts option, you’ll see the two presets Apple supplies: Standard and Batch. You can also choose from various sizes for each to fit your personal needs. The Standard layout is good for simple work such as outputting a single Final Cut Pro (FCP) project for DVD authoring. The Batch layout is good for more complex work, such as when you’re encoding several FCP projects or video files, and you may be making several different versions of one or more videos for web, DVD, archiving, etc.

figure 1

Step 2: Create Your Own Window Layout
You can create your own window layout too. Arrange the windows in any manner you wish by resizing and positioning them. When you like the layout you have, go to the Windows menu and choose Save Layout. There’s also a "Manage Layouts..." option in the Windows menu that will bring up a layout management interface. You can rename them, delete them, add the current layout to the list, etc. Your saved layouts also appear in the Layouts menu.

Your custom layouts can be transferred to any Final Cut system you wish. If you edit on a Mac that’s not yours, you can still feel right at home.

Customizing of windows, keyboard shortcuts, button bars, etc., is available on nearly all of the FCS 2 apps. I have a USB flash drive that travels with me so in only a few short minutes any Final Cut system I sit in front of will mirror my own. Your custom layouts are stored in the following directory path: Users/Üsername/Library/Application Support/Compressor/Layouts (Figure 2, below).

figure 1

Step 3: Compression Workflow
To begin working in Compressor, you can take the direct route of using the Export To Compressor command in apps like FCP or Motion, or you can launch Compressor and use the Add File button to grab a source file from a hard drive. Then you’ll see your source file listed in the Project window.

One note about exporting directly from FCP: When you use this method, your render files in FCP are ignored. FCP will hand each frame’s raw data to Compressor to do the encoding. This results in slightly improved image quality, but it takes longer and ties up FCP during the compression process. Which method you use is a personal choice depending on your specific needs.

The Project window is normally in the upper left-hand corner of your screen, and aside from the Preview window, it will usually be the largest window on the screen. In this window you’ll see your source media, whether an FCP Sequence, Motion project file, LiveType project file, QuickTime file, or other type of supported file (there are too many to list here). It shows a thumbnail of your source file with its name and a scrub slider below it. You can use the scrub slider to scrub through your source file’s thumbnail. To the right of that thumbnail is just empty space. This is where your outputs will be placed and where you’ll specify the output location and name. Once a preset is selected you can right-click on the output field, which by default reads Source in bold letters. By choosing the Other option, you can specify a different location to save the newly compressed file.

The Settings window is where you choose an output type. The presets are arranged in tidy folders for easy navigation. When you select a format, you simply drag the folder to your source in the Project window and drop it. Everything you need is there—one step, poof, you’re done. You can select other encodes to add to your list of output files in the Project window. I can add H.264 for web video and an iPod+iPhone to my DVD outputs.

The Inspector window is where you can tweak the encode settings. This window will reflect the settings of the output highlighted in the Project window. If I have a high-definition video loaded as my source, I highlight the SD DVD MPEG-2 setting in my Project window, then configure the specifics as to format, bitrate, aspect ratio, etc., in the Inspector window.

If I had a longer source file, I would go to the Summary button at the top of the Inspector window (under Description name), check the Estimated File Size, and, if that were more than 3.5 or 3.7, I’d go to the Encode button, to the Quality tab, and bring my Average Bit Rate down. I would then double-check the file size and readjust until I achieved a file size suitable to fit on a DVD-5 disc.

The Preview window will compare your source with your intended output. If you’re doing really heavy compression, this function is very valuable to make sure you’re not getting things too pixelated and fuzzy. You can switch between the source and output aspect ratios, edit/view/add chapter markers, scrub and play back the file, set In and Out points, and more. There is a split-screen slider at the top so that you can easily judge the output quality of your final product (right side) compared to your source (left side), as shown in Figure 3 below.

figure 1

The In and Out points will actually limit how much of the file is used in the output file. For example, let’s say I have a 90-minute wedding video. I want to make sure my output file is not going to be too overly compressed and full of artifacts. I can select an area with a lot of movement (like people dancing to a fast song), set In and Out points to only include a few minutes of it, then encode that small bit. That way, I only have a few minutes of encoding time, and I can properly judge my final encode’s quality.

Step 4: Choose Encoding Parameters
When compressing for SD DVD, you shouldn't use an Average Bit Rate greater than the default 6.2Mbps. Even though the DVD specs state that DVDs can play up to 9Mbps, that has to include video, audio, metadata, closed captioning stream, and on and on. That bandwidth has to be shared by all the assets on that disc. Video can be encoded retaining quality at much lower rates. I had a project so long, I used an ABR of 3.5 and it looked like a "good" VHS tape. Don’t let your Maximum Bit Rate go much above your Average. By default it’s set to 7.7 with the ABR at 6.2, so you can figure that as the maximum amount of wiggle room you want to let your encode have. Audio can be left at defaults in Compressor for DVD encoding for excellent quality.

If you’re like me and you shoot/edit in HD, save the down conversion to SD until this encoding stage. You’ll preserve much more quality this way. Your SD conversion will still look better than if you had originally shot on SD video. Select a regular DVD preset—it’s as simple as that. Highlight your MPEG-2 in the Project window, go to the Inspector, hit the Encoder button, and be sure the Stream Usage is set to SD DVD. In the Video Format tab, confirm you’re set to a 16:9 aspect ratio, leave the rest at default (NTSC, 29.38, Progressive) and do the balancing act between file size and Average Bit Rate as discussed previously. You can also optionally click the button next to Frame Rate and Field Dominance to turn those drop-down menus on and change them if you wish. But I’ve always found the defaults work just great.

For H.264 compression I’ll discuss web video settings specifically. H.264 is a very cool codec to use for web video, and Flash now supports it. Using the Export > QuickTime Conversion option in FCP works just fine too. Compressor gives you a little more control, but either method produces really nice files. To change the frame size, in the Inspector go to the Geometry button and use the Dimensions drop-down menu to select a common frame size. Choose the Encode button, click the Settings button for Video, and you’ll be able to adjust frame rate, etc. I’ve lowered the Compressor Quality slider to just under Medium and had great-looking results. Set Data Rate and Keyframe settings to Automatic, unless you’re an encoding guru and really know what you’re doing. I find a frame rate of 15fps also works well to keep the visual quality up and file size down. I always keep Best Multi-Pass selected too. The difference in encoding time is not overly drastic, and the quality it keeps is worthwhile (Figure 4, below).

figure 1

To adjust the H.264 audio setting, click the Settings button just like you did for Video settings. I recommend you always use ACC as your format for great quality and small file size. Use stereo for music that is stereo and mono for just voice. I’ve lowered the Rate setting to 22.050 kHz and had great audio. Some upload sites such as Ning don’t like it, so you’ll have to use the more standard 24.000 kHz rate. Check the Show Advanced Settings box and choose "Normal" for your Quality. If there are subtleties in your sound you’re worried about, "Best" is cool to use; it won’t increase your file size much. A Sample Size of 8 is fine, but 16 will do slightly better. I almost always use 8 unless there’s good music; in that case, I use 16. I’ve never found a need to go above that for web video.

Submit Your Encode
When all your settings are tweaked and you’re ready to output, click the Submit button in the lower right of the Project window. You won’t see much happen, but that’s OK—simply click the Batch Monitor button in the top right of your screen to see the progress of your encodes (Figure 5, below). This means that while the files are encoding, you can continue to work in your Compressor screen without interruption, or simply quit out of Compressor.

figure 1

If you submit the short sample encode as I just mentioned (once it’s done and you’ve checked it), you can remove your In/Out points in the Preview window and encode the whole source file without having to relaunch and reconfigure your compression schemes and settings. This is because Compressor and the Batch Monitor are separate applications, although they are married to each other. Such is life, eh?

I hope this has helped you gain a little more of a grasp on the new Compressor 3. It does a fantastic job of encoding and converting, such as from HD to SD or from NTSC to PAL. I highly recommend the Apple Pro Training Series books Compressor Quick Reference Guide and QuickTime Quick Reference Guide. They’re very enlightening. You can find them for less than $30 online. Together they’ll equip you with tools and abilities you never knew your Final Cut system had. Until next time, happy editing—or should I say, encoding!

Ben Balser (benb at bbalser.com) is an Apple Certified Trainer based in southeast Louisiana. He teaches Final Cut Studio for LA Tech College and the N.O. Video Access Center. Contact Ben with Final Cut Studio questions, and he will try to address them in future tutorials.