Express Yourself

Smoothness and Packet Controls
The final video-related compression control relates to Video Complexity and Packet Size. According to the Help file and very useful and detailed tool tips, complexity controls encoding speed, with 0–2 used for live, depending upon your encoding hardware, and 3–5 optimized for offline encoding. Technically, this value controls functions that can extend encoding times, like search patterns for interframe redundancies and the like.

To get a feel for the time difference produced by the various values, I ran two encoding test-runs on my HP xw8400 Dual Processor, Quad-Core computer, one at a complexity setting of zero, the other at five. In both tests, I encoded a 1-minute source file with variable low and high motion content to VC-1 Main Profile format at 895Kbps (480x360@30fps) using 2-pass CBR.

At a complexity setting of zero, the file took 39 seconds to encode, which jumped to 3:40 at a setting of five. When I compared the files, I definitely noticed better quality on the clip encoded at a setting of five. Unless you’re time-constrained, you should consider running all encoding runs at a complexity setting of five.

A/B Compare
Then it struck me: Rather than encoding separate files, why not try Expression Encoder’s A/B Compare to perform the same analysis? The theory is simple—you want to compare multiple encoding parameters before finalizing encoding parameters. So you choose your first set of parameters, then enter A/B Compare Mode by clicking the eponymous button. Then you drag the green markers in the timeline panel to the frames you’d like to compare, and click the Build Preview button.

After performing this action once, you have two items to compare: the original file and the encoded file, which has limited utility. However, if you change any encoding parameter, the Build Preview button becomes active, and you can click it to create another alternative to compare.

You can display the two videos side-by-side or in a split screen view that works similarly to Apple’s Compressor. You choose which encoding alternative to display in each window (or on which side in the split screen display) with the A and B drop-down lists.

How do you keep track of which alternative is which? The encoding properties for the encoding run shown on the right (in the B list box) appear in the Video Profiles menu. It’s definitely a neat feature, and it provides a more advanced preview function than any other encoder I’ve seen.