monline

Libx264 has various preset profiles that determine how fast (and at what compression ratio + quality) it's going to work. I've run a simple, 450KB file through this on a pretty outdated server with an older (v0.6) ffmpeg. Here're the timing results (measured in seconds) for each preset profile ...

• ultrafast: 0.95
• superfast: 1.52
• veryfast: 2.94
• faster: 4.47
• fast: 8.31
• medium: 9.71 (default)
• slow: 15.07
• slower: 31.69
• veryslow: 61.53
• placebo: 145.38

The timing itself is irrelevant (you'll use different hardware and ffmpeg), but the scale isn't. Looking at the numbers you can get a feeling for how each preset relates to the others in respect of speed.