68k Mac Video Settings
This documents an attempt at finding reasonable video encoding settings for 68k Macs running System 7. Apple's QuickTime samples from 7.6.1 and OS8 era use Cinepak at around 320x240 2175kbits/sec at 15fps, so that seems like a good starting point. Target systems were 68(LC)040 based at 25 to 33Mhz. Playback over AppleShare is also desireable, as 11minutes of Cinepak at 320x240 with a reasonable bitrate is approx 200MB, which is a lot of space for these legacy machines.
Legacy Encoding on Mac OS X
All video is starting out in modern formats and the desired result is as high quality and smooth playback as possible on legacy systems. So, we start encoding on modern systems using legacy codecs. The best way to do this seems to be QuickTime Pro on Mac OS X. ffmpeg and mencoder only have a cinepak decoder, no encoder. However, on 10.5 legacy codecs are disabled by default (they can be enabled in the QuickTime PreferencePane under the Advanced tab). On 10.6, you need the QuickTime 7 Player installed, which is an optional install included on your installation media. Once installed, legacy codecs aren't enabled and there is no PreferencePane to enable them. The following command should enable them:
qtdefaults write LegacyCodecsEnabled yes. Once enabled, encoding is accomplished simply by opening a video file in QuickTime 7 Player, and exporting it with the proper settings.
Results
Trying to do 24fps or higher on an 040 machine seemed like too much. I was getting frame drops and jerky playback, even at lower resolutions or bitrates. However, for TV clips and the like, 15fps is just too slow. You end up losing some key moments, like a giraffe being hit by a speeding train in Robot Chicken. You can usually infer what happened, but it's like inferring the punchline from a joke. Ultimately, I ended up encoding at 24fps, 320x240, 1800kbps Cinepak. This is about the best playback settings I could get. It was watchable, but not terribly enjoyable.