Decoding h264

Many video files (including the ones on this site) are often distributed as files which use a codec called h264. This is a highly efficient codec which offers a high rate of visual quality along and compression (i.e. looks great, small filesize). The downside of h264 is that the videos takes a substantial amount of processing power to decode and display; many computers, even decently modern ones, are unable to do this in real-time and thus h264 playback can be choppy or even unplayable.

The easiest solution is to convert the video to another codec that is not as compact but can be decoded more easily. I would recommend using a free utility called MPEG Streamclip, which can be found at Squared 5. You will want to open your h264-encoded video file (.mp4's from this site) and re-encode them to another codec. The sample settings below can be reached by exporting the file with File->Export to MPEG-4, and should produce files that are playable on most computers.

Note that this will produce a file that is significantly larger than the original h264 file. If you want to reduce filesize, you can lower the quality setting, or reduce the frame size (be sure to maintain the aspect ratio - use something like 960x540 for 1920x1080 video to keep the 16:9 width:height ratio), though this will reduce the visual quality.