I have placed a number of video samples at http://www.bound2burst.net/test.html using the same sequence as before, but with output in Quicktime, MP4 and WMV at a resolution of 1280x720 pixels but with five different bitrates. The file sizes are listed, and the clip is always 35 seconds long.
Obviously, I am looking for the lowest acceptable bitrate to keep the file sizes as small as possible without sacrificing all that HD has to offer. At the upper end, the file size is around 70 MB per minute which is clearly too high for downloads, except for very short clips. Obviously, one could produce a 5-minute clip at a high bitrate, but the downside is that the file would be more expensive because now the Dreamhost download fee we pay is bigger (it is $1 for every 400 MB). Short clips would be equivalent in cost to Clips4Sale prices of around $1 per minute.
Dropping down to a bitrate of 4000 kbps, the file size is around 32 MB per minute, making a 20-minute movie clip 640 MB. It's doable, but again the price will have to increase to cover the extra bandwidth for download.
In my opinion, the old 2,500 kbps option is too low and the movie quality suffers badly for it. This shows much less with DV 640x480 pixels, which is what I have been using, but with HD the loss is great. It does give a file size of around 18 MB per minute (the DV versions were around 15 MB per minute of video).
Please play the various formats and bitrates and let me know what you think so that I can provide you with the quality and file sizes you can live with.
Thanks for your time,
Dave.
P.S. I am also in touch with several people who have more experience than I with manipulating video encoding, and I hope that they can help me improve on the above values.