Export from QT Pro as AVI reduces quality of video drastically

Question

I need AVI for poor PC users in family.
Original video is AVI from a Samsung digital still camera, saved and edited in QTPro 7.2 on iMac.
Export as AVI using Default or Highest Quality Settings, results in a severe degradation of colour tonal gradation - which was OK in the original AVis (viewable in Quicktime), and in QT.
It looks like the number of colours has been reduced from thousands to hundreds ( ? 256)
Filesize is similar- MOV 41.6 MB, AVI 39.5 MB.

Answer 1

The only detail given in the Samsung Pro 815 manual is "file type .avi (MJPEG)". I used default Cinepak compression to export as .avi
Now we're getting somewhere. Motion JPEG is a common video codec used by certain digital camera manufacturers in the AVI container. It is a moderate compression/higher quality codec. Cinepak is an older, high efficiency video codec probably better suited to smaller resolution use. Comparing CinePak to MJPEG would, in some ways, be like comparing MPEG-4 to H.264. In both cases the video data rate of your final "Cinepak" AVI needs to be on the order of 2.0-2.5 times the data rate of your original "MJPEG" AVI file for equivalent quality. While I do not normally deal with such files, a previous poster ask for help in converting his Casio (MJPEG/DVI ADPCM) files for use in iMovi '08. Wile the original file is not of the highest quality, I prepared a clip to compare the original "MJPEG" AVI video track with the final "Cinepak" AVI track. (For comparison purposes, these two tracks were stored in an MOV file container so they could be compared on a "frame-to-frame" basis.) If interested, here is the URL for this comparison.
http://homepage.mac.com/jrwalker4/.Public/CIMG8145Comp.mov
For QT7 Pro to edit the original .avi clips, they have to be saved as .mov.
Strange. I can convert directly from the "MJPEG" AVI to "Cinepak" AVI file.
This is instantaneous, and causes no quality loss. No file conversion or re/de/compression seems to occur.
Correct.
Exporting Cinepak .avi obviously requires considerable processing, so it seems that the codec used in the Samsung .avi is native to QT
This codec basically sequences a series of still JPEG photos in either the AVI or MOV file container. As such it is compatible with probably any system capable of viewing JPEG photos and opening either file container. This compatibility is probably the reason this codec was selected in the first place by the camera manufacturer.
The issue is clearly that the QT7 >Cinepak .avi export process (?deliberately) degrades video quality, without reducing file size, even though it claims to be using "Best" quality and "millions" of colours.
Each codec has its own characteristics. If a small file is what you want, then reduce the resolution of your movie or accept the reduction in quality at its current resolution. If quality is your main concern, then increase your video data rate so it can store as much of the original quality as it can at the current resolution or simply switch to a more modern codec, Microsoft ended support for the AVI file container a decade ago.
Is there a secret QT setting, or plug-in, which will do the export without loss of quality, to an .avi or other format which bog-standard WMP on XP will play?
As demonstrated in the sample file above, the only setting that needs to be changed is the data rate. As to other possible compression formats, you could use more modern codecs like WMV 9 (Flip4Mac) or DivX 6.