Submitted a real time HD video shot at 25 fps saved as MP4 with ambient sound and had this rejection from Dreamstime:

"For best quality when submitting time lapses or computer generated graphics please use the required format (Quicktime MOV) and codec (PhotoJPEG or MJPEG A/B) with a compression between 70% and 90%. Make sure you are using the highest quality source to minimize degradation due to compression."

Odd as it's not time lapse or computer generated.  They taken MP4 previously I don't use MOV due to the lack of a MAC (Windows PC)

They have me stumped any ideas?

Thanks Gannet

I tried saving a test file as MOV motionjpeg and the file was huge but the playback was really crappy looking compared to MP4

Perhaps I'll just ignore Dreamstime for video uploads.  Pond 5 took them with no problems. 

Here is a short tutorial how to get clips through MPEG Streamclip: http://video-stock.org/quick-and-simple-quicktime-photo-jpeg-stock-video-exporting/