I stated to upload some footages to some stock sites in recently, I use my Canon Eos 7d to shoot them. About the code, the camera saved as H.264, but I found most files in stock site are Photo-jpeg. The P-jpeg is much bigger than H.264, as a 20s footage, in H.264 the size is about 250MB, but when I convert it to P-jpeg it becomes more than 1GB, it's a huge expand.

So this is the problem, does it necessary to convert the H.264 to P-jpeg? if I convert, the quality of the footage will be decrease? or what is the real different between H.264 and P-jpeg except the size.

 I have been upload more than 80 files in SS\POND5\Motionelements and get accepted, I think it's ok for stock site to submit H.264, but I don't know the sale situation. I have not get a sale for now, I am a totally newbie in stock footage

I convert to photo JPEG. I think your problem might be that you are saving the files at max quality. All sites state to save in high quality, not max because it creates a huge file with no discernible quality difference. P JPEG is a more generally accepted codec. What software are you outputting with?

After effects CC