randomly accessible CG archive format

Hi. Some of you may know that 7z is great for compressing similar BMP files. However it is not randomly accessible. So I thought if we can use x264 (in RGB lossless mode) to pack the CGs, then we can overcome this problem while maintain that level of compression ratio.

So are any of you x264 experts? I have put the full technical questions at http://forum.doom9.org/showthread.php?p=1588582

There is no way around the fact that all the information required to reconstruct the desired file will need to be read.

But for 7zip, if I need to reconstruct one image, I need to read every image prior to that. With x264 I just need to read the I-frame and respective P-frame (referencing to that I-frame).