Howto mix two CVBS Video streams?

[Altera_Forum]

Hi, I'm planning to do a Picture-In-Picture application using 2 Video ADC and a Cyclone FPGA with some SDRAM attached. 

 I know how in principle stuff is digitized, sync codes extracted and colorspace converted so that one can store a frame in the external SDRAM.  I'm not shure how to syncronize two video streams, because the framerates will have a slow drift because the 2 cameras attached are free running and not synchronized.  So once a while I have to drop a frame when e.g. CAM1 "overtakes" CAM2, do I?  Is the mixing normally done on a line base or is it better to do it frame by frame?  How do I resize a picture?  Does anyone have good literature about scaling algorithms and / or video processing in general?  Markus

[Altera_Forum]

Past analog video systems always used a central sync supplied to each camera. With digital video, frame buffering may be used instead. Image scaling is applied to full frames anyway. 

 Altera, by the way, has a collection of Megafunctions for digital image processing, e. g. a scaler.