So I'd like to stream video from an RTSP stream using OpenCV, and immediately save the raw video to a file without decoding. We need high performance and might be processing as many as 500 cameras on one machine. Which means that even though typically small and 2% CPU, the extra 10x CPU needed to decode every frame adds up. When I run with ffmpeg command line it's getting so little usage it shows 0.0% CPU.
The recommendation I've seen before is just use ffmpeg, reason I'd like OpenCV is: A) We might need to do some image analysis in the future, wouldn't be on all frames though, just a small sample of them, so all still need to be saved frame by frame to file without decoding, but some will separately be decoded. B) Simpler to implement than ffmpeg (that in the future would need to pass select frames to OpenCV)
Edit: I've tried using VideoWriter::fourcc('X', '2', '6', '4'), and -1 in order to try to skip encoding. Seems like it goes ahead and does it anyway even though it's already in that format?
Thoughts? Thanks!