How to write frames to a video file?

I am currently writing an application that read frames from camera, modify them, and save them into a video file. I'm planing to do it with ffmpeg. There's rarely a documentation about ffmpeg. I can't find a way. Does any know how to do it?

I need it to be done on unix, and in C or C++. Does any can provide some instructions?

Thanks.

EDIT:

Sorry, I haven't write clearly. I want some developer APIs to write frames to a video file. I open up camera stream, I get every single frame, then I save them into a video file with those APIs available in ffmpeg's public apis. So using command line tool actually doesn't help me. And I've seen output_example.c under the ffmpeg src folder. It's pretty great that I may copy some parts of the code directly without change. And I am still looking for a easier way.

Also, I'm thinking of porting my app to iPhone, as far as I know, only ffmpeg has been ported on iPhone. GStreamer is based on glib, and it's all GNU stuff. I'm not sure if I can get it work on iPhone. So ffmpeg is still the best choice for now.

Any comments is appreciated.

Solution

This might help get you started - the documentation is available, but newer features tend to be documented in ffmpeg's man pages.

The frames need to be numbered sequentially.

ffmpeg -f image2 -framerate 25 -i frame_%d.jpg -c:v libx264 -crf 22 video.mp4

-f defines the format
-framerate defines the frame rate
-i defines the input file/s ... %d specifies numbered files .. add 0's to specify padding, e.g. %05d for zero-padded five-digit numbers.
-vcodec selects the video codec
-crf specifies a rate control method, used to define how the x264 stream is encoded
video.mp4 is the output file

For more info, see the Slideshow guide.