FFmpeg - Add frames to MP4 in multiple calls

Question

I'm trying to use FFmpeg to create an MP4 file from user-created content in an Android app.

The user-created content is rendered with OpenGL. I was thinking I can render it to a FrameBuffer and save it as a temporary image file. Then, take this image file and add it to an MP4 file with FFmpeg. I'd do this frame by frame, creating and deleting these temporary image files as I go while I build the MP4 file.

The issue is I will never have all of these image files at one time , so I can't just use the typical call:

ffmpeg -start_number n -i test_%d.jpg -vcodec mpeg4 test.mp4

Is this possible with FFmpeg? I can't find any information about adding frames to an MP4 file one-by-one and keeping the correct framerate, etc...

Answer 1

Use STDIO to get the raw frames to FFmpeg. Note that this doesn't mean exporting entire images... all you need is the pixel data. Something like this...

ffmpeg -f rawvideo -vcodec rawvideo -s 1920x1080 -pix_fmt rgb24 -r 30 -i - -vcodec mpeg4 test.mp4

Using -i - means FFmpeg will read from the pipe.

I think from there you would just send in the raw pixel values via the pipe, one byte per color per pixel. FFmpeg will know when you're done with each frame since you've passed the frame size to it.