gstreamer: v4l2src/filesrc x264enc appsink
This Makefile is generic for all *.c files below.
For each *.c file, just a simple modification is required.
v4l2-enc-appsink.c
file-enc-appsink.c
The gstreamer pipeline is v4l2src--srccapsfilter--timeoverlay--x264enc--enc_queue--appsink.
It will save 20s of the h264 video.
The gstreamer pipeline is filesrc--videoparse--timeoverlay--x264enc--enc_queue--appsink.