Append A Frame (PNG) FFMPEG To existing video, Make changes all the video - libx264

I want to append a frame to existing video by using ffmpeg.

p0.png, p1.png and p2.png (3 frames)

by this command ffmpeg generate first video:

ffmpeg -framerate 4 -f image2 -s 1280x720 -i p%d.png -vcodec libx264 -b 80k test1.mp4

Then i want to append a frame to last of video, but total video in HEX-View will be changed. I use this comm开发者_C百科and to append:

ffmpeg -framerate 4 -f image2 -s 1280x720 -t 1 -i new_pic.png -i test1.mp4 -vcodec libx264 -b 80k test2.mp4

Please see image below:

Please see this screen shot

But i want only append some hex code to end of first video....

Please help me. Thanks

I tried many commands. I did not get any results