import os
import subprocess

def freezeLastFrame(tmpdir, fVideoStream, freeze_s, fVideoStreamOut):
    try:
        # import subprocess, os

        E = os.environ.copy()
        E.update({
            'TMP': tmpdir,
            'SRC': fVideoStream,
            'FREEZE_S': str(freeze_s),
            'DST': fVideoStreamOut
        })

        cmd = '''
            cd "$TMP"
            
            FFMPEG="ffmpeg  -y  -hide_banner  -nostats"

            # get last frame
            NFRAMES=`ffprobe -show_streams "$SRC" 2> /dev/null | grep nb_frames | head -1 | cut -d \= -f 2`
            let "LAST_FRAME=$NFRAMES-1"
            
            $FFMPEG  -i $SRC  -vf select=\\'eq\(n,$LAST_FRAME\)  -vframes 1  LAST_FRAME.jpg
            
            # make last-frame-frozen video
            FRAMERATE=`ffprobe  -v 0  -of csv=p=0  -select_streams 0  -show_entries stream=r_frame_rate  "$SRC"`
            $FFMPEG  -loop 1  -framerate 1  -i LAST_FRAME.jpg  -r "$FRAMERATE"  -t "$FREEZE_S"  LAST_FRAME.mp4  # -pix_fmt yuv420p
            
            # Produces list.txt like this:
            #     file foo.mp4
            #     file 'bar with spaces.mp4'
            printf "file %q\\n"  "$SRC" LAST_FRAME.mp4  > list.txt
            
            # concatenate
            # $FFMPEG  -f concat  -safe 0  -i list.txt  -c copy  "$DST"  # problem: sometimes get green-screen for LAST_FRAME.mp4 duration
            $FFMPEG -i "$SRC"  -i LAST_FRAME.mp4 -filter_complex "[0:v] [1:v] concat=n=2:v=1 [v]"  -map "[v]" "$DST"

            # from https://stackoverflow.com/questions/7333232/how-to-concatenate-two-mp4-files-using-ffmpeg
            '''

        # subprocess.Popen( cmd, env=E )
        subprocess.check_output(cmd, shell=True, env=E, executable="/bin/bash")

    except subprocess.CalledProcessError as e:
        print('freezeLastFrameIfVideoShorter Error:' + str(e))

    except:
        print('freezeLastFrameIfVideoShorter unknown Error!')

    return fVideoStreamOut

freezeLastFrame(tmpdir='.', fVideoStream='./SampleVideo_1280x720_1mb.mp4', freeze_s=3, fVideoStreamOut='out.mp4')