Simple solution to show frame number and frame time in VLC or other video players.

frame_subtitles.py

""" @xvdp
Simple solution  to Show frame number and frame time with VLC or other video players
Make a subtitle file

caveats:
  only tested in linux
  requires ffmpeg / only tested with ffmpeg 4.3
  only tested with limited number of .mov and .mkv files
  it may fail if ffprobe reports nb_frames, DURATION or frame_rate with keys not parsed here.
  
 ffplay -i my_video.mp4 -vf "subtitles=my_video_subtitles.srt"
"""

import sys
import os
import os.path as osp
import json


def frame_subtitles(filename, stream=0):
    """ creates frame number and frame time from video
    """
    nb_frames, frame_rate = ffmpeg_stats(filename, stream)
    make_subtitle(filename, nb_frames, frame_rate, stream)

def make_subtitle(filename, nb_frames, frame_rate, stream=0):
    """ 
    nb_frames and some form of frame_rate you can get from ffprobe
    depending on how video was recorded there may be an avg_frame_rate and DURATION pr...
    """
    fname = osp.abspath(filename)
    assert osp.isfile(fname), f"file not found {fname}"
    name = f"{osp.splitext(fname)[0]}_frames.srt"
    print(f"Making Frame / Frame time subtitle file {filename} stream [{stream}] -> {name}")

    sub = ""
    last_frame = frame_to_time(0, frame_rate)
    for i in range(nb_frames):
        next_frame = frame_to_time(i+1, frame_rate)
        sub += f"{i+1}\n{last_frame} --> {next_frame}\n\t{i+1}\t{last_frame}\n\n"
        last_frame = next_frame
    with open(name, 'w', encoding='utf8') as _fi:
        _fi.write(sub)


def ffmpeg_stats(filename, stream=0):
    """ return (nb_frames, frame_rate) from video filename
    """
    _cmd = f"ffprobe -v quiet -print_format json -show_format -show_streams {filename}"
    with os.popen(_cmd) as _fi:
        stats = json.loads(_fi.read())

    if 'streams' in stats:
        videos = [s for s in stats['streams'] if s['codec_type'] == 'video']
    assert videos is not None, f'no video streams found in {filename}'

    if len(videos) > 1:
        print(f"video {filename} cotains {len(videos)} streams, processing stream={stream}")
    _stats = videos[stream]

    _frame_rate_keys = [k for k in _stats if 'frame_rate' in k]
    assert len(_frame_rate_keys), f"no frame_rate keys found in  {filename}\n{json.dumps(_stats)}"
    frame_rate = eval(_stats[_frame_rate_keys[0]])

    if 'nb_frames' in _stats:
        nb_frames = eval(_stats['nb_frames'])
    elif 'tags' in _stats and 'DURATION' in _stats['tags']:
        duration = _stats['tags']['DURATION']
        seconds = sum(x * float(t) for x, t in zip([3600, 60, 1], duration.split(":")))
        nb_frames = round(seconds * frame_rate)
    else:
        print(f"neither 'nb_frames' and 'DURATION' found in stream\{json.dumps(_stats)}")
        return None

    return nb_frames, frame_rate

def frame_to_time(frame=0, frame_rate=30):
    """convert frame number to time"""
    t = frame/frame_rate
    _t = int(t)
    return f"{(_t//3600)%24:02d}:{(_t//60)%60:02d}:{_t%60:02d}.{(int((t - _t)*1000)):03d}"


if __name__ == "__main__":
    assert len(sys.argv) > 1, "usage: $ python frame_subtitles.py <video_file>"
    frame_subtitles(sys.argv[1])