CODEWITHSUNDEEP
pythonffmpeg
Mark C
Mark C

Reputation: 141

Losing frames when clipping videos with ffmpeg

I seem to be losing frames when I clip videos up with ffmpeg.

Here are the steps I take:

[Get the Frame number to cut on] -> [turn the frame number into hh:mm:ss.ms format] -> [Run ffmpeg process]

Here is the code:

import subprocess

def frames_to_timecode(frame,frameRate):
    '''
    Convert frame into a timecode HH:MM:SS.MS
    frame = The frame to convert into a time code
    frameRate = the frame rate of the video
    '''
    #convert frames into seconds
    seconds = frame / frameRate

    #generate the time code
    timeCode = '{h:02d}:{m:02d}:{s:02f}'.format(
    h=int(seconds/3600),
    m=int(seconds/60%60),
    s=seconds%60)

    return timeCode

frameRate = 24.0

inputVideo = r"C:\Users\aquamen\Videos\vlc-record-2018-10-23-17h11m11s-SEQ-0200_animatic_v4_20180827_short.mp4"
outputVideo = r"C:\Users\aquamen\Videos\ffmpeg_test_clip001.mp4"
ffmpeg = r"C:\ffmpeg\ffmpeg-20181028-e95987f-win64-static\bin\ffmpeg.exe" 

endFrame = frames_to_timecode(29,frameRate)
startFrame = frames_to_timecode(10,frameRate)

subprocess.call([ffmpeg,'-i',inputVideo,'-ss',startFrame,'-to',endFrame,outputVideo])

Here is a image of the original video and the clipped video with the time codes showing a frame was lost in process. The time code should show 00:01:18:10 instead its 00:01:18:11.

Original Video that clip was taken from

Clipped Video that's missing the frame

Upvotes: 0

Views: 1177

Answers (1)

Mark C
Mark C

Reputation: 141

So a friend of mine figured this out. So if you divide the frame by the fps (Frame/fps) you get the point of when that frame needs to be cut with the -ss but the problem is by default python rounds the 12 decimal place. So you need to NOT round the number and give ffmpeg only up to 3 decimal places.

So here is my revised code for any one running into this problem. If you want to cut a video on the Frame number use this:

import subprocess


def frame_to_seconds(frame,frameRate):
    '''
    This will turn the frame into seconds.miliseconds
    so you can cut on frames in ffmpeg
    frame = The frame to convert into seconds
    frameRate = the frame rate of the video
    '''
    frameRate = float(frameRate)
    seconds = frame / frameRate
    result = str(seconds - seconds % 0.001)

    return result

inputVideo = "yourVideo.mp4"

outputVideo = "clipedVideo.mp4"
ffmpeg = r"C:\ffmpeg\bin\ffmpeg.exe" 

frameRate = 24

subprocess.call([ffmpeg,
                 '-i',inputVideo,
                 '-ss',frame_to_seconds(10,frameRate),
                 '-to',frame_to_seconds(20,frameRate),
                 outputVideo])

Upvotes: 4

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