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• Extracting frame out of video based on time in seconds

  20 avril 2024, par Vicky

  I'm developing a web-based video editing tool where users can pause a video and draw circles or lines on it using canvas. When a user pauses the video, I retrieve the current playback time in seconds using the HTML5 video.currentTime property. I then send this time value along with the shape details to the server. On the server-side, we use FFmpeg to extract the specific paused frame from the video. The issue I'm encountering is a frame mismatch between the one displayed in the browser and the one generated in the backend using FFmpeg.

  


  I've experimented with various approaches for this process.

  


  Extracting frame based on time. Example : in this case time is 3.360 second.

  


  


  ffmpeg -i input.mp4 -ss 00:00:03.360 -frames:v 1 frame.jpg

  


  


  Converting time to frame number using the following logic : Math.round(video.currentTime * fps)

  


  


  ffmpeg -i input.mp4 -vf "select=eq(n,101)" -vsync vfr frame.jpg

  


  


  


  ffmpeg -i input .mp4 -vf "select='lt(t,3.360)lt(3.360-t,1/31.019)',setpts=N/(31.019TB)" -vsync 0 frame.jpg

  


  


  The challenge I'm facing is that sometimes the frame I see in the browser at the pause time doesn't match the one generated in the backend using FFmpeg. How can I solve this problem ? If it's an issue with currentTime, are there any other approaches I can try ?

  


• Revision 513157e093 : Scatter-based scantables. This gains about 0.2% on derf, 0.1% on hd and 0.4% on

  25 mars 2013, par Ronald S. Bultje

  Changed Paths : Modify /configure Modify /vp9/common/vp9_entropy.c Modify /vp9/decoder/vp9_dequantize.c Scatter-based scantables. This gains about 0.2% on derf, 0.1% on hd and 0.4% on stdhd. I can put this under an experimental flag if wanted, just trying to get my patch queue in shape. Change-Id : (...)

• Splitting multiple videos into shorter based on frame count

  15 décembre 2022, par LEstvs

  I can cut the video based on seconds, for example, I can cut the video from second 0 to second 10 and from second 10 to second 20. But I need to cut the video from frame 0 to frame 250 and from frame 250 to frame 500 because of some error due the counting of second. Does anyone has any idea about this ?

  


  Here is the code I use to cut based on seconds :

  


  required_video_file = "H8.avi"

with open("Z:/temp/Letícia/Videos/teste/times.txt") as f:
    times = f.readlines()

times = [x.strip() for x in times] 

for time in times:
    starttime = int(time.split('-')[0])
    endtime = int(time.split("-")[1])
    ffmpeg_extract_subclip(required_video_file, starttime, endtime, targetname=str(times.index(time)+1)+".avi")