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• Extracting frames every second of all videos in folder

  20 octobre 2023, par Sparkiepandas

  I am trying to extract a frame every second of a video, while having multiple videos in a folder. I got it working for 1 video like this, but I think I am messing up my loop for all videos. Below is the code for 1 video that works.

  



  import cv2
pathOut = r"C:/Users/Me/Out/"
vidcap = cv2.VideoCapture(r'C:\Me\Desktop\test.mp4');
count = 0
success = True
while success:
    success,image = vidcap.read()
    print('read a new frame:',success)
    if count%30 == 0 :
         cv2.imwrite(pathOut + 'frame%d.jpg'%count,image)
    count+=1


  



  With the loop for all videos I made it up like this.

  



  import os
import cv2
pathOut = r"C:/Users/Me/Out/"
count = 0
success = True
counter = 1
listing = os.listdir(r'C:/Users/Me/videos/train')
for vid in listing:
    vid = r"C:/Users/Me/videos/train/"+vid
    cap = cv2.VideoCapture(vid)
    count = 0
    counter += 1
    while success:
        success,image = cap.read()
        print('read a new frame:',success)
        if count%30 == 0 :
             cv2.imwrite(pathOut + 'frame%d.jpg'%count,image)
        count+=1


  



  My vid loop does not seems to work because it is only taking one video. Then it states false, probably because there are no frames left, but I do not know how to push it forward to the next video. I think I need to do some minor adjustment, does anybody have any idea what exactly ?

  


• Why is accessing these particular videos with ffmpeg far slower than usual ?

  8 novembre 2017, par user779159

  If I run ffmpeg -ss $TIME -i $URL -frames:v 1 -filter:v $FILTER file.jpg -v trace to get a screenshot of a video from a remote website, it normally runs quite quickly. But videos from a different website are taking much longer to run.

  All videos from one particular website are very slow. I’ve compared two videos that are 3-4MB, one from a website where ffmpeg works almost instantly (0.5 seconds) and another from a website where it works terribly slowly (15 seconds).

  Here’s the trace output for the slow video http://pastebin.pl/view/raw/4df9fb06. And here’s trace output for the fast video http://pastebin.pl/view/raw/4b590932.

  Can you identify any reason why one video is so much slower compared to all the other videos ? The ffmpeg command I ran is the one from above and the same for both videos. How can I speed this up ?

  The slow video downloads a few seconds slower than the fast video, but I don’t think the ffmpeg command should be showing such a major difference between the two files.

• FFMPEG concatenating videos with and without audios

  6 juillet 2023, par najam ulhassan

  I'm concatenating multiple videos using FFMPEG, with and without audios to certain videos, i'm using following command but FFMPEG generating error over (:a audio filer) Stream specifier ':a' in filtergraph description, matches no streams.
Even I'm using anullsrc for videos having no sound.

  


  Command :

  


  ffmpeg -i Video_202306_23_102709.mp4 -i Video_202306_23_102838.mp4 -i Screenshot_298.mp4 -i MG16885528.mp4
-f lavfi -i anullsrc=channel_layout=stereo:sample_rate=48000
-filter_complex
[0:v]scale=1280x720:force_original_aspect_ratio=decrease,pad=1280x720 :-1 :-1,setsar=1,fps=24,format=yuv420p[v0] ;
[1:v]scale=1280x720:force_original_aspect_ratio=decrease,pad=1280x720 :-1 :-1,setsar=1,fps=24,format=yuv420p[v1] ;
[2:v]scale=1280x720:force_original_aspect_ratio=decrease,pad=1280x720 :-1 :-1,setsar=1,fps=24,format=yuv420p[v2] ;
[3:v]scale=1280x720:force_original_aspect_ratio=decrease,pad=1280x720 :-1 :-1,setsar=1,fps=24,format=yuv420p[v3] ;
[0:a]aformat=sample_rates=48000:channel_layouts=stereo[a0] ;
[1:a]aformat=sample_rates=48000:channel_layouts=stereo[a1] ;
[2:a]aformat=sample_rates=48000:channel_layouts=stereo[a2] ;
[3:a]aformat=sample_rates=48000:channel_layouts=stereo[a3] ;
[v0][a0][v1][a1][v2][a2][v3][a3]concat=n=4:v=1:a=1[v][a]
-map "[v]" -map "[a]" -c:v libx264 -crf 28 -c:a aac
-movflags +faststart FinalTempVideo.mp4

  


  I'm following this query Concatenate Video in ffmpegby llogan,
It seems the :a filter is not utilize with the videos having no sound, but issue is that I couldn't distinguish between the videos having audio or not.
Moreover anullsrc is not making it a fix.