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• Is there a way to prevent black frames from appearing at the start of a video when using -c:v copy ?

  11 juillet 2023, par MethanE

  My task seems simple. Using ffmpeg in terminal, I'm trying to pass through the exact video settings minus the audio, and i've been successful, except for the fact that the videos start with a frame of black before the actual video plays.

  


  currently using this :

  


  for i in *.*;do ffmpeg -i "$i" -an -c:v copy "${i%.*}_noaudio.mp4";done


  


  My current thought is it may be related to the error I'm getting (the vid still exports), but I'm not certain :
Missing key frame while searching for timestamp : 1001

  


  Input video metadata :

  


  Metadata :
major_brand : XAVC
minor_version : 16785407
compatible_brands : XAVCmp42iso2
creation_time : 2021-09-12T20:13:46.000000Z
Duration : 00:00:17.52, start : 0.000000, bitrate : 107315 kb/s
Stream #0:0(und) : Video : h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709), 3840x2160 [SAR 1:1 DAR 16:9], 96798 kb/s, 23.98 fps, 23.98 tbr, 24k tbn, 47.95 tbc (default)

  


  Googling led me to try not using -c:v copy as there might be a glitch related to h264 keyframes and instead using -c:v libx264 but i really don't want to have to re-encode as I don't want to lose any quality. The file I tried this on went from 135 mb down to 6.

  


  Thanks for your help. Kind of a newb at this.

  


• ffmpeg overlay picture is a black rectangle

  6 juin 2023, par robert

  I'm trying to overlay several images over an existing video, with the first image coming in with a fade-in effect. But instead I'm getting a black rectangle in place of the picture. But if I skip the fade-in and just put [img0] after decrease like so decrease[img0] then it works (but without fade in)

  


  please advise. TY

  


  -y
-i "G:\...\Videos\BLANK.mp4" 
-i "G:\...\Front\1.jpg" 
-i "G:\...\Front\2.jpg" 
-i "G:\...\Front\3.jpg" 
-i "G:\...\Front\4.jpg" 
-i "G:\...\Front\5.jpg" 
-i "G:\...\Front\6.jpg" 

-filter_complex [1:v]scale=880:545:force_original_aspect_ratio=decrease,fade=t=in:st=2.6:d=1[img0];
[0:v][img0]overlay=x='if(lte(2.6-t,0),450,NAN)':y='if(lte(2.6-t,0),5,NAN)':enable='between(t,2.6,4)'[v0];
[2:v]scale=880:545:force_original_aspect_ratio=decrease[img1];
[v0][img1]overlay=x='if(lte(4-t,0),450,NAN)':y='if(lte(4-t,0),5,NAN)':enable='between(t,4,5.6)'[v1];
[3:v]scale=880:545:force_original_aspect_ratio=decrease[img2];
[v1][img2]overlay=x='if(lte(5.6-t,0),450,NAN)':y='if(lte(5.6-t,0),5,NAN)':enable='between(t,5.6,6.3)'[v2];
[4:v]scale=880:545:force_original_aspect_ratio=decrease[img3];
[v2][img3]overlay=x='if(lte(6.3-t,0),450,NAN)':y='if(lte(6.3-t,0),5,NAN)':enable='between(t,6.3,6.9)'[v3];
[5:v]scale=880:545:force_original_aspect_ratio=decrease[img4];
[v3][img4]overlay=x='if(lte(6.9-t,0),450,NAN)':y='if(lte(6.9-t,0),5,NAN)':enable='between(t,6.9,7.4)'[v4];
[6:v]scale=880:545:force_original_aspect_ratio=decrease[img5];
[v4][img5]overlay=x='if(lte(7.4-t,0),450,NAN)':y='if(lte(7.4-t,0),5,NAN)':enable='between(t,7.4,7.9)'[v5];

 -map [v5] -map 0:a -c:v libx264 -c:a copy "G:\...\Videos\ffmpeg\output.mp4"


  


• ffmpeg black screen issue for video video generation from a list of frames

  11 mai 2023, par arlaine

  I used a video to generate a list of frames from it, then I wanted to create multiple videos from this list of frames.
I've set starting and ending frames indexes for each "sub video", so for example,
indexes = [[0, 64], [64, 110], [110, 234], [234, 449]], and those indexes will help my code generate 4 videos of various durations. The idea is to decompose the original video into multiple sub videos. My code is working just fine, the video generated.

  


  But every sub video start with multiple seconds of black screen, only the first generated video (so the one using indexes[0] for starting and ending frames) is generated without this black screen part. I've tried changing the frame rate for each sub_video, according to the number of frames and things like that, but I didn't work. You can find my code below

  


  for i, (start_idx, end_idx) in enumerate(self.video_frames_indexes):
    if end_idx - start_idx > 10:
        shape = cv2.imread(f'output/video_reconstitution/{video_name}/final/frame_{start_idx}.jpg').shape
        os.system(f'ffmpeg -r 30 -s {shape[0]}x{shape[1]} -i output/video_reconstitution/{video_name}/final/frame_%d.JPG'
              f' -vf "select=between(n\,{start_idx}\,{end_idx})" -vcodec libx264 -crf 25'
              f' output/video_reconstitution/IMG_7303/sub_videos/serrage_{i}.mp4')


  


  Just the ffmpeg command

  


  ffmpeg -r 30 -s {shape[0]}x{shape[1]} -i output/video_reconstitution/{video_name}/final/frame_%d.JPG -vf "select=between(n\,{start_idx}\,{end_idx})" -vcodec libx264 -crf 25 output/video_reconstitution/IMG_7303/sub_videos/serrage_{i}.mp4