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• 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


  


• How to use command of ffmpeg on android

  23 janvier 2015, par user2830969

  I download ffmpeg static from http://ffmpeg.gusari.org/static/ and I run command

  ./ffmpeg -i inputFile.mp4 -vf drawtext="fontsize=60:fontfile=/usr/share/fonts/truetype/freefont/FreeSerif.ttf:fontcolor=green:text=AAAA:x=(w-max_glyph_w)/2:y=h/2-ascent" outputFile.mp4 

  it work fine on my desktop.
  I want to use this command to run in android. I copy ffmpeg file to my android app to run command but it not work.

  public ProcessRunnable create() {
  
          if (inputPath == null || outputPath == null) {
  
              throw new IllegalStateException("Need an input and output filepath!");
  
          }   
  
  
  
          final List<string> cmd = new LinkedList<string>();
  
           public ProcessRunnable create() {
  
          if (inputPath == null || outputPath == null) {
  
              throw new IllegalStateException("Need an input and output filepath!");
  
          }   
  
  
  
          final List<string> cmd = new LinkedList<string>();
  
  
  
          cmd.add(mFfmpegPath);
  
          cmd.add("-i");
  
          cmd.add(inputPath);
  
          cmd.add("-vf");
  
          cmd.add("drawtext=\"fontsize=60:fontfile=/system/fonts/DroidSans.ttf:fontcolor=green:text=AAAA:x=(w-max_glyph_w)/2:y=h/2-a
  
          cmd.add(mFfmpegPath);
  
          cmd.add("-i");
  
          cmd.add(inputPath);
  
          cmd.add("-vf");
  
          cmd.add("drawtext=\"fontsize=60:fontfile=/system/fonts/DroidSans.ttf:fontcolor=green:text=AAAA:x=(w-max_glyph_w)/2:y=h/2-ascent\"");
  
          cmd.add(outputPath);
  
          Log.w("Command", cmd.toString());
  
          final ProcessBuilder pb = new ProcessBuilder(cmd);
  
          return new ProcessRunnable(pb);
  
      }
  
  </string></string></string></string>

  please tell me know "How can I do that ?" thanks so much

• Add multiple timecodes to single audio file (.mkv ?) resulting from concatenating several (timecode-based) audio files

  6 juin 2020, par user3497017

  I first converted two .WAV files into .MKV files inserting timecode for each of this file. Then I concatenated these two .MKV files as inputs (each .MKV including one timecode inside). However timecodes were not maintained in the final output.MKV. I tried :

  



   1. ffmpeg -f concat -i mylist.txt -c copy output.mkv  
 2. mkvmerge -o output.mkv 1.mkv + 2.mkv


  



  with mylist.txt containing :

  



  file '1.mkv'
file '2.mkv'


  



  But the final file output.mkv resulting from such a concatenation has lost timecodes in case 1. In case 2, there is only one time code that has been preserved (from input 2.mkv) at the end. According to mediaInfo command line. I was expecting 2 times codes issued from 1.mkv and from 2.mkv. But is it the right approach ? (Is it even do-able ?)

  



  To summarize, my goal is to insert multiple time codes along with / inside a single audio file (.WAV, or .MKV, or whatever). Here is a sreenshot that technically depicts my purpose enter image description here