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• How to automate ffmpeg to split and merge parts of video, and keep the audio in sync ?

  9 décembre 2024, par Tree

  I have a Python script that automates trimming a large video (2 hours) into smaller segments and then concatenating them without re-encoding, to keep the process fast. The script runs these ffmpeg commands :

  


  import subprocess

# Extract chunks
segments = [(0, 300), (300, 600), (600, 900)]  # example segments in seconds
for i, (start, length) in enumerate(segments):
    subprocess.run([
        "ffmpeg", "-i", "input.mp4", "-ss", str(start), "-t", str(length),
        "-c", "copy", "-reset_timestamps", "1", "-y", f"chunk_{i}.mp4"
    ], check=True)

# Create concat list
with open("list.txt", "w") as f:
    for i in range(len(segments)):
        f.write(f"file 'chunk_{i}.mp4'\n")

# Concatenate
subprocess.run([
    "ffmpeg", "-f", "concat", "-safe", "0",
    "-i", "list.txt", "-c", "copy", "-y", "merged_output.mp4"
], check=True)


  


  All chunks come from the same source video, with identical codecs, resolution, and bitrate. Despite this, the final merged_output.mp4 sometimes has audio out of sync—especially after the first chunk.

  


  I’ve tried using -ss before -i to cut on keyframes, but the issue persists.

  


  Question : How can I ensure correct A/V sync in the final concatenated video when programmatically segmenting and merging via ffmpeg without fully re-encoding ? Is there a way to adjust the ffmpeg commands or process to avoid audio desynchronization ?

  


• How to convert 7sec Video to Gif Android

  21 août 2014, par Donnie Ibiyemi

  Am making an app that convert shot video clips to Gif. i was wondering if there was a libary that directly converts videos to gifs on the Fly on Android.

  I’ve tried to extract all the frames of the video and encode them into a gif but am only getting the the first frame of the video. my code is below :

           public static final int GIF_DELAY_BETWEEN_FRAMES = 100;  
  
           public static final float SPEED_RATIO = 1.1f; 
  
  
  
           Uri videoFileUri=Uri.parse(mOutputFile.toString());
  
          FFmpegMediaMetadataRetriever retriever = new FFmpegMediaMetadataRetriever();
  
          retriever.setDataSource(mOutputFile.getAbsolutePath());
  
           rev = new ArrayList<bitmap>();
  
          MediaPlayer mp = MediaPlayer.create(RecorderActivity.this, videoFileUri);
  
           int millis = mp.getDuration();
  
           for(int i=1000000;itest.gif");
  
              outStream.write(generateGIF());
  
              outStream.close();
  
           }catch(Exception e){
  
              e.printStackTrace();
  
           }
  
  
  
  
  
          public byte[] generateGIF() {
  
          ByteArrayOutputStream bos = new ByteArrayOutputStream();
  
          AnimatedGifEncoder encoder = new AnimatedGifEncoder();
  
          encoder.setDelay((int)(GIF_DELAY_BETWEEN_FRAMES * (1 / SPEED_RATIO)));
  
          encoder.start(bos);
  
          for (Bitmap bitmap : rev) {
  
              encoder.addFrame(bitmap);
  
          }
  
          encoder.finish();
  
          return bos.toByteArray();
  
       }
  
  </bitmap>

  Please help me guys...thanks

• FFMPEG with moviepy

  5 novembre 2023, par Shenhav Mor

  I'm working on something that concatenate videos and adds some titles on through moviepy.

  


  As I saw on the web and on my on pc moviepy works on the CPU and takes a lot of time to save(render) a movie. Is there a way to improve the speed by running the writing of moviepy on GPU ? Like using FFmpeg or something like this ?

  


  I didn't find an answer to that on the web, so I hope that some of you can help me.
I tried using thread=4 and thread=16 but they are still very very slow and didn't change much.

  


  My CPU is very strong (i7 10700k), but still, rendering on moviepy takes me for a compilation with a total of 8 minutes 40 seconds, which is a lot.

  


  Any ideas ?Thanks !
the code doesnt realy matter but :

  


  def Edit_Clips(self):

    clips = []

    time=0.0
    for i,filename in enumerate(os.listdir(self.path)):
        if filename.endswith(".mp4"):
            tempVideo=VideoFileClip(self.path + "\\" + filename)

            txt = TextClip(txt=self.arrNames[i], font='Amiri-regular',
                           color='white', fontsize=70)
            txt_col = txt.on_color(size=(tempVideo.w + txt.w, txt.h - 10),
                                   color=(0, 0, 0), pos=(6, 'center'), col_opacity=0.6)

            w, h = moviesize = tempVideo.size
            txt_mov = txt_col.set_pos(lambda t: (max(w / 30, int(w - 0.5 * w * t)),
                                                 max(5 * h / 6, int(100 * t))))

            sub=txt_mov.subclip(time,time+4)
            time = time + tempVideo.duration

            final=CompositeVideoClip([tempVideo,sub])

            clips.append(final)

    video = concatenate_videoclips(clips, method='compose')
    print("after")
    video.write_videofile(self.targetPath+"\\"+'test.mp4',threads=16,audio_fps=44100,codec = 'libx264')