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• Accurate progress update using FFmpeg

  16 mai 2019, par ClassA

  I’m currently showing the progress inside onProgress, as shown below :

  @Override
  
      public void onProgress(String message) {
  
  
  
          Pattern pattern = Pattern.compile("time=([\\d\\w:]{8}[\\w.][\\d]+)");
  
  
  
          if (message.contains("speed")) {
  
              Matcher matcher = pattern.matcher(message);
  
  
  
              if (matcher.find()) {
  
                  String tempTime = String.valueOf(matcher.group(1));
  
                  String[] arrayTime = tempTime.split("[:|.]");
  
  
  
                  long currentTime = TimeUnit.HOURS.toMillis(Long.parseLong(arrayTime[0]))
  
                              + TimeUnit.MINUTES.toMillis(Long.parseLong(arrayTime[1]))
  
                              + TimeUnit.SECONDS.toMillis(Long.parseLong(arrayTime[2]))
  
                              + Long.parseLong(arrayTime[3]);
  
  
  
                  //Length of video in milliseconds
  
                  long timeToExportInMillis = rightThumbTimeRef - leftThumbTimeRef;
  
  
  
                  //Calculate percentage
  
                  long percent = 100 * currentTime / timeToExportInMillis;
  
  
  
                  //Set percentage to TextView
  
                  percentText.setText(percent + " %");
  
  
  
              }
  
          }
  
      }

  The problem I have is that the progress gets updated like this :

  0 - 9 - 17 - 30 - 38 etc. (till 100)

  I would like to show the progress without skipping values, like :

  0 - 1 - 2 - 3 - 4 etc. (till 100)

  ---

  I’m not even sure if this is possible because the update of currentTime (above) depends on FFmpeg’s progress output, any advice would be appreciated.

• 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 ?

  


• lavf/gif : Add an option max_gif_delay to limit the frame duration.

  29 mars 2015, par Carl Eugen Hoyos

  lavf/gif : Add an option max_gif_delay to limit the frame duration.
  Allows playback for the sample from ticket #4369 in less than 18 hours.
  

  • [DH] doc/demuxers.texi
  • [DH] libavformat/gifdec.c