Recherche avancée

Sur d’autres sites (7130)

• avcodec/mpeg12dec : Don't initialize unused parts of ScanTable

  24 février, par Andreas Rheinhardt

  avcodec/mpeg12dec : Don't initialize unused parts of ScanTable
  The MPEG-1/2 decoders don't need ScanTable.raster_end
  
  (as the coefficients are unquantized as they are parsed).
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
  

  • [DH] libavcodec/mpeg12dec.c

• Revision 33331 : simplifier les petitions : le tableau des signatures utilise les classe ...

  27 novembre 2009, par cedric@… — Log

  simplifier les petitions : le tableau des signatures utilise les classe generiques table.spip et autre qui lui permet d’etre par defaut dans le theme. Les class specifiques sur chaque element restent utilisables pour affiner si (...)

• 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 ?