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• How to use the actual frame numbers in filenames using ffmpeg when extracting frames ? [closed]

  2 juin 2024, par Joan Venge

  Basically I am using ffmpeg to extract every Nth frame from a video. But the filenames appear sequentially from 1 to X. I want to use the actual frame numbers so if it's every 30th frame, then the filenames should be 0, 30, 60, etc. Is this possible ?

  


  I am doing this in Python using this function :

  


  def extract_and_compress_frames(directory, frame_interval=1, crop_width=192, crop_height=108, offset_x=0, offset_y=0):
    for filename in os.listdir(directory):
        if filename.endswith(".trec"):
            # Construct full file path
            trec_path = os.path.join(directory, filename)
            mp4_path = os.path.join(directory, filename.replace(".trec", ".mp4"))
            frames_dir = os.path.join(directory, filename.replace(".trec", ""))
            
            # Rename .trec to .mp4
            os.rename(trec_path, mp4_path)
            
            # Create directory for frames
            os.makedirs(frames_dir, exist_ok=True)
            
            if frame_interval == 1:
                # Calculate crop positions for bottom-right corner after scaling to 1080p
                scaled_width = 1920
                scaled_height = 1080
                crop_x = scaled_width - crop_width - offset_x
                crop_y = scaled_height - crop_height - offset_y
                
                # Extract and compress all frames using ffmpeg with quality adjustment
                ffmpeg_cmd = [
                    'ffmpeg', 
                    '-i', mp4_path,
                    '-vf', f"fps=60,scale=1920:1080,crop={crop_width}:{crop_height}:{crop_x}:{crop_y}", 
                    '-q:v', '10',  # Adjust the quality, 1 (best) to 31 (worst), 2 for good quality
                    os.path.join(frames_dir, '%06d.jpg')  # 6 digits for padding, starting from 0
                ]
            else:
                # Use frame interval and scale to 720p
                ffmpeg_cmd = [
                    'ffmpeg',
                    '-reinit_filter', '0',
                    '-i', mp4_path,
                    '-vf', f"fps=60,scale=1920:1080,crop={crop_width}:{crop_height}:{1920-crop_width-offset_x}:{1080-crop_height-offset_y},drawtext=text='%{{n}}':start_number=1:fontcolor=white:bordercolor=black:borderw=3:fontsize=50,select='not(mod(n\\,{frame_interval}))'",
                    '-fps_mode', 'vfr',
                    '-q:v', '10',  # Adjust the quality, 1 (best) to 31 (worst), 2 for good quality
                    os.path.join(frames_dir, '%06d.jpg')  # 6 digits for padding, starting from 0
                ]
            
            subprocess.run(ffmpeg_cmd)
            
            # Rename back to .trec
            os.rename(mp4_path, trec_path)
            
            print(f"Processed {filename}")


  


  But this gives me sequential numbers, not the actual frame numbers but the frame numbers I draw over the images, they represent the actual frame numbers.

  


  Basically ffmpeg is able to get the current frame and draw it on the image using :

  


  drawtext=text='%{{n}}'


  


  The question is about getting that value out to the filenames.

  


• avcodec/diracdec : Check slice numbers for overflows in relation to picture dimensions

  22 juillet 2018, par Michael Niedermayer

  avcodec/diracdec : Check slice numbers for overflows in relation to picture dimensions
  Fixes : signed integer overflow : 88 * 33685506 cannot be represented in type 'int'
  
  Fixes : 9433/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_DIRAC_fuzzer-5725943535501312
  Found-by : continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
  
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavcodec/diracdec.c

• avcodec/ppc/h264dsp : Fix left shifts of negative numbers

  4 avril 2024, par Andreas Rheinhardt

  avcodec/ppc/h264dsp : Fix left shifts of negative numbers
  PPC equivalent of c756b3fca240df75ffa28e75f2eb34834c10294d.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
  

  • [DH] libavcodec/ppc/h264dsp.c