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• Play video using ffmpeg

  17 juin 2023, par MCD

  The following code stuck in the middle of the video. I want to play the video start at start_seconds and end at end_seconds.

  


  import subprocess
import cv2
import numpy as np
import subprocess

def play_video_with_ffmpeg(video_path, start_seconds, end_seconds):
print(start_seconds)

    # Set the desired frame size
    width = 920
    height = 600
    
    # Set the window position
    print("here")
    window_x = 600  # X position
    window_y = 10  # Y position
    cv2.namedWindow('Video Player', cv2.WINDOW_NORMAL)
    cv2.moveWindow('Video Player', window_x, window_y)
    
    # Build the ffmpeg command to skip to the desired start time and end time
    command = [
        'ffmpeg',
        '-ss', str(start_seconds),
        '-i', video_path,
        '-t', str((end_seconds - start_seconds)),
        '-vf', f'scale={width}:{height}',
        '-r', '30',
        '-f', 'image2pipe',
        '-pix_fmt', 'bgr24',
        '-vcodec', 'rawvideo',
        '-'
    ]
    
    # Open a subprocess to execute the ffmpeg command
    process = subprocess.Popen(command, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
    
    # Create a buffer to hold the frame data
    buffer_size = width * height * 3
    frame_buffer = bytearray(buffer_size)
    
    while process.poll() is None:
        # Read the frame from the subprocess stdout into the buffer
        bytes_read = process.stdout.readinto(frame_buffer)
    
        if bytes_read == buffer_size:
            # Convert the frame buffer to a numpy array
            frame = np.frombuffer(frame_buffer, dtype='uint8').reshape((height, width, 3))
    
            # Resize the frame
            frame_resized = cv2.resize(frame, (width, height), interpolation=cv2.INTER_AREA)
    
            # Display the frame
            cv2.imshow('Video Player', frame_resized)
    
            if cv2.waitKey(1) & 0xFF == ord('q'):
                break
    
    process.stdout.close()
    process.stderr.close()
    cv2.destroyAllWindows()


  


  I expect to play the video start from start_second and end at end_second. I used cv2.set but it took long time to play from start_second.

  


• Play video using ffmpeg subprocess

  17 juin 2023, par MCD

  The following code stuck in the middle of the video. I want to play the video start at start_seconds and end at end_seconds.

  


  import subprocess
import cv2
import numpy as np
import subprocess

def play_video_with_ffmpeg(video_path, start_seconds, end_seconds):
print(start_seconds)

    # Set the desired frame size
    width = 920
    height = 600
    
    # Set the window position
    print("here")
    window_x = 600  # X position
    window_y = 10  # Y position
    cv2.namedWindow('Video Player', cv2.WINDOW_NORMAL)
    cv2.moveWindow('Video Player', window_x, window_y)
    
    # Build the ffmpeg command to skip to the desired start time and end time
    command = [
        'ffmpeg',
        '-ss', str(start_seconds),
        '-i', video_path,
        '-t', str((end_seconds - start_seconds)),
        '-vf', f'scale={width}:{height}',
        '-r', '30',
        '-f', 'image2pipe',
        '-pix_fmt', 'bgr24',
        '-vcodec', 'rawvideo',
        '-'
    ]
    
    # Open a subprocess to execute the ffmpeg command
    process = subprocess.Popen(command, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
    
    # Create a buffer to hold the frame data
    buffer_size = width * height * 3
    frame_buffer = bytearray(buffer_size)
    
    while process.poll() is None:
        # Read the frame from the subprocess stdout into the buffer
        bytes_read = process.stdout.readinto(frame_buffer)
    
        if bytes_read == buffer_size:
            # Convert the frame buffer to a numpy array
            frame = np.frombuffer(frame_buffer, dtype='uint8').reshape((height, width, 3))
    
            # Resize the frame
            frame_resized = cv2.resize(frame, (width, height), interpolation=cv2.INTER_AREA)
    
            # Display the frame
            cv2.imshow('Video Player', frame_resized)
    
            if cv2.waitKey(1) & 0xFF == ord('q'):
                break
    
    process.stdout.close()
    process.stderr.close()
    cv2.destroyAllWindows()


  


  I expect to play the video start from start_second and end at end_second. I used cv2.set but it took long time to play from start_second.

  


• avformat/matroskaenc : Check for failure when writing SeekHead

  29 décembre 2019, par Andreas Rheinhardt

  avformat/matroskaenc : Check for failure when writing SeekHead
  mkv_write_seekhead() would up until now try to seek to the position where
  
  the SeekHead ought to be written, write the SeekHead and seek back. The
  
  first of these seeks was checked as was writing, yet the seek back was
  
  unchecked. Moreover the return value of mkv_write_seekhead() was unchecked
  
  (the ordinary return value was the position where the SeekHead was written).
  This commit changes this : Everything is checked. In the unseekable case
  
  (where the first seek may nevertheless work when it happens in the buffer)
  
  a failure at the first seek is not considered an error. In any case,
  
  failure to seek back is an error.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavformat/matroskaenc.c