Video Playback: Difference between revisions

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win.close()
win.close()
core.quit()
core.quit()
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Example demonstrating if video and audio encoding are correct:
<syntaxhighlight lang="python" line>
import subprocess
import json
file_path = "C_dyad1_video2_241123.mp4"
def check_video_file(file_path):
    try:
        # Run ffprobe to get file metadata in JSON format
        result = subprocess.run(
            [
                "ffprobe",
                "-v", "error",
                "-show_streams",
                "-show_format",
                "-print_format", "json",
                file_path
            ],
            stdout=subprocess.PIPE,
            stderr=subprocess.PIPE,
            text=True
        )
        metadata = json.loads(result.stdout)
    except Exception as e:
        print(f"Error running ffprobe: {e}")
        return
   
    # Check for video stream
    video_stream = next((stream for stream in metadata['streams'] if stream['codec_type'] == 'video'), None)
    if video_stream:
        # Check video codec
        video_codec = video_stream.get('codec_name')
        if video_codec == 'h264':
            print("Video codec: H.264")
        else:
            print(f"ERROR: Video codec is NOT H.264 (Found: {video_codec})")
        # Extract and report frame rate
        if 'r_frame_rate' in video_stream:
            raw_frame_rate = video_stream['r_frame_rate']
            calculated_frame_rate = eval(raw_frame_rate)  # Convert string like "30/1" to float
            print(f"Frame rate: {calculated_frame_rate:.2f} FPS (raw: {raw_frame_rate})")
        else:
            print("ERROR: Could not determine raw frame rate from metadata.")
        # Check for constant frame rate
        if video_stream.get('avg_frame_rate'):
            avg_frame_rate = eval(video_stream['avg_frame_rate'])
            if abs(avg_frame_rate - calculated_frame_rate) < 0.01:
                print("Frame rate: Constant")
            else:
                print(f"ERROR: Frame rate is NOT constant (avg_frame_rate: {avg_frame_rate:.2f} FPS)")
        else:
            print("ERROR: Could not determine average frame rate consistency.")
       
        # Check for frame drops
        try:
            frame_info_result = subprocess.run(
                [
                    "ffprobe",
                    "-v", "error",
                    "-select_streams", "v:0",
                    "-show_entries", "frame=pkt_pts_time",
                    "-of", "csv=p=0",
                    file_path
                ],
                stdout=subprocess.PIPE,
                stderr=subprocess.PIPE,
                text=True
            )
            # Filter out empty or invalid lines
            frame_times = [
                float(line.strip()) for line in frame_info_result.stdout.splitlines()
                if line.strip()  # Exclude empty lines
            ]
            expected_interval = 1.0 / calculated_frame_rate  # Expected time between frames
            frame_drops = [
                i for i, (t1, t2) in enumerate(zip(frame_times, frame_times[1:]))
                if abs(t2 - t1 - expected_interval) > 0.01  # Tolerance for irregularity
            ]
            if frame_drops:
                print(f"ERROR: Detected frame drops at frames: {frame_drops}")
            else:
                print("No frame drops detected.")
        except Exception as e:
            print(f"Error analyzing frames for drops: {e}")
    else:
        print("ERROR: No video stream found")
   
    # Check for audio stream
    audio_stream = next((stream for stream in metadata['streams'] if stream['codec_type'] == 'audio'), None)
    if audio_stream:
        # Check audio codec
        audio_codec = audio_stream.get('codec_name')
        if audio_codec == 'pcm_s16le':
            print("Audio codec: WAV (PCM)")
        else:
            print(f"ERROR: Audio codec is NOT WAV (PCM) (Found: {audio_codec})")
       
        # Check sample rate
        sample_rate = audio_stream.get('sample_rate')
        if sample_rate == "44100":
            print("Audio sample rate: 44.1 kHz")
        else:
            print(f"ERROR: Audio sample rate is NOT 44.1 kHz (Found: {sample_rate} Hz)")
    else:
        print("ERROR: No audio stream found")
   
    # Check synchronization
    if video_stream and audio_stream:
        video_start_pts = float(video_stream.get('start_time', 0))
        audio_start_pts = float(audio_stream.get('start_time', 0))
        if abs(video_start_pts - audio_start_pts) < 0.01:  # Tolerance for synchronization
            print("Video and audio are synchronized.")
        else:
            print(f"ERROR: Video and audio are NOT synchronized. Start difference: {abs(video_start_pts - audio_start_pts):.3f} seconds")
    else:
        print("ERROR: Could not determine synchronization (missing video or audio streams).")
# Example usage
if __name__ == "__main__":
    check_video_file(file_path)


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Retrieved from "https://tsgdoc.socsci.ru.nl/index.php/Video_Playback"