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• why do andorid camera and gopros not use b-frames ?

  26 août 2021, par Photo_Survey

  I am using ffmpeg to extract the gop-structure of videos, which I recorded with my Smartphone (Samsung Galaxy A51) and my GoPro (Hero 7 Black).
The gop-structures I get all look like this : IPPPPPPPPPPPPPP. The videos of the different devices only differ in the number of P-Frame per gop-structure. The ffmpeg code I used fpr this is the following :

  


  ffprobe -show_frames inputvideo.mp4 -print_format json
Now my question is why the encoders of both devices don't use B-Frames ? Is is it because the encoding of B-Frames is more complicated for the Hardwar or something like this ?

  


• Audio lag in Ffmpeg on Android 360P vide capture after 30 minutes

  15 août 2019, par Jagadish Channagiri

  We are currently run video capture on Android Samsung S9 and few other Android devices, FFmpeg version 4.0.1, Javacversion 1.4.2, Android minSdkVersion 21, and compileSdkVersion 28. After 30 minutes or so, between the range 33 - 36 minutes, the audio lags video. I really do not understand why this happens. Any ideas or suggestions would be highly appreciated.

• Flask app using OpenCv crash when i start recording

  17 mai 2023, par Mulham Darwish

  I build this flask app to live stream security cameras and the live stream works with the screenshot function but when start recording it crash but few times same code it worked and saved the video here the code. with the html file using js.

  


  from flask import Flask, render_template, Response, request
import cv2
import os
import time
import threading
import requests

app = Flask(__name__)

# Define the IP cameras
cameras = [
    {'url': 'rtsp://****:*****@******', 'name': 'Camera 1'},
    {'url': 'rtsp://****:*****@******', 'name': 'Camera 2'},
    {'url': 'rtsp://****:*****@******', 'name': 'Camera 3'},
    {'url': 'rtsp://****:*****@******', 'name': 'Camera 4'}
]

# Create a VideoCapture object for each camera
capture_objs = [cv2.VideoCapture(cam['url']) for cam in cameras]
stop_events = {i: threading.Event() for i in range(len(cameras))}
# Define the directory to save the recorded videos
recording_dir = os.path.join(os.getcwd(), 'recordings')

# Ensure the recording directory exists
if not os.path.exists(recording_dir):
    os.makedirs(recording_dir)

# Define the function to capture and save a video
def record_video(camera_index, stop_recording):
    # Define the codec and file extension
    fourcc = cv2.VideoWriter_fourcc(*'mp4v')
    file_extension = '.mp4'

    # Get the current timestamp for the filename
    timestamp = time.strftime("%Y%m%d-%H%M%S")

    # Define the filename and path
    filename = f'{cameras[camera_index]["name"]}_{timestamp}{file_extension}'
    filepath = os.path.join(recording_dir, filename)

    # Create a VideoWriter object to save the video
    width = int(capture_objs[camera_index].get(cv2.CAP_PROP_FRAME_WIDTH))
    height = int(capture_objs[camera_index].get(cv2.CAP_PROP_FRAME_HEIGHT))
    fps = int(capture_objs[camera_index].get(cv2.CAP_PROP_FPS))
    video_writer = cv2.VideoWriter(filepath, fourcc, fps, (width, height))

    # Capture frames and write them to the file
    while True:
        if stop_recording.is_set():
            break  # stop recording if stop_recording is set
        ret, frame = capture_objs[camera_index].read()
        if ret:
            video_writer.write(frame)
        else:
            break

    # Release the VideoWriter object and the VideoCapture object
    video_writer.release()
    capture_objs[camera_index].release()

@app.route('/')
def index():
    # Render the index page with the list of cameras
    return render_template('index.html', cameras=cameras)

def generate(camera_index):
    # Generate frames from the video feed
    while True:
        ret, frame = capture_objs[camera_index].read()
        if not ret:
            break

        # Encode the frame as JPEG
        _, jpeg = cv2.imencode('.jpg', frame)

        # Yield the frame as a Flask response
        yield (b'--frame\r\n'
               b'Content-Type: image/jpeg\r\n\r\n' + jpeg.tobytes() + b'\r\n')

@app.route('/video_feed')
def video_feed():
    # Get the camera index from the request arguments
    camera_index = int(request.args.get('camera_index'))

    # Generate the video feed
    return Response(generate(camera_index),
                    mimetype='multipart/x-mixed-replace; boundary=frame')

@app.route('/record', methods=['POST'])
def record():
    # Get the camera index from the request form
    camera_index = int(request.form['camera_index'])

    stop_recording = stop_events[camera_index]  # get the stop_recording event for the camera
    thread = threading.Thread(target=record_video, args=(camera_index, stop_recording))
    thread.start()  # start a thread to record video

    # Return a response indicating that the recording has started
    return 'Recording started.'

@app.route('/stop_record', methods=['POST'])
def stop_record():
    # Get the camera index from the request form
    camera_index = int(request.form['camera_index'])

    # Set the stop_recording event for the corresponding camera thread
    stop_events[camera_index].set()

    # Return a response indicating that recording has been stopped
    return 'Recording stopped.'

@app.route('/screenshot', methods=['POST'])
def take_screenshot():
    # Take a screenshot of the video stream and save it as a file
    camera = capture_objs[int(request.form['camera_id'])]
    success, frame = camera.read()
    if success:
        timestamp = time.strftime("%Y%m%d-%H%M%S")
        filename = f'screenshot_{timestamp}.jpg'
        cv2.imwrite(filename, frame)
        return 'Screenshot taken and saved'
    else:
        return 'Failed to take screenshot'

if __name__ == '__main__':
    app.run()


  


  I tried to update ffmpeg to the latest version and installed pip install opencv-python-headless and installed pip install opencv-python but most of the time i come to this crash code

  


  * Serving Flask app 'run'
* Debug mode: off
WARNING: This is a development server. Do not use it in a production deployment. Use a production WSGI server instead.
 * Running on http://127.0.0.1:5000
Press CTRL+C to quit
127.0.0.1 - - [17/May/2023 13:24:11] "GET / HTTP/1.1" 200 -
127.0.0.1 - - [17/May/2023 13:24:11] "GET /video_feed?camera_index=0 HTTP/1.1" 200 -
127.0.0.1 - - [17/May/2023 13:24:11] "GET /video_feed?camera_index=1 HTTP/1.1" 200 -
127.0.0.1 - - [17/May/2023 13:24:11] "GET /video_feed?camera_index=2 HTTP/1.1" 200 -
127.0.0.1 - - [17/May/2023 13:24:11] "GET /video_feed?camera_index=3 HTTP/1.1" 200 -
127.0.0.1 - - [17/May/2023 13:24:44] "GET / HTTP/1.1" 200 -
127.0.0.1 - - [17/May/2023 13:24:45] "GET /video_feed?camera_index=3 HTTP/1.1" 200 -
127.0.0.1 - - [17/May/2023 13:24:45] "GET /video_feed?camera_index=0 HTTP/1.1" 200 -
127.0.0.1 - - [17/May/2023 13:24:45] "GET /video_feed?camera_index=1 HTTP/1.1" 200 -
127.0.0.1 - - [17/May/2023 13:24:45] "GET /video_feed?camera_index=2 HTTP/1.1" 200 -
[h264 @ 0x5605285fc5c0] error while decoding MB 28 29, bytestream -9
[h264 @ 0x560529110040] error while decoding MB 15 37, bytestream -6
[h264 @ 0x560528624980] error while decoding MB 45 45, bytestream -23
[h264 @ 0x5605286f1900] error while decoding MB 50 34, bytestream -7
[h264 @ 0x5605285fc5c0] error while decoding MB 25 9, bytestream -17
[h264 @ 0x5605292b0080] error while decoding MB 28 41, bytestream -5
[h264 @ 0x560528660040] error while decoding MB 101 45, bytestream -17
[h264 @ 0x5605285fc5c0] error while decoding MB 42 44, bytestream -5
[h264 @ 0x5605286f1900] error while decoding MB 118 42, bytestream -9
[h264 @ 0x560529110040] error while decoding MB 92 43, bytestream -5
[h264 @ 0x560528660040] error while decoding MB 99 34, bytestream -11
[h264 @ 0x56052932b0c0] error while decoding MB 92 36, bytestream -13
[h264 @ 0x560528667ac0] error while decoding MB 44 54, bytestream -5
[h264 @ 0x560529110040] error while decoding MB 93 33, bytestream -7
[h264 @ 0x5605286dd880] error while decoding MB 27 37, bytestream -19
[h264 @ 0x560528660040] error while decoding MB 66 56, bytestream -9
127.0.0.1 - - [17/May/2023 13:36:45] "POST /record HTTP/1.1" 200 -
Assertion fctx->async_lock failed at libavcodec/pthread_frame.c:175
Aborted (core dumped)