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• Flash Media Server Recording Delay

  14 novembre 2011, par Corey

  I have an application where a user can record themselves singing along to a song. Once I receive the NetStream status event 'Record.Start' I start playing an audio file. Once the audio completes, I stop recording. Next, I have a script that runs FFMPEG to combine the recorded video/audio with the same music file. The problem I'm finding is that there is a noticeable delay between the recorded audio and the music. It seems also that this delay depends on network speed as it varies depending on the network. Can I determine this delay through the FMS dynamically ?

• libavformat/hls : add support for decryption of HLS media segments encrypted using...

  21 septembre 2021, par Nachiket Tarate

  libavformat/hls : add support for decryption of HLS media segments encrypted using SAMPLE-AES encryption method
  Apple HTTP Live Streaming Sample Encryption :
  https://developer.apple.com/library/ios/documentation/AudioVideo/Conceptual/HLS_Sample_Encryption
  Signed-off-by : Nachiket Tarate <nachiket.programmer@gmail.com>
  
  Signed-off-by : Steven Liu <lq@chinaffmpeg.org>
  

  • [DH] libavformat/Makefile
  • [DH] libavformat/hls.c
  • [DH] libavformat/hls_sample_encryption.c
  • [DH] libavformat/hls_sample_encryption.h
  • [DH] libavformat/mpegts.c

• Python OpenCV VideoCapture Color Differs from ffmpeg and Other Media Players

  17 avril 2024, par cliffsu

  I’m working on video processing in Python and have noticed a slight color difference when using cv2.VideoCapture to read videos compared to other media players.

  


  

  


  I then attempted to read the video frames directly using ffmpeg, and despite using the ffmpeg backend in OpenCV, there are still differences between OpenCV’s and ffmpeg’s output. The frames read by ffmpeg match those from other media players.

  


  

  


  Below are the videos I’m using for testing :

  


  test3.webm

  


  test.avi

  


  Here is my code :

  


  import cv2
import numpy as np
import subprocess

def read_frames(path, res):
    """Read numpy arrays of video frames. Path is the file path
       and res is the resolution as a tuple."""
    args = [
        "ffmpeg",
        "-i",
        path,
        "-f",
        "image2pipe",
        "-pix_fmt",
        "rgb24",
        "-vcodec",
        "rawvideo",
        "-",
    ]

    pipe = subprocess.Popen(
        args,
        stdout=subprocess.PIPE,
        stderr=subprocess.DEVNULL,
        bufsize=res[0] * res[1] * 3,
    )

    while pipe.poll() is None:
        frame = pipe.stdout.read(res[0] * res[1] * 3)
        if len(frame) > 0:
            array = np.frombuffer(frame, dtype="uint8")
            break

    pipe.stdout.close()
    pipe.wait()
    array = array.reshape((res[1], res[0], 3))
    array = cv2.cvtColor(array, cv2.COLOR_RGB2BGR)
    return array

ORIGINAL_VIDEO = 'test3.webm'

array = read_frames(ORIGINAL_VIDEO, (1280, 720))

cap = cv2.VideoCapture(ORIGINAL_VIDEO, cv2.CAP_FFMPEG)
while cap.isOpened():
    ret, frame = cap.read()
    if not ret:
        break
    print(frame.shape)
    cv2.imshow("Opencv Read", frame)
    cv2.imshow("FFmpeg Direct Read", array)
    cv2.waitKeyEx()
    cv2.waitKeyEx()
    break
cap.release()


  


  I’ve attempted to use different media players to compare cv2.VideoCapture and ffmpeg’s frame reading, to confirm that the issue lies with opencv. I’m looking to determine whether it’s a bug in OpenCV or if there are issues in my code.

  


  EDIT :

  


  Just use the following code to check the difference between opencv read and ffmpeg read.

  


  cv2.imshow('test', cv2.absdiff(array, frame)*10)
cv2.waitKey(0)


  


  Here is the result :