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• How to parse WMV (ASF) file ? Can't find length of data packets

  9 mars 2018, par bukkojot

  I try to parse WMV (ASF) files without any SDK, just by decoding raw bytes. Now I have problem with ASF_Data_Object, where I can’t find length of data packet. More precise, Single payload data packet.

  See image :
  

  Here I have 9 packets, but unable to find size of individual packet. How I can determine border between packets ?

  I think, my problem at byte 0x411, where field "Length type flags". As you can see, here 0 value, so all flags are zero. Even Packet Length Type.

  
  

  Yes, 0 value here allowed here. But how to read this type of content ?

  This is now compressed payload, as replication data is 8, not 1. So, this is single payload without additional fields of size.

  Sample of WMV file : https://files.catbox.moe/b51l2j.wmv

• How to extract good quality frame in pixel format from live mpeg-ts stream ?

  2 février 2024, par Aven

  I use the command below to stream my ts file for my programe :

  


  ffmpeg -re -i independent_frame.ts -f mpegts udp://127.0.0.1:10002


  


  Below is the code of my programe, I'm trying to extract each frame in pixel format from the stream by using FFmpeg, but I found the quality is not good as it should be of the extracted frame ( I know OpenCV can do this, But I have other reason have to use FFmpeg ). I tried to put -qscale:v 2 in FFmpeg command, but it seems change nothing. Does anyone know how to enhance the frame quality in this case ? Thanks !

  


  stream = 'udp://127.0.0.1:10002'
H, W = 720, 1280

command = [ 'ffmpeg',
            '-i', stream ,
            '-pix_fmt', 'bgr24', # brg24 for matching OpenCV
            '-qscale:v', '2', 
            '-f', 'rawvideo',
            'pipe:' ]

# Execute FFmpeg as sub-process with stdout as a pipe
process = subprocess.Popen(command, stdout=subprocess.PIPE, bufsize=10**8)#10**8

# Load individual frames in a loop
nb_img = H*W*3

# Read decoded video frames from the PIPE until no more frames to read
num = 0
while True:
    # Read decoded video frame (in raw video format) from stdout process.
    buffer = process.stdout.read(W*H*3)

    # Break the loop if buffer length is not W*H*3 (when FFmpeg streaming ends).
    if len(buffer) != W*H*3:
        break

    img = np.frombuffer(buffer, np.uint8).reshape(H, W, 3)
    num +=1

    if num == 435:
        cv2.imwrite('435.png', img)
        cv2.imshow('img', img)  # Show the image for testing
        cv2.waitKey(0)
        cv2.destroyAllWindows()
        break

process.stdout.close()
process.wait()
cv2.destroyAllWindows()


  


• Download encrypted TS files from video stream

  8 janvier 2021, par albertma789

  Following this post, I usually download transport stream (.ts) files by using the browser's developer console to find the URLs of the .ts files and then I use wget to download them. After that I use the ffmpeg -f concat method to combine them into an mp4 file.

  



  Recently I come across a site that streams videos and I used the same method to download all the .ts files. The site is here. After I downloaded all the individual .ts files, I use ffmprobe to check the file format but realized the .ts files cannot be understood by ffmpeg/ffmprobe. While the site uses http (not https) I thought the streams are not encrypted so I tried to open the .ts file in an hex editor but I don't know what format it is (but they don't look like zip/gz). My question is : are the transport steams encrypted ? If yes, is there a way to decrypt them ? If not ? Can anyone point me to the right direction such that I can make ffmpeg understand them ?

  



  An example transport stream (first & second) are here and here but the link might expire in a bit. In that case you will need to open the site in developer console to find the updated link to the .ts files.

  



  The site uses JW Player 8.0.0