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• Downloading an HLS stream : ONLY in sync when downloading with ffmpeg. Possible explanations ? [closed]

  20 janvier 2024, par R.JEON

  I'm trying to download a livestream that is just a plain hls with no encryption.
I usually use streamlink, but this site I'm trying to use recently doesn't output a correct video/audio synced output when downloaded with streamlink/yt-dlp/nm3u8dl etc.

  


  The only option that produces the correct output with the audio and video in sync is ffmpeg, but ffmpeg is very user-unfriendly and lacks functionality related to retries when connection is lost, and etc.

  


  This is super weird cuz when I play the hls stream using VLC or any other livestream supported players, they are on sync. But what I do noticed is that when I play them on a player, the audio is mute for a second or two and then plays the audio correctly.

  


  Can anyone possibly explain the cause of this situation and probably a fix ? I would love to use streamlink instead of ffmpeg.

  


• Video has audio data, but no sound on Android

  1er septembre 2022, par youxiong

  I have download a video on android, but when I play it, there is no sound. Below is the output of FFMpeg.

  


    Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf58.48.100
  Duration: 00:00:43.24, start: 0.000000, bitrate: 643 kb/s
  Stream #0:0[0x1](und): Video: h264 (Baseline) (avc1 / 0x31637661), yuv420p(progressive), 864x480 [SAR 1:1 DAR 9:5], 547 kb/s, 21.05 fps, 30 tbr, 90k tbn (default)
    Metadata:
      handler_name    : VideoHandler
      vendor_id       : [0][0][0][0]
  Stream #0:1[0x2](und): Audio: aac (Main) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 89 kb/s (default)
    Metadata:
      handler_name    : SoundHandler
      vendor_id       : [0][0][0][0]


  


  And also, I can play it with sound on windows using some powerful media player.

  


  Can I make some codec transfer using ffmpeg to make the video play on Android.
Thank you.

  


• Live video stream on server (PC) from images sent by robot through UDP

  3 février 2018, par Richard Knop

  Hmm. I found this which seems promising :

  http://sourceforge.net/projects/mjpg-streamer/

  ---

  Ok. I will try to explain what I am trying to do clearly and in much detail.

  I have a small humanoid robot with camera and wifi stick (this is the robot). The robot’s wifi stick average wifi transfer rate is 1769KB/s. The robot has 500Mhz CPU and 256MB RAM so it is not enough for any serious computations (moreover there are already couple modules running on the robot for motion, vision, sonar, speech etc).

  I have a PC from which I control the robot. I am trying to have the robot walk around the room and see a live stream video of what the robot sees in the PC.

  What I already have working. The robot is walking as I want him to do and taking images with the camera. The images are being sent through UDP protocol to the PC where I am receiving them (I have verified this by saving the incoming images on the disk).

  The camera returns images which are 640 x 480 px in YUV442 colorspace. I am sending the images with lossy compression (JPEG) because I am trying to get the best possible FPS on the PC. I am doing the compression to JPEG on the robot with PIL library.

  My questions :

  1. Could somebody please give me some ideas about how to convert the incoming JPEG images to a live video stream ? I understand that I will need some video encoder for that. Which video encoder do you recommend ? FFMPEG or something else ? I am very new to video streaming so I want to know what is best for this task. I’d prefer to use Python to write this so I would prefer some video encoder or library which has Python API. But I guess if the library has some good command line API it doesn’t have to be in Python.

  2. What is the best FPS I could get out from this ? Given the 1769KB/s average wifi transfer rate and the dimensions of the images ? Should I use different compression than JPEG ?

  3. I will be happy to see any code examples. Links to articles explaining how to do this would be fine, too.

  Some code samples. Here is how I am sending JPEG images from robot to the PC (shortened simplified snippet). This runs on the robot :

  # lots of code here
  
  
  
  UDPSock = socket(AF_INET,SOCK_DGRAM)
  
  
  
    while 1:
  
      image = camProxy.getImageLocal(nameId)
  
      size = (image[0], image[1])
  
      data = image[6]
  
      im = Image.fromstring("YCbCr", size, data)
  
      s = StringIO.StringIO()
  
      im.save(s, "JPEG")
  
  
  
      UDPSock.sendto(s.getvalue(), addr)
  
  
  
      camProxy.releaseImage(nameId)
  
  
  
    UDPSock.close()
  
  
  
    # lots of code here

  Here is how I am receiving the images on the PC. This runs on the PC :

    # lots of code here
  
  
  
    UDPSock = socket(AF_INET,SOCK_DGRAM)
  
    UDPSock.bind(addr)
  
  
  
    while 1:
  
      data, addr = UDPSock.recvfrom(buf)
  
      # here I need to create a stream from the data
  
      # which contains JPEG image
  
  
  
    UDPSock.close()
  
  
  
    # lots of code here