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• Trying to tonemap 14-bit grayscale video

  12 janvier 2018, par Trevor

  I’m trying to generate h.264 video from raw 2-byte gray video (14-bit range encoded in 16-bit values). I can do something like :

  ffmpeg -f rawvideo -pix_fmt gray16le -s:v 1280x720 -r 60 -i input.raw -c:v libx264 output.mp4

  And I get video but it’s pretty dark, not sure if it’s clipping, doing a linear remap, or storing the 16-bit data and VLC is doing the remap. ffprobe is reporting Video: h264 (High 4:4:4 Predictive) (avc1 / 0x31637661), yuvj444p(pc), 1280x720, 108 kb/s, 60 fps, 60 tbr, 15360 tbn, 120 tbc

  I was figuring I’d use the tonemap filter to make a better mapping. I added a filter before the output file with -vf.

  • tonemap=hable errors Impossible to convert between the formats supported by the filter 'graph 0 input from stream 0:0' and the filter 'auto_scaler_0'
  • zscale=transfer=linear,tonemap=hable errors Impossible to convert between the formats supported by the filter 'Parsed_tonemap_1' and the filter 'auto_scaler_1'
  • zscale=transfer=linear,tonemap=hable,zscale=transfer=bt709,format=yuvj444p errors code 3074: no path between colorspaces

  I’m not sure where to proceed from here...

• hwcontext_vdpau : implement av_hwdevice_get_hwframe_constraints()

  13 janvier 2018, par wm4

  hwcontext_vdpau : implement av_hwdevice_get_hwframe_constraints()
  In addition, this does not allow creating frames contexts with sw_format
  
  for which no known transfer formats exist. In theory, we should check
  
  whether the chroma format (i.e. the sw_format) is supported at all by
  
  the vdpau driver, but checking for transfer formats has the same effect.
  Note that the pre-existing code adds 1 to priv->nb_pix_fmts[i] for
  
  unknown reason, and some checks need to account for that to check for
  
  empty lists. They are not off-by-one errors.
  

  • [DH] libavutil/hwcontext_vdpau.c

• 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