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• Streaming mp4a to localhost using udp and ffmpeg

  2 août 2017, par noswoscar

  I am using the following command to stream a video and it’s audio to localhost :
  ffmpeg -re -i out.mp4 -map 0:0 -vcodec libx264 -f h264 udp ://127.0.0.1:1234 -map 0:1 -acodec libfaac -f mp4a udp ://127.0.0.1:2020

  FFmpeg is not recognising my audio codec and my audio format so I get the following error message :
  Error

  What audio format and codec do I need to use ? The codec information of the video I wish to send is as follows :
  Codecs used

  When I convert the audio track to mp3 I can run the above command and stream the video and audio properly. However I dont want to convert all my video audio-tracks to mp3.

  (I am confused by all the encoders, decoders, codec names in the ffmpeg documentation) Is there a way of finding the right encoder to use with the mp4a audio codec other than reading the whole list of codecs and options ?

  Thanks.

• How to get frames from HDR video in scRGB color space ?

  5 mars 2018, par Виталий Синявский

  I want to create a simple video player that will show HDR video on HDR TV. For example, this "LG Chess HDR" video. It is encoded with HEVC, its bit depth is 10 bit, pixel format is YUV420P10LE and it has metadata abount BT2020 color space and PQ transfer function.

  In this NVIDIA article I found the next :

  The display driver takes the scRGB back buffer, and converts it to the
  standard expected by the display presently connected. In general, this
  means converting the color space from sRGB primaries to BT. 2020
  primaries, scaling to an appropriate level, and encoding with a
  mechanism like PQ. Also, possibly performing conversions like RGB to
  YCC if that display connection requires it.

  It means that my player should render pixels in the scRGB color space (linear encoding, sRGB primaries, full range is -0.5 through just less than +7.5). So I need to get frames from the source video in this color space somehow, preferably in FP16 pixel format (half float, 16 bits per one color channel). I come to the following simple pipeline to render videos to HDR :

  source HDR video in BT2020 color space with applied PQ -> [some video library] -> 
  
  -> video frames with colors in scRGB color space -> [my program] ->
  
  -> rendered video on HDR TV with applied conversions by display driver

  I’m trying to use FFmpeg as this library and do not understand how to get frames from the source HDR video in scRGB color space.

  I use sws_scale FFmpeg method now to get frames and know about filters API. But I did not found any information and help about how to transparantly get frames in scRGB using these functionality without parsing metadata for all source videos and create custom video filters for them.

  Please, tell me what I can do to get frames in the scRGB color space using FFmpeg. Can someone tell other libraries with which I can do it ?

• How I can receive MJPEG stream via RTSP with resolution more than 1080p

  21 septembre 2018, par chuchuchu

  There is a problem :
  When I get a video stream with a resolution of 1080 and below - everything is fine.
  But if I select a stream with a resolution higher than 1080 on the camera, an error occurs.
  FFMPEG :

  [mjpeg @ 0x7f5488003e40] [IMGUTILS @ 0x7f5494acb4f0] Picture size 0x0 is invalid

  If I open a stream in the player I get a disparate image :

  [mjpeg @ 0x7fd9f8043b20] error y=91 x=16
  
  [mjpeg @ 0x7fd9f8043b20] error dc

  I repeatedly recompiled and reinstalled various versions of the ffmpeg, the problem is not solved.

  I suspect that there is a restriction for video stream over 1080p, but I can not find any description or solution.
  And I found next string in rfc "RTP Payload Format for JPEG" :

  The maximum width is 2040 pixels.

  but it is dated 1998. I know for certain that this stream on the RTSP receives in the resolution I need, but I can not understand how.

  Please, tell me the way to the solution. I’m using Ubuntu 16.04 amd64.
  Perhaps there is an alternative way to receive a rtsp-stream without using a ffmpeg ?? Since all ways known to me are using ffmpeg.