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• How to deal ffplay being too slow playing iPhone's videos ?

  8 janvier 2020, par Mikhail T.

  Trying to play a 3840x2160 video recorded by an iPhone 7 (@30fps), I get frequent pauses — in the video, music keeps playing.

  



  This happens both in firefox and when ffplay is invoked to play the file directly — from command-line. The CPU is a dual E6700 @3.20GHz — not super fast, but it should be able to play smoothly, shouldn't it ? Video is Intel's "series 4" integrated chipset — again, not a speed-daemon, but it should be adequate... Support for Intel's VA API is included.

  



  I build ffmpeg-4.1 from source using FreeBSD port. As you can see, the port has a maddening amount of options — including several different ones for the 264-codec.

  



  Any suggestions for improving the decoding speed to the point, where it is watchable by a human ? Thank you !

  


• MovieWriter FFwriter unavailable. Trying to use pillow instead

  17 février 2020, par Life is Good

  I have created a bar chart race in Matplotlib and now I am trying to save it into a gif file. I have imported the relevant library :

  import matplotlib.animation as animation
  
  plt.rcParams['animation.ffmpeg_path'] = '‪C:\\Program Files\\FFmpeg\\bin\\ffmpeg.exe'
  
  FFwriter = animation.FFMpegWriter()

  Here is the code I used to create my animation :

  fig, ax = plt.subplots(figsize=(15, 8))
  
  animator = animation.FuncAnimation(fig, draw_barchart, frames=range(1999, 2015))
  
  HTML(animator.to_jshtml()) 

  However, when I searched for the writers, there are only two of them :

  animation.writers.list()

  

  I had already installed FFmpeg following a tutorial on Wikihow, and I am also able to run FFmpeg from the command line, so I don’t understand why it is not showing up. When I try to save my animation into a gif, I get this error message :
  

  Would anybody be familiar with this error message, please ? Thank you very much.

• Loss packets from RTP streaming decoded with ffmpeg

  29 avril 2020, par anaVC94

  Hope someone could help me. I am trying to apply a neural network (YOLOv2) to perform object detection to a RTP stream which I have simulated in local using VLC, with the "using RTP over TCP" mark as true.
The stream is 4K, 30fps, 15Mb/s. I am using OpenCV C API I/O module to read frames from the stream.

  



  I am using the common code. I open the RTP as follows :
cap = cvCaptureFromFile(url);

  



  And then I perform capture in one thread like :
IplImage* src = cvQueryFrame(cap);

  



  and, on another thread, the detection part.

  



  I know OpenCV uses ffmpeg to capture video. I am using ffmpeg 3.3.2. My problem is that when I receive the stream, a lot of artifacts appear. The output I get is :

  



  top block unavailable for requested intra mode -1
[h264 @ 0000016ae36f0a40] error while decoding MB 40 0, bytestream 81024
[h264 @ 0000016ae32f3860] top block unavailable for requested intra mode
[h264 @ 0000016ae32f3860] error while decoding MB 48 0, bytestream 102909
[h264 @ 0000016ae35e9e60] Reference 3 >= 3
[h264 @ 0000016ae35e9e60] error while decoding MB 79 0, bytestream 27231
[h264 @ 0000016a7033eb40] mmco: unref short failure
[h264 @ 0000016ae473ee00] Reference 3 >= 3


  



  over and over again, and there are too many packet losses that I can't see anything when showing the received frames. However, it doesn't happen to me when I stream over RTP other lower quality videos such as HD in 30fps or like that. It is also true that the 4K has a lot of movement (it is a Moto GP Race).

  



  I have tried :
- Reduce the fps of the streaming.
- Reduce the bitrate 
- ffplay either doesn't show correctly the input frames, but VLC does (don't know why).
- Force TCP transmission.
- Force input fps doing cvSetCaptureProperty(cap, CV_CAP_PROP_FPS, 1);

  



  Why is this happening and how can I improve the packet losses ? Is there any way or something else I can try ?

  



  Thanks a lot