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• avformat/udp : increase the default buffer size of a receiving socket to 384K

  14 janvier 2020, par Marton Balint

  avformat/udp : increase the default buffer size of a receiving socket to 384K
  It is a common mistake that people only increase fifo_size when they experience
  
  drops, unfortunately this does not help for higher bitrate (> 100 Mbps) streams
  
  when the reader thread simply might not receive the packets in time (especially
  
  under high CPU load) if the default 64 KB of kernel buffer size is used.
  New default is determined so that common linux systems can set this buffer size
  
  without tuning kernel parameters.
  Signed-off-by : Marton Balint <cus@passwd.hu>
  

  • [DH] doc/protocols.texi
  • [DH] libavformat/udp.c

• FFMPEG conversion from .H264 to MP4 playing too fast

  28 juin 2017, par NickR

  I accidentally deleted a video file but managed to save it with a recovery tool. The video was however corrupted, but I managed to repair that and now have a .h264 file.

  The file plays ok in the VLC player. There are a few glitches but on the whole its 98% perfect. However I now need to convert that into a more useable format (mp4 say).

  Ive downloaded the FFMPEG tool and have managed to pretty easily copy into mp4 with the following command line instruction :

  ffmpeg -i repairedVid.h264 -c copy repairedVid.mp4

  The problem is that the video is playing much too fast. I’ve done some research tried some tweaks that seem to have worked for other people (like forcing frame rate and changing the -vsync) :

  ffmpeg -i repairedVid.h264 -c copy repairedVid.mp4 -vsync 2 -r 23.976

  Ive also tried the crude approach of slowing the video down like this, but this was more of a long shot and I don’t think is the right way to go about it

  ffmpeg -i repairedVid.mp4 -filter:v "setpts=1.5*PTS" repairedVid.mp4

  This is the output when the video copies to MP4. Looks like it might have a clue to the problem (the video should be much longer than 4:40 minutes) :

  frame=13459 fps=1118 q=-1.0 size= 4102773kB time=00:04:40.65 bitrate=119756.4kbiframe=13459 fps=1117 q=-1.0 Lsize= 4102928kB time=00:04:40.65 bitrate=119761.0kbits/s speed=23.3x
  video:4102773kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead : 0.003784%

  I’m totally new to FFMPEG and not having much luck. Any advice would be great.

  Thanks in advance

• Opencv cv2.VideoCapture('file.avi') shows first frame then throws exception

  3 novembre 2014, par holografix

  I’m trying to read a .avi included in the OpenCV original package, it’s called 768x576.avi and shows a few people walking around a street.

  The code below shows what seems to be the 1st frame and runs for a few seconds before returning an Exception.

  import cv2
  
  cap = cv2.VideoCapture('768x576.avi')
  
  cap.isOpened() # returns True
  
  cap.get(3); cap.get(4) # returns 768 and 576
  
  
  
  while (True):
  
      ret, frame = cap.read()
  
      cv2.imshow('frame', frame)

  Hands me this error after a few secs on the cv2.imshow line, I think it means the returned frame had no data associated it in.

  error: /tmp/opencv-7y6HHt/opencv-2.4.9/modules/highgui/src/window.cpp:261: error: (-215) size.width>0 && size.height>0 in function imshow

  I have no idea why this is happening, I’m running Yosemite, brew installed Python, OpenCv and Ffmpeg.

  opencv: stable 2.4.9, HEAD
  
  http://opencv.org/
  
  /usr/local/Cellar/opencv/2.4.9 (219 files, 38M) *
  
  
  
  ffmpeg: stable 2.4.2 (bottled), HEAD
  
  https://ffmpeg.org/
  
  /usr/local/Cellar/ffmpeg/2.4.2 (199 files, 40M) *
  
    Poured from bottle
  
  From: https://github.com/Homebrew/homebrew/blob/master/Library/Formula/ffmpeg.rb
  
  ==> Dependencies
  
  Build: pkg-config ✔, texi2html ✘, yasm ✘
  
  Recommended: x264 ✔, faac ✔, lame ✔, xvid ✔