Recherche avancée

Sur d’autres sites (12844)

• How to create a named pipe in Windows ?

  10 février 2023, par Che

  Is it possible without much effort (e.g. in command line or powershell), to create a named pipe ?

  


  My goal is to write continously to that pipe from a ffmpeg-process.

  


  Without opening a Pipe at first the following command

  


  ffmpeg -i "path\to\my\File\name of my File" -f webm \\.\pipe\from_ffmpeg


  


  fails to

  


  


  "\.\pipe\from_ffmpeg : No such file or directory"

  


  


  In the big picture, I want to read a Live-Web-Video-Stream to analyze it and take live-actions based on that.
I am working with OpenCV in Java on a Windows machine. At the moment I have different ffmpeg-processes, which record different sectors (i.e. pixels (45, 45, 100, 100) and (200, 200, 100, 100) (x, y, height, width). The results are saved as jpg files in the filesystem and are then opened in a Java Process. This works, but I think I would significantly gain performance by not taking the long way over the files but to directly pipe my input into the Java-Process.

  


  I know there's an option to live-capture videostreams via open-CV but the framework does not support as many formats as ffmpeg does.

  


• Preserve presentation timestamp from RTSP to VP8 with ffmpeg

  28 juillet 2020, par Pamphile

  I'm applying a ffmpeg filter on a RTSP stream and outputting it as VP8/IVF :

  


  ffmpeg -rtsp_transport tcp -i "rtsp://localhost/myrtspstream" -vf v360=fisheye:equirect -c:v libvpx -deadline realtime -f ivf pipe:1


  


  Here are the successive presentation timestamps from the input RTP packets (consistent with 15 FPS and a 90 000 Hz timebase) :

  


  0
5850
11970
18000
23850
...


  


  I want to preserve these presentation timestamps in the ouput.
Unfortunately, the presentation timestamps of the output frames are : 1, 2, 3, 4, 5...

  


  I've tried many timestamp-related ffmpeg options, such as copyts/setpts/vsync, without any success.

  


  I know the PTS in the input are primarily related to packets whereas they are related to frames in the output, but still, is it somehow possible to preserve them from input frames to output frames ?

  


  Context : I have object-tracking data associated to each input frame. As I want to associate them to the output frames, my primary goal is to associate input and output frames. Looking at the timestamps is one way of doing it I could think of.

  


• Grid/Mesh warping of videos with OpenCV

  2 février 2017, par andreas

  I would like to do some warping with OpenCV applied on Videos. Here is a demo in Javascript which perfectly explains what I want to achieve via OpenCV :

  http://persistent.info/web-experiments/distortion/
  Please select "Tron Legacy" in the drop down menu "Datasource"

  Here is also screenshot of the demo :

  Screenshot of the Demo

  I am not an expert in OpenCV, but as far as I know there are only methods about camera calibration which deals with distortions (but only with special ones like radial and tangential distortions). For my purpose, I need a more general approach.

  The overall goal : apply some kind of "filter" on any video which generates this kind of distortion, based on a grid which can be adjusted via drag and drop by a user. This filter does not have to work in real time. Hence, if you know any other frameworks which can be used for this, please let me know :-) I´ve checked the filter section of FFMPEG, but it seems that also these filters are not appropriate.

  Thanks for your help !!