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• avconv save 10 frames and update them in cycle

  12 août 2016, par Flash Thunder

  The way I am saving frames from camera is :

  avconv -f video4linux2 -i /dev/video0 -r 5 output_%04d.png

  Seems to be working fine... but... I need to save only 10 frames and overwrite the saved first saved all the time... any way to do that ? I need to be able to save frames and process them in other application... but process may take longer than record.

  Tried to save one frame and overwrite it, but the problem is that file is being used and it simply doesn’t work.

• How to save html5 video effects

  5 novembre 2014, par CurlyFro

  i have a video file and I’d like to apply different effects like blur, black&white, etc via JavaScript and save the output to a file.

  i can probably do this with FFMPEG but it looks too complicated.

  seriously.js looks awesome but i don’t know how to save the rendered effect to a file. does anyone know how to do this ?

• How to write v4l2 application with vivid (virtual video driver) for capturing video ?

  8 janvier 2016, par ransh

  I am trying to understand how to write v4l2 application.
  There is very well example in http://linuxtv.org/downloads/v4l-dvb-apis/capture-example.html , so I wanted to try to use it for capturing video with vivid (virtual device driver).

  I tried several resolution, pixelformat, different inputs,
  but on trying to display the captured file, it always has a sync problems ( the test bars of the video are keep moving in the horizontal axis).
  I tried to change resolution, pixelformat, in both capture application or player , but nothing helps.

  I compiled the v4l2 API example AS-IS from :
  http://linuxtv.org/downloads/v4l-dvb-apis/capture-example.html
  with minor modification in the —force part of the example (I also tried the example as is without modifications but it did not help), so that I choose hd input , and 1920x1080 resolution, V4L2_PIX_FMT_YUV420 (also tried V4L2_PIX_FMT_YUV422P) , progressive.

    if (force_format) {
  
              input = 3;  // <<-- HD input device
  
              if (-1==xioctl(fd,VIDIOC_S_INPUT,&input))
  
              {
  
               errno_exit("VIDIOC_S_INPUT");
  
              }
  
              fmt.fmt.pix.width       = 1920;
  
              fmt.fmt.pix.height      = 1080;
  
              fmt.fmt.pix.pixelformat = V4L2_PIX_FMT_YUV420; // <<- tried also V4L2_PIX_FMT_YUV422P
  
              fmt.fmt.pix.field       = V4L2_FIELD_NONE; // <- trying to capture progressive
  
  
  
              if (-1 == xioctl(fd, VIDIOC_S_FMT, &fmt))
  
                      errno_exit("VIDIOC_S_FMT");
  
  
  
      } else {

  I run the application with (the compiled code using pixelformat = V4L2_PIX_FMT_YUV420 trial ) :

  ./v4l2_example -f -o -c 10  > cap_yuv420p.yuv 

  And (the compiled code using pixelformat = V4L2_PIX_FMT_YUV422P trial )

  ./v4l2_example -f -o -c 10  > cap_yuv422p.yuv 

  I’ve tried to play them with :

  ffplay -f rawvideo -pixel_format yuv420p -video_size 1920x1080 -i cap_yuv420p.yuv 

  And

  ffplay -f rawvideo -pixel_format yuv422p -video_size 1920x1080 -i cap_yuv422p.yuv 

  These are the captured video files from my above trials :

  https://drive.google.com/folderview?id=0B22GsWueReZTUS1tSHBraTAyZ00&usp=sharing

  I probably am doing something wrong.
  Is there any idea what’s wrong in my configurations or how I can debug it better ?