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• Fade picture in ffmpeg on Android NDK

  14 mars 2012, par sherman

  I used ffmpeg methods without any problems. But I want to modify ffmpeg library to add visual effect between switching videos, if it is possible.

  Please help me regarding this. Thanks in advance.

• Video Seek Scroll (60FPS)

  9 avril 2022, par Enijar

  Trying to achieve an effect of seeking through a video when the page is scrolled. This has been achieved by exporting all frames of the video to JPEG images, pre-loading the images, and rendering them to a canvas. However, this approach uses a lot of bandwidth and takes a long time to load on slow networks.

  


  Trying to achieve the same effect by rendering a video to a canvas does not play as smoothly as the image-based approach.

  


  Here is a working demo with the video-based approach :

  


  https://codesandbox.io/s/infallible-chaum-grvi0r?file=/index.html

  


  Since HTMLMediaElement.fastSeek() doesn't have widespread browser coverage, how can one achieve a realtime playback rate of 30-60 FPS ?

  


  Here is the relevant code for the effect (see CSB link above for the full code) :

  


  const video = document.querySelector("video");
const canvas = document.querySelector("canvas");
const ctx = canvas.getContext("2d");

(function tick() {
  requestAnimationFrame(tick);

  const { scrollHeight, clientHeight, scrollTop } = document.body;
  const maxScroll = scrollHeight - clientHeight;
  const scrollProgress = scrollTop / maxScroll;

  canvas.width = document.body.clientWidth;
  canvas.height = document.body.clientHeight;

  // This is the line that causes the issue
  video.currentTime = video.duration * scrollProgress;

  ctx.clearRect(0, 0, canvas.width, canvas.height);
  ctx.drawImage(video, 0, 0, canvas.width, canvas.height);
})();


  


• how to make any filter's value that accept integer value be a function of the timestamp in ffmpeg ? [closed]

  30 novembre 2023, par rosner altamira

  For example, i am trying to apply blur effect to video in ffmpeg using gblur filter, i want the blur strength to gradually increase from 0 to 50 in 2 secs starting at 5 secs and fade back from 50 to 0 in 3 secs thus finishing at 15 secs. In summary the blur is between 5 and 15 secs but from 5 to 7, the effect will gradually grow from 0 to 50 and from 12 to 15 it will fade from 50 back to 0.

  


  here is what i tried :

  


  


  ffmpeg -i test-video.mp4 -loop 1 -t 5 -i test-image.jpg -filter_complex "[0:v]gblur=sigma='if( lte(t,5) + gte(t, 15), 0, if( between(t, 7, 12), 50, min( max(25t - 125, 0), max(-16.67t + 250, 0) ) ) )':enable='between(t,5,15)'[bg] ;[1:v]fade=in:0:30[ol] ;[ol]fps=fps=15[ol] ;[bg][ol]overlay=(W-w)/2 :(H-h)/2:enable='between(t,5,15)'[out]" -map "[out]" -map 0:a output_video.mp4

  


  


  Expectations :

  


  


  [0:v]gblur=sigma='if( lte(t,5) + gte(t, 15), 0, if( between(t, 7, 12), 50, min( max(25t - 125, 0), max(-16.67t + 250, 0) ) ) )':enable='between(t,5,15)'[bg] :

  


  


  The blur strength depends dynamically on the time (t) as described above, controlled by the expression.
The enable parameter ensures that this filter is only applied between 5 and 15 seconds.

  


  


  [1:v]fade=in:0:30[ol] :
[ol]fps=fps=15[ol] :
[bg][ol]overlay=(W-w)/2 :(H-h)/2:enable='between(t,5,15)'[out] :

  


  


  The overlay input should be faded in for 2 secs starting from 5secs and will last 10secs (same time for the blur)

  


  As result, i am getting Invalid char error. Seems like sigma does not accept the "t" timestamp variable.