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• avcodec/vp3 : Fix "runtime error : left shift of negative value"

  4 décembre 2015, par Michael Niedermayer

  avcodec/vp3 : Fix "runtime error : left shift of negative value"
  Fixes : 5c6129154b356b80bcab86f9e3ee5d29/signal_sigabrt_7ffff6ae7cc9_7322_d26ac6d7cb6567db1b8be0159b387d0b.ogg
  Found-by : Mateusz "j00ru" Jurczyk and Gynvael Coldwind
  
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavcodec/vp3.c

• mp4 Vj Animation video lagging hi res video

  21 février 2020, par Ryan Stone

  I am trying to get a video to play inside a video tag at the top left hand corner of my page, it loads ok, the resolution is good and it seems to be looping but it is lagging very much, definatly not achieving 60fps it is in mp4 format and the resolution on the original mp4 is 1920x1080 it is a hi resolution vj free loop called GlassVein, you can see it if you search on youtube. On right clicking properties it comes up with the following inforamtion ;

  Bitrate:127kbs
  Data rate:11270kbps
  Total bitrate:11398kbs
  Audio sample rate is : 44khz
  filetype is:VLC media file(.mp4)
  (but i do not want or need the audio)

  & it also says 30fps, but I’m not sure i believe this as it runs smooth as butter on vlc media player no lagging, just smooth loop animation

  I have searched on :https://trac.ffmpeg.org/wiki/Encode/AAC for encoding information but it is complete gobbldygook to me, I don’t understand a word its saying

  My code is so far as follows ;

      <video src="GlassVeinColorful.mp4" autoplay="1" preload="auto" class="Vid" width="640" height="360" loop="1" viewport="" faststart="faststart" mpeg4="mpeg4" 320x240="320x240" 1080="1080" 128k="128k">  
  
      </video>

  Does anyone know why this is lagging so much, or what I could do about it.
  it is a quality animation and I don’t really want to loose an of its resolution or crispness.. the -s section was originally set to 1920x1080 as this is what the original file is but i have changed it to try and render it quicker...

  Any helpful sites, articles or answers would be great..

  2020 Update

  The Solution to this problem was to convert the Video to WebM, then use Javascript & a Html5 Canvas Element to render the Video to the page instead of using the video tag to embed the video.

  Html

  <section>
  
          <video src="Imgs/Vid/PurpGlassVein.webm" type="video/webm" width="684" height="auto" muted="muted" loop="loop" autoplay="autoplay">
  
                 <source>
  
                 <source>
  
                 <source>
  
          </source></source></source></video>
  
          <canvas style="filter:opacity(0);"></canvas>
  
  </section>

  Css

  video{
  
     display:none !important;
  
     visibility:hidden;
  
  }

  Javascript

      const Canv = document.querySelector("canvas");
  
      const Video = document.querySelector("video");
  
      const Ctx = Canv.getContext("2d");
  
  
  
      Video.addEventListener('play',()=>{
  
        function step() {
  
          Ctx.drawImage(Video, 0, 0, Canv.width, Canv.height)
  
          requestAnimationFrame(step)
  
        }
  
        requestAnimationFrame(step);
  
      })
  
  
  
      Canv.animate({
  
          filter: ['opacity(0) blur(5.28px)','opacity(1) blur(8.20px)']
  
      },{
  
          duration: 7288,
  
          fill: 'forwards',
  
          easing: 'ease-in',
  
          iterations: 1,
  
          delay: 728
  
      })

  I’ve Also Used the Vanilla Javascript .animate() API to fade the element into the page when the page loads. But one Caveat is that both the Canvas and the off-screen Video Tag must match the original videos resolution otherwise it starts to lag again, however you can use Css to scale it down via transform:scale(0.5) ; which doesn’t seem to effect performance at all.

  runs smooth as butter, and doesn’t loose any of the high resolution image.
  Added a slight blur 0.34px onto it aswell to smooth it even more.

  Possibly could of still used ffmpeg to get a better[Smaller File Size] WebM Output file but thats something I’ll have to look into at a later date.

• php exec command to encode video to h.264 mp4 file using ffmpeg and x264 tool on ubuntu

  7 avril 2012, par matt

  I have a dedicated server with ffmpeg and the x264 tool installed. I can encode any video and works really well. But now I need to encode videos to play on iPads, iPhones... the format needs to be mp4 and using the h.264 codec.

  I'm using PHP to enconde videos, I'm just looking for an exec command to do the above encoding.
  what I'm using for the other videos is :

  exec("ffmpeg -i movie.mov -sameq -acodec mp3 -ar 22050 -ab 32 -f flv -s 1280x720 movie.flv");

  I just need something similar to that for encoding mp4
  by the way, I can't use libx264. I can only use the x264 tool

  Cheers