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• Convert video to exactly the same stream type of other video in ffmpeg

  14 avril 2014, par user1750371

  Maybe this is a silly question, didn't manage to find a clear answer anywhere.

  I need to use ffmpeg to convert a given video to exactly the same format another video has, including bitrate, video and audio codecs... everything. The goal is to concat both videos into a single file, independently of the original formats.

  Is there an easy way to do this or do I have to build a complex command line input specifying all parameters ?

  The concat demuxer is not enough... maybe something with filter_complex ?

  Thanks and sorry for the bother.

• Evolution #4658 (Nouveau) : Améliorer la classe .offscreen

  11 février 2021

  Bonjour,

  Ayant eu un cas où la classe n’avait pas caché complètement un border à un élément, j’ai cherché comment on faisait de manière moderne et accessible.

  Fichier à modifier : https://git.spip.net/spip/dist/src/branch/master/css/clear.css#L74

  Méthodes : https://webaim.org/techniques/css/invisiblecontent/#techniques

  Donc, il faudrait remplacer la méthode actuelle par :
  

  <span class="CodeRay"><span class="class">.offscreen</span> {
      <span class="key">position</span>: <span class="value">absolute</span>;
      <span class="key">left</span>: <span class="float">-10000px</span>;
      <span class="key">top</span>: <span class="value">auto</span>;
      <span class="key">width</span>: <span class="float">1px</span>;
      <span class="key">height</span>: <span class="float">1px</span>;
      <span class="key">overflow</span>: <span class="value">hidden</span>;
  }
  </span>
  Télécharger

  ou plus moderne :
  

  <span class="CodeRay"><span class="class">.offscreen</span> {
      <span class="key">clip</span>: <span class="error">r</span><span class="error">e</span><span class="error">c</span><span class="error">t</span>(<span class="float">1px</span>, <span class="float">1px</span>, <span class="float">1px</span>, <span class="float">1px</span>);
      <span class="key">clip-path</span>: <span class="error">i</span><span class="error">n</span><span class="error">s</span><span class="error">e</span><span class="error">t</span>(<span class="float">50%</span>);
      <span class="key">height</span>: <span class="float">1px</span>;
      <span class="key">width</span>: <span class="float">1px</span>;
      <span class="key">margin</span>: <span class="float">-1px</span>;
      <span class="key">overflow</span>: <span class="value">hidden</span>;
      <span class="key">padding</span>: <span class="float">0</span>;
      <span class="key">position</span>: <span class="value">absolute</span>;
  }
  </span>
  Télécharger

• VP8 Codec SDK "Aylesbury" Release

  28 octobre 2010, par noreply@blogger.com (John Luther)

  Today we’re making available "Aylesbury," our first named release of libvpx, the VP8 codec SDK. VP8 is the video codec used in WebM. Note that the VP8 specification has not changed, only the SDK.

  What’s an Aylesbury ? It’s a breed of duck. We like ducks, so we plan to use duck-related names for each major libvpx release, in alphabetical order. Our goal is to have one named release of libvpx per calendar quarter, each with a theme.

  You can download the Aylesbury libvpx release from our Downloads page or check it out of our Git repository and build it yourself. In the coming days Aylesbury will be integrated into all of the WebM project components (DirectShow filters, QuickTime plugins, etc.). We encourage anyone using our components to upgrade to the Aylesbury releases.

  For Aylesbury the theme was faster decoder, better encoder. We used our May 19, 2010 launch release of libvpx as the benchmark. We’re very happy with the results (see graphs below) :
  

  • 20-40% (average 28%) improvement in libvpx decoder speed
  • Over 7% overall PSNR improvement (6.3% SSIM) in VP8 "best" quality encoding mode, and up to 60% improvement on very noisy, still or slow moving source video.

  

  
  

  

  
  

  

  
  

  The main improvements to the decoder are :
  

  • Single-core assembly "hot spot" optimizations, including improved vp8_sixtap_predict() and SSE2 loopfilter functions
  • Threading improvements for more efficient use of multiple processor cores
  • Improved memory handling and reduced footprint
  • Combining IDCT and reconstruction steps
  • SSSE3 usage in functions where appropriate

  On the encoder front, we concentrated on clips in the 30-45 dB range and saw the biggest gains in higher-quality source clips (greater that 38 dB), low to medium-motion clips, and clips with noisy source material. Many code contributions made this possible, but a few of the highlights were :
  

  • Adaptive width and strength alternate reference frame noise suppression filter with optional motion compensation.
  • Transform improvements (improved accuracy and reduction in round trip error)
  • Trellis-based quantized coefficient optimization
  • Two-pass rate control and quantizer changes
  • Rate distortion changes
  • Zero bin and rounding changes
  • Work on MB-level quality control and bit allocation

  We’re targeting Q1 2011 for the next named libvpx release, which we’re calling Bali. The theme for that release will be faster encoder. We are constantly working on improvements to video quality in the encoder, so after Aylesbury we won’t tie that work to specific named releases.

  WebM at Streaming Media West

  Members of the WebM project will discuss Aylesbury during a session at the Streaming Media West conference on November 3rd (session C203 : WebM Open Video Project Update). For more information, visit www.streamingmedia.com/west.

  John Luther is Product Manager of the WebM Project.