Recherche avancée

Sur d’autres sites (8725)

• convert f4v to mp4 with ffmpeg

  9 août 2013, par Winnie Oldright

  Trying to convert f4v to mp4 with ffmpeg

  This file

  FFmpeg :

  ffmpeg -i input.f4v -vcodec copy -acodec copy output.mp4

  In output i have black screen in video and no sound but track seconds are incrementing properly.

  What i'm doing wrong ? Or maybe i need mpg or some other file type in out put (output file type should supports in android).

• 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.

  

• Wave Goodbye ; What About VP8/WebM ?

  7 août 2010, par Multimedia Mike — Multimedia PressWatch

  Some big news in the geek community this past week came in the form of Google’s announcement that it would no longer be caring about its vaunted Wave technology. I was mildly heartbroken by this since I had honestly wanted to try Google Wave. Then I remembered why I never got a chance to try it : they made it an exclusive club at the beginning. I really did try to glean some utility out of the concept by reading documentation and watching videos and I had some ideas about how I might apply it. Then again, I try to think of a use for nearly any technology that crosses my path.

  It still struck me as odd : Why would Google claim that no one was interested in their platform when they wouldn’t give anyone a chance to try it out ? A little digging reveals that Google did open it for general use back around May 18. That date sounds familiar... oh yeah, VP8 was open sourced right around the same time. Maybe that’s why I don’t remember hearing anything about Wave at the time.

  But now I’m wondering about VP8 and WebM. How long do you think it might be before Google loses interest in these initiatives as well and reassigns their engineering resources ? Fortunately, if they did do that, the technology would live on thanks to the efforts of FFmpeg developers. A multimedia format has a far more clear-cut use case than Google Wave.