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• Anomalie #2465 (Nouveau) : critère {", "} et espace superflu

  23 décembre 2011, par denisb -

  soit la boucle a le résultat produit : a[espace],[espace]a[espace],[espace]a alors qu’on attendrait : a,[espace]a,[espace]a le saut de ligne entre a et produit cet espace surnuméraire. a donne le résultat attendu.

• More Weird VP8 Encodings

  10 décembre 2010, par Multimedia Mike — VP8

  When I announced that I had transitioned my VP8 encoder’s status from "toy" to "working", Jim L. lamented the loss of humorous posts about oddly encoded images output from my encoder. Not so ! There are still plenty of features that I have yet to implement, each of which carries the possibility of bizarre images.

  For example, I dusted off my work-in-progress intra 4x4 encoding, fixed a few of the more obvious bugs, and told the encoder to encode the first block in 4x4 mode and the rest in the usual, working, debugged 16x16 mode. The results of the first pass surprised me :

  
  
  

  The reason this surprised me was that I intuitively expected one of 2 outcomes :

  • Perfect image right away since everything is correct (very unlikely but not outside the realm of possibility)
  • Total garbage with, at most, the first macroblock looking somewhat legible ; this would be due to having some of the first macroblock correct but completely desynchronizing the bitstream for the purpose of decoding the rest of the coefficients.

  I absolutely did not expect the first macroblock to look messed up but for the rest of the picture to look fine. For fun, I reversed the logic and encoded the first block as 16x16 and the rest with the experimental 4x4 mode :

  
  
  

  If you examine carefully, you will see that the color planes are correct (though faint). There just isn’t much going on in the luma plane. This made sense when I noticed the encoder was encoding a blank (undefined, actually) set of luma coefficients for 4x4 mode macroblocks due to a bug. This helps to rationalize the first image as well— the first macroblock was encoding nonsense for the first macroblock which messed up the macroblocks which immediately surrounded it. Eventually, macroblock decoding got back on track when the prediction modes weren’t relying on the errantly decoded macroblocks.

  After I fixed that bug, I let the 4x4 mode rip through the whole image. That’s when I got what I am terming the "dark and gritty reboot of Big Buck Bunny" :

  
  
  

  Fortunately, this also turned out to be traceable to a pretty obvious code bug.

  One day, this VP8 encoder might do the right thing while implementing all of the algorithm’s features. In the meantime, it’s at least entertaining to watch it make mistakes.

• VeriSilicon and WebM Support

  24 janvier 2011, par noreply@blogger.com (John Luther)

  Guest blogger Tomi Jalonen is Director of Product Marketing for Hantro video IP at VeriSilicon

  2011 is shaping up to be an exciting year at VeriSilicon Holdings in terms of WebM support. With the new year upon us, I want to share some updates about the work we are doing at VeriSilicon to move the WebM platform forward.

  VeriSilicon has been a longtime partner of On2/Hantro (Hantro is the video IP brand that Google acquired with On2 Technologies) and we were among the first hardware partners to commit to WebM video when the codec was open-sourced last year. After promoting WebM to the semiconductor industry during 2010, we’re excited that at CES 2011 the first tablet supporting WebM with full 1080p resolution was demonstrated. VeriSilicon licensed the WebM IP to this tablet manufacturer and provided engineering support to bring the technology to the showroom floor.

  In addition to licensing IPs, this year we’ll be taking the WebM experience a step further by taping out several application processor chips—including the WebM video IP for Android phones, xPad, and Google TV—to accelerate the deployment of WebM and HTML5 video playback into the market.

  The entire VeriSilicon team is very excited about the future of WebM. We believe that the availability of high-quality, optimized WebM hardware video IP, combined with other VeriSilicon audio and multimedia IP, will be a key ingredient for semiconductor companies to create competitive consumer products. After the launch of WebM, the interest in hardware-accelerated WebM video has been immense and we will continue working with the WebM Project to enable WebM and VP8 in many more chips in 2011.