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• Why iFrame is a good idea

  15 octobre 2009

  I’ve seen some hilariously uninformed posts about the new Apple iFrame specification. Let me take a minute to explain what it actually is.

  First off, as opposed to what the fellow in the Washington Post writes, it’s not really a new format. iFrame is just a way of using formats that we’ve already know and love. As the name suggests, iFrame is just an i-frame only H.264 specification, using AAC audio. An intraframe version of H.264 eh ? Sounds a lot like AVC-Intra, right ? Exactly. And for exactly the same reasons - edit-ability. Whereas AVC-Intra targets the high end, iFrame targets the low end.

  Even when used in intraframe mode, H.264 has some huge advantage over the older intraframe codecs like DV or DVCProHD. For example, significantly better entropy coding, adaptive quantization, and potentially variable bitrates. There are many others. Essentially, it’s what happens when you take DV and spend another 10 years working on making it better. That’s why Panasonic’s AVC-Intra cameras can do DVCProHD quality video at half (or less) the bitrate.

  Why does iFrame matter for editing ? Anyone who’s tried to edit video from one of the modern H.264 cameras without first transcoding to an intraframe format has experienced the huge CPU demands and sluggish performance. Behind the scenes it’s even worse. Because interframe H.264 can have very long GOPs, displaying any single frame can rely on dozens or even hundreds of other frames. Because of the complexity of H.264, building these frames is very high-cost. And it’s a variable cost. Decoding the first frame in a GOP is relatively trivial, while decoding the middle B-frame can be hugely expensive.

  Programs like iMovie mask that from the user in some cases, but at the expensive of high overhead. But, anyone who’s imported AVC-HD video into Final Cut Pro or iMovie knows that there’s a long "importing" step - behind the scenes, the applications are transcoding your video into an intraframe format, like Apple Intermediate or ProRes. It sort of defeats one of the main purposes of a file-based workflow.

  You’ve also probably noticed the amount of time it takes to export a video in an interframe format. Anyone who’s edited HDV in Final Cut Pro has experienced this. With DV, doing an "export to quicktime" is simply a matter of Final Cut Pro rewriting all of the data to disk - it’s essentially a file copy. With HDV, Final Cut Pro has to do a complete reencode of the whole timeline, to fit everything into the new GOP structure. Not only is this time consuming, but it’s essentially a generation loss.

  iFrame solves these issues by giving you an intraframe codec, with modern efficiency, which can be decoded by any of the H.264 decoders that we already know and love.

  Having this as an optional setting on cameras is a huge step forward for folks interested in editing video. Hopefully some of the manufacturers of AVC-HD cameras will adopt this format as well. I’ll gladly trade a little resolution for instant edit-ability.

• Bye Bye FATE Machine

  4 septembre 2010, par Multimedia Mike — FATE Server

  This is the computer that performed the lion’s share of FATE cycles for the past 1.5 years before Mans put a new continuous integration system into service. I’ve now decided to let the machine go. I can’t get over how odd this feels since this thing is technically the best machine I own.

  
  
  

  It’s a small form factor Shuttle PC (SD37P2 v2) ; Core 2 Duo 2.13 GHz ; 2 GB RAM ; 400 GB SATA HD ; equipped with the only consistently functional optical drive in my house (uh oh). I used it as my primary desktop from March 2007 – November 2008, at which point I repurposed it for FATE cycles.

  As mentioned, the craziest part is that this is technically the best computer in my house. My new EeePC 1201PN isn’t at quite the same level ; my old EeePC can’t touch it, of course ; the Mac Mini has a little more RAM but doesn’t stack up in nearly all other areas. But the Shuttle just isn’t seeing that much use since the usurpation. I had it running automated backup duty for multimedia.cx but that’s easy enough to move to another, lower-powered system.

  Maybe the prognosticators are correct and the PC industry has matured to the point where raw computing power simply doesn’t matter anymore. I fancy myself as someone who knows how to put CPU power to work but even I don’t know what to do with the computing capacity I purchased over 3 years ago.

  Where will the Shuttle go ? A good home, I trust– I know a family that just arrived in the country and could use a computer.

• Anomalie #2477 : Plugin activé mais pas activé

  24 mars 2012, par jluc -

  Dans d’autres circonstances (d’autres applications), il faut installer PUIS activer. Les significations des termes ’activation’ et ’installation’, tels qu’utilisées dans SPIP, ne sont pas illogiques dans l’absolu, mais il me semble impossible de comprendre a priori ce que l’un veut dire par (...)