Monter en HDV, démystifier le casse-tête!

Editing native HDV (.m2t files)

HDV is packaged into mpeg2-ts (transport stream), or .m2t, so it can easily fit onto a minidv tape. HDV 720p compresses at around 19 mbps (megabytes per second); HDV 1080i/p is compressed at around 25 mbps. Of course, on paper that seems like a little too much compression, but even casual viewers or users of HDV know how great it looks and sounds. It’s also around 3.5 mb per second, like DV, so HDV file sizes won’t be so large.

Because it's .m2t, similar to how video is compressed for DVDs (though its mpeg2 compression is only a program stream), it was originally very difficult to edit. In fact, with the exception of Apple?s Final Cut Pro (www.apple.com/finalcutstudio) and Sony Vegas 7, most video editors find editing .m2t files to be very hard on older systems.  And yes, all major NLEs support HDV editing, but everyone of them prefer you use the DI.

DI (Digital Intermediate)

Enter the DI, or Digital Intermediate; instead of capturing and editing in native HDV, you use a software application, like CineForm’s excellent product AspectHD (www.cineform.com), to capture and convert on-the-fly to a different flavor of HD, usually uncompressed. The downside is you lose HDV’s size (around 13 gb for an hour of footage) in favor of ease of use. These new files can be anywhere from 40 - 60 gb per hour of footage, depending on quality settings!

A Look at the NLE Solutions

Avid and Edius both use their own brand of DI, but many editors enjoy using CineForm?s products with Premiere Pro, which is also coming back to the Mac in 2007 (www.adobe.com/premierepro), or Sony Vegas (www.sony.com/vegas).  Sony Vegas 7 came a long way from version 6 with handling native HDV editing.  New, fast systems can produce full playback without problems, though many editors enjoy working with DIs, or proxy solutions for older, slower computers.  I'll take a look at proxies in a moment.

After editing with the DI, it’s easy to go back to tape as HDV by using the same application that created the DI. Usually it’s just an output function, some patience as it goes back to HDV, then hitting record on your HDV VTR or camera.

Along with Premiere Pro returning to the Mac, CineForm is working on porting its apps to the Mac sometime in 2007, with an announcement around NAB in April. Many Final Cut Pro editors are happy about this news, as are many Windows-based NLE cutters.

Also, Apple provides the Apple Intermediate Codec (AIC) to create and edit with a DI. In fact, you can only capture and edit with the AIC in iMovie HD (www.apple.com/ilife) and Final Cut Express HD (www.apple.com/finalcutexpress). For a comparison of the Apple professional and consumer NLE solutions, go to www.apple.com/finalcut.
One note, if you decide to capture and cut in native HDV vs. the AIC with the latest version of Final Cut Pro, you won’t be able to see what you’re cutting on your calibrated monitor. This is due to cutting .m2t, and until you output to tape, you won’t see anything. An expensive way around it is to buy an uncompressed HD capture card (like BlueFish, AJA, DeckLink, etc.) to convert the HDV signal to HD when monitoring your edit, not upon capture.

You’ll also need to convert that digital audio to analog with an A/D, D/A (analog to digital, digital to analog) so you can hear it on your speakers. That can add to the overall budget of your Final Cut Studio system. I personally don’t have the card or A/D, D/A, so I just edit on a high-res computer monitor that supports HD aspect ratios (look for anything with a vertical resolution of 720 and up). The sound is routed from my computer to speakers.

Proxy Editing

In the beginning, aside from JVC, no NLEs supported native HDV editing. Frederic Haubric’s Lumiere HD (www.lumierehd.com) helped solve that problem for Mac editors. It captures the footage, then goes through a couple of steps to create a working video file (I recommend simply using DV) that can be edited. And like CineForm, when you’re finished editing, going back to tape in native HDV was easy.

On the PC side, there’s VASST’s GearShift (www.vasst.com), which works very similar to both CineForm and Lumiere HD. Once captured, you can “shift gears” and create a DV file to cut on, then “shift gears” again to output to HDV.

Many have wondered if either proxy editors, which converts the footage to something easier to edit on (not exactly a DI), would fade away with native and improved HDV capabilities in the popular NLEs. Not so, because you may be cutting on a slower computer, or a laptop, which can slow you down with either native HDV or an HD Digital Intermediate.

Using GearShift or Lumiere HD on an older system can save you money, and prevent you from having to buy a new computer every year or so. Also, if a new camera comes out that isn’t supported yet, like Final Cut Pro (FCP), which didn’t support 720p24 or Canon’s 24F, until very recently, you can use a proxy editor, if it’s supported there, to capture and edit these new HDV frame rates.

Hardware-Based Systems

In addition to the capture cards mentioned above which show your edits on a preview monitor when using Final Cut Pro or any NLE, you can also capture uncompressed and edit without converting to a DI on-the-fly.

Avid and Edius both offer hardware-based systems, such as the Avid Xpress Pro (www.avid.com/xpresspro) and Avid Liquid (www.avid.com/liquid), and the Edius NX Express (www.canopus.com/products/nlesystems.php). Matrox (www.matrox.com/video/products/rtx2/home.cfm) does, as well, with its RT.X2 system, which comes bundled with Adobe Premiere Pro and the Production Bundle.

Conclusion

Remember, if you edit in native HDV (.m2t), unless you?re working with a new, fast computer with the newest version of the NLE of your choice, you will run into issues with the playback. For users with older systems, work with a DI (Digital Intermediate), like CineForm?s, or those built into Apple?s NLE apps, Avid and Edius. It may increase the size of the footage, but editing will be much easier and smoother, depending on the speed of your system.  You can use a DI on a new system, as well.  If file size needs to stay small, or you?re not ready to upgrade your older computer, try a proxy editor, like VASST?s GearShift for Windows, or Lumiere HD for Macs.

Also keep in mind, both Edius and Avid provide their own DI solutions, that work great for those platforms. Matrox offers accelerated editing with their products that work with Adobe Premiere Pro.

There are plenty of solutions out there, and many depend on which system you use (Windows vs. Apple), the speed, hard drive space, etc. If you’re comfortable with your NLE, and it’s up-to-date, chances are you can start cutting HDV right now! Happy editing!

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article tiré de Creative Mac