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Avid Xpress Pro Adds HDV Capability

Features ability to mix different resolutions on the same timeline By Charlie White

Avid Xpress ProAvid Xpress Pros long-awaited HDV capability is now available, and that same feature will be released for Media Composer Adrenaline later this month. When Avid designed its HDV implementation, its goal was flexibility, with the HDV workflow the same as it is for other formats, including the ability to mix resolutions on the timeline. As an added enticement, Avid has dropped the ?HD from its Xpress Pro nomenclature, offering this new HDV editing capability at no extra cost. We tested Xpress Pros HDV ingest, editing and output routine, assessing how the application would fit into a real-world editing situation.

Exactly what is happening in the real world? Theres a wholesale transition going on, with production houses and editing boutiques, traditionally steeped in standard-definition video production, expanding into high-definition work while still keeping one foot in the standard definition arena. The result is that many production facilities are not only using HDV by itself, but are using it to supplement other HD formats such as DVCPro HD and HDCam. Even though lots of the video acquisition is happening in HD, still, the majority of the final product output is standard definition. Yes, this is an awkward time for HDV production, where there is the option to go up-market to more expensive HD formats, but hardly any place to go down-market theres no DVD equivalent at this writing. Some producers are opting to go to Windows Media 9 or 10 (now called VC-1), which you can do with this version of Xpress Pro. Also now shipping with Avid products is the excellent H.264 codec, which is bundled with the new version 4.0 of Sorenson.

With this new implementation, Avid has figured out how to make HD clips coexist with standard definition clips. Avids philosophy is right on the money, where it anticipates the transition from standard definition to high definition will take a while. The fact is that numerous producers, editors, directors and production facilities possess a multitude of standard definition footage and equipment, and for some time to come will need to mix these formats together with HD footage. Given that virtual Tower of Babel of video formats, Avids mission is currently to feature the ability to use all different formats on the same timeline. Striving to allow users to work with HD without feeling the pain of all that extra data, Avid set out to let users of Xpress Pro play back as many edits as possible in real time, no matter what the resolution. Whether it succeeded at that is largely a matter of how fast the host computers processors are. So, if youre considering editing HD on Xpress Pro, the first order of business is to procure the fastest machine you can find. 

In our testing of Xpress Pro, it appears that Avid has met its objective of matching the editing functionality of its other formats while editing HDV footage?the HDV workflow is identical to editing with DV except for increased render times, and HDV appears as just another format. Thankfully, the rendering takes place after the editing is done, because Avids implementation concentrates on quick ingest of the footage. It works like this: As it imports HDV transport streams, it de-muxes the signal, which means it separates the audio and video. Avids technique doesnt touch the actual data at this stage, which remains native as it goes into the computer. Its when the editing begins that challenge presented itself to Avids programmers. When choosing an ?HDV Project and adding SD clips in the timeline, other software requires that you render to see any footage that is not in the native format of the project.  Avid wanted to let editors see any other footage in real time, any conversion (like an upconvert of DV to HD) happens at the end of the process.

According to Avid engineers, the software had to go through major changes in order to execute the HDV format, which is compressed using a method called ?long-gop where only some frames (called ?I-frames) contain all of the frames information, where long groups of pictures (GOP) consist of just the information thats changed between each I-frame. Not only did the developers have to find ways to edit between these groups of pictures, it also had to enable playback before and after these edits took place. Thats a tall order, and is typical of editing using the HDV formats long-GOP format, no matter who developed the software.

Since HDV (and incidentally, DVCPro HD) is created in 1440 x 1080i, Avid has made choices of ways to deal with this ?thin raster resolution?its called that because the full raster of 1080i footage is 1920x1080. So, Avid gives you a choice of dealing with your footage in either 1440x1080 or 1920x1080. I noticed that if youre scaling HDV to the full-raster, there will be lower real-time effects performance. Certainly HDV is a much easier format with which to work, but if youre doing multilayered composites or mixing with other HD flavors, Avid recommends running the timeline in a full raster 1920 format. Any new media such as graphics and titles are automatically rendered in their outstanding high-definition codec, called DNxHD, , which is better suited for multi-layering.  

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