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Editing with AVCHD

By Ron Seifried

When first introduced in 2006, AVCHD was designed to be the format of choice to bring HD video capture to the masses of camcorder users looking to upgrade to high definition. Designed to record to tapeless media formats such as optical disc and solid state, AVCHD (Advanced Video Codec High Definition) delivers a high-definition picture at consumer prices. And being a tapeless format, editing with today's ubiquitous non-linear editing systems would be a logical fit, right? Not exactly. The primary concept is to fit as much data into the smaller storage media as is available. In its infancy, AVCHD has some drawbacks compared to HDV when it comes to editing, but that has been changing as the format has been getting popular for its convenience factor.

AVCHD's maximum bit rate is 18Mbits/s (2.25MB/s) when recorded to solid state using MPEG-4, Part-10, also know as H.264. As a tapeless format, AVCHD is a true non-linear application, meaning that footage can be accessed instantly on the drive without fast-forwarding or rewinding, and scenes can be deleted in-camera. This is great for users looking to get to a specific place on the recorded media instantly, but not practical when you want to do some serious editing. The other main advantage to having solid state recording media is that files can be transferred to computers at up to 30MB/s, just as though you were moving files from one directory into another in your Windows or Mac OS. This is a much faster rate than the real-time transfer rate of most other current tape transfers. AVCHD can record up to 1080p today, and theoretically, to resolutions as high as 2K. As hard drives and flash memory evolve to larger capacities at lower prices, more data can be stored. It is also easier to take JPEG still photos and store them on the same media as the video, unlike in the past, when a separate flash drive had to be dedicated to still images.

Without getting into an AVCHD vs. HDV war, we have to broach the still controversial subject of which format is "better." Today, HDV renders better picture quality, but that will change as the H.264 encoders in cameras improve with higher bitrates. With AVCHD, you are dependent on the solid state media included, meaning that if the camera breaks down in the field, chances are that the recorded footage will be lost. HDV is a tape format, so it is still using the same "old-school" technology of recording used since the dawn of video. If the AVCHD camera's drive gets full, you need to download it to a computer for backup; with HDV, simply change the tape. Archiving HDV is much more convenient, thanks to the fact that the HDV tape is the archival data. With AVCHD, you need to back the data up on a separate drive, whether it is hard disk or optical media. And of course, there is the editing process.

The main issue with editing AVCHD footage is that it is long-GOP (group of pictures), an inter-frame compression version of MPEG-4 that compacts data for multiple frames together. This makes it difficult to view or edit individual frames because some of the data in "frame #3" may be in "frame #2," expanding the compression over several frames, making editing more difficult, with longer render times. Processor speeds are an important piece of the puzzle, with resources being used up for decoding, editing, and output with effects in real time, slowing down overall system performance.

The audio portion of the codec, however, utilizes either Dolby Digital or Linear PCM, which is not a concern for rendering. It should also be noted that AVCHD/MPEG-4 will not play on standard-definition DVD's, only on the high-definition Blu-ray optical format. If you want to record to standard-def DVD's, footage will need to be encoded to the MPEG-2 codec.

As with any new technologies, third party software vendors need time to develop and beta-test feature sets before releasing them to the general public. This was once the case when it came to AVCHD editing, but that has changed, and here's why.

Final Cut's Log and Capture window is required to ingest AVCHD clips.
Final Cut's Log and Capture window is required to ingest AVCHD clips.

The latest version of Apple Final Cut Pro (ver. 6.0.3) has addressed the AVCHD question, somewhat. Available only on Intel-based Macs via the USB 2.0 port, AVCHD is transcoded via the Log and Transfer window, using the Apple Intermediate codec or ProRes 422. Clips appear as thumbnails, set in and out points, and then queued up while previewing or ingesting more footage. Because it is transcoded, the actual ingest time will increase exponentially, depending on the processor speed. When previewing AVCHD in the Log and Transfer window, no high-speed searching is available. Preview is available only on a Mac Pro workstation. And without sounding like an oxymoron, there is no support for standard-definition AVCHD data. Final Cut Express 4 supports AVCHD in the same way as the Pro version. Although iMovie does support AVCHD, it is limited to 960-by-540 resolution.

On the Windows side, most editing applications support AVCHD. Sony Vegas Pro 8 supports most AVCHD cameras with a streamlined work flow, with output available to Blu-ray disc. The Sony Vegas Movie Studio family of products only supports Sony AVCHD camcorders. Although considered a consumer-level product, Pinnacle Studio v. 11 is probably the most intuitive way to edit AVCHD at a very affordable price. Available in three different bundles, only Studio Plus and Ultimate has AVCHD support. Ultimate offers the advantage to edit with Dolby 5.1 encoding and green-screen functionality.

Adobe Premiere currently does not support AVCHD, but MainConcept's MPEG Pro HD 3 supports the H.264 standard with presets for AVCHD. MainConcept has a 15-day trial period for editors who want to test the waters before jumping in, available directly from the manufacturer's website only. Adobe does have an extensive SDK (Software Development Kit) program that lets third party developers create useful plug-ins that enhance the primary editing application. Adobe does believe that AVCHD will be a mainstay for years to come, so I am sure the next major upgrade to CS4 will see support. But being last in the AVCHD editing market does not necessarily mean the worst. Adobe was last out of the gate for P2 support, but arguably has the best solution, with no rewrapping or transcoding of the files.

AVCHD has been a controversial subject since its introduction. The horsepower needed to edit the format, combined with some mainstream post-production manufacturers' limited support, add to end-users' apprehension in working with the AVCHD. This is not the last word on AVCHD, as most of the editing developers will continue to improve upon this unique work flow. As is always the case in software development, keep a close eye on software patches and upgrades to your editing program's support site for the latest revisions.

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