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The Amen Corner: Preserving Native HDV
Posted Mar 7, 2008 Print Version     Page 1of 1

In last month's Amen Corner we talked about three high-definition acquisition formats: HDV, AVCHD, and H.264. This month we’re going to talk about the quest for native HDV editing. This topic comes out of an experience I had at the end of 2007. I was writing a white paper on high-definition Flash streaming, and I was trying to find ways to capture raw native HDV files that could be used crossplatform with no modification. This column will focus on getting footage in and out of the editing system while maintaining HDV’s original quality.

The quest started when I was doing a review of Adobe’s CS3 Production Premium software for Streaming Media magazine. In that review, Paul Schumtzler of Braintrust Digital helped me do comparative tests of editing workflows for HDV and DV. We found the process under Premiere Pro CS3 to be quite similar, although output to streaming formats took quite a bit longer for HDV than DV; no surprise, given the higher resolution of HDV.

The next step was to do tests where native HDV files were captured and then immediately transcoded to a streaming format, such as Flash. Having done work in Premiere in native HDV, I assumed I would be able to grab any of the HDV editing tools, capture the footage, and transcode the files on any platform. I was wrong.

Unlike DV, which can be moved from machine to machine with no changes, native HDV editing isn’t quite so mainstream. HDV uses an MPEG-2 transport stream, meaning the audio and video files are interweaved or multiplexed together (muxed, as most compressionists would say). The native file extension is either .m2t or .mpg, for MPEG-2 Transport Stream or MPEG, respectively.

The first tool I used to capture HDV was iMovie ’08, since I really like the way it handles automatic logging and it is good at ignoring other formats on a tape (such as DV) during capture. Unfortunately, iMovie ’08 and Final Cut Express are crippled by the use of Apple Intermediate Codec (AIC), which throws away some image information and is not supported by Apple’s QuickTime. This means that content captured in AIC cannot be played on Windows machines or even on Macs that don’t have iMovie ’08 or Final Cut loaded. The original reason for the creation of AIC was to allow lower-powered machines to work with HDV, but given the fact that all machines with iMovie ’08 are Intel and at least dual-core, Apple’s decision to stick with AIC is based on antiquated logic.

Undeterred, I moved up a notch to Final Cut Pro 6. FCP does capture HDV but not with the standard .m2t (or even .mpg) extension. Final Cut’s scratch captures are listed as .mov files, and the Movie Inspector feature in QuickTime shows the footage as HDV1080i60, with the HDV resolution as the correct 1440x1080 and the frame size as 1920x1080, meaning that it is correctly extrapolating the additional lines. But converting Final Cut’s HDV footage (even the scratch footage) into an .m2t extension isn’t so easy. Apple apparently is doing something with its HDV files that adds a proprietary twist. Changing the extension to .m2t or .mpg did absolutely nothing. In fact, any extension confused some native MPEG tools, such as Handbrake; the spinning-death "beach ball" kicked in and never stopped.

Another confirmation that the Apple HDV files don’t conform to the HDV MPEG-2 LongGOP spec was the fact that MPEG Streamclip (an MPEG tool used to change names and trim .mpg or .m2t clips without converting the files) could open it on the machine on which it was captured (i.e., a Mac that had Final Cut Pro 6 installed). Opening it on any other Mac with the MPEG-2 Playback Component, however, yielded a white screen in the MPEG Streamclip window with an audio bar directly across the middle. This means the codec only works with Final Cut and not with QuickTime, rendering the files unusable for machine-to-machine and platform-to-platform transfer. A bit of research revealed that Apple splits the audio and video files upon capture, which means that they aren’t really native HDV to begin with.

So I switched to Premiere Pro CS3. It worked like a charm, capturing a lovely .mpg file. I was able to open the file on Mac and Windows machines, even if Premiere wasn’t loaded on that particular machine. I was also able to rename the file with the .m2t extension and to proceed with any other MPEG tool. Premiere Pro lacks the grace of intelligent logging in to iMovie ’08, but as a Mac program capturing raw HDV transport streams, Premiere trounces iMovie, Final Cut Express, and Final Cut Pro.

I could have used Premiere Pro CS3 on the Windows platform as well, but I had success with one other Windows capture tool: Canopus EDIUS Neo. I set Neo to capture only HDV footage, which it then broke down into clips based on each time the record button was hit to start or stop the recording (Canopus calls this "clip divisions"). In the bin and on the editing timeline, Neo presents timecode start/stop times, but clips themselves, as shown in Windows Explorer, are only numbered sequentially as Cap000(001).m2t, Cap000(002).m2t, etc. EDIUS compensates by being the only capture tool I used that could output an .m2t file that worked crossplatform and natively in transcoding programs such as Sorenson Squeeze with a name change to an .mpg extension.

Tim Siglin (writer at braintrustdigital.com) writes and consults on digital media business models and "go to market" strategies. He is chairman of Braintrust Digital, a digital media production company, and co-founder of consulting firm Transitions, Inc.

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