The problems of editing high-definition video

The Performance mailbox has been full of messages concerning recent columns which didn’t quite fit into our normal Q & A section, so we’ll fire through a few of them here.

Howard Smith recently wrote in on the problems of editing high-definition (HD) video.

Like many owners of HD camcorders, Howard found his system just wasn’t up to the task of smoothly editing footage, so built a new one with this in mind.

Sadly, despite employing an AMD Athlon 64 X2 6000, Nvidia Geforce 9800GTX and 2GB RAM the stuttering while editing remained, although the final renders were much quicker.

This appears to be par for the course. The AVCHD format employed by the majority of HD camcorders is complex and designed for efficient acquisition and storage as opposed to ease of editing.

During the editing process the software needs to access individual frames both for preview and navigation purposes, along with the final render.

This is easily done with formats like MiniDV and Motion JPEG because they compress each frame separately.

But formats like MPEG2 and AVCHD encode multiple frames at once and it’s not as easy to dip-in and grab a desired frame. Instead it must be generated on-the-fly using data across a sequence of frames.

AVCHD makes this even more difficult by employing particularly complex compression. So the delay in generating these frames is what’s responsible for choppy performance while editing.
In the long term, hardware will become sufficiently quick to resolve the problem we’re a while away from that yet.

In the meantime, clever editing software can ease the pain by either working on lower resolution ‘proxy’ files before switching them for the originals on the final render, or more simply, converting the tough formats into something that’s more editing friendly – like a variant of Motion JPEG.

High-end audio on a PC
We continue to receive a number of messages about high-end hifi audio on a PC, in particular the Benchmark DAC1 PRE which can act as a superb external USB sound card in addition to being a top-notch digital-to-analogue converter, pre-amplifier and headphone amplifier.

Visit the Benchmark Media website and look out for the latest DAC1 HDR version, which adds a remote control.