HD camcorders take one step forward, two steps back

HD camcorders take one step forward, two steps back

Panasonic and Sony announced today that they're working on technology to record HD video on Secure Digital (SD) cards. That makes sense, given that Panasonic has a huge investment in SD manufacturing, but thankfully, it also makes sense from a technological standpoint for camcorders. The write speed for HD-DVD (PDF) and Blu-ray, mini versions of which are the current contenders for HD camcorders, are currently limited to about 4.5MB per second; even the theoretical maximum transfer rate for Blu-ray is only about 55MB per second. That's fine for playback, but real-time DVCPro HD-quality recording requires 12.5MB per second, and uncompressed 720p or 1080i takes 45MB per second or more. They could probably handle HDV, but IMHO, that's a stopgap format to allow everyone to continue using MiniDV tapes.

In contrast, SD cards today can handle 22MB per second, and the current controller interface can handle 66MB per second. And manufacturers can ramp up capacities far faster than with optical formats. In addition, obtaining the higher transfer rate with an optical drive requires spinning the disc faster, which results in a noisier mechanism. I bet a camcorder microphone is bound to pick that up. Plus, SD is more durable and easier to work with, especially in the field, and I believe it's cheaper to implement an SD solution than an optical-based one.

But...alas, there's always a but. In conjunction with the SD work, the two companies are also plowing ahead with promoting a recording format that can fit HD on mini DVD discs. AVCHD, which stands for the marriage of the MPEG-4 Advanced Video Coding (a.k.a. H.264) and HD, has a maximum transfer rate of 2.3MB per second. That's not bad. But even though AVC is a high-quality MPEG-4 codec, it's designed to produce a high-quality playback stream from high-quality source material that's passed through complex, iterated, variable-bit-rate compression--not real-time compression from iffy source video.

Furthermore, they're imposing this suboptimal encoding solution on SD-based recording, rather than aiming higher and taking advantage of the format's available bandwidth.

I dunno. Maybe they have some magic algorithms up their sleeves that can produce silk playback out of a sow's video. Or maybe I'm just seen too much bad MPEG-4 and MPEG-2 video come out of camcorders, despite the occasional exception in a higher-end model.

Guess I'll just have to wait and see.

 

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