Two of a kind

The latest updates of the DIVX and Quicktime codecs have turned up within a few weeks of each other. Can they really change the way we watch video on our PC's?

You wait all year for a video codec, then two come along at once. Within a few weeks of each other, DivX 6.0 and QuickTime 7.0 have arrived, each offering unique features intended to push computer video formats to a different level.

Although the new version of DivX is a much more fundamental upgrade, both codecs are heavily aimed at a format that has yet to take off in Australia - HD (high-definition) video.

DivX 6.0

The sixth incarnation of DivX heralds a coming of age. Originally a dodgy hack of Microsoft's MPEG-4 implementation with MP3 audio, DivX was rewritten from the base MPEG-4 standard a few years ago. From DivX 4.0 onwards, the codec was entirely legitimate. But version 6.0 goes well beyond DivX's roots, taking it in a more mainstream direction. Up to now, the flavours of MPEG-4 - XviD and 3ivx - have focused on the improved compression available compared with MPEG-2. But MPEG-4 has a lot more to offer than better-quality video at lower data rates.

The original specification borrowed the track-based container system from QuickTime, so MPEG-4 supports lots of other things besides audio and video. Text, sprites, textures, synthesised music and images can all be included, as well as navigation markers. But, besides the odd company logo and some third-party subtitling, little of MPEG-4's potential has been tapped.

With DivX 6.0, however, some of the more advanced features are finally being called upon. The headline news is the DivX Media Format, which adds a host of options to a DivX video file.

Chief among these are menus and chapter points, making the video file fully navigable like a DVD. Viewers will need the DivX 6.0 codec and the Player, although that's a free download. The navigation will also work in other DivX-compatible players such as Windows Media Player, but a navigation tool will be loaded along with the file. DivX, Inc. claims that certified set-top players will support these features in the near future, too.

The DivX Media Format has also added direct support for subtitles and multiple audio tracks. Subtitles were already possible with DivX, but you had to install a number of third-party utilities to get them working.

With the XSUB system, they are included inside the DivX file itself, and different languages can be chosen on the fly, as with a DVD.

Similarly, support for multiple audio tracks allows the selection of alternative language dialogue, but can also include specific mixes for different speaker setups. Finally, the DivX Media Format supports the inclusion of metadata such as author or title using the new XTAG system.

Although the main changes with DivX 6.0 are these navigational features, no new codec would be complete without grand claims about improved compression efficacy. According to the company, DivX 6.0 makes 40 per cent smaller files than 5.0. It also compares well with the competition, squeezing video over 20 per cent more than H.264 standard. Compared to Microsoft's WMV 9.0, DivX, Inc. claims a 17 per cent space saving with HD footage and 21 per cent over DVD-quality encodes.

The download options for DivX have been altered and simplified. There are now only two different ways to get DivX - the free Play Bundle, and the $US19 Create Bundle.

The Play option includes the Player and standard DivX 6.0 codec. For $US19, Create adds the Pro version of the codec and a Converter utility. This simple app lets you choose a DivX profile, then drag and drop your footage to encode to DivX as a batch.

For those who like to try before they buy, Create can be downloaded in trial format, including six months of DivX Pro usage - but there are just 15 days before the Converter times out.

DivX 6.0 Pro adds professional encoding features such as the Feedback Window, which allows frame-by-frame tweaking of settings. Psychovisual enhancements improve video quality by considering human visual processes.

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QuickTime 7.0

MPEG-4 is the most important element of Apple's latest version of QuickTime, too. However, in QuickTime 7.0's case it's the new AVC (advanced video coding) development of MPEG-4, which is also known as H.264. With QuickTime already offering the interactivity DivX has just added to its codec, better compression was the more pressing need.

In particular, Apple has been showcasing QuickTime's HD capabilities, which are complemented nicely by the newly added support for up to 24 channels of surround sound.

The company claims its H.264 implementation offers the same quality as MPEG-2, but with a file of between a half and a third the size.

Most importantly, H.264 comĀ­pression allows HD footage to be squeezed into the same 8Mbps data rate as a normal DVD.However, it's worth noting that the recommended system specifications for QuickTime 7.0 HD footage on a PC are sky high. For 720p HD recorded at 1280x720, you'd need a dual 2.8GHz Xeon!

The Mac requirements, in contrast, are just a single-processor 1.8GHz G5. WMV and DivX also need a pretty fast PC for HD - a 3GHz system is recommended. But at least that is a regular desktop these days. Apple is going to have a hard time convincing Windows users it's the HD format of choice with such stratospheric requirements.

As with DivX, the basic QuickTime 7.0 codecs and Player are available as a free download, but you have to shell out for the Pro version. It's not yet available for Windows, but the Mac OS version is $44.95. QuickTime 7.0 Pro adds the ability to create H.264 video and surround soundtracks, and VB Script automation, plus the usual full-screen playback.

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Although both DivX 6.0 and QuickTime 7.0 bring HD video to the PC, they have their sights set on something even bigger: the next optical media generation, HD-DVD or Blu-ray Disc. The HD-DVD format currently favours WMV 9.0 and H.264 compression for video content, and Apple has joined the consortium behind Blu-ray with QuickTime 7.0's H.264 support. DivX, on the other hand, has announced a host of partners for DivX-certified products, including set-top player manufacturers. So while DivX 6.0 and QuickTime 7.0 are primarily aimed at computers, they're looking to break out of the PC box towards the wider world of consumer electronics, just like Microsoft with its Media Center Edition and Xbox.