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Sony & Panasonic intro HD camcorder format - AVCHD - using 8cm DVDs

by Bob Crabtree on 15 May 2006, 14:07

Tags: Panasonic (TYO:6752)

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AVCHD logo

Sony and Panasonic have announced the specs for a new high-def consumer camcorder standard using mini (8cm) DVDs, rather than the Mini-DV tape used by the HDV camcorder standard launched in late 1994. The new standard, AVCHD, encompasses hi-def recording in six different formats, plus standard-resolution PAL and NTSC. The companies say that they're getting ready to license AVCHD to other makers but don't give any indication when the first products are likely to arrive in store. For reasons that will be clear below, though, the launch could take place very soon.

In Europe, AVCHD camcorders are expected to offer two main hi-def recording options. One has 1080 horizontal lines, with images refreshed as 50 interlaced half-screens (or fields) per second, a format abbreviated to 1080/50i. The other is of a lower-resolution - 720-line - but with 50 full screens refreshes progressively per second (720/50p). The same two resolutions will be used in the USA but running at 60 interlaced half-screens and 60 full screens per second (1080/60i and 720/60p). See the section below - Interlaced and progressive explained - to better understand the significance of these two variants.

There are two further hi-def options within the standard, both progressive and recording at the frame rate used for commercial movies - 24 frames per second - the idea being to produce a look that is more like film and less obviously a video recording. One uses 1080 lines (1080/24p), the other 720 (720/24p). What neither company has said, though, is whether these will be offered as standard or, as we suspect, only built in to more upmarket models aimed at commercial movie makers (or film students) on very low budgets that don't allow for the use of film cameras.

Both companies have also been quite coy about the type of discs that will be supported but it's our expectation that these will be DVD-R (which existing standard-def disc camcorders from Sony and Panasonic can use), plus DVD-RW (which Sony's SD models can also use) and DVD-RAM (a technology invented by Panasonic and also supported on its SD disc camcorders).

What may be the case, though, is that camcorders will be built to support only two of the three formats - DVD-R and one other - but we hope not, for the sake of simplicity and maximum compatiblity.

The capacity of 8cm discs is 1.46GB per side (1.36GB formatted) and is set to stay that way until the arrival of Dual Layer DVD-R discs in an 8cm size, whenever that might be. Verbatim announced at the beginning of the year that it would introducing 8cm Double Layer discs in the competing write-once format, DVD+R, but nothing seems to have come of that because no camcorder yet supports those discs (perhaps we now know why!). And we've heard nothing from Verbatim or any other media maker about the possible arrival of 8cm Dual Layer DVD-Rs.

So, at the outset, it looks like the formatted capacity will be limited to 1.36GB. This, rather amazingly, is reckoned to give 20 mins of high-def, though at 720p, we'd assume. Not bad considering that 720/50p has over four times the resolution of SD PAL and a standard-definition camcorder can only record 10 minutes more.

But, it may turn out to be the case that the 20 mins figure also applies to 1080i recordings - the video Codec might add some padding to 720p recordings so that the on-disc data stream of both resolutions is the same.

That's quite possible because AVCHD uses a very clever and very space-efficient video Codec. This - Lord help us - is known by three names - MPEG-4 Part 10, H.264 and AVC (Advanced Video Coding), the latter being from where the new camcorder standard derives part of its name.

To save confusion (or perhaps more likely, so as not to cause offence), the standard rolls them all into one and calls the Codec MPEG-4 AVC/H.264. On the audio side, AVCHD uses either the Dolby Digital (AC-3) Codec or a lossless Linear PCM Codec. These, far from co-incidentally, are also mandatory parts of the forthcoming Blu-ray Disc standard that Sony and Panasonic are both supporting in its battle against the rival high-def DVD standard HD DVD (see this HEXUS.HD article explaining the different audio standards on Blu-ray and HD DVD).

Know, too that Blu-ray Disc uses quite an old and inefficient video Codec, MPEG-2, and therefore needs very high-capacity discs to record hi-def - the smallest capacity 12cm single-layer disc will be 23GB unformatted and the capacity of an equivalent 8cm disc will be 7.8GB.

We've prepared an at-a-glance overview of the tech specs provided in the original, rather lightweight, AVCHD press release - click on the image below to see a bigger version. But as you can see, some details aren't fully elaborated, such as the type of disc. What's also not clear is whether the MPEG-4 AVC/H.264 Codec is used for Standard Definition recordings, rather than the less-efficient MPEG-2 that's also used on SD disc camcorders, as well as for Blu-ray.

You might assume from the chart that it's MPEG-4 AVC/H.264 but had that been so, we'd have expected Panasonic and Sony to make it quite clear because, we presume, it would allow more than 30mins of SD footage to be recorded to disc - something worth boasting about (unless that is, they don't want the disparity to seem so large!).

AVCHD specsAVCHD initial specs (click for larger image)

You might also be wondering why Panasonic and Sony have bothered introducing another HD disc format when their baby, Blu-ray, is just around the corner.

Yoshikazu Ochiai, a spokesman for Sony, has been widely quoted on the net as saying that, initially, Blu-ray Disc drives will be just too expensive, too big and too power-hungry to be used in camcorders but our view is that there's a bit more to it than that.

It is true that Blu-ray Disc is still in its infancy (well, actually, it's not been born yet) and so enjoys no economies of scale. And it's also probably true that it runs hot and uses a lot of power. However, there are some particular reasons for opting for a system based on standard 8cm DVD media. Doing so means that AVCHD is able to use the same drive/burner mecha-deck as the SD optical disc camcorders that are already in mass-production - and so can be implemented not just cheaply but also very quickly (a similar trick that HDV was able to play by using the mechadecks from MiniDV standard-def camcorders). So there's every possibility of seeing AVCHD camcorder models announced by Sony and Pansonic for sale this Christmas.

In addition, of course, there is no requirement in a consumer camcorder for elaborate copy-protection systems of the sort that Blu-ray Disc hardware uses to prevent the copying of hi-def movies, so it makes little sense to use Blu-ray.

Perhaps more significant of all, neither Sony nor Panasonic wants to create a camcorder format that genuinely rivals the quality of the current formats they sell to broadcasters and production facilities for very big bucks - for fear of loosing lucrative business.

And it's worth noting that AVCHD itself is partly crippled to stop this from happening - and not just by having HD recordings limited to 20 minutes or less. More significant is the fact that AVCHD uses relatively crude colour (chroma) sampling - 4:2:0 - to prevent colour being of sufficiently high fidelity to be acceptable to broadcasters. Sony and Panasonic may turn round and say that the reason for doing this is to help reduce the data rate but although that is a by-product, it's not, we believe, the main reason.

Interlaced and progressive explained

Interlaced - as used with 1080/60i and 1080/50i (that's what the 'i' stands for) - refreshes the screen in two goes. It changes what's seen on every other picture line in one pass and the remaining lines in the next. The refresh rate will vary from country to country. In the UK it's 25 frames per second and involves, in effect, 50 half-screens per second. The way in which an interlaced signal is handled means that, potentially, there can be problems with rolling lines but usually only in larger displays and even then, that shouldn't be noticeable if the set is working properly. In theory, 1080i may also show artefacts caused by fast-moving objects but until we'd had a lot more time in front of different types of HD footage, we're unwilling to be drawn into the progressive vs interlaced debate.

Progressive - as used with 720/60p, 720/50p, 720/24p and 1080/24p - changes the complete image you see on screen in one go, so each new screenful is, in effect, like a single frame on a roll of movie film. Progressive, theoretically, guarantees smooth-looking pictures because it won't show any rolling lines, nor artefacts caused by fast-moving objects. The refresh rate can vary from country to country and from application to application. AVCHD is able to record progressive at 50 or 60 full frames per second - and we'd expect that to produce very sharp, clear pictures - and also at 24-frames-per-second for a cod film-look mode.

Combining 1080 and progressive promises the
best of both worlds - the highest resolution paired with the smoothest picture, so the fact that AVCHD supports 1080 progressive could be seen as something of a coup. Until its announcement, there was little obvious prospect of 1080 progressive being used in the foreseeable future - not for HDTV transmission nor for HD discs. Sony and Panasonic, though, both make HD sets capable of showing 1080 progressive and we see that as another reason why the two companies are introducing AVCHD - to grow sales of these very upmarket HDTV sets.

Update - May 15, 18:50 - Panasonic says it's going to be using the AVCHD standard for recording video to SD memory cards!

This is what the company's release says:

Panasonic Begins Development of Technology for Recording HD Images onto SD Memory Cards Based on the AVCHD Standard for Digital Video Cameras

Osaka, Japan – Panasonic, the brand for which Matsushita Electric Industrial Co., Ltd. is known, today announced that it has begun developing technology to record digital HD (high-definition) images onto SD Memory Cards, following the AVCHD standard for HD digital video cameras. The company is also constructing a new environment for editing and playing back the images.

With the expected adoption of HD broadcasting in many countries and the widespread sales of HD TVs, people will be able to view HD images at home with increasingly enhanced viewing environments. The development of new device technology for the home video market is prompting a major switch in recording media to discs and SD Memory Cards (solid-state memory), which are easier to use and more convenient than tape media.

This new HD video recording technology for SD Memory Cards will conform to the AVCHD standard, which uses a highly efficient compression encoding technology to record 1080i*1 or 720p*2 HD images onto 8-cm DVD discs. It will use MPEG-4 AVC/H.264 to compress video files, and Dolby Digital (AC-3) or Linear PCM for audio files. This combination makes it possible to develop HD video cameras that are compact yet deliver high-quality images and sounds.
*1:1080i -- An HD standard based on interlaced scanning using 1080 effective scanning lines
*2:720p -- An HD standard based on progressive scanning using 720 effective scanning lines

“Believing that the SD Memory Card is the recording media best suited for video cameras, Panasonic has already released a professional-use HD video camera that uses SD Memory Card technology”, said Mr. Akihiro Nakatani, Director of Video Camera Business Unit, Panasonic AVC Networks Company. “Panasonic's efforts to develop the technology to record HD images onto SD Memory Cards and construct a new playback and editing environment, in addition to its establishing the AVCHD standard for 8-cm DVDs, will serve to further stimulate development of products that take advantage of the characteristics of both media.”

Lots to think about, then, so we'd be keen to hear your thoughts on this new HD camcorder standard over in the


Wikipedia - MPEG-4 Part 10, H.264 and AVC
Wikipedia - Chroma sampling
Adam Wilt - Picture sampling (with some useful images)
Blu-ray and HD DVD audio standards - HEXUS.HD
Sony Europe - AVCHD press release
DVdoctor - Forum thread about AVCHD
Panasonic - Press release about AVCHD and SD memory cards