The HD Codec Revolution - TvTechnology

The HD Codec Revolution

At NAB2004, a lot of the excitement was generated by companies who have come up with very clever ways of wrangling that high bandwidth HD signal into an NLE's software.
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Not so long ago, just the ability to get HD into an edit system was considered headline news. But at NAB2004, a lot of the excitement was generated by companies who have come up with very clever ways of wrangling that high bandwidth HD signal into an NLE's software - sometimes with hardware assistance and sometimes without - bringing HD post production capabilities within reach of an ever increasing community of editors.

AVID

Just a year after unleashing its DNA hardware/software "Digital Nonlinear Accelerator" combination, Avid Technology reached into its alphabet soup once again and presented us with DNxHD technology which, as Avid says, delivers "mastering quality" HD media with storage bandwidth and capacity requirements rivaling those of uncompressed standard definition files.

"Avid has come up with some very powerful encoding and compression technology over the years," begins Charlie Russell, Senior Product Marketing Manager for the Post Solutions Group at Avid, "so we gave our development team the challenge of letting editors access high definition files with the quality and ease they have grown to expect from standard definition Avid editing."

The first NLE to ship with Avid DNxHD will be Avid DS Nitris this summer followed by Avid's Media Composer Adrenaline in the fall. Avid Xpress Pro will be able to handle DNxHD internally but won't be capable of capturing it. Before the end of the year, however, Avid Xpress Pro will be ready and raring to capture the HDV format that is being supported by a growing consortium of developers. "We are big believers of HDV in Xpress Pro land," Russell tells us, "so we are building a long GOP editor that will let Xpress Pro handle HDV in its native format. The system will utilize DNxHD for titles and effects and mix them with HDV files on the same timeline."

DNxHD captures high definition material through a standard HD-SDI connection as a SMPTE 292M bitstream into the Nitris or Adrenaline hardware. Whatever the HD format or frame rate, Avid's DNxHD keeps it in the original resolution while retaining the full raster of the active video. Avid President and CEO David A. Krall likes to call his team "rasterfarians" because of their determination not to discard parts of the video image. "We don't want to throw pixels on the floor," Russell smiles. "If you are not at full resolution, things get muddy during post production."

In addition, DNxHD can capture Panasonic's native 100 Mbps DVCPRO HD over FireWire from Panasonic's new AJ-HD1200A deck, the first HD production VTR to offer a FireWire (IEEE 1394) interface.

Once on disk, DNxHD lets you edit, composite and color correct with 10-bit color depth even if you captured at 8-bit. The trade-off is that 10-bit video requires slightly more compression. Avid DNxHD also uses the recently standardized MXF wrapper so media can be exchanged with any other MXF-compliant system. In a decision welcomed by third party software developers, Avid is actually licensing its DNxHD source code at no charge right off its Web site, www.avid.com

APPLE

Apple's software-only Final Cut Pro has been elevated to Final Cut Pro HD with the upgrade from last year's Final Cut Pro 4 being provided at no cost to existing users. In fact, Mac users who had Software Update activated in their G4 and G5's running OS X were automatically informed of its availability.

"The significance of the release of Final Cut Pro HD is that editors will be able to work with multiple streams of DVCPRO HD video without changing the way they work," says Richard Kerris, Apple's senior director of Professional Applications. "Our surveys tell us that within 18 months, 40 percent of Final Cut Pro editors will need to deal with HD material."

Final Cut Pro HD can input DVCPRO HD via FireWire directly from Panasonic's AJ-HD1200A deck. If the DVCPRO HD production was shot in 720p at 24 frames per second, Final Cut Pro HD only needs to import a data rate of around 40 Mbps so editors will be able to cut multiple streams of HD material even on a PowerBook.

Final Cut Pro software has always been resolution-independent, so if an editor wants to invest in an SDI-HD board such as Pinnacle's CinéWave Version 4.6, they can load in even uncompressed video in any of the popular formats to be stored onto the system's hard drive through the DVCPRO HD codec. Upon completion, the outboard card can reconvert the edited high definition material into any desired flavor of HD.

Editing in Final Cut Pro HD proceeds in real time with up to four streams of 720p/24 HD material. More data rich 1080i/30 footage will necessarily be limited to a single stream, and many of its effects will require rendering. But that's still some impressive performance from a $999 package of editing software for people already using Apple's Panther level of OSX.

CANOPUS

As a key component in its new EDIUS HD NLE that ships this month, Canopus Media Technologies has developed a new compression/decompression technology called Canopus HQ codec as an alternative to its own proprietary Canopus HD codec designed to handle DVCPRO HD.

Canopus president/CEO Hiro Yamada says this was the result of increasing CPU processing power. "When we started work on EDIUS HD about two years ago," Yamada says, "we designed our Canopus HD codec to down sample 1080i HD luminance to 1280 samples per line and made the chroma sub-sampling follow the 4:2:2 structure, resulting in 640 chroma samples per line. As the processing power increased we wanted to enhance the compression to be able to handle Sony's HDCAM 1440 horizontal pixel resolution and boost HDCAM's 3:1:1 chroma/luma sampling ratio to 4:2:2 to provide more color information. That was the beginning of our quest to produce the Canopus HQ codec."

Another important feature of the Canopus HQ Codec is variable bitrate support which adjusts designated bitrates to allocate the maximum amount of data to complex images that require it, and a minimum amount of data to simpler pictures. Most importantly, the Canopus HQ codec can scale the chrominance sub-sampling based on the image content. Canopus claims this variable bitrate encoding ensures that each frame gets the appropriate amount of data required to produce the highest quality HD video the NLE system is capable of.

Actually, on EDIUS HD you can start editing in real time using the Canopus HD codec at 1280 resolution. But if you need better quality you can switch to the HQ codec in 1440 mode which re-quires more CPU power. The two can even be mixed on the same timeline.

"Some of our Canopus HQ sub-sampling is performed in software, some in hardware," Yamada explains. "For an HD editing system to be truly efficient, a high-quality HD codec solution with an emphasis on processing speed and image quality is essential, and the scalable Canopus HQ Codec fulfills both of these requirements."