HD editing on the go

Today, DV and DVCPRO (25Mb/s, 50Mb/s and 100Mb/s) are routinely edited on laptops. Depending on your perspective, this either increases the pressure to edit 24/7 or affords you the luxury of working at a location of your choosing. With the dramatic increase in the use of MPEG-2-based HD, many editors are now looking for laptops that provide the performance necessary for portable nonlinear editing.

HD challenges

There two types of MPEG-2 HD: HDV (either 720p or 1080i) and XDCAM HD. HDV is available in a range of frame rates and is relatively simple to support. The 1080i version (HD2) literally has the same data rate as DV. Therefore, storage requirements and disk bandwidth are identical to DV, DVCAM and DVCPRO. However, because of the nature of long-GOP MPEG-2 media, the requirement for processing power is significantly greater than that required by intraframe codecs — no matter their bit rate.

The increased computational load is required at two points in the editing process. Whenever native HDV is viewed or processed by special effects, the MPEG-2 data stream must be decoded. In the case of multistream effects, all streams must be decoded. With the current generation of computers, multistream long-GOP editing has been computation bound so there has not been a concern about laptop disk performance.

When, however, intermediate codecs are used, because HDV is recompressed to a far less efficient codec, the requirement for RAID 0 has ruled out the use of most laptops. As we will learn later, new laptops that incorporate powerful processors will enable a greater number of HDV streams to be handled. This, in turn, will increase the requirement for higher bandwidth hard disks, including RAID 0.

The more significant issue is the processing load required whenever the HD signal must be encoded using an interframe codec. Obviously, one such codec is HDV (or XDCAM HD), but there are others. In my experience, Microsoft's VC-1 codec delivers the highest quality at the lowest bit rate. Although strongly supported by Apple, AVC has not yet been used for commercial HD DVD or Blu-ray discs. But like VC-1, AVC requires enormous number crunching capability during the encoding process.

As many of us know, exporting a timeline to HDV can require a painfully long encode time. With Blu-ray burners already on the market, the current near-real-time process of creating an NTSC DVD will soon be replaced by an overnight encode job.

HD hardware solutions

Moving the entire HD production process to a laptop will require significantly more powerful laptops. Almost a year ago, Intel introduced a powerful chip called Core Duo, which features 151 million transistors, a 2MB L2 cache and two CPUs on one chip (dual cores). All Core Duos are 32-bit processors.

Apple recently moved to Intel-based processing using Duo chips. The 65nm chip offers optimized performance per clock cycle, while drawing no more power than a Pentium M. There are multiple versions of the Core Duo: T2300 (1.66GHz), T2400 (1.83GHz), T2500 (2.0GHz) and T2600 (2.16GHz).

The chip's front side bus (FSB) clock speed is 533MHz or 667MHz. Maximum FSB bandwidth is 5.3GB/s, which means DDR2-533 RAM (PC2-4200/4300) will be fast enough, unless the laptop has an Intel GMA950 graphics performance accelerator (GPA). If it has one, DDR2-667 RAM (PC2-5300/5400) should be installed.

Manufacturers are already upgrading laptops to include the second generation of the chip, called Core 2 Duo. It has 291 million transistors and is also built using a 65nm process. It features an FSB bandwidth of 8.5GB/s. Although DDR2-533 RAM has a bandwidth of 8.5GB/s, it may introduce “wait” states, so DDR2-667 RAM (PC2-5300/5400) should ideally be installed when using this processor.

Except for the entry-level versions, which you should avoid, all models have a 4MB L2 cache and support Intel's 64-bit instruction set (EM64T) plus SSE3. EM64 support enables Apple's OS X to return to 64-bit operation.

You may wonder why Intel released two seemingly identical processors in a little over six months. The answer lies in Intel's goal to design processors that can manage the maximum possible number of instructions per clock cycle while using the minimum energy consumed per instruction. This required five architectural advances to the way a processor handles instructions and data:

  • Wide Dynamic ExecutionThis enables a processor to perform four parallel processes simultaneously.
  • Advanced Smart Cache.This means that both cores can access the huge 4MB L2 cache where data in use is stored. Each core can obtain, or exchange, data without having to access the FSB or RAM.
  • Smart Memory AccessThis allows each core to obtain or exchange data without having to access FSB or RAM. A core processor has eight “prefetcher” units: two data and one instruction prefetcher per core plus two prefetchers as part of the shared L2 cache. A prefetcher obtains data that might be needed using speculative algorithms.
  • Intelligent Power CapabilityThis turns off unused processing units and even single transistors. Another key to reducing consumption power is Intel's Enhanced SpeedStep, which reduces the clock speed when the system is idle or under a low load.
  • Advanced Digital Media BoostThe most important to video production, this supports encoding, transcoding and compression. These functions all use vectors — a series of values that are modified by the same streaming SIMD extensions (SSE) operation. Intel has extended the SSE instruction data width to 128-bits.

There are three high-power versions: T7200 (2GHz), T7400 (2.16GHz) and T7600 (2.33GHz). The Core 2 Duo's FSB clock speed is 533MHz or 667MHz. Core 2 processors can shut down unnecessary parts of a processor. According to Intel, Core 2 Duo offers more than a 20 percent performance increase for processor-intensive tasks as compared to previous-generation laptops with Core Duo processors.

Of course, CPUs alone do not make a computer. Every laptop is built around a chipset that glues the processor components together. Intel now offers the 945GM and 945PM (part of the current Napa platform) and will soon offer the 965GM and 965PM Northbridge chip. (The 945GM and 965GM include the Intel GPA.)

The newer 965 (part of the Santa Rosa platform coming out early next year) offers the ability to run DDR2 RAM at 800MHz (for the coming 2.4GHz T7700 Core 2 Duo that will have an 800MHz FSB), support for 2GB memory chips (allowing 4GB using two SO-DIMMs), DirectX 10 compatible graphics, and up to a 50 percent increase in video performance over the 945.

Support for 4GB of RAM in a laptop is going to remove one of the last obstacles to moving compositing applications from a desktop to a laptop. The Santa Rosa platform's Southbridge (ICH8M chip) will support three Serial ATA II (3Gb/s data rate) ports and 10 USB 2.0 ports.

It's more than the CPU

In the next nine months, laptop computers will undergo RAID technology advances that will further improve their performance, allowing them to support not only MPEG-2, but also AVCHD and AVC-I. In addition, both Blu-ray and HD DVD burners will become a critical component of laptops.

Sony is now shipping its second-generation Blu-ray equipped laptop — the 8.4lb, 2GHz T7200-based, $3550 VAIO VGN-AR270 CTO. It features 2GB of 533MHz (PC2-4200) RAM, 17in WUXGA (1920 × 1200), GeForce Go 7600GT with 256MB VRAM, and a PCMCIA slot that will accept P2 cards. The AR270 has a pair of 120GB 5400rpm SATA drives in a RAID 0 configuration. (Those with extreme power lust can purchase a 2.33GHz T7600 equipped AR270 for $4100. RAID 0 storage options go up to 400GB.)

Blu-ray drives support blue-laser (BD-ROM, BD-R and BD-RE) and red-laser (DVD-R, DVD+R, DVD±RW, DVD-RAM write, CD-R and CD-RW) operation. The ability to burn red-laser DVDs with AVC and VC-1 encoded content should enable one to create high-definition SL/DL DVDs that can be played on an HD DVD player. Likewise, the AR270 should be able to play these discs. However, Sony does note that high bit-rate AVC and VC-1 encoded DVDs cannot be played on the machines.

The Sony laptop can be ordered with Windows XP Professional and supports Blu-ray using InterVideo's WinDVD BD and Ulead's BD Disc Recorder. It can drive HDTVs and 5.1 audio systems using its HDMI and SP/DIF ports.

Our future

Intel has already announced a Core 2 Quadro that packs two 2.66GHz Core 2 Duo chips with 8MB L2 cache. The four cores are packed inside a single package. Reports claim H.264 and WMV-HD encoding performance increased up to 80 percent when compared to the 2.66GHz Core 2 Duo.

When 45nm and 32nm technology is implemented, the four (or more) cores can be placed on a single die. It should then be possible to manufacture a “mobile” version.

Where is Intel going? Work is already being done on an 80-core design. Its projected performance is expected to hit one teraFLOP. It seems inevitable that someday, one of these chips will find its way into a laptop. I can't wait.

Steve Mullen is owner of Digital Video Consulting, which provides consulting and conducts seminars on digital video technology.