Portability-HD Acquisition

While it is clearly possible to achieve high levels of processing performance in a portable laptop solution, the major limitation will be professional level I/O.  There are few simple solutions, but a fair number of possible work-arounds.

The simplest solution that provides HD-SDI input to a laptop is the Motu V3HD.  Connected via Firewire, it allows capture of digital and analog High-Definition video signals at DVCPro-HD quality.  Limited to 1280 pixels in width, and 100Mb/s, this is a lower end HD solution, but bears mention none the less.  I have not personally used one, but it is supposed to be compatible with Premiere Pro CS3, as well as Final Cut Pro.  The data rate and processing requirements allow this format to be used on most high end consumer laptops, but those looking for full resolution 1920×1080 solutions must look farther.

The next solution is currently only available to Mac users in Final Cut Pro, but is a significant  technological development.  AJA’s “I/O HD” is a Firewire800 based solution that can capture and playback full resolution material, with 10bit color, in Apple’s new ProRES codec.  Although not a PC based solution, it does enable mobile users to capture high quality, full resolution footage.

Anything beyond that will involve a bit of creativity, and what follows is highly speculative.  Newer laptops have replaced PCMCIA card slots with ExpressCard slots.  The new formfactor is much simpler, and has two basic internal variations.  The slot has pins available to interface directly into the USB subsystem (480Mb/s) or directly into the Southbridge via the PCIe x1 interface (2000Mb/s).  The PCIe interface provides an ExpressCard slot with enough bandwidth to support uncompressed HD video, at least 10bit 422 at 1080i/p.  RGB 444 might even be possible at 24fps, but that would depend on how much overhead was imposed by the interface itself, among other things.  This bandwidth has been utilized in the design of the ExpressCard option for the CalDigit HDPro, but having a single slot with the capability of transfering video at uncompressed data rates leaves us with a problem.  If the ExpressCard slot is being used to connect some form of video I/O interface, how do I connect my storage at uncompressed speeds.  Unless you find a laptop with two ExpressCard slots, you will not be able to use both at once.  I guarantee that the capture card is necessary for realtime full resolution HD acquisition, so how can we do it without using the high speed storage?  Compressing the video becomes the obvious solution.  So a capture solutionis needed that allows realtime compression, and can be jury-rigged to connect to an ExpressCard slot at PCIe x1 bandwidth.

A company named Magma has developed a solution that really opens up the available options.  Their ExpressBox Pro product allows a PCIe card to be inserted and connected to a laptop via an ExpressCard slot.  At the very least, PCIe x1 cards can be expected to work, and ideally higher end PCIe x4 based capture cards may function properly as well.  After all, the HD video data itself is usually well under 200MB/s, depending on the specific settings and format.

The first option that comes to mind are the Intensity cards from BlackMagic Design.  They allows full resolution capture of 1080i/p at up to 10bit color in the 422 YUV colorspace, over HDMI or analog on the Intensity Pro.  Convienently, Blackmagic also makes an HD-SDI to HDMI converter, the HDLink, so we can use this to pump HD-SDI into the Intensity card.  Blackmagic also has a MotionJPEG codec that we can capture directly into, so it would seem that they offer a fairly complete solution to our problem.

Another option using the same hardware is to use Cineform compression, as detailed here.  In my experience Cineform’s compression results in a higher quality final picture than Blackmagic’s current implementation of MotionJPEG codec.  The downside of using Cineform is that they don’t support live playback, out of the Intensity card the way Blackmagic’s codecs do. If you have an external monitoring device available, this can be a very helpful option when trying to edit on a small laptop screen.  To Cineform’s credit, they allow you to use the secondary display output from your laptop as a full screen video output if your graphics card supports it.

Our next PCIe x1 based solution is the RT.X2 from Matrox.  Although I have not been able to confirm that this has ever been successfully used in this capacity, it remains a theoretical possibility.  The RT.X2 would be advantagous in that it would offload much of the compression processing from the laptop CPU to the PCIe card.  It would allow analog HD capture, but would be limited to 1440 horizontal resolution, and would allow preview via DVI or analog HD.  On the positive side, with hardware acceleration, Matrox’s MPEG I-Frame codec would probably give the best creative editing performance of any of the solutions we are examining here.  Realtime effects and exporting would be advantagous for the editing process, but the original footage acquired would not be as high quality to begin with.

In theory, the Magma ExpressBox could support other cards.  While the bandwidth is limited to the 2000Mb/s (200-250MB/s) of the ExpressCard’s PCIe x1 bandwidth, the phyical connector in the box is a PCIe x16 slot.  It would be interesting to know if it would support an AJA LHe or a Decklink HDPro.  The AJA card would allow 10bit capture into the Cineform ProspectHD codec at full resolution, and Decklink might allow RGB 444 capture at 24fps.

There is one more Blackmagic based option that I know isn’t fully developed yet, but seems very close.  The Blackmagic Multibridge is based on the same technology that allows the Magma ExpressBox to work, external PCIe.  If an ExpressCard could be fabricated that interfaced the ExpressCard PCIe x1 bus to the DVI shaped cable that the Multibridge uses, that would be a great solution.  When the first Multibridge Extreme was released, it was listed to be compatible with PCIe x1 slots, at least at SD resolutions.  PCIe x1 has the bandwidth for HD if used efficiently, and the Multibridge has many I/O options, so I think it would be the ideal portable solution.  I know it can capture to MotionJPEG, and I believe Cineform includes capabilities to capture from it into their codec as well.  I have not been able to confirm that, but it is implied on their website.

The last option I will mention has been discussed and rumored about for years, but I have yet to see a product hit the market.  Why not have an ExpressCard with HD-SDI I/O directly on it?  Heat will be an issue that needs to be overcome, and mini-BNC connector could be used to improve the form factor of the physical connections.  Ideally if it was a Blackmagic product, it would support live capture into MotionJPEG, Cineform, and ProRES on a Mac, for maximum possible market.  If/When it gets developed, I know it will sell well, assuming it functions correctly in an established normal workflow.  Realtime compression will be required for any laptop solution, but this doesn’t have to be accomplised in the card itself, it just has to be compatible with it being done by the CPU.  I look forward to seeing a product like this released, as it would greatly enhance the workflow for portable post-production solutions.

Tags: AJA, Blackmagic, Cineform, Compression, Matrox, Multibridge, PCIe