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DeckLink Deconstructed

Feb 1, 2005 12:00 PM, By Steve Mullen

Blackmagic’s line of HD I/O and acceleration cards facilitates several levels of HD editing.

Charts
Decklink Differences
Capture Data Rates

Australia's Blackmagic Design has been leading the way to all-digital video production by delivering low-cost SDI and HD-SDI input/output boards for PCs and Macs. The company creates both the hardware and software for its wide selection of products, a wealth of options that can lead to confusion.

Recently I've been exploring various high-end HD editing solutions — visiting websites maintained by Blackmagic Design, AJA Video Systems, Canopus, and Pinnacle Systems — and I'm now convinced that the more engineering-oriented the company, the more confusing its site.

It's as though the company's engineers were so worried you might overlook a product feature that every possible function is thrown onto the site in no particular order. Often complicating this “1,001 features” approach is that many versions of the same basic product are available — each with some specific feature added. One yearns for a simple “Y offers all the features of X with the addition of A and B” statement. (See Table 1 for such a breakdown of Blackmagic's DeckLink line.)

Before I get into a practical tutorial on editing HDV with Blackmagic's powerful, cost-effective line of video I/O cards, it's helpful to begin my discussion of these editing solutions by laying out the functions provided by the four versions: DeckLink HD, DeckLink HD Plus, DeckLink HD Pro 4:2:2, and DeckLink HD Pro Dual Link 4:4:4. Let's start with the base model, which has an incredibly low MSRP of only $595.

DeckLink HD

DeckLink HD is the baseline DeckLink solution. Every higher-end unit has the features of the DeckLink HD plus certain additional capabilities.

Blackmagic claims DeckLink HD is the first video capture card to use 133MHz PCI-X technology. For HD work on Macintosh systems, it should be plugged into a PCI-X slot. (More about this later.) Any dual-processor G5 system with OS X 10.3 can be used to support HD production. For SD work, however, it can be plugged into a 66MHz or 33MHz G5 PCI slot. DeckLink HD is also compatible with the standard 33MHz PCI slots in the older Apple G4 systems for standard-definition work.

Any DeckLink board can also be installed in a PC. Drivers for both OS X and Microsoft Windows are supplied. Moreover, media files are compatible between platforms.

Every DeckLink board has a 10-bit SDI input, supported by a BNC connector. This input is switchable between SMPTE-259M (SDI) and SMPTE-292M HD (HD-SDI). Up to eight 48KHz (16-bit) embedded audio channels can be carried within either an SDI or HD-SDI connection. You connect your deck to this port. No sync generator required, as DeckLink generates sync.

Two BNC connectors output 10-bit SDI or HD-SDI signals. One connector provides a signal to your monitor while the other provides a feed to your deck. Both ports carry up to eight 48KHz (16-bit) embedded audio channels. When you play a timeline, uncompressed HD video can be downconverted in realtime to standard definition. The 16:9 video is output as anamorphic video.

An RCA jack provides an SPDIF/AES digital audio monitoring output. The RCA jack outputs two channels of 48KHz (16-bit) digital audio.

A 15-pin DIN connector provides a Sony-compatible RS-422 serial control signal. By providing deck control, DeckLink eliminates the need to purchase a USB-to-RS-422 adapter. All DeckLinks include a Blackmagic Deck Control utility that provides a complete solution for automated capture as well as playback of media to deck using RS-422 serial control.

Timecode information obtained via VITC through the RS-422 port enables 3:2 pulldown removal from NTSC video. This enables capture to 23.98fps progressive video.

All DeckLink boards can input NTSC and PAL via SDI. The DeckLink HD boards input — via HD-SDI — these 1080i signal formats: 23.98fps, 24fps, 25fps, and 29.97fps. Both 59.94fps and 60fps 720p signal formats are accepted.

Upon SD input, the uncompressed digital video can be stored to disk using SD codecs. Upon HD input, the uncompressed digital video can be stored to disk using the following Blackmagic codecs: Online JPEG (not available with 720p signals and not the same as Apple's RT Extreme Photo-JPEG), uncompressed 8-bit, uncompressed 10-bit, and 10-bit RGB 4:4:4. Additionally, the incoming video can be stored to disk using the Blackmagic DVCPRO HD codec at 720p59.94, 720p60, 1080i23.98, 1080i24, 1080i25, and 1080i29.97.

According to the Blackmagic website, DVCPRO HD is “accelerated” by the DeckLink boards. The site neglects to say how or when acceleration is provided. (The company confirms that it's really QuickTime and RT Extreme that perform the acceleration.)

The DeckLink boards can output these digital formats: NTSC and PAL via SDI, plus 720p and 1080i via HD-SDI. When playing NTSC or PAL DV timelines you can, without rendering, output via SDI to an NTSC or PAL VTR. DeckLink automatically handles image-resolution differences (480 vs. 486 lines) and field order differences (odd vs. even) between DV and other formats.

The Blackmagic boards have several other capabilities. You can output video from non-QuickTime applications such as Adobe Photoshop. Realtime RAM preview is supported in Adobe After Effects, Apple Shake, and Discreet Combustion. You can also render from Adobe After Effects and Final Cut Pro using the Blackmagic 64-bit (10 bits per channel) RGB codec. Therefore you can bring uncompressed 10-bit video from Digital Betacam and D5 into After Effects and then render out very high-quality images.

Blackmagic Design’s suggested system configuration for DeckLink HD boards (Click image for larger view).

DeckLink HD Plus

The DeckLink HD Plus replaces the connector that supports RS-422 with a breakout cable that provides both RS-422 connector and an RCA jack for an SPDIF/AES audio input. The RCA jack inputs two channels of 48KHz (16-bit) digital audio. A second RCA jack on the breakout cable outputs an audio word-clock signal. A TriSync/genlock input (BNC) jack is also available on the breakout cable. The DeckLink HD Plus has an MSRP of $995.

DeckLink HD Pro

The top-of-the-line DeckLink HD Pro adds two capabilities that the DeckLink HD Plus does not have. The breakout cable has three BNC connectors that supply RGB or YUV 14-bit SD/HD analog component output. You'll use these connections to feed an SD or HD monitor, projector, or flat-screen display. The DeckLink HD Pro 4:2:2 (single-link) model has an MSRP of $1,495.

Installation and Setup

The DeckLink HD Pro Dual Link 4:4:4 model (MSRP of $1,995) is the same as the 4:2:2 HD Pro model, but has an additional BNC connector that accepts a second channel of HD-SDI. (When playing 4:4:4 1080 tapes, two HD-SDI channels are required.) You'll use this connector if you connect a Sony HDCAM SR deck.

The DeckLink HD Pro ships with not a single sheet of paper. Thankfully, the installation procedure was well documented by a PDF file. This documentation came in handy when I tried, and tried, to insert the DeckLink into the upper (PCI-X) slot in a dual 2GHz G5 PowerMac. Reading the instructions, I learned I had to — very carefully — apply pressure in such a way to cause a BNC assembly to push aside a plug located on the Mac's motherboard. Blackmagic suggests if you lack courage to apply the pressure, you can use another slot. (This, of course, begs the question of why a PCI-X board was designed that doesn't fit.)

Once the hardware was installed, I downloaded the OS X version 4.6 software from the Blackmagic site. After rebooting, the first sign the DeckLink was installed was that the OS X Dock, which I keep on the left side of my monitor, had gone missing. Checking the Displays Panel showed the DeckLink display to the left of the Apple Desktop. I moved the DeckLink display to the bottom of the Desktop and the Dock came back.

I connected the DeckLink to an HD LCD projector. My projector accepts 720p59.94, 720p60, 1080i59.94, and 1080i60, so I set the display to 1920x1080 at 30Hz. To view your timeline, you must use View > Video Playback within FCP HD to select the signal format of the timeline's video. To view either DVCPRO HD or Online JPEG, use an 8-bit setting with an appropriate frame rate. When not displaying video input or output from a DeckLink, the extended OS X Desktop is displayed. (Image quality naturally depends on the native resolution of your monitor.)

Using the OS X Sound Panel, I set audio input to the PowerMac's analog input and so did not use the DeckLink's SDI/HD-SDI embedded audio or SPDIF input. However, I could have used an analog-to-SPDIF converter to obtain an SPDIF signal. DeckLink audio input options — embedded (channels 1-2 or channels 3-4) and SPDIF — were available on the OS X Sound Panel. Likewise, DeckLink digital audio output was available on the Sound Panel.

Working Blackmagic

I've given up expecting that if I spend $1,500 I will get a printed manual. But to ship an expensive product with a PDF file containing a long list of random “comments” by engineers is simply unacceptable. In fact, as I discovered when I printed the DeckLink “manual,” many pages were lacking a page number. My guess is that Blackmagic assumes one will simply choose the appropriate Final Cut Pro Capture and Sequence Preset without worrying about the details.

This guess seemed to prove correct. Upon launching FCP HD I could choose from a list of several dozen Blackmagic options. Each option defined a signal format and a codec. My plan was to source three types of HD: 720p60 plus 720p59.94 and 1080i59.94. When one outputs analog component video from a JVC HD1, HD10, or CU-VH1US mini-deck, the 720p29.97 HDV is decoded to and output from the camcorder. I set the output option to No Convert, in which every frame is sent twice (1/60 second apart) to yield 720p60 video.

To obtain HD video at 720p59.94 and 1080i59.94, I sent the camcorder's 720p29.97 MPEG-2 via an IEEE 1394 cable to a JVC HM-DH30000U D-VHS deck. This deck was then set to output analog component at either 720p59.94 (No Convert) or 1080i59.94 (720p To 1080i). The reason I wanted to obtain 720p59.94 is that it is the most popular DVCPRO HD 720p format. Meanwhile, the 1080i59.94 signal served as a surrogate for the HD analog component video sourced by a Sony HDR-FX1 HDV camcorder.

In my tests I connected the analog component output from my HDV camcorder or D-VHS deck to an AJA HD10A. The converter accepts YPbPr analog via three BNC jacks. (A DIP switch on the HD10A allows you select either 59.94Hz or 60Hz video input.) The HD10A digitizes the analog input to an HD-SDI bit stream. I used a 75-ohm coax cable to connect the converter to the Blackmagic input BNC.

I used the Audio/Video Settings option to make duplicates of the settings I planned to use. For the 720p60 preset I changed the audio input to Internal Analog Input. For the 720p59.94 and 1080i59.94 presets I changed the audio input to Internal Optical Input. Additionally, for 720p59.94 I set the Digitizer Input to “Blackmagic HDTV 720 59.94” and frame rate to 59.94. Note that when using either the Online JPEG or the DVCPRO HD codecs, the Digitizer Input should be set to 8 bits. (Once when creating custom presets, FCP locked up, requiring a power-off to restart OS X.) In all cases I set Deck Control to Non-controllable Device.

I captured to both Blackmagic 8-bit and 10-bit codecs to an Apple Xserve RAID. I also captured to Blackmagic's Online JPEG codec and to DVCPRO HD. Table 2 displays the data rates associated with these signal formats and codecs.

When stepping through a 720p59.94 timeline I noticed that four steps were required for each source frame, so when editing I used only 720p60 and 1080i59.94 source material. (Naturally, when stepping through the 720p60 material, two steps were required to advance one source frame.)

When you create Sequences, make sure to select the appropriate Blackmagic presets. Frankly, I find that a major mindset change is necessary in order to work with uncompressed video without the benefit of realtime effects. Naturally, when I switched to DVCPRO HD, using Apple's RT Extreme, I was able to use FCP's realtime effects on multiple streams. Now I could edit HD in realtime. I'll be glad when computers become so fast that one doesn't have to choose between uncompressed quality and realtime productivity.

I reviewed the DeckLink HD Pro, but the DeckLink HD may be of particular interest to those working with either 720p or 1080i HDV. By using an analog-to-HD-SDI converter, you can directly digitize HDV to disk without the long waits for MPEG-2 decoding. And, digitizing to DVCPRO HD, you can work in realtime on almost any PowerMac without needing an expensive RAID. Moreover, if you own an HD monitor with an HD-SDI input, you can view timeline playback in HD. Not bad for under $600.

If you own an HDTV monitor, you'll more likely want a DeckLink HD Pro because the board's built-in converter will let you use your display. I'd be happier if Blackmagic offered a “DeckLink HD” at $1,000 that simply added analog component output. And I'd be ecstatic if Blackmagic had the courage to offer a board with HD analog component input — despite the potential copy-protection issues. It would be wonderful to eliminate the analog-to-SDI converter and its power supply. Such a board would be ideal for working with the newly arriving HDV camcorders.

Once your production is edited, there are many export options. A DVCPRO HD timeline can, of course, be output via FireWire to a Panasonic AJ-HD1200A VTR. A timeline, no matter what HD codec you used, can be output via the HD-SDI port. Alternately, an NTSC or PAL version can be downconverted in realtime and output via SDI from a 1080i59.94 or 1080i50 timeline, respectively. Unlike when using an external downconverter, the digital audio is perfectly synced to video.

While I haven't talked about working with SD, a DeckLink HD is a fantastic investment for an editor working with any format — SD or HD.

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