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Innovations: Tracking Network Developments

JoeCo’s BlackBox BBR64-MADI Recorder and BBR-Dante Recorder

JoeCo’s BlackBox BBR64-MADI Recorder and BBR-Dante Recorder

The customer requirement for the original BlackBox Recorder was evident from years of talking to users across the industry from live recording specialists through TV and film sound designers. These users needed a compact, simple-to-use device for capturing live audio to a universally readable file format that would, among other things, simplify and speed up the ingest of the audio material into workstations for subsequent post production, while simultaneously taking generic, do-everything operating systems out of the recording process.

Soon aft er the Bl ackBox Recorder’s initial release, customers began requesting these benefits on digitally connected systems, most notably for MADI data streams from existing equipment and Dante networking to take advantage of the forthcoming AVB protocols. Initial specifications for both the MADI and Dante versions were based on the same fundamental principles as the original model, with each version offering 24-channel recording like its predecessor.

However, we appreciated that 24 into 64 was an inelegant solution requiring three systems to record the full 64 channels of a MADI stream, so we aimed to increase the channel count to 32 to create a more cost-effective solution. Expanding the channel count of the BlackBox required a major rewrite of our bespoke operating system to accommodate the number of open files that it would have to handle. Conversion of the 32-bit code base to 64-bit was undertaken during early 2011, and the benefits of this change would also improve performance for our existing user base. We had also decided, where possible, to make as much of the hardware interface common between both new products as the task could be conveniently divided up into similar logical blocks.

As the hardware development progressed, we started performing tests of the new operating software on the existing BlackBox platform. These initial tests were encouraging, enabling about 40 channels of recording, which surpassed our initial aims. A more detailed analysis identified the memory subsystem as the chief bottleneck, and we calculated that improvements in this area might gain us an even greater channel count. So, we created a couple of development boards with an improved memory subsystem and then began the painstaking software optimization that saw the channel count slowly creep from 40 up to about 54 over a few weeks. The 54 channels were tantalizingly close to our new goal, but as it didn’t even accommodate legacy MADI (56-channel), it might as well have still been a mile away.

Going back to the drawing board, we analyzed what facilities might still be further optimized in the core software. The software was still capable of creating a full internal headphone mix, but we realized that very few customers would ever want to create a full headphone mix from such a massive track count without a full user interface. Some rapid calls to potential users concluded that a Pre- Fade Listen (PFL) facility, enabling the user to check individual or pairs of channels, would be more than adequate, as levels would have to be set at the mic preamp stage on the console anyway.

Making this change saw the channel count break through the 64-channel barrier, and over the next few weeks, we were able to tidy up the loose ends and ensure that we had a stable and consistent basis for the new product with more than enough headroom. From prior experience with BlackBox, we knew that typical 7,200 rpm drives would have adequate bandwidth for recording 64 channels—the 80 Mbits/sec requirement is comfortably below the 480 Mbits/sec bandwidth on our dedicated USB2 bus.

Now that we knew how many channels we were able to record, it was time to think about how best to communicate the status of the recording to the user. The main screen would obviously be used to show the “normal” information common to all BlackBox Recorders, such as the audio and clock source, recording time and time remaining on the disk, as well as song name and number—but, how best to provide confidence metering?

After further tests, we determined that using a bicolor LED on each channel would, through a variable modulation scheme, give us green through yellow to red with full brightness control. In the final product, the channel LEDs flash dull red when record enabled and glow solidly when in record; as signal is received on a particular channel, the LED shows the level varying from dull green through yellow to red, while a peak signal will turn the LED bright red. Meanwhile the PFL bus places the mono or stereo bus signal onto a pair of 12-segment LED meters as well as the headphone output for any channel requiring further inspections.

This metering scheme works particularly well as the levels have to be set at the console’s mic preamp stage anyway. The general metering therefore acts as an indication that a good signal is being received, while the PFL allows the user to hone in on channels that look like they need attention.

Finally, we needed to check interoperability with other manufacturers’ equipment. A few minor incompatibilities were revealed by the initial tests: Some products had undocumented control commands for stage boxes and remote mic preamps buried within their MADI data stream. These issues were rapidly worked through and further visits to manufacturers were arranged to check that we had resolved all the issues.

The BlackBox MADI and Dante systems were released in August 2011 and are already being used on some major tours. The unique combination of being able to record up to 64 channels to a universal disk and file format in one rack unit (1RU) weighing less than 5 lbs is proving a huge success with touring companies the world over. One system comprising four BBR64-MADI units is currently being used to record 256 channels of audio every night.

Whether used as a backup system to a DAW on a concert tour or the primary recorder for a broadcaster, the BlackBox MADI and Dante systems provide a unique solution to large-scale, live, multitrack recording.

Joe Bull is the managing director of JoeCo.