Testing the Vitec MGW Ace and MGW D265 for HEVC Encode/Decode
When I first saw the prototype for the Vitec Media Gateway (MGW) Ace in February 2015, I was struck by two facts: The HEVC-based unit wasn’t much bigger than the H.264-based real-time encoders that Vitec had shown me before—making it ideal for field use—and the Ace had all the markings of a product that could be useful in the burgeoning 4K video market.
I was only half right. The MGW Ace is indeed ideal for field use, but its primary focus is in the sub-4K mid- and low-bitrate range in which its primary target customers—military, security, and surveillance users—typically operate.
Now that the MGW Ace has been on the market for almost 6 months, after launching at the National Association of Broadcasters (NAB) show in early April 2015, Streaming Media agreed to do a review of the shipping unit. It was in the running for several awards at the IBC show in Amsterdam at time of our review, which was done at Vitec’s booth. Along with the encoder, we also took a look at a newer, complementary product: the hardware-based MGW D265 decoder. As its naming convention implies, it is a hardware-based H.265 decoder, which allows content acquired in HEVC to be played back without requiring a robust computer to decode the H.265 content.
This review, for those of you following the licensing issues surrounding H.265/HEVC, is set against a backdrop of uncertainty for widespread HEVC adoption. Having said that, the MGW Ace and D265 form an end-to-end HEVC hardware encode/decode solution, which means that users of this closed system can choose to bypass both the licensing and higher computational requirements of a software-based H.265 decode.
In addition, the Ace-D265 combination offers some unique features, such as Zixi integration in the D265, that help address network intermittency issues. Our review will briefly cover those end-to-end features.
The MGW Ace, though, is not limited to delivering only to the D265, a key factor for those considering using the Ace with a traditional media server. So we will also touch on interoperability of the Ace with software-based decoders.
Under the Hood
MGW Ace is all about real-time delivery. As such, this FPGA-based encoding solution delivers H.265 in either 4:2:0 or 4:2:2 at resolutions up to 1080p.
Eli Garten, Vitec’s VP of product management, answered a few of the questions we had about the exclusion of 4K resolutions, as well as the option of 4:2:0 versus 4:2:2 compression,.
“We developed one codec with two modes,” Garten says. “Each is optimized to a different use case group: one for high-rate broadcast content and another for ISR-specific imagery with very low rates.”
Garten noted that the intelligence, surveillance, and reconnaissance (ISR) communities don’t really have a way to consume 4K content in the field, especially since many of the real-time streams generated need to go to field operatives watching content on mobile phones or other small form-factor devices.
Garten added that the ISR community often has to deal with low-bandwidth requirements that aren’t necessarily an issue for broadcast content acquisition. The result was a single HEVC codec inside the Ace that branches to two modes, depending on the use case, “each of which behaves differently and uses different HEVC tools to offer the best processing approach for each vertical.
“We only have one set of parameters, a very broad one,” Garten says, noting that the parameters are based on how the user configures the output settings (bitrate, frame rate, resolution, metadata etc.).
“Also, based on what content we detect using our algorithm,” he says, “we calibrate many other codec settings internally to produce the best compresses video. The main point is that we decided that encoding military footage requires a different approach than encoding general content and broadcast footage, and have developed specific handling for each use case so that the visual experience in each vertical will be perfect.”
One Input, Dual Outputs
Input interfaces on the MGW Ace range from composite to SDI, including the singleBNC connector 3G, HD/SD-SDI input. In addition, the Ace includes HDMI v1.3 and DVI-I inputs, with the former capable of carrying at least two channels of embedded audio.
In terms of video signals, the Ace goes beyond 1080p60 to offer up to 1080p @85Hz, meaning that high-motion acquisition is possible. It also supports a gamut of raster sizes below 1920x1080, bottoming out at 720x480.
Audio inputs include embedded audio on both the HDMI and SDI connectors, as well as a multipin connector that allows balanced and unbalanced analog audio.
In addition, given its use in ISR and military settings, the Ace offers metadata processing, conforming to NATO requirements for KLV and STANAG metadata.
Besides the single-input option—and accompanying metadata—the Ace has the proverbial ace up its sleeve when it comes to handling legacy H.264 devices. In a nod to the need to offer H.264 encoding, the Ace has a secondary H.264 encoding chip. This means the Ace can stream to both H.264 software decoders as well as hardware-based H.264 decoders that might be used for proxy streaming.
The Ace contains several additional ports, some of which are not yet active as of this writing. The company says they will be activated via firmware updates at a later date.
These ports include the second Gigabit Ethernet port. While we don’t have any solid detail, since the port is not yet active, it would seem logical the second Gigabit Ethernet port would allow H.265 and H.264 to be streamed on two discrete IP addresses or to replicate a single H.264 or HEVC stream to dual networks for additional redundancy.
“We support both transport streams and elementary streams,” says Garten. “But we currently offer only one stream at a time, so no support for two concurrent input streams.”
In addition, two BNC connectors used for output—SDI out and DVB/ASI out—are dormant until the firmware update. Our opinion is that Vitec should cover these ports until such a time as they are active, as potential buyers may design a system using these Ethernet and BNC ports, only to find out the ports are currently inactive.
The Ace has two front-panel slots for recording content locally. The first is a standard USB 2.0 connector, to which a USB flash drive or external hard drive can be attached. The second is a protected SD card slot. Once the two screws and small faceplate are removed, the SD card can be inserted and the faceplate reattached. By using a removable faceplate, the Ace protects the SD card from exterior elements,
Receiving the Stream
When it comes to hardware decoding, the MGW D265 is more than just an H.265/HEVC decoder. The D265 has hardware decoding for both MPEG-2 Transport Streams (M2TS) as well as H.264 IP streams.
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