VITEC和低延迟的艺术

Just prior to the 2014 NAB show, I had a chance to visit the Silicon Valley offices of VITEC, a company with a similar sounding name to Vitec Group, but a totally different strategy.

VITEC is an amalgamation of several legacy streaming and video production companies that our longtime readers will likely be familiar with: VITEC bought Focus Enhancements’ Videonics and Proxsys product lines and as well as technologies from Optibase, the Israeli company that brought the Media Gateway series of low-latency MPEG blade servers to market. 这两种情况, the parent company went off in a different direction—Focus Enhancements to build chipsets and Optibase in to corporate real estate—leaving VITEC CEO and founder Philippe Wetzel with an opportunity to acquire known products to integrate in to his own vision.

在加州森尼维尔举行的会议期间., I had the chance to test an impressive newer version of the Media Gateway (MGW) series of low-latency encoders. Dubbed the Sprint line of encoders and decoders, these units follow the legacy of several MGW units that come in various shapes and sizes: from the MGW Pico, about the size of a cigarette package and with no moving parts—including no fans—to rack-mounted multi-HDMI or SDI-based units.

VITEC claims that Sprint has “the fastest HD H.264 broadcast-quality codec in the industry” in both the 4:2:0 and 4:2:2 color space. 像这样, the company says it’s equally at home in harsh operating environments such as medical devices and military engagements as well as in more staid environments like an IPTV deployment.

最小的单位, 没有风扇，也没有活动部件的那个, actually sells at a premium due to its small size but workhorse reputation. The MGW Pico takes encodes in approximately 65 milliseconds, 或者两帧标准29帧的视频.97帧每秒(fps)的速率.

伊莱加滕, VITEC的产品管理副总裁, told me that military deployments of the Pico are commonplace, as soldiers in combat conditions need something both rugged and small in order to be able to fit in the cramped quarters of a Humvee or other close combat situations. And the combination of rugged housings and low latency communications are not just an added feature but the sole reasons that VITEC products are specified.

Garten walked me through several key demonstrations of the Sprint technology, backing up the claims of sub one-frame video latency that is essentially the same—or slightly faster than—a frame-buffered baseband video transmission.

“MGW Sprint needs 4 milliseconds for encoding and another 4 milliseconds for decoding,加藤说。, noting that a frame of video takes place approximately 30 times per second, 或者每34毫秒.

“MGW Sprint units can stream full HD 1080p video and audio, 点对点或点对多点, 以少于一个视频帧的延迟,加藤说。, “practically matching the latency of hard-wired, 未压缩的基带视频系统.”

来测试这些单元, Garten set up a demonstration of side-by-side monitors, with one displaying a direct loop-through signal from the encoder (a pre-encoded signal) and the other displaying the decoded content, so that I could see just how close the IP delivery tracked with the original content.

This is the type of test that only a company confident in its technology would demonstrate, 但就像所有好的怀疑论者一样, I asked to be able to pull the Ethernet cable from the switch and plug it back in again. 在一次演示中, 解码器未能返回, but it turned out that was due to an optional setting, in which the encoder’s signal loss is set to trigger the decoder to wait. 一旦这个设置改变了, all subsequent testing of unplugging and plugging back in the Ethernet cable worked just like a hard-wired video signal transmission.

Oh, and did I mention that there was zero perceptible lag in the video signal between the pre-encoded loop-through signal and the final decoded signal? 令人印象深刻, 退一步说, having seen way to many “low latency” demonstrations with perceptible delay of a frame or three.

“The unrivaled latency helps customers take advantage of multicast and unicast streaming video in demanding applications,加藤说。, “such as those requiring real-time experience and instantaneous response.”

The company will showcase these and other low-latency products at the upcoming International Broadcasting Convention (IBC) held next week in Amsterdam’s RAI Conference Centre. Closer to home, in mid-November, the company will also display at CCW SatCon at the Javits Center.