When choosing a product for live stream processing, half the battle is knowing what to search for. Do you want a live transcoder, a video processing unit (VPU), a video coding unit (VCU), Scalable Video Processor (SVP) or something else? If you’re not quite sure what these terms mean and how they relate, this short article will educate you in four minutes or less.
In the Beginning, There Were Transcoders
Simply stated, a transcoder is any technology, software or hardware, that can input a compressed stream (decode) and output a compressed stream (encode). FFmpeg is a transcoder, and for video-on-demand applications, it works fine in most low-volume applications.
For live applications, particularly high-volume live interactive applications (think Twitch), you’ll probably need a hardware transcoder to achieve the necessary cost per stream (CAPEX), operating cost per stream, and density.
For example, the NETINT Video Transcoding Server, a single 1RU server with ten NETINT T408 Video Transcoders, can deliver up to 80 H.264/HEVC 1080p30 streams while drawing under 250 watts. Performed in software using only the CPU, this same output could take up to ten separate 1RU servers, each drawing well over 250 watts.
The NETINT T408 Video Transcoder.
Speaking of the T408, if Websters defined a transcoder (it doesn’t), it might have a picture of the T408 as the perfect example of a transcoder. Based on custom transcoding ASICs, the T408 is inexpensive ($400), capable (4K @ 60 FPS or 4x 1080p60 streams), flexible (H.264 and HEVC), and exceptionally efficient (only 7 watts).
What doesn’t the T408 do? Well, that leads us to the difference between a transcoder and a VPU.
The difference between a transcoder and a Video Processing Unit (VPU)
First, the T408 doesn’t scale video. If you’re building a full encoding ladder from a high-resolution source, all the scaling for the lower rungs is performed by the host CPU. In addition, the T408 doesn’t perform overlay in hardware. So, if you insert a logo or other bug over your videos, again, the CPU does the heavy lifting.
Finally, the T408 was launched in 2019, the first ASIC-based transcoder to ship in quite a long time. So, it’s not surprising that it doesn’t incorporate any artificial intelligence processing capabilities.
What is a Video Processing Unit (VPU)?
What’s a Video Processing Unit? A hardware device that does all that extra stuff, scaling, overlay, and AI. You see this in the transcoding pipeline shown below, which is for the NETINT Quadra.
When it came to labeling the Quadra, you see the problem; It does much more than a video transcoder. Not only does it outperform the T408 by a factor of four, it adds AV1 output and all the additional hardware functionality. It’s much more than a simple video transcoder, it’s a video processing unit (VPU).
As much as we’d like to lay claim to the acronym, it actually existed before we applied it to the Quadra. It’s not surprising. It follows the terminology for CPU (central processing unit) and GPU (graphical processing unit). And, if Websters defined VPU (it doesn’t). Oh, you get the point. Here’s the required Quadra glamour shot.
The NETINT Quadra Video Processing Unit.
VCUs and M(SVP)
While NETINT was busy developing ASIC-based transcoders and VPUs for the mass market, large video publishers like YouTube and Meta produced their own ASICs to achieve similar benefits (and produce more acronyms). In 2021, when Google shipped their own ASIC-based transcoder called Argos, they labeled it a Video Coding Unit, or VCU.
Like the T408 and Quadra, the benefits of this ASIC-based technology are profound; as reported by CNET, “Argos handles video 20 to 33 times more efficiently than conventional servers when you factor in the cost to design and build the chip, employ it in Google’s data centers, and pay YouTube’s colossal electricity and network usage bills.” Interestingly, despite YouTube’s heavy usage of the AV1 codec, Argos encodes only H.264 and VP9, not AV1.
In May 2023, Meta released their own ASIC, which, like Argos, outputs H.264 and VP9, but not AV1. Called the Meta Scalable Video Processor (MSVP), the unit delivered impressive results, including “a throughput gain of ~9x for H.264 when compared against libx264 SW encoding…[and] a throughput gain of ~50x when compared with libVPX speed 2 preset.” Meta also noted that the unit drew only 10 watts of power, which is skimpy but also about 43% higher than the T408.
Of course, neither Google or Meta sells their ASIC to third parties, so if want the CAPEX and OPEX efficiencies that ASIC-based VPUs deliver, you’ll have to buy from NETINT.
Of course, neither Google or Meta sells their ASIC to third parties, so if want the CAPEX and OPEX efficiencies that ASIC-based VPUs deliver, you’ll have to buy from NETINT. The bottom line is that whether you call it a transcoder, VPU, VCU, or MSVP, you’ll get the highest throughput and lowest power consumption if it’s powered by an ASIC.
