SipRadius AV1 Live Encoding Uses Intel Arc GPUs
Over the last couple of years, we have written quite regularly on the development of the VVC codec and especially on the progress in implementing real time encoders using that codec. However, we have featured the AV1 codec less often and so we were intrigued to see that at NAB, SipRadius LLC had shown live AV1 encoding, so we followed up to find out more and interviewed Sergio Ammirata PhD, the founder and Chief Scientist at the firm.
Ammirata started by explaining the background to his firm and how it had developed into a significant supplier of technology for the broadcast industry.
The first products developed by the firm in 2006 were Wi-fi access points, used outdoors and with ranges up to a mile. The technology base was the company’s own Linux version and it developed products based on this platform to allow the distribution of video. The company worked closely with DVEO who OEMed the products. There was a wide range of hardware products, all based on the same core platform. However, in 2020, that partnership ended, which was unfortunate timing given the impact of Covid on the broadcast business.
A Covid-induced Pivot
In classic business school case study style, the challenge of Covid became an opportunity for the company. Broadcasters were struggling to create professional content when staff and presenters were stuck at home. SipRadius realized that its technology could provide professional level video distribution to those presenters over the internet. One of the first presenters to use it was Jimmy Fallon in the US for his home broadcasts. The firm started working closely with NBC which was keen to adopt the low latency high quality distribution that the technology enabled. The technology allowed a team of just two technicians and a presenter to create high quality live content away from the studio – a critical point during the epidemic.
The companies realized that the technology enabled even more functions when the pandemic was over and NBC started to replace earlier ip-based video distribution that it had used. It found that the SipRadius technology could provide access to any of its video streams to anybody in the organization without needing to be in a studio facility. That was a powerful motivator for wider roll-out. SipRadius had a further advantage, Ammirata explained, that because all of its code and technology was developed in house, it was able to pass multiple stringent security audits.
Security Is Essential
The security system also allows central control of access to the streams, so the hardware has the capability of ‘everything, everywhere’ with low latency (0.5s ‘glass to glass’, Ammirata told us) and high quality, but the access can be controlled according to policy. The software can be aligned with corporate ‘Single Sign On’ processes and the stream chain is authenticated and encrypted to the final user. Individual channels can be assigned in a controlled way to users.
Initially, the playback was via browsers on computing systems, but one particular user insisted that he just wanted a box to connect to a TV for access to all the video, so the firm developed one. Now, that product has been widely rolled out with NBC and Universal Studios as well as broadcasters outside the US such as the BBC, and with rumors that some movie studios are using it, Ammirata revealed. NBC’s local partners in the US are also using the system and 100 per week are still being installed.
Limited Bandwidth a Challenge
Unfortunately, bandwidth on the NBC system was limited by the VPN used by the firm, to 4 Mbps, so streams have to be relatively low in bitrate. Ammirata told us that in this respect, the use of AV1 is a real advantage as, in his experience, the color performance of 4:2:0 video in AV1 is very close to the quality of 4:2:2 in H.264 AVC, allowing lower bitrate streams to be used.
SipRadius, as can be seen, tends to like the open source software and Ammirata said that it uses the Opus audio codec alongside AV1 for the video.
A particular advantage of the Opus codec is that if there is an interruption to the stream, noise is generated and this helps with other features to make the codec resilient to packet loss. He claims the same advantage for AV1 over H.264 and said that his side by side tests show fewer visible artifacts when packets are dropped, compared to the MPEG codecs.
A Test of AV1 v H.264
One project that confirmed this was a test of FullHD and 4K 60P transmission from 16 cameras in Australia to Spain during a sports event. Half the streams were sent using AV1 and the other half with H.264. He told us that the AV1 streams showed much less visible degradation when packets were lost. The color quality was also similar in AV1 4:2:0 to the MPEG streams in 4:2:2.
Turning to the live encoding shown at NAB, Ammirata told us that the encoding was done using Intel Arc GPU AIBs. One reason for that choice of platform is that these cards were not having supply chain challenges and are very reasonably priced. CPU-based solutions could not encode live, he said. Part of the reason for this, he clarified, is that AV1 is extremely asymmetric – with very complex encoding but reduced decoding requirements compared to some other codecs.
The SipRadius GPU-based encoding is performed with just two to three frames of latency, with full system latency (from SDI in to SDI out) in 10-20 frames. At NAB, the video data was delivered in an MPEG-TS stream (which the firm can also support with the JPEG-XS codec).
Decoding of AV1 is supported in software using the DAV1D code, but Ammirata believes that 18% of devices these days have hardware support for AV1 decoding.
Of course, we had to ask about the formats supported and FullHD is the critical requirement at the moment for its clients, with 4K support being developed. At the moment, 8K has not yet been supported in real time, so VVC stays in the lead in this regard.
