Video: RIST Unfiltered – Q&A Session

RIST is a protocol which allows for reliable streaming over lossy networks like the internet. Whilst many people know that much, they may not know more and may have questions. Today’s video aims to answer the most common questions. For a technical presentation of RIST, look no further than this talk and this article

Kieran Kunhya deals out the questions to the panel from the RIST Forum, RIST members and AWS. Asking:
Does RIST need 3rd party equipment?
Is there an open-source implementation of RIST?
Whether there are any RIST learning courses?
as well as why companies should use RIST over SRT.
RIST, we hear is based on RTP which is a very widely deployed technology for real-time media transport and is widely used for SMPTE 2022-2 and 6 streams, SMPTE 2110, AES67 and other audio protocols. So not only is it proven, but it’s also based on RFCs along with much of RIST. SRT, the panel says, is based on the UDT file transfer protocol which is not an RFC and wasn’t designed for live media transport although SRT does perform very well for live media.

“Why are there so many competitors in RIST?” is another common question which is answered by talking about the need for interoperability. Fostering widespread interoperability will grow the market for these products much more than it would with many smaller protocols. “What new traction is RIST getting?” is answered by David Griggs from AWS who says they are committed to the protocol and find that customers like the openness of the protocol and are thus willing to invest their time in creating workflows based on it. Adi Rozenberg lists many examples of customers who are using the technology today. You can hear David Griggs explain RIST from his perspective in this talk.

Other questions handled are the licence that RIST is available under and the open-source implementations, the latency involved in using RIST and whether it can carry NDI. Sergio explains that NDI is a TCP-based protocol so you can transmit it by extracting UDP out of it, using multicast or using a VizRT-tool for extracting the media without recompressing. Finally, the panel looks at how to join the RIST Activity Group in the VSF and the RIST Forum. They talk about the origin of RIST being in an open request to the industry from ESPN and what is coming in the upcoming Advanced Profile.

Watch now!

Rick Ackermans Rick Ackermans
RIST AG Chair,
Director of RF & Transmission Engineering, CBS Television
David Griggs David Griggs
Senior Product Manager, Media Services,
AWS Elemental
Sergio Ammirata Sergio Ammirata
RIST AG Member,
Chief Science Officer, SipRadius
Adi Rozenberg Adi Rozenberg
RIST Forum Director
AG Member, Co-Founder & CTO, VideoFlow
Ciro Noronha Ciro Noronha
RIST Forum President and AG Member
EVP of Engineering, Cobalt Digital
Paul Atwell Paul Atwell
RIST Forum Director,
President, Media Transport Solutions
Wes Simpson Wes Simpson
RIST AG Co-Chair,
President & Founder,
Kieran Kunhya Kieran Kunhya
RIST Forum Director
Founder & CEO, Open Broadcast Systems

Video: The next enhancement for RIST

Continuing the look at RIST, the developing protocol which allows for reliable streaming over the internet – even in the event of packet loss, we have a look at a key feature on the roadmap.

The core proposition of RIST is to produce an interoperable protocol which brings the internet into the list of ways to contribute and distribute low-latency video. It’s resilient to packet loss due to it’s ability to re-request packets which have been lost yet is light enough for video streaming. In another talk at IBC, we learn about the latest developments which have added security and many other features to the list of capabilities.

Here, Adi Rozenberg from VideoFlow explains how this will further be extended by upcoming work to allow the source stream to reduce in bitrate in response to reduced capacity in the network. With RIST’s ARQ – the technology which requests missing packets – we find that the retransmissions can actually aggravate bitrate constrictions particularly when they are permanent. Adi proposes the only real way to solve lack of bandwidth issues is to reduce the bitrate of the source.

RIST already includes NULL packet removal so that NULL packets aren’t transmitted and are re-inserted at the remote end. This is usually a great start in reducing the bitrate of the stream. However more is needed, we need a way to tell the encoder to reduce the bandwidth of the video stream itself. This can be accomplished by RTCP.

Adi identifies the problem of identifying when extra bandwidth has returned as a reduction of bandwidth is quickly and easily signalled with retransmissions, but excess bandwidth silently returns. The system gradually increases the encoder bandwidth to always be probing the current balance of bandwidth and bitrate.

This works well when there is a single encoder and a single decoder. When there are multiple decoders, life is more difficult. The solution offered to this is to create a ladder of bitrates all of which are adaptable. Now the destination can switch between profiles. This can be extended to MPTS (Multi-Program Transport Streams) whereby, depending on the destination, services in the MPTS are dropped in order to recover bandwidth. A mechanism is used which prioritises services depending on the destination (i.e. German channels are de-prioritised on delivery to France).

The session ends with a Q&A on stream switching details and use in stat mixing.

Watch now!

Adi Rozenberg Adi Rozenberg