Video

Video: Adaptive Bit Rate video delivery (MPEG-DASH)

Posted on by Russell Trafford-Jones

MPEG-DASH has been in increasing use for many years and while the implementations and versions continue to improve and add new features, the core of its function remains the same and is the topic of this talk.

For anyone looking for an introduction to multi-bitrate streaming, this talk from Thomas Kernen is a great start as he charts the way streaming has progressed from the initial ‘HTTP progressive download’ to dynamic streaming which adapts to your bandwidth constraints.

Thomas explains the way that players and servers talk and deliver files and summarises the end-to-end distribution ecosystem. He covers the fact that MPEG DASH standardises the container description information, captioning and other aspects. DRM is available through the common encryption scheme.

MPD files, the manifest text files, which are the core of MPEG-DASH are next under the spotlight. Thomas talks us through the difference between Media Presentations, Periods, Representations and Segment Info. We then look at the ability to use the ISO BMFF format or MPEG-2 TS like HLS.

The DASH Industry Forum, DASH-IF, is an organisation which promotes the use of DASH within businesses which means that not only do they do work in spreading the word of what DASH is and how it can be helpful, but they also support interoperability. DASH264 is also the output from the DASH-IF and Thomas describes how this specification of using DASH helps with interoperability.

Buffer bloat is still an issue today which is a phenomenon where for certain types of traffic, the buffers upstream and locally in someone’s network can become perpetually full resulting in increased latency in a stream and, potentially, instability. Thomas looks briefly at this before moving on to HEVC.

At the time of this talk, HEVC was still new and much has happened to it since. This part of the talk gives a good introduction to the reasons that HEVC was brought into being and serves as an interesting comparison for the reasons that VVC, AV1, EVC and other codecs today are needed.

For the latest on DASH, check out the videos in the list of related posts below.

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Speaker

Thomas Kernen Thomas Kernen
Staff Staff Architect, NVIDIA
Co-Chair SMPTE 32M Technology Committee, SMPTE
Formerly Technical Leader, Cisco,

Video: Panel Discussion on RIST

Posted on by Russell Trafford-Jones

RIST is a streaming protocol which allows unreliable/lossy networks such as the internet to be used for critical streaming applications. Called Reliable Internet Stream Protocol, it uses a light-touch mechanism to request any data that’s lost by the network. As losses are often temporary and sporadic, the chances are that the data will get through the second or, perhaps, third time. For a more in-depth explanation of RIST, check out this talk from Merrick Ackermans

The panel here at the IBC 2019 IP Showcase give an brief definition of RIST and then examine how far they’ve got with the ‘Simple Profile’ of RIST calling out things that are yet to be done. Still on the to-do list are such things as ‘pull’ streams, encryption, simplifying the port structure and embedding control.

Fixed Key encryption comes under the microscope next asking whether there’s a practical threat in terms of finding the key but also in terms of whether there are any side-channel attacks in a ‘non-standard’ encryption. The fixed key encryption has been implemented in line with NIST protocols but, as Kieran highlights, getting enough eyes on the detail is difficult with the specification being created outside of an open forum.

The panels covers the recent interop testing which shows overall positive results and then discusses whether RIST is appropriate for uncompressed video. Already, Kieran points out, Amazon Direct Connect is available in 100s of Gb/s links and so it’s completely possible to do uncompressed to the cloud. RTP is over 20 years old and is being used for much more than ever imagined at the time. As technology develops, use of RIST will also develop.

What are the other uses for RIST? Videoconferencing is one possibility, creating a generally secure link to equipment and ingest into the cloud are the others offered.

The panel fishes by looking to the future. Asking how, for instance, the encoder could react to reduced quality of the link. How much of the all the technology needed should be standardised and what features could be added. Sergio Ammirata suggests opening up the protocol for the bandwidth estimation to be requested by any interested device.

This session, bringing together DVEO, OBS, Zixi and Net Insight finishes with questions from the audience.

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Speakers

Sergio Ammirata Sergio Ammirata
Deployments and Future Development,
DVEO
Kieran Kunhya Kieran Kunhya
Founder,
Open Broadcast Systems
Uri Avni Uri Avni
Founder,
Zixi
Mikael Wånggren Mikael Wånggren
Senior Software Engineer,
Net Insight
Ciro Noronha Ciro Noronha
Executive Vice President of Engineering,
Cobalt Digital

Video: Scaling Live OTT with DASH

Posted on by Russell Trafford-Jones


MPEG DASH is a standard for streaming which provides a stable, open chain for distribution detailing aspects like packaging and DRM as well as being the basis for low-latency CMAF streaming.

DASH Manifest files, text files which list the many small files which make up the stream, can be complicated, long and take a long time to parse, demonstrates Hulu’s Zachary Cava. As the live event continues, the number of chunks to describe increases and so manifest files can easily grow to hundred of KB and eventually to megabytes meaning the standard way of producing these .mpd files will end up slowing the player down to the point it can’t keep up with the stream.

Zachary goes over some initial optimisations which help a lot in reducing the size o the manifests before introducing a method of solving the scalability issue. He explains that patching the mid file is the way to go meaning you can reference just the updated values in the latest .mpd.

With on-secreen examples of manifest files, we clearly see how this works and we see that this method is still compatible with branching of the playback e.g. for regionalisation of advertising or programming.

Zachary finishes by explaining that this technique is arriving in the 4th edition of MPEG-DASH and by answering questions from the audience.

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Speaker

Zachary Cava Zachary Cava
Video Platform Architect.
Hulu

Video: Broadcast 101 – Audio in an IP Infrastructure

Posted on by Russell Trafford-Jones

Uncompressed audio has been in the IP game a lot longer than uncompressed video. Because of its long history, it’s had chance to create a fair number of formats ahead of the current standard AES67. Since many people were trying to achieve the same thing, we find that some formats are compatible with AES67 – in part, whilst we that others are not compatible.

To navigate this difficult world of compatibility, Axon CTO Peter Schut continues the Broadcast 101 webinar series with this video recorded this month.

Peter starts by explaining the different audio formats available today including Dante, RAVENNA and others and outlines the ways in which they do and don’t interoperate. After spending a couple of minutes summarising each format individually, including the two SMPTE audio formats -30 and -31, he shows a helpful table comparing the,

Timing is next on the list discussing PTP and the way that SMPTE ST 2059 is used then packet time is covered explaining how the RTP payload fits into the equation. This payload directly affects the duration of audio you can fit into a packet. The duration is important in terms of keeping a low latency and is restricted to either 1ms or 125 microseconds by SMPTE ST 2110-30.

Peter finishes up this webinar talking about some further details about the interoperability problems between the formats.

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Speaker

Peter Schut Peter Schut
CTO,
Axon