The SMPTE ST 2110-40 standard specifies the real-time, RTP transport of SMPTE ST 291-1 Ancillary Data packets. It allows creation of IP essence flows carrying the VANC data familiar to us from SDI (like AFD, closed captions or ad triggering), complementing the existing video and audio portions of the SMPTE ST 2110 suite.
This presentation, by Bill McLaughlin from EEG, is an updated tutorial on subtitling, closed captioning, and other ancillary data workflows using the ST 2110-40 standard. Topics include synchronization, merging of data from different sources and standards conversion.
Building on Bill’s previous presentation at the IP Showcase), this talk at NAB 2019 demonstrates a big increase in the number of vendors supporting ST 2110-40 standard. Previously a generic packet analyser like Wireshark with dissector was recommended for troubleshooting IP ancillary data. But now most leading multiviewer / analyser products can display captioning, subtitling and timecode from 2110-40 streams. At the recent “JT-NM Tested Program” event 29 products passed 2110-40 Reception Validation. Moreover, 27 products passed 2110-40 Transmitter Validation which mean that their output can be reconstructed into SDI video signals with appropriate timing and then decoded correctly.
Bill points out that ST 2110-40 is not really a new standard at this point, it only defines how to carry ancillary data from the traditional payloads over IP. Special care needs to be taken when different VANC data packets are concatenated in the IP domain. A lot of existing devices are simple ST 2110-40 receivers which would require a kind of VANC funnel to create a combined stream of all the relevant ancillary data, making sure that line numbers and packet types don’t conflict, especially when signals need to be converted back to SDI.
There is a new ST 2110-41 standard being developed for additional ancilary data which do not match up with ancillary data standardised in ST 291-1. Another idea discussed is to move away from SDI VANC data format and use a TTML track (Timed Text Markup Language – textual information associated with timing information) to carry ancillary information.
With an enjoyable retro feel, this accessible video on understanding how analogue video works is useful for those who have to work with SDI rasters, interlaced video, black and burst, subtitles and more. It’ll remind those of us who once knew, a few things since forgotten and is an enjoyable primer on the topic for anyone coming in fresh.
Displaced Gamers is a YouTube channel and their focus on video games is an enjoyable addition to this video which starts by explaining why analogue 525-line video is the same as 480i. Using a slow-motion video of a CRT (Cathode Ray Tube) TV, the video explains the interlacing technique and why consoles/computers would often use 240p.
We then move on to timing looking at the time spent drawing a line of video, 52.7 microseconds, and the need for horizontal and vertical blanking. Blanking periods, the video explains are there to cover the time that the CRT TV would spend moving the electron beam from one side of the TV to the other. As this was achieved by electromagnets, while these were changing their magnetic level, and hence the position of the beam, the beam would need to be turned off – blanked.
The importance of these housekeeping manoeuvres for older computers was that this was time they could use to perform calculations, free from the task of writing data in to the video buffer. But this was not just useful for computers, broadcasters could use some of the blanking to insert data – and they still do. We see in this video a VHS video played with the blanking clearly visible and the data lines flashing away.
For those who work with this technology still, for those who like history, for those who are intellectually curious and for those who like reminiscing, this is an enjoyable video and ideal for sharing with colleagues.
The ST 2110-40 standard specifies the real-time, RTP transport of SMPTE ST 291-1 Ancillary Data packets. It allows to create IP essence flow carrying VANC data known from SDI (like AFD, closed captions or triggering), complementing the existing video and audio portions of the SMPTE ST 2110 suite.
In this video, Bill McLaughlin introduces 2110-40 and shows its advantages for closed captioning. With video, audio and ancillary data broken into separate essence flows, you no longer need full SDI bandwidth to process closed captioning and transcription can be done by subscribing to a single audio stream which bandwith is less than 1 Mbps. That allows for a very high processing density, with up to 100 channels of closed captioning in 1 RU server.
Another benefit is that a single ST 2110-40 multicast containing closed captioning can be associated with multiple videos (e.g. for two different networks or dirty and clean feeds), typically using NMOS connection management. This translates into additional bandwidth savings and lower cost, as you don’t need separate CC/Subtitling encoders working in SDI domain.
Test and measurment equipment for ST 2110-40 is still under developmnent. However, with date rates of 50-100 kbps per flow monitoring is very managable and you can use COTS equipment and generic packet analyser like Wireshark with dissector available on Github.
VP Product Development
This webinar will provide an overview of the recent revision of bitmap subtitles and the recent specs for UHD Subtitles.
The DVB specification for TTML-based Subtitling Systems, approved in July 2017, has now been complemented by a revision of the existing specification for bitmap subtitles, creating a comprehensive suite of subtitling specifications from DVB. This approval also marks the completion of the current generation of specifications for Ultra High Definition Television – DVB UHD-1.
The agenda for the webinar is:
•Bitmap subtitle specification (EN 300 743) Update (DVB Bluebook A009)
•New DVB TTML specification (Bluebook A174)
•Deployment considerations DVB Subtitling
Experts conducting the webinar include:
Dr. Peter Cherriman, Senior R&D Engineer, BBC Research & Development and Chair of the TM-SUB
Paul Szucs, Senior Manager, Technology Standards, Sony Europe
Stefan Pöschel, Engineer, Production Technologies, IRT
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