See also: IRC log
<scribe> scribe: nigel
Andreas: Welcome everyone to this
joint meeting of the W3C Timed Text Working Group and EBU
Timed
... Text groups.
... I chair the EBU group, and Nigel is a chair of both of the
groups.
Nigel: Do we all know each other?
Andreas: We mostly met yesterday but introductions could be useful for some people.
Marco: I'm Marco Slik, an R&D
engineer at NPO in the Netherlands involved in the very broad
spectrum
... of playout distribution and access services, I joined the
EBU group a few years ago.
Gary: Hi, I work at Brightcove, we do online video with video.js and the web player and I focus on WebVTT
Thierry: Thierry Michel, W3C team contact for this WG
Nigel: Just an admin statement
for me, which is that as a W3C WG meeting any IPR contributed
here
... needs to be cleared. TTWG members have already made this
commitment, if any non-TTWG members
... contribute any substantive material that ends up in a W3C
Recommendation track document then as
... Chair I will need to get a similar commitment from the
contributor.
... That's the formality over, in terms of IPR!
... Can I check everyone is aware of IRC and the minuting of
this meeting?
Andreas: Yes, I will send the links around too.
Nigel: Just to let everyone know
that this meeting will be scribed on IRC and that the log will
be
... turned into public-visible minutes after the meeting. If
you do not wish something to be minuted
... please tell me before you say it!
Andreas: One of the reasons we
meet together today is the shared interest in live TTML.
... We had a discussion at the TPAC meeting in Lyon a few
months ago and also some other discussions
... in the EBU group about this.
... There was a discussion of the submission of EBU-TT Live to
W3C. At TPAC we decided we needed
... more information about the plans of the groups regarding
live and standards activities.
... So we thought this meeting would be a perfect opportunity
to discuss this.
... The main part will be dedicated to this topic.
... By introduction we have some example from operation, Nigel
from BBC, and the open source
... activity of the EBU-TT Live Interoperability Toolkit.
... Matt from Red Bee, and Marco from NPO and I will bring in
requirements from some German
... broadcasters.
... After that we will look at the live standards
activity.
... Also as we're here today we can widen the scope a little
bit.
... I talked to people before. My interest would be to check
how much we can bring TTWG and EBU TT
... activities together and doing more work in W3C.
... [missed a bit]
... We have concrete examples of multiRowAlign and
linePadding.
... The order is not fixed yet, we have a list of topics on the
wiki page.
... We can discuss where to start.
Nigel: Thanks for that, as you
have said we have a list of topics on the wiki page.
... Looking at the schedule, what should we look at first?
Andreas: Let's begin concrete
with EBU extensions and then dive into live.
... Then come back to cooperation and collaboration of the
groups at the end of the meeting.
Andreas: Some information I shared
-> [pointer to Andreas summary mail] Andreas's summary text
Andreas: The main question is if
the two vocabulary items ebutts:multiRowAlign and
ebutts:linePadding
... If it makes standards work of W3C easier we would be able
to allow them to be maintained in the TTWG.
... If there's interest in W3C group to do this.
... Otherwise we can keep it in the EBU TT group scope.
... I sent an email to the EBU reflector making a proposal, and
have had no objections to that proposal.
... From whatever date, multiRowAlign and linePadding are
maintained and at the end controlled no longer
... by EBU but by W3C. EBU will not make any changes to
them.
... If there is another EBU spec then it can reference any
updated definition in a W3C spec.
... This allows easier maintenance and adoption of bug fixes
found during W3C activities.
... The general idea is to update the items for clarification
and bug fixing.
... If completely new requirements come up that are not
satisfied by them then it may be better to add
... two completely new items in the TTML namespace. If for some
reasons semantics change then it is in
... the interests of the EBU group that they are backward
compatible with the existing EBU definitions.
... If W3C has control then they maintain it and it is their
decision process how to deal with updates.
... We currently have at least 4 members who are in both groups
then I do not see any conflict.
Matt: Is there any precedence for this?
Frans: I'm not aware of this exact case.
Glenn: When you say hand over control are you assuming a namespace change?
Andreas: No
Glenn: The proposal is a
syntactic transfer but cede control to the W3C of that subset
of the EBU owned
... namespace?
Andreas: Yes
... Pierre as editor of IMSC, the question is if there is any
benefit. I think it is clear it would be maintained
... in IMSC scope.
Pierre: There's always a benefit in having a single forum to address issues.
Glenn: If the formal definition
moves to IMSC, would it be feasible to define, say in TTML3,
two new
... attributes of the same name but in the TTML namespace?
Pierre: To me that's a separate issue.
Glenn: Well they're both in W3C control
Pierre: That's true today
Matt: Would they be equivalents?
Glenn: I've objected to including
foreign namespaces in TTML in the past.
... That's not true for IMSC which is a profile that adds
vocabulary from other places like EBU-TT.
... That was completely appropriate in IMSC, but it has never
been the case that TTML refers to foreign
... namespaces. If we do this then we should have a plan or
intent to bring them into the TTML style
... namespace and define them equivalently.
Pierre: That's orthogonal, we could do that today.
Glenn: If you think that's possible, then that's okay.
Andreas: Your proposal is to duplicate semantics but give it a different name or namespace?
Glenn: 1. Move formal definition
into IMSC, same namespace, words etc so it is consistently
defined.
... 2. Define the same names and semantics in a TTML namespace.
At that point the IMSC spec could be
... updated to refer to the TTML namespace semantics if it
wants to and also say it is available in the EBU
... namespace.
Andreas: This has been discussed
in the past and EBU has said that is not the intent to
duplicate existing
... vocabulary items, and that duplication makes no sense.
Personally I think that is the best strategy.
... We use the EBU vocabulary items because they are
established, implemented and we don't want to
... make other implementations have to change to a new
vocabulary with no need.
... This is formally not needed but it goes together. If the
overall intent is to duplicate the EBU namespace
... items without adding new functionality that would not
really justify bringing over the control of the
... EBU namespace items. We had this discussion in the past and
the position has not changed.
Glenn: We have to recognise that
IMSC and TTML are different and have different
conventions.
... We have followed different restrictions. As a primary
language definition it does not reference any
... foreign namespaces, just the core XML namespaces and those
defined in TTML itself.
... Other than this potentially we have never discussed a
proposal or accepted one to refer to foreign namespace.
Pierre: I don't see why we need
it.
... W3C could decide today to create a duplicate attribute.
We've had that discussion. I don't see what is different.
Glenn: Bringing them in to IMSC
will not satisfy requirements for TTML that are not IMSC
users.
... Everything is in the TT namespaces.
Pierre: We can have that discussion (again).
Glenn: I have no objection to
making use of the EBU technology. It is great, proven,
deployed, and I don't
... want to seem like I'm denigrating EBU in this regard.
... As Editor of the primary core language definition I have to
stand by certain principles of language
... consistency and this is one I'm going to insist on.
Andreas: Possibly it is best to
follow Pierre's proposal and concentrate on what is on the
table.
... This would be to hand over control of the items
multiRowAlign and linePadding only into W3C for
... adoption by IMSC and nothing else.
... What is the opinion of the other members present?
Matt: I think it seems sensible. The one question for me is the overall strategy and context?
Frans: Pragmatism
Matt: It doesn't make sense to
have multiple definitions of the same thing and then the
community would
... need to do the same work twice.
... We would like to contribute to the biggest circle in the
venn diagram unless there's a proposal that is
... hyper-specific. We would like to break down the notion that
captions and subtitles are different from
... country to country because in my experience they are not.
Interoperability is the goal.
Frans: I totally agree, this
makes sense and we should be pragmatic not thinking about not
invented here
... concerns.
Andreas: I see nodding from
Marco, no objection from W3C side.
... I will share the proposal from the EBU with the Timed Text
group.
Pierre: I think a liaison is needed, and an issue on IMSC to adopt in the next version.
Nigel: I'm not sure if a liaison is needed.
Pierre: For future generations a standalone piece of paper that explains what happened would be useful.
Andreas: I can make a proposal offline and check it with both groups to go forward.
Nigel: That is okay for me too.
Andreas: [shows list of EBU
specs]
... EBU-TT Part 1 v1.2, the base of every standard we
published, intended originally for exchange and archive,
... as the successor to STL.
... Not in TTML2: linePadding, multiRowAlign
... Not in IMSC: smpte, clock timebase, markerMode, clockMode,
cell length metric except for linePadding
... EBu-TT-D, same scope as IMSC, a subset of IMSC. Includes
multiRowAlign and linePadding.
... EBU-TT Live, subtitle contribution over IP. As well as
multiRowAlign and linePadding, there are four
... attributes not in TTML2 or in IMSC, sequenceIdentifier,
sequenceNumber, authorsGroupIdentifier,
... authorsGroupControlToken.
... EBU-TT Part M is definition of metadata elements, no
compatibility issue because TTML and IMSC allow
... adding metadata.
... Also we have some complementary documents.
... A recommendation how to map EBU STL to EBU-TT Part 1.
... A recommendation for carrying EBU-TT-D in ISO BMFF.
... A carriage spec for carrying EBU-TT Live over
WebSocket.
...
... A question I have is for not just EBU-TT Live, but also
part 1 and EBU-TT-D how they could converge
... with the TTML specs. Later we have an EBU group meeting,
this will be one part of the discussion there.
... Looking at the minimal part that is not inside IMSC or TTML
I see some option really to possibly
... make use of some W3C specs to satisfy the use case we
originally thought of with part 1 and Live.
... EBU-TT-D is already solved by IMSC, EBU-TT-D is just more
restricted.
Glenn: The idea is to identify
areas of difference as you have summarised, and then find ways
to...
... I guess I'm not clear on the next step - update the EBU
specs? Or some action on W3C side?
Andreas: The background is the
situation that if you go to the industry and ask about
information about
... TTML they say there are so many profiles they don't know
which ones to support. They don't implement
... a complete set. That's not a good situation, so I think it
would help to limit the set of standards that
... needs to be implemented, and I really like simple solutions
so in my simplified view, for example for
... part 1 we could say for production and exchange, just use
IMSC, but then check if everything in IMSC
... now satisfies this use case, and if not, make an addition
or some other change so that, out there, where
... we need implementation, people know they just need to
implement IMSC.
Glenn: Thinking aloud, I'm
wondering if part of the problem with all these profiles is
that very few clients
... if any actually do the profile processing that is defined
by TTML in the sense that it actually verifies
... if the profile asks for features to be supported and acts
accordingly if they are not.
... I felt always bad about the history of the EBU's adoption
of TTML when it ruled out use of the profile
... system which I thought then and still think is a mistake
because it removes the ability of the client to
... refer to the author defined profile information. I'm not
suggesting anything, but it may be that the fact
... that very few clients use the profile is part of the
problem.
Andreas: Try to look forward not backward.
Glenn: I agree.
Nigel: Chicken and egg problem -
if profile adoption is not there then it is hard to specify it,
and TTML
... implementation is already big enough without including
profiles.
Andreas: Question for Pierre, do you see a path to adding EBU-TT Part 1 syntax into IMSC if there's a gap?
Pierre: We can look at it, it is
not worth creating another flavour/layer/profile but if they
are useful
... in production only but not distribution then maybe there is
genuinely a need for another flavour.
Frans: There has been little
drive to change the production side, more the distribution
side.
... So EBU-TT has not been well adopted.
Matt: We've made a lot of EBU-TT
output, everything for BBC since 2014. We probably could derive
some
... useful stats on the number of EBU-TT documents.
... Ofcom has recently published a statement about the
extension of accessibility regulation to online
... video platforms, which included something about standards
support. There was an attempt to try to
... persuade the regulator to add guidance or stronger to
direct content providers to use particular formats.
... We have one client for whom we make 13 or 14 different
variants of the same data. That's driven by
... probably no good reason, but the proliferation has caused
fogginess. Anything we can do to reduce
... that will be very valid and valuable. If you read that
statement, [missed a bit] those are not small
... amounts of money, having one format that could be
propagated to every platform would be very
... useful.
Andreas: Useful comments. From my
experience IMSC for example [missed a bit]
... but the value of having one format overweights possibly the
extra work for features that may not be
... needed. Most of the things we leave out are not really a
problem in the implementation. It is more the
... parts we brought in, with multiRowAlign, lineGap etc are
the tricky parts.
... To actively give the message that you need to implement
full IMSC coming from different standards
... organisations would definitely help I think. One of the
main questions we can look at already for
... IMSC is timecode. We had discussions with lots of people,
lots of stakeholders are not yet ready to
... go away from timecode.
Pierre: And a lot of them use it
badly. We really have to understand the use cases extremely
well.
... In the modern world timecode will not work 99.99% of the
time with component based media.
Frans: I can only agree it must
be use case driven.
... That's the most important for production.
Marco: When you want to transition you have to support some things... [missed a bit]
Pierre: It will not work with online media.
Marco: I will not manage to get
away from smpte timecode in 3 years, but we could maybe start
the timecode
... clock at zero for example.
Pierre: I don't think saying timecode can not or must be used is the answer, it's a lot more nuanced.
Andreas: I do not think we can
say we see a better future and will not help you now.
... For German broadcasters we need an incentive to change from
STL.
... We thought we did that with EBU-TT but they did not use
it.
Frans: When we started the work
the premise was that STL can not do the things we want but
in
... production people have not hit that wall yet.
Matt: Yes, we have not hit that
inflection point. We're getting more foreign languages, like
Mandarin.
... We can't do live captioning in Mandarin, in 608 or
Teletext, but we need an answer before people
... invent something that won't work.
Glenn: A character coding issue?
Matt: Yes but the broadcast standards don't support those characters.
Pierre: Contribution of HD single
language content is a solved problem. We're not competing with
ATSC or 608.
... We're talking about worldwide online distribution of
content.
Matt: Precisely. We're working with an online entity that has no SDI platform.
Andreas: That's a good start into the discussion, I propose we move over.
Pierre: On that topic, since
we're all together, if we are serious about trying to
rationalise this it would
... probably be a good idea to set aside a day at a workshop to
really get to the bottom of it, and get
... people to tell us what they are doing and want to do
otherwise we will make a wrong decision.
Frans: We tried to do this a number of years ago for EBU-TT Live.
Pierre: For instance EBU-TT Part 1, who are the target users?
Andreas: Everyone who uses STL.
Matt: I can collate data from most UK broadcasters.
Frans: I do think there is point to verifying proposed pain points with users.
Andreas: From the experience of
the live workshop it was a bit chaotic and was hard to bring
together.
... It was good at that time, but as you say everyone goes to
their domain and community and we come
... back maybe in the same kind of circle.
Pierre: Next opportunity is maybe
IBC.
... It would be awesome to end up with a single format across
the entire chain, not for old applications.
Andreas: yes and if we are committed I'm sure we will get others onboard.
Matt: Clients ask us how to give flesh to the ecosystem
Frans: We need to give a roadmap
Matt: And state the benefits.
Nigel: That Live workshop was in
the same room as this meeting in 2012, and one of the reason it
was
... chaotic was that people wanted to address not just the
workflow we had in scope but at least one step
... further, like speech to text engines.
Frans: I agree, we need to focus on the use cases.
nigel: [describes EBU-TT Live and the Live Interoperability Toolkit] - Frans took notes.
<inserted> BBC subtiltes 100%, includes all live programmes.
<inserted> Stateful Teletext based (legacy) technology is used for this.
<inserted> Does NOT support future requirements, such as live streaming of bespoke events, cloud encoding, etc.
<inserted> When studying the standards supporitng this authoring-to-encoding part of the workflow.
<inserted> EBU-TT was the obvious choice (the BBC was already producing in EBU-TT).
<inserted> EBU-TT-Live (Tech 3370) specifies how you can send a stream of text chunks to facilitate this scenario; with 0 or 1 documents 'active' at any time.
<inserted> The EBU-TT-Live Toolkit validated the spec and helps implement it: https://github.com/ebu/ebu-tt-live-toolkit
<inserted> Timed changes do not have to be explicit ('just send a new document') as was demoed in the SwissTXT demonstration at EBU PTS 2019 for example.
<inserted> SMPTE timecode is not allowed (as you cannot do match on it).
<inserted> Carriage using web sockets has been defined.
<inserted> EBU-TT-Live / TTML carriage in RTP for use in SMPTE 2110 ("IP replacement of SDI") is being worked on; BBC has submitted an RFC for TTML carriage in RTP.
Matt: Background to fit into
that.
... [shows slides]
... We're a subtitle vendor, and a few years ago wanted to
replace our live captioning platform. We were
... surprised at the lack of forwards thinking in the market. I
was in this group already at that point and
... could see that the world would change and Teletext would
not work.
... We built our own java based captioning tool called
Subito.
... Effectively internally it makes TTML.
... Can output Teletext, Nufor, 608, Cavena, EBU-TT Live, and
can do those simultaneously, applying
... the constraints in real time.
... We did our first presentation at PTS 2 years ago, and did
some work using the LIT. We had a basic but
... brittle proof of concept. More recently using for our
customers.
... Development challenges, managing pre-conceptions of HTML
and XML ignoring good EBU documentation
... ignoring format details because of lack of understanding of
the use case, so deviating from the spec.
... Partly caused by lack of reference examples and
material.
... Bad habits like using line breaks for positioning.
... Ignoring test materials that are free like the Interop
Toolkit.
... Challenges about reformatting, we focused on conveying the
intent of the captioner to the stream.
... But how to cope if presentation format is a different
aspect or applies other constraints?
... In the implementation side we didn't think enough about
that. No practical constraints, but need to
... avoid developers making inappropriate solutions.
... We created a multichannel Distribution Node. Originally we
required consumers to connect in, what we now
... have is scalable and supports multiple destinations.
... Testing is difficult, need a 24/7 delivery
destination.
... Security: not an issue with 608 or Nufor, wide open or
limited in format.
... We've implemented Auth0 with security based on IPv4
lockdown approach.
... Haven't implemented handover functions, the idea that you
may have more than one source of
... caption documents, and we have a model in Part 3 for
passing over control seamlessly so everyone
... knows who is in control and where their data is going.
Needs more ecosystem, lacking at the moment
... for testing and demonstration.
... "flying hours" - if we have used libraries with memory
leaks etc then eventually things will go wrong.
... Until we have solid real world use we can't be 100% sure it
is robust.
... Used for Department of Parliamentary Services, Australia
with a web feed.
... Extended proof of concept, due to launch imminently.
... Second is "Intersub", real time transcript service.
Currently Newfor, plan to migrate to Part 3, which
... will simplify the stack and remove newfor handling
deduplication code.
Andreas: Really good, thank you,
very interesting!
... Next up, Marco.
Marco: [trouble presenting]
Andreas: I will take over and we
come back to Marco.
... Our broadcasters are fine most of the time. They look for
new solutions if current tech cannot solve
... their use cases.
... One problem in the past is live streaming of broadcast
programmes with closed captions, not burned in,
... on the distribution channel.
... All of the chain is standardised especially at the end.
There are stable and good standards to package
... EBU-TT-D and IMSC into MP4 and deliver it with DASH and
HLS.
... To encourage implementation we did a demo that has been
online for 1 or 2 years where we use the
... live broadcast signal and take out the subtitles and bring
it into IMSC and deliver it over HLS and DASH.
... [shows live Bavarian broadcaster BR's output]
... Teletext subtitles translated into IMSC.
... How it works: for the encoding and packaging, receive SDI
with embedded teletext subtitles in the VANC.
... They decode it and then translate it to TTML and package it
in MP4 for the client. That works.
... But what if you have a non-broadcast workflow, for an
online only platform with no broadcast chain.
... And our broadcasters say they have a couple of
internet-only live events and they do not want to buy
... whole broadcast systems for these events to subtitle them.
One way it could be done is that at the
... packaging side you receive the video and audio together and
synchronise it and deliver as MP4 to the client.
... The scenario we would like to solve is to use EBU-TT Live
for the contribution to the encoding layer.
... Also we would like to get people together like we did in
the past with this CMAF/DASH demo.
... The challenge we have at the moment is to find a packager
and encoder that would implement
... EBU-TT Live and the synchronising mechanism.
... It would also be possible to use a legacy format like
Newfor and transmit teletext information.
Matt: Newfor is not an open
standard. Everyone who has a copy of it has inherited it rather
than been
... able to obtain it!
Andreas: And all of them use a different variation of this protocol.
Pierre: Who created Newfor?
Matt: Sysmedia, a guy called
Andrew Lambourne who now works at the University of Sheffield
Hallam I think.
... It's a simple serial style wrapper around the core Teletext
page instruction, with a session, flow management,
... and wraps up what literally should be on the screen.
Andreas: What we see as a chance
is the next Olympics. We have heard they want to offer much
more
... online than on broadcast, and they need to provide
captions. That's the goal and we are really looking
... for a good working solution here.
Matt: We did some work with
Channel 4 in the UK, who broadcast the paralympics. They wanted
to make
... it all accessible online and the only solution was to hire
a crate of kit from the US, go to SDI and back
... out again, and doing that all cost quite a lot of money.
The requirements really do exist.
Andreas: Marco, can we hand over to you?
Marco: [presents slides]
... [Status subtitle market]
... Global overview of what you all said, to make clear the
Europe subtitle volume is extensive.
... Most countries have regulation with additional European
regulation that will probably end up with
... having 100% hearing impaired subtitling. About 50% of
Europe uses translation subtitles as well.
Pierre: Checking my assumption, 5 years ago a lot of subtitling for translation but there is no [missed]
Frans: Different per country
Marco: The view is that accessibility needs to be at a higher level.
Frans: Increasing pressure, depends how far people can go because of money.
Pierre: On the accessibility standpoint, what is the coverage in Europe?
Frans: Subtitling only (captioning), 100% in NW Europe.
Marco: 95% on all content.
Matt: Many countries it is only the public service broadcaster.
Andreas: In Germany main channels 100%, major public ones, commercial ones down to 20%.
Marco: Will change with new EU regs.
Frans: Not sure timing
Matt: Equivalent of the US regs
Pierre: Public and commercial broadcasters?
Frans: Not equal
Andreas: Media industry requirements not so strict.
Matt: Strange things - some
countries have more stringent regs because of their governments
but
... tech affects ability to deliver.
Pierre: Statement that penetration will increase is because of regulation or cost?
Marco: Regulation mainly.
group: [everyone wants to see data on that!]
Marco: On the translating part, a
lot of countries have burned in subtitles too.
... Differs between countries, in Netherlands it is all foreign
language.
... [Subtitle market status]
... Shift from linear broadcast to on-demand and OTT.
... New requirement for different devices not knowing
Teletext.
... Teletext used in broadcast facilities, page 888 for the
viewer, being phased out.
... Equipment is end of life, end of support, no new companies
offering solutions.
... Typically something I run into, no Teletext support in
encoders.
... Current support only goes to 7 lines, I need 15 or
16!
... Current tech support is cut off but IP protocols not there
- we really need to do something new.
... New players on the market, mainly internet startups.
... Know a lot about new world interfaces.
... Need standardisation to get this streamlined.
... Increasing demand for good access services and
customisation on client side, so not sending
... a rendered subtitle image but sending text so the front
ends can customise.
... New volumes - non-audio videos without subtitles
... Looking at new functionality for web players, extra
metadata etc.
... [EBU-TT as replacement]
... File based, not for today. Teletext based - all
proprietary, being phased out.
... [Live transport in the chain] - picture from EBU spec,
slightly modified.
... Live part from authoring facility to playout, then playout
to encoding.
... EBU-TT Live -> EBU-TT-D/IMSC for player rendering and
DVB
... [NPO's live subtitle chain]
... Live subtitle department done with one editor for simple
programmes, and 3 editors for more complex
... talking heads programmes, with respeaking, correcting and
cueing, with video delays. Very demanding
... for respeaking, so change editor roles during the
programme.
... Also trying to do automated subtitling, really a challenge
at the moment.
... Then playout, file based with STL and Cavena at the moment,
need to go real time to encoder.
... As Andreas said, Newfor and Teletext are the old world.
Looking toward having a new world approach
... where styling and formatting are equal and extendable
through all devices.
... So we want block based subtitling, handover between
editors, time relationship is SMPTE based but
... not always 'do it now' but could be late file delivery with
overlaid live subtitles, then ingested during
... playout for replay later.
... Looking at media timecode in next generation which should
last at least 3 years.
... Need to fan out to multiple destinations.
... Timebase processing (delay compensation)
... Lowest delay NOW (remote capability) is needed
... Same for file based playout.
... SMPTE timecode, timebase correction, fan out to multiple
destinations, timed metadata.
... A TTML based approach really important for timed
metadata.
... In encoder, fan-in from multiple sources, then synchronise
ABR and DVN stream transport,
... subtitles and timed user metadata,
... join other worlds like HbbTV.
... [Needed] Widest standardization as possible.
... Currently have momentum to get rid of old world possibly,
but tools not available for new world yet.
... Really frustrating.
... Good to mention need for multiple languages including right
to left. We have a huge amount of Arabic
... in Holland.
... Near real-time in parallel to SMPTE 2110 ideally in future,
encapsulated in distribution for client renderers.
... I hope to have some support for aligning positioning
especially for converting from Teletext to new world.
... EBU-TT Part 2 includes some guidance.
... Would like to do the translation as early as possible in
the chain.
Andreas: Thank you for that
honest but realistic view of what is happening and what the
challenges are.
... Propose a break now for 15 minutes maximum.
... Return at 11:05.
Nigel: Thank you for those
presentations - they were really great!
... [return from break]
Andreas: Can we start with a summary from yesterday?
Nigel: Not sure exactly what you're referring to?
Andreas: Yesterday it came up
what could be done with EBU-TT Live and how to handle it in
W3C.
... TTWG will have a new kind of layout a bit like CSS, where
some functionality is taken out of the main
... specification and put into modules. This opens up a more
flexible approach to address current
... requirements and parallelise activities so they do not
block each other.
... In this context one of the proposals was to take the
functionality and possibly the vocabulary of
... EBU-TT Live in a module published by W3C which then can be
used by any profile of TTML, could be
... EBU-TT, IMSC or whatever.
... From my impression that's where it ended, it's a feasible
approach.
... There are other questions how it could look at the end and
the mechanics e.g. a submission from EBU
... as a W3C member. It is a feasible approach.
Glenn: Clarifying my thinking on
modularisation approach and how it is not exactly like
CSS.
... In CSS they carved up the existing functionality of CSS2
into pieces and called them modules.
... I'm not assuming and would oppose doing the same thing here
with TTML3 because there are so many
... interlinked semantics between the different components and
it would create quite a bit of effort to
... carve it into pieces and I don't see any advantage in
evolution because it is fairly stable.
... What I see happening is in the context of TTML3 creating a
new framework for modules to allow
... new functionality to exist that is not in TTML2.
... To the extent that we can put it into different module
documents proceed on that basis.
... It may turn out that there are some substantive changes not
in TTML2 2nd Ed that are appropriate
... for making in the core of TTML3 that are not in modules,
but to the extent that we don't separate
... functionality then that would be the best approach,
allowing parallelisation of work and editorial
activities.
... Especially for new well identified groups of functionality
such as live.
... Just communicating my understanding because that's what I'm
going to operate on.
... If people differ from that I'd like to hear about it.
Andreas: I think it would work
well for this use case, and it would also be good to discuss
why we have
... the discussion. Right now EBU-TT Live is complete and is
out there. What are the benefits of bringing
... into W3C?
... 1. To encourage vendor support, by having a global
solution.
... 2. I know there are ideas and requests for updates of
functionality. Here it is better to do it in one
... group rather than separate groups.
Nigel: Add one more, which is it
would allow us to make a thing like IMSC Live, which currently
seems to
... be excluded by EBU-TT Live even though in principle it is
possible to make IMSC-conformant EBU-TT Live
... documents, I don't think that seems obvious to the wider
world.
... Also there are some useful constructs permitted in IMSC
that are excluded by EBU-TT Live.
Andreas: That's right, and you
also point to an important issue that EBU-TT Live is first a
description
... of how a live TTML workflow should look, with some
additional syntax and semantics.
... It is bound to EBU-TT syntax definition, so limited to what
is in EBU-TT Part 1.
Marco: Two main topics: The transport mechanism and the syntax of the documents.
Andreas: Right.
Nigel: In the EBU specs we've tackled them as separable things.
Andreas: So 3 things: Workflow, Carriage mechanisms, and the payload.
Marco: What I meant was the transport and how we encapsulate the handshake in mechanisms.
Andreas: There are clear benefits
also in the EBU group, and everyone involved in standardising
EBU-TT Live
... is convinced of the usefulness here.
... It would be useful to hear from others in TTWG, Pierre,
Glenn.
Pierre: Yes, I don't have a very
strong opinion about applying only to IMSC or to TTML as a
module, I'm
... happy either way, whichever works best.
... I think it would be good to apply to IMSC somehow if it is
possible.
... Last time I saw it it was merely a couple of additional
attributes with no impact on visual presentation.
... The only feedback on the document that I have already
shared is it is too long.
... Otherwise it seems like a good idea. I like the idea of
trying to focus development on the technical
... specifications in a single place. The requirements can come
from other groups.
group: [general agreement]
Frans: I totally agree, that is
the main point.
... A second point is ease of marketing, branding, so
considering a complete IMSC based future could be
... very attractive as the main thing people know about. We
should embrace the best candidate we have
... and it is IMSC, that gives us the biggest chance of
adoption.
Pierre: Specifically on EBU-TT
Live and authoring, with SMPTE 2110 and the brave new world, it
would be
... really good for this community to help folks pick the right
technology, or someone will pick SMPTE-TT
... and say that's what we're doing now.
... My feedback to Nigel is the more we can do to narrow what
goes over 2110 the better otherwise we
... will have disappointment, otherwise someone will implement
TTML over 2110 and it won't work
... between vendors.
Matt: I would like to see removal
of specific protocols for individual markets, in favour of
global ones
... To avoid lossy transcode, reworking, and support new
languages.
... I've had conversations about Punjabi, Hindi, Mandarin,
Cantonese (bizarrely), Arabic, they all need some
... kind of kludge.
Pierre: Can we talk about 2110, how can we contribute positively?
Nigel: On the point about TTML vs
IMSC for this, there are other uses of TTML than subtitles,
which
... may benefit from live contribution, like AD, as agreed
yesterday, so it makes sense to put it there.
... On the 2110 issue, have to use TTML because that is what
has the IANA registration.
... Also want to encourage use of codecs parameter from the
beginning to avoid the non-adoption problem.
... Also we will need other specs like in SMPTE, NMOS and EBU
to complete the suite.
Frans: [scribe missed]
Andreas: We are here because we
want to work more closely together. This work counts the
same,
... need to focus on working together and make sure as Pierre
says that the major stakeholders align
... on one approach to solving a specific problem.
... Parallel solutions won't help.
... I'm not so familiar with IETF. Two forms of collaboration.
One is publish something and let the domain
... submit some feedback, send comments back. This works not
that well in the past because of workload.
... The other is getting together in a room and talking through
the problem.
... I'm not sure about this particular work, BBC is submitter
so that is helpful. The relevant people
... should come together and at least discuss this paper and
agree it is the right approach.
... For SMPTE I'm not sure.
Nigel: I've already received a request to discuss in W3C TTWG and am happy to do that.
Frans: Putting together a timeline would be useful.
Pierre: To better understand
2110, there's a bunch of specifications for audio and video but
is there any
... about timed text today?
Nigel: No there isn't yet.
Pierre: I'd like to come back to that.
Andreas: Okay, from the feedback
so far I haven't heard anybody objecting the approach to bring
the
... EBU-TT Live activity into W3C at least to mirror the most
important parts of EBU-TT Live as a module
... in a W3C spec.
Nigel: Is it clear to everyone what the syntax, semantics and general approach is?
Andreas: We may not have time to go through it.
Nigel: Just want to check if there is enough awareness to make a general decision.
Glenn: What's the decision?
Andreas: To bring the EBU-TT Live work into W3C
Glenn: Sounds good to me, mutatis mutandis.
Frans: To make IMSC Live?
Andreas: First to bring into
TTML, second should we say it is our goal to make IMSC usable
together with
... this module, if it is a profile or an addition to IMSC has
to be found out.
... The other thing I think is also important is to bring over
these two attributes like multiRowAlign.
... Do we say the EBU-TT Live attributes are now handled in W3C
space?
Glenn: A more practical question - do we have a prospective editor?
Andreas: We clarified this yesterday Nigel will be.
Pierre: Do we need to make a decision today?
Andreas: Let us see if we are ready for a decision!
Pierre: On the namespace?
Andreas: What do you mean?
Concrete proposal: move the syntax and semantics into a TTML3
module
... without changing syntax, then add to IMSC Live.
Glenn: I mentioned yesterday I
would be amenable to enabling foreign namespace vocabulary
in
... modules, so that could work for this and for multiRowAlign
and linePadding.
... That would also in my mind be a potential incorporation of
those into the TTML core but that is a
... future process to think about. By then it may be that we
have acceptance of the use of foreign
... namespaces in TTML.
Pierre: On the relationship with
IMSC, maybe the jury is still out, but my understanding is that
these are
... timing attributes added to a TTML document?
Glenn: Almost like metadata.
Pierre: Exactly, they're permitted additions that don't affect presentation.
Andreas: Apart from timebase clock
Nigel: Like a pre-processor that affects the time during which the document is active, otherwise yes the same.
Pierre: We can just do it.
Andreas: Both a technical and a marketing side to this.
Frans: So we could end up in an
ideal case in a few years with everything IMSC and the world is
simple,
... that would be the best solution, forgetting TTML, EBU-TT
all the rest of it.
Matt: It is being adopted already
without a second thought, seemingly, so it is free of
geographical boundaries
... already I would say.
Andreas: I don't think we need a
final decision on this depth, but if we agree then we should
prepare the
... next steps and propose it and do something similar as the
two styling attributes.
... For me it is clearer we should handover maintenance and
control of this to W3C.
Nigel: If we are writing a
liaison, a piece of paper, we can either cover all of it, or
have two, one for
... styling and one for live.
... I've heard enough that there is consensus on our
requirements issue to take it forward for this year.
Pierre: A member submission would be the best thing.
Nigel: Quite a lot of overhead in doing that, I'd rather start in W3C with an empty thing.
Andreas: Proposing to hand over
control over EBU-TT Live to TTWG, to republish EBU-TT Live as a
module,
... further updates of EBU-TT Live done in the TTWG and not the
EBU Timed Text group.
Nigel: EBU should have the freedom to iterate its specs if it wants to do so.
Frans: Query if we want to update
EBU-TT Live or brand everything as IMSC Live.
... That's an important consideration. I would be in favour of
steering everything towards IMSC.
Nigel: I don't disagree, maybe EBU should publish something explaining this position to the world.
Andreas: We are making an
important shift, we may need to discuss this further. For me it
makes more
... sense to make a cut and say we transfer it now to another
organisation and will not update further.
... For the two vocabulary items we hand over control and if
there are further EBU specfications we can
... publish a new spec referencing.
Frans: What if there is a bug in EBU-TT Live?
Andreas: If there is a short term need then we can do that otherwise we should not.
Frans: I am not sure what timelines we are talking about.
Marco: Isn't it about securing EBU requirements in a future spec?
Frans: I feel confident about that.
Andreas: We have enough shared
members, we can collect requirements from the EBU and bring it
into
... the new W3C spec but do not publish in EBU scope.
Marco: That makes it clearer to the rest of the world.
Frans: It is all about simplicity. In spirit we all agree.
Andreas: Long term goal is agreed, need to figure out how it would work in the short term.
Nigel: Checking in on the agenda,
we've covered almost all the topics, 15 minutes to go.
... Pierre asked to come back to SMPTE 2110, and Andreas you
wanted to come back to something too?
Andreas: [shares screen]
... We have these two attributes, and part 1, and EBU-TT-D and
part M.
... Starting with EBU-TT-D, one approach we could take that
would benefit industry is to say we stop
... work on EBU-TT-D and point to IMSC for any future update,
or missing functionality or bug fixes.
... That would be a clear message.
... We should try to elaborate if we can do something similar
for Part 1 and Live.
Nigel: I think a key point here
is how we handle smpte and clock timebases, which are in EBU-TT
and TTML
... for a reason, and not in IMSC also for good reasons. Can
media time only work in playout scenarios?
Marco: As a broadcaster, I can say it won't work for the next 3 years.
Andreas; Stick with what works and is available.
Pierre: Exactly, that's what you
have to do.
... You can adopt EBU-TT Part 1 today and constrain it. 3 works
is a realistic horizon to work with
... vendors and service providers and say in 3 years we plan
not to use timecode for those workflows.
Marco: We always have legacy from
our archives so we need some timebase transcoding
somewhere.
... It's already on my list. I think I'm forward looking within
the range of broadcast views!
Frans: Absolutely. This is a very
critical thing, we need to spell out the transition scenario,
how does this
... work, what do you encounter in practice. If we cannot we
are not in a good situation.
Marco: We have to guarantee that what is in EBU-TT now remains the same in large part for IMSC.
Pierre: Looking at the differences, is that the sum total?
Andreas: Those are the main
things on a quick look. The really substantive things are
timecode and cell.
... Cells are manageable by translation to %.
Pierre: Especially with IMSC 1.1 we have rh and rw so there is a lossless 1:1 translation from cell.
Andreas: There's more work to be
done that's clear.
... To say it is simple, everything IMSC, wherever it is, I see
some kind of agreement that this is the long
... term goal, and possibly to come together and discuss it
maybe at IBC. We can try to set up a new
... joint meeting at IBC.
Pierre: What's the timeline for
submission of EBU-TT Live and EBU-TT Part 1?
... And starting that convergence process.
Andreas: For Part 1 it is
different, we haven't started the discussion. For Live it is
easier, depends on
... Nigel who has the most work on it.
Pierre: That could be part of what we try to do this year with IMSC.
Frans: To do the transfer, this year?
Pierre: Yes, as well as other additions to IMSC that we have discussed, like embedded fonts.
Nigel: I'm not clear what needs to be done to IMSC though?
Pierre: Exactly, that is why I am optimistic.
Andreas: The live module can be done this year.
Pierre: And make a goal to resolve differences with EBU-TT Part 1.
Andreas: That is more complex, I don't see Part 1 alignment this year.
Pierre: If we are targeting 3
years it would be ideal to do it this year.
... I think it would be different if there had been broad
adoption of EBU-TT Part 1.
Frans: I agree. We need a clear understanding of how it is used.
Marco: For example live ingest - how do you translate that to time expressions in a Part 1 document.
Pierre: What we saw yesterday is
the bigger issue with live is not the timebase, but the
separation of
... flows of audio/video and subtitles.
Frans: But part 1 not live.
Pierre: This will never be used
in live?
... What would it be used for?
Frans: Prepared content
Pierre: Why use timecode?
Marco: To synchronise with the playout server.
Frans: Longer discussion!
Andreas: We can schedule for live
in W3C, for part 1 we need further discussions and we should
have
... this kind of coming together.
... What about this goal to be at IBC.
Nigel: Logistical issue of timing of meetings - TPAC is very close to IBC, I can't be at both probably.
Frans: IBC is where we can collect user input. We need that.
Andreas: We don't necessarily need the people in the room but we need the feedback channeled through us.
Frans: IBC is an opportunity to meet industry people.
Pierre: Do we present results or gather feedback?
Frans: Both, there is not enough time to gather information about timecode usage at IBC
Andreas: A half day workshop would be useful, after the standards people get together.
Pierre: So present results at IBC.
Frans: That would be great.
Pierre: I'm pretty confident that
North America is happy to use IMSC for production, I'll hear
more in 2 weeks.
... For live I don't know.
Matt: Live is typically 608 originated and delivered straight into EEG or Evertz encoders. It is ripe for evolution.
Pierre: I don't know about live,
I'm pretty sure IMSC will be good enough, I've not heard any
objection to that.
... Would be good to hear from EBU members.
Frans: It is an extremely early stage.
Andreas: We can cover Live and
EBU-TT-D at IBC.
... Then we can start to get out the message about part 1 but I
agree with Frans it is more complicated.
... This overall meeting would be good.
... Nigel you say they are close together?
Pierre: The only way I could do TPAC is to be there for a day and a half.
Andreas: For the TTWG we had the
idea to move the regular meeting out of TPAC. That would be a
question
... if we would move the meeting to Amsterdam.
Pierre: Tokyo would be a lot
closer in travel time than Fukuoka!
... By the way I did complain to W3M and they said they don't
have IBC and NAB on their calendars!
... They said it would be a good idea.
... The AC meeting is right on top of NAB and TPAC on top of
IBC.
Andreas: To sum up we try to move
forward offline with EBU-TT Live as quickly as possible and we
also
... have some discussion about EBU-TT-D and Part 1 and share
info soon.
... Then we propose to both groups to have a domain meeting
where we present our results but also a
... face to face meeting that would be joint EBU and TTWG. We
have absent TTWG people today so we have
... to propose it.
Pierre: If you're organising meetings at IBC you're not going to make it to TPAC.
Matt: I would go to IBC but not TPAC.
Frans: So hold an industry meeting and a joint meeting both at IBC?
Matt: I'd request immediately
before IBC or after, not during.
... So we travel to Amsterdam once and stay.
... If we could do it on the Thursday that would be good for
me.
... I will be busy after then.
Andreas: That makes sense.
Matt: I'm usually exhausted by the Tuesday.
Andreas: We need to discuss this in the TTWG.
Pierre: If TTWG is not going to meet at TPAC that would be good to know as early as possible.
Andreas: It would be good to send a message out at IBC.
Matt: Possibly arrange a presentation, say in the innovation presentation area.
Andreas: Those are the things that come to my mind. Anything else we need to discuss or finalise?
Pierre: Is it bad not to attend TPAC?
Thierry: There's nothing
mandatory but it is convenient for coordinating with other
groups. There are no
... rules about it, it is just for convenience.
... The dates for meeting would be?
Andreas: We need to check it offline.
Pierre: Either Thursday 12th Sep or Tuesday 17th.
Andreas: If nothing else we can close the joint meeting.
Nigel: Thank you everyone, a good
morning's work and good discussion, we can adjourn now.
... [adjourns meeting]