RE: {minutes} HTML WG media telecon 2013-03-19 - MSE bug discussion and liaison questions

Minutes -> http://www.w3.org/2013/03/19-html-media-minutes.html


                               - DRAFT -

                  HTML Media Task Force Teleconference

19 Mar 2013

   [2]Agenda

      [2] http://lists.w3.org/Archives/Public/public-html-media/2013Mar/0046.html


   See also: [3]IRC log

      [3] http://www.w3.org/2013/03/19-html-media-irc


Attendees

   Present
          +1.650.485.aaaa, paulc, +31.20.460.aabb,
          +44.178.442.aacc, +44.175.349.aadd, +44.173.776.aaee,
          +44.122.365.aaff, +1.831.457.aagg, pal, SimonW, markw,
          Steve_Morris, stevep, Cecile_Marc, ddorwin, jon,
          jdsmith, adrianba, acolwell, BobLund,
          Michael_Thornburgh, giuseppep, David_Corvoysier, skaiser

   Regrets
   Chair
          Paul Cotton

   Scribe
          Adrian Bateman

Contents

     * [4]Topics
         1. [5]Roll call, introductions and selection of scribe
         2. [6]MSE Liaison questions and new bugs
         3. [7]MSE Liaison bugs
         4. [8]Adjournment
     * [9]Summary of Action Items
     __________________________________________________________

   <trackbot> Date: 19 March 2013

   <paulc> Good morning, Adrian (evening in Beijing)

   <jon> zakim aabb is me

   <adrianba> ScribeNick: adrianba

   <scribe> Scribe: Adrian Bateman

Roll call, introductions and selection of scribe

   paulc: this is a call of the Media Task Force of the HTML WG
   ... focus on Media Source today - alternate every two weeks
   ... ask for people to identify themselves
   ... objective to get through liaison questions and first bugs
   ... to give them feedback on bugs
   ... hope editors ready for that - know there have been some
   responses on individual bugs
   ... I'm Paul Cotton, from Microsoft, co-chair

   adrianba: Adrian Bateman, Microsoft, Internet Explorer team

   <Michael_Thornburgh> i'm from Adobe

   [... members of the call identifying themselves]

   <jon> I'm Jon Piesing from TP Vision, what used to be the TV
   business of Philips. I'm the chair of the browser group in OIPF
   and of the specification group in HbbTV.

   <SimonW> Simon Waller from Samsung, I work on IP
   standardisation for TVs in OIPF and HbbTV

   <Steve_Morris> I'm Steve Morris from Espial, working in both
   HbbTV and OIPF

   <giuseppep> Giuseppe from Opera, working on Opera TV product.
   co-chair of the web&tv and also active in OIPF and HbbTV

   <stevep> Stephen Perrott from the BBC in the UK. Here as part
   of the OIPF and DTG guest contingent.

   paulc: that's done the introductions

   <jbHenry> I'm J.B. Henry, from Orange group, working with HbbTV
   (and also OIPF)

MSE Liaison questions and new bugs

   <acolwell> Aaron Colwell from Google. I work on Chrome HTML5
   video and I'm editor of the Media Source Extension spec.

   <David_Corvoysier> I'm from Orange, both attending W3C HTML WG
   & Web &TV IG and OIPF

   <guy> Guy Paskar, Peer5, Peer assisted delivery network
   utilizing MSE for creating the video from multiple sources.

   paulc: first topic is the question from the liaison groups

   <stephane> Stephane Lejeune and Alain Tholon with NDS in France
   working on HbbTV.

   MSE questions from Open IPTV Forum, HbbTV and the UK DTG

   <BobLund> Bob Lund from CableLabs working on browsers for TV,
   and DLNA and W3C related efforts.

   <nsm> Nigel Moore - Sony Europe. Working on IPTV and web
   standards for CE devices in DTG, OIPF and HbbTV groups.

   [10]http://lists.w3.org/Archives/Public/public-html-media/2013M

   ar/0039.html

     [10] http://lists.w3.org/Archives/Public/public-html-media/2013Mar/0039.html


   <ddorwin> David Dorwin from Google Chrome; co-editor of
   Encrypted Media Extensions.

   <paulc> Response:
   [11]http://lists.w3.org/Archives/Public/public-html-media/2013M

   ar/0048.html

     [11] http://lists.w3.org/Archives/Public/public-html-media/2013Mar/0048.html


   <skaiser> Stefan Kaiser from Fraunhofer FOKUS, working on
   adaptive streaming / DASH applications

   paulc: Q1. Are there plans for test cases for MSE?

   acolwell: i was under the impression that the process requires
   this

   paulc: process in W3C is specs go through series of Working
   Drafts
   ... First WD has been published, typically publish new WD every
   3 months
   ... when the WG is done, it approves going into Last Call, Last
   Call Working Draft, and then look for public review
   ... once all comments are processed, spec moves to Candidate
   Recommendation
   ... that transition requires WG approval and approval of W3C
   Director
   ... at this stage there is a public call for implementations
   ... usually need test cases to show interop and that spec is
   clear enough for third party to implement from spec
   ... not unusual for there to be test cases before CR
   ... only at CR is mandatory
   ... is there a reason for the question?

   jon: for the three organisations a test suite is important
   ... we were not that familiar with w3c practice
   ... the only immediate question is one of timescales
   ... think we're done with this question

   SimonW: i think this will be covered with schedule

   paulc: Q2. Do you believe MSE contains the features needed for
   a DASH player that fully supports the DASH profiles defined by
   MPEG and by DASH-IF? If a DASH player on top of MSE could only
   support a subset of these profiles, is there any information on
   what could not be supported?

   markw: for iso bmff i'm fairly sure MSE can support a DASH
   player
   ... haven't done this for MPEG2-TS

   acolwell: also my assessment

   BobLund: we provided bitstream definition for MPEG2-TS and this
   was driven by requirements for DASH support

   adrianba: appreciate specific bug reports if people think
   something is missing or broken

   Q3. Has any thought gone into how MSE could be used with a
   media element whose playback rate was other than 0 or 1?
   Particularly rates greater than 1 or less than 0.

   acolwell: two ways this could be handled
   ... this should be signaled by setting rate on media element
   just like the non MSE case
   ... either just append faster because media engine needs faster
   ... or if you could use difference sourcebuffers for more
   sophisticated output (e.g. key frame) and switch tracks with
   html5

   SimonW: what happens to the timelines if you switch
   sourcebuffer and then you switch back
   ... you want to switch into a different time

   acolwell: my assumption, if you're using a different buffer
   you're still using the real timeline
   ... so it's really just track selection
   ... the current playback position is just moved forward
   normally
   ... depending which sourcebuffer you're using you might only be
   decoding keyframes
   ... but they're all the same timeline

   <adrianba_> ScribeNick: adrianba_

   paulc: Q4: Is there a complete description for the handling of
   encrypted content with an embedded DRM?

   acolwell: this is covered by EME
   ... there was care taken to make sure encryption cases were
   handled but not called out

   <paulc> EME = Encrypted Media Extensions

   acolwell: because some people want to support MSE but not
   necessarily encryption

   See
   [12]http://lists.w3.org/Archives/Public/public-html-media/2013M

   ar/0048.html for example

     [12] http://lists.w3.org/Archives/Public/public-html-media/2013Mar/0048.html


   <markw> yep, that's correct

   johnsim: same for ISO

   jon: that is the answer i was expecting

   <adrianba> ScribeNick: adrianba

   paulc: we've kept MSE and EME separate but there are people
   planning to implement both
   ... Q5. The broadcasters in our 3 organisations have a
   requirement to know when a particular advert starts being
   played and stops being played so that they can report this
   information back to an advertising server. It seems to us that
   the (only?) way to achieve this with with MSE is to remember a)
   where in the timeline the advert has been inserted (as defined
   by timestampOffset) and b) the length of the advert. As the
   content is played, the app wo

   uld poll the currentTime property of the media element and test
   if this was within an advert. Is this how you ... would expect
   this requirement to be met with MSE?

   acolwell: this is one way to do it
   ... i would expect to use the existing html5 text track to do
   this
   ... create text cues with the metadata
   ... for the start and end
   ... when the playback reaches those cues it will fire an event
   ... without the need for polling
   ... could use inband tracks for this too

   BobLund: here at cablelabs we've implemented both approaches
   and would be happy to provide details to anyone interested

   paulc: thanks for the offer

MSE Liaison bugs

   paulc: may have been more bugs filed - there were 5 when i
   created the agenda

   <paulc>
   [13]https://www.w3.org/Bugs/Public/show_bug.cgi?id=21298


     [13] https://www.w3.org/Bugs/Public/show_bug.cgi?id=21298


   <BobLund> Contact b.lund@cablelabs.com for implementation
   details of using text tracks for advertisement audits

   paulc: each bug has a history in it

   Bug 21298 - making it easier for people to understand MSE

   [14]https://www.w3.org/Bugs/Public/show_bug.cgi?id=21298


     [14] https://www.w3.org/Bugs/Public/show_bug.cgi?id=21298


   acolwell: the actionable piece here was about creating a
   diagram
   ... about how appended data flows through the system
   ... open to more suggestions but this is for implementers so a
   lot of prose makes it difficult to keep clear what is normative
   ... could create a separate document for content owners

   SimonW: helpful to have a high level overview for how it all
   works together
   ... a separate document perhaps
   ... for example implementation guidelines for apps

   paulc: not uncommon to produce a primer in W3C
   ... for example XML Schema
   ... Part 0 is the primer and read more often than the normative
   spec
   ... that model or introductary material in an annexe also
   possible

   jon: if you want good feedback need to reduce the learning
   curve

   Bug 21299 - memory management in MSE

   <paulc>
   [15]https://www.w3.org/Bugs/Public/show_bug.cgi?id=21299


     [15] https://www.w3.org/Bugs/Public/show_bug.cgi?id=21299


   [16]https://www.w3.org/Bugs/Public/show_bug.cgi?id=21299


     [16] https://www.w3.org/Bugs/Public/show_bug.cgi?id=21299


   acolwell: this bug is around what assumptions MSE is making
   about how memory is managed
   ... easiest way to think about this is SourceBuffers contain
   trackbuffers
   ... which hold timeranges
   ... remove() allows removing ranges from the timeline
   ... only assumption is that you have these buffers of coded
   frames and you can remove time ranges
   ... and encoding dependencies are taken into account
   ... don't believe any other assumptions about algorithms or
   methods of storage

   jon: this section was added after our F2F
   ... two immediate things spring to mind
   ... does the app have to call remove()

   acolwell: not required any more for remove to be called
   ... we did have this requirement for a while but went back to
   the original model
   ... intent is that if you don't call remove then UA will manage
   buffer for you
   ... and attempt to ensure playback doesn't stall
   ... if app wants different algorithm then it can use remove
   ... also heard that some apps have contractual obligations
   about how much can be buffered

   jon: that alleviates one concern - would apps know enough to
   meaningfully call remove
   ... but if use case is limit for rights reason then that's fine

   acolwell: if app happens to know something, for example if user
   executes a seek and knows won't need old data then app could
   remove
   ... this might be info UA doesn't have

   Bug 21300 - lack of clarity around appendStream

   [17]https://www.w3.org/Bugs/Public/show_bug.cgi?id=21300


     [17] https://www.w3.org/Bugs/Public/show_bug.cgi?id=21300


   acolwell: MSE spec doesn't talk about what creates Stream
   object
   ... MSE doesn't care but common use case is XHR
   ... XHR is XMLHttpRequest object
   ... primarily how apps that use MSE will fetch media data from
   the media server
   ... using JavaScript to initiate HTTP requests

   Bug 21301 - timelines in MSE and HTML5

   [18]https://www.w3.org/Bugs/Public/show_bug.cgi?id=21301


     [18] https://www.w3.org/Bugs/Public/show_bug.cgi?id=21301


   acolwell: if we don't have questions, how do we close bugs?

   paulc: want to answer these at the end
   ... but if editors think they've answered the question, they
   resolve the bugs

   jon: the other option would be for the chairs to have an
   offline discussion

   bug 21301

   acolwell: this was a clarification of terms - spec uses
   presentation timeline and timeline without being defined
   ... so resolution is to use 'media timeline' which HTML5 uses
   ... trivial change

   Bug 21302 - Support for inserting adverts as non-fragmented MP4
   files

   [19]https://www.w3.org/Bugs/Public/show_bug.cgi?id=21302


     [19] https://www.w3.org/Bugs/Public/show_bug.cgi?id=21302


   acolwell: my suggestion is not to support this but i'm not sure
   how to attack this bug
   ... non-fragmented files do not follow the model of everything
   else in the spec
   ... and while i understand current ad systems do not support
   fragmented files i think they will
   ... adding this might cause legacy helpful in the short term
   but not the long term

   jdsmith: while it is technically possible to make this work it
   is definitely a problem
   ... [some of the problems listed]
   ... our position is to not spend time on this

   acolwell: seems like a business problem not a technical problem

   jdsmith: tools are available to do this processing

   jon: the reason you didn't get a response is i don't think you
   have the advertising-funded broadcasters here
   ... need to get them to think about this

   <jon> Correction: The people who aren't here are the
   advertising-funded broadcasters.

   acolwell: if it's not clear already i think you'll face strong
   pushback on supporting non-fragmented MP4

   Bug 21333 - consequences of requirement in section 8 on
   initialisation segments

   [20]https://www.w3.org/Bugs/Public/show_bug.cgi?id=21333


     [20] https://www.w3.org/Bugs/Public/show_bug.cgi?id=21333


   jon: typical example is you might have a content item where
   there is one video track and the audio track is multi-channel
   ... video might be the same codec but audio is different
   ... other example is content has multiple audio tracks but ad
   doesn't
   ... this seemed to force us into different SourceBuffers
   ... what user experience would you get at the change between
   SourceBuffers

   adrianba: [summarises comments in the bug]

   acolwell: channel count can be supported in a single
   sourcebuffer but codec change, as adrian says, for
   implementation reasons you don't usually support codec changes
   mid-presentation, especially for hardware decoding

   <markw> I was going to agree this is a Media Element problem:
   what happens when you play a normal media file in which one
   audio track stops and another starts at some point in time ?
   Does the Media Element automatically switch tracks ?

   acolwell: so using two sourcebuffers to handle this would mean
   there is a track change
   ... track changes are not considered seamless at this time

   jon: this needs more discussion
   ... if an audio track disappears that would seem to require a
   sourcebuffer change
   ... we want something as seamless as possible
   ... for ad insertion

   acolwell: that's not because of the spec - the content you're
   using forces this
   ... because you're using content that can't be guaranteed to be
   seamless

   <jon> There's at least one more bug to come.

   paulc: chairs are going to have to continue our discussions
   ... ask editors to continue to close bugs as appropriate and
   keep discussing others
   ... liaison guests - please let us know which need more
   clarifications
   ... also would you like another meeting after a subsequent
   meeting on your side
   ... mark as NEEDSINFO or whatever is appropriate
   ... i'll work with liaison chairs to make sure process is
   understood

   acolwell: should some questions that are clarification be mails
   instead of bugs
   ... bugs are for things that need to be changed
   ... mails for discussion

   paulc: yes, if there are questions that should be answered by
   reading spec, can start in the list

   <giuseppep> can non HTML WG members give contributions to the
   group?

   paulc: tend to encourage to use bugs when can point to specific
   point in the spec and have a proposal for changes
   ... will provide minutes to our partners

   jon: like to express thanks for time and energy put into
   answering questions

Adjournment

   paulc: adjourned, thanks

   <jon> ?

   <jon> quit

Summary of Action Items

   [End of minutes]


__________________________
From: Paul Cotton 
Sent: Friday, March 15, 2013 2:41 PM
To: public-html-media@w3.org
Cc: Jon Piesing; Giuseppe Pascale; Aaron Colwell <acolwell@google.com> (acolwell@google.com); Adrian Bateman; Mark Watson
Subject: RE: {agenda} HTML WG media telecon 2013-03-19 - MSE bug discussion and liaison questions

We are expecting some guests at the Tue Mar 19 meeting.  Since these guests may not be familiar with W3C meeting etiquette here a few pointers.

All meeting participants are expecting to logon to the IRC channel used by the meeting ie #html-media.  We use this chat facility to identify meeting participants, take meeting notes and to manage the speakers queue.  The W3C provides a browser-based IRC facility that can be accessed via http://irc.w3.org/   

The IRC channel is controlled by a software BOT named Zakim.  The documentation for Zakim can be found at http://www.w3.org/2001/12/zakim-irc-bot.html 
For most participants the only instructions needed will be needed are the commands used to identify yourself and to add yourself to the speakers queue (q+).  

Given that we will have guests at this meeting I will try to use both Zakim and oral instructions to manage the speakers queue.  But it will certainly help if our guests can review the Zakim instructions and try out the IRC channel in advance.

Please let me know if you have any questions that I might be able to answer before the meeting.

/paulc

Paul Cotton, Microsoft Canada
17 Eleanor Drive, Ottawa, Ontario K2E 6A3
Tel: (425) 705-9596 Fax: (425) 936-7329

From: Paul Cotton [mailto:Paul.Cotton@microsoft.com] 
Sent: Friday, March 15, 2013 9:43 AM
To: public-html-media@w3.org
Cc: Jon Piesing; Giuseppe Pascale; Aaron Colwell <acolwell@google.com> (acolwell@google.com); Adrian Bateman; Mark Watson
Subject: {agenda} HTML WG media telecon 2013-03-19 - MSE bug discussion and liaison questions

The HTML WG media teleconference meeting will occur on 2013-03-19 for up to 60 minutes from 15:00Z to 16:00Z.

http://timeanddate.com/s/2c86


Beijing 23:00, Tokyo midnight, Amsterdam/Oslo 16:00, London/Dublin 15:00, New Jersey/York 11:00, Kansas City 10:00, Seattle/San Francisco 08:00.

Chair of the meeting: Paul Cotton
Scribe: TBD

(See the end of this email for dial-in and IRC info.)

== Agenda ==

1. Roll call, introductions and selection of scribe

2. Previous meeting minutes
http://www.w3.org/2013/03/05-html-media-minutes.html


3. Review of action items
https://www.w3.org/html/wg/media/track/

None.

4. Baseline documents 

a) Media Source Extensions editor's draft: 
http://dvcs.w3.org/hg/html-media/raw-file/tip/media-source/media-source.html

Status as of Mar 15:  Last updated on Mar 12:
http://lists.w3.org/Archives/Public/public-html-media/2013Mar/0037.html


5. Discussion of outstanding bugs

a) Media Source Extensions bugs: 
http://tinyurl.com/6pdnzej
Status as of Mar 4: 8 bugs (see list at end of agenda)

6.  MSE Liaison questions and new bugs

a) MSE questions from Open IPTV Forum, HbbTV and the UK DTG
http://lists.w3.org/Archives/Public/public-html-media/2013Mar/0039.html 

Q1. Are there plans for test cases for MSE?

Q2. Do you believe MSE contains the features needed for a DASH player that fully supports the DASH profiles defined by MPEG and by DASH-IF? If a DASH player on top of MSE could only support a subset of these profiles, is there any information on what could not be supported?

Q3. Has any thought gone into how MSE could be used with a media element whose playback rate was other than 0 or 1? Particularly rates greater than 1 or less than 0.

Q4. In section 8, it says;

>The combination of an initialization segment and any contiguous sequence of media segments associated with it must:
..
>If a track is encrypted, provide any encryption parameters necessary to
>decrypt the content (except the encryption key itself)

Is there a complete description for the handling of encrypted content with an embedded DRM?

Q5. The broadcasters in our 3 organisations have a requirement to know when a particular advert starts being played and stops being played so that they can report this information back to an advertising server. It seems to us that the (only?) way to achieve this with with MSE is to remember a) where in the timeline the advert has been inserted (as defined by timestampOffset) and b) the length of the advert. As the content is played, the app would poll the currentTime property of the media element and test if this was within an advert. Is this how you would expect this requirement to be met with MSE?

b) MSE Liaison bugs

i.  Bug 21298 - making it easier for people to understand MSE
https://www.w3.org/Bugs/Public/show_bug.cgi?id=21298


ii. Bug 21299 - memory management in MSE
https://www.w3.org/Bugs/Public/show_bug.cgi?id=21299 

iii. Bug 21300 - lack of clarity around appendStream
https://www.w3.org/Bugs/Public/show_bug.cgi?id=21300 

iv. Bug 21301 - timelines in MSE and HTML5
https://www.w3.org/Bugs/Public/show_bug.cgi?id=21301  

v. Bug 21302 - Support for inserting adverts as non-fragmented MP4 files
https://www.w3.org/Bugs/Public/show_bug.cgi?id=21302 
 
7. Other Business

8. Chair and Scribe for next meeting

9. Adjournment

== Dial-in and IRC Details ==

Zakim teleconference bridge:
   +1.617.761.6200, conference 63342 ("media")
https://www.w3.org/Guide/1998/08/teleconference-calendar#s_5366


Supplementary IRC chat (logged):
   #html-media on irc.w3.org port 6665 or port 80

IDâ–² 
Product 
Comp 
Assignee 
Status 
Resolution 
Summary 
Changed 
20714 
HTML WG 
Media So 
adrianba@microsoft.com 
NEW 
--- 
timestampOffset in live case 
Tue 22:01 
20760 
HTML WG 
Media So 
adrianba@microsoft.com 
NEW 
--- 
<video> Expose statistics for tracking playback quality 
2013-01-29 
21276 
HTML WG 
Media So 
adrianba@microsoft.com 
NEW 
--- 
Some instances of throwing append error should call endOfStream 
Wed 21:08 
21298 
HTML WG 
Media So 
adrianba@microsoft.com 
NEW 
--- 
making it easier for people to understand MSE 
08:27:09 
21299 
HTML WG 
Media So 
adrianba@microsoft.com 
NEW 
--- 
memory management in MSE 
08:33:58 
21300 
HTML WG 
Media So 
adrianba@microsoft.com 
NEW 
--- 
lack of clarity around appendStream 
08:39:58 
21301 
HTML WG 
Media So 
adrianba@microsoft.com 
NEW 
--- 
timelines in MSE and HTML5 
08:43:39 
21302 
HTML WG 
Media So 
adrianba@microsoft.com 
NEW 
--- 
Support for inserting adverts as non-fragmented MP4 files 
08:58:24 
8 bugs found.

Paul Cotton, Microsoft Canada
17 Eleanor Drive, Ottawa, Ontario K2E 6A3
Tel: (425) 705-9596 Fax: (425) 936-7329

Received on Tuesday, 19 March 2013 16:18:54 UTC