[me] minutes - 3 April 2018

available at:

also as text below.

Thank you for joining the call, all!
And thanks a lot for double checking the minutes, Chris!




      [1] http://www.w3.org/

                               - DRAFT -

                       Media and Entertainment IG

03 Apr 2018


      [2] https://lists.w3.org/Archives/Member/member-web-and-tv/2018Mar/0003.html


          John_Luther, Ali_Begen, Kaz_Ashimura, Chris_Needham,
          Chris_O'Brien, Giri_Mandyam, Jonh_Luther,
          Masaru_Takechi, Francois_Daoust, Geun-Hyung_Kim,
          Mark_Vickers, Tatsuya_Igarashi, Will_Law


          Chris, Mark, Igarashi



     * [3]Topics
     * [4]Summary of Action Items
     * [5]Summary of Resolutions

   Chris: Thanks for joining the call today.
   ... What I'd like to is have an open discussion about Media
   Source Extensions.
   ... This is well-implemented and deployed in browsers, in use
   by several client libraries.
   ... So it seems that now is a good time to review and look at
   possibilities for v2.
   ... We should gather use cases for a potential update to the
   MSE spec
   ... that reflect our collective requirements.


      [6] https://www.w3.org/wiki/images/8/8c/Mse-eme-v2-use-cases-reqs-wave.pdf

   Chris: This document was distributed several years ago by CTA
   ... It includes several use cases, such as client-side
   ad-insertion, etc.
   ... Is this document and its requirements still valid?
   ... Use cases include ad insertion, splicing of differently
   encoded media, etc.
   ... There's a section called "Playback of live content". MSE
   as-is enables
   ... live streaming, but there are additional use cases not
   addressed in v1,
   ... such as fast start up, and switching between streams.
   ... (goes through section "2 MSE Use Cases")
   ... Are there other new use cases/requirements that IG members
   ... There are open issues against the MSE spec, marked as
   vNext: [7]https://github.com/w3c/media-source/milestone/1
   ... For low latency streaming, issue 21 discusses allowing
   application control over the buffering model

      [7] https://github.com/w3c/media-source/milestone/1

   <cpn> [8]https://github.com/w3c/media-source/issues/21

      [8] https://github.com/w3c/media-source/issues/21

   Chris: The HTML Media Extensions WG that produced MSE has gone
   into maintenance mode

   <cpn> [9]https://www.w3.org/html/wg/

      [9] https://www.w3.org/html/wg/

   Chris: So we should consider how to proceed with future work to
   update MSE. Should we recharter that WG?
   ... Or take our use cases to the Web Incubator CG?
   ... The Media Playback Quality spec has been moved to the Web
   Incubator CG.
   ... This API is intended to give information in real time about
   rendering quality, metrics such as dropped frames.

   <cpn> [10]https://github.com/WICG/media-playback-quality

     [10] https://github.com/WICG/media-playback-quality

   Chris: The IG should review this draft to see if it's enough or
   needs any changes
   ... Any comments so far?

   Mark: I co-chair this IG, and also co-chair the CTA WAVE
   ... The document was posted on the list, but MSE was nearing
   completion at the time.
   ... The agreement at that time was for new work for MSE and EME
   to go to the Web Incubator group.
   ... The approach there is more as a prototyping project,
   working code,
   ... rather than spec work followed by implementation.
   ... Media Playback Quality is doing this, that is my

   Chris: That's my understanding as well.
   ... So, what we'll need to do is write some specific proposals
   for the WICG.
   ... Examples I've seen there often have an "explainer" document
   that describes the use cases,
   ... together with a draft spec.
   ... That would be a possible way we could take this forward,
   and then get feedback from the WICG.

   Mark: There's another issue about this.
   ... Next generation features based on requests,
   ... most of the features people didn't think adding it to 1.0
   would be good.
   ... One of the issues that implementers may be concerned is
   feasibility of changing the media pipeline.
   ... What would be the changes for media pipeline with usual
   browser implementations?
   ... Consider a simple example such as changing the number of
   audio channels dynamically.
   ... MPEG transport systems support this. There are periodic
   messages in the transport stream.
   ... One could go from a main program, e.g., with English and
   Spanish audio tracks,
   ... and change to only English, and then add Spanish again for
   the main program.
   ... This is a much smaller change to discuss than one that
   involves changing codecs or format.
   ... And it's one that is not supported by the media pipeline
   with current browsers.
   ... We should understand what restrictions exist, and how to
   ... Makes it a larger effort to get implementations.

   Chris: I don't think there's anybody from the implementer side
   on the call to comment on this.
   ... Let's think about the next steps for the IG.
   ... We could review the use cases and submitting these ideas to
   ... And then review how things progress in WICG.
   ... But we do need to work much more closely with the browser
   ... discussion about implementations.

   (Mark rejoins)

   Chris: I have another question. Do any of the use cases we're
   ... have dependencies on changes to technologies outside of
   ... e.g., MPEG DASH or CMAF?

   Mark: It is absolutely reasonable for the M&E IG to work on
   ... Maybe let's prioritize the requirements, which we then
   submit to the other groups.
   ... This was recorded on the wiki a couple years ago, but no
   active work since then.
   ... We could have impact now, possibly by creating a Task Force
   in the IG.
   ... The accessibility guys also could join.

   Chris: This makes sense.

   Ali: Some comments on MPEG DASH.
   ... MPEG DASH can work with MSE, but they're not
   interdependent. DASH works in non browser / MSE environments.
   ... Looking at the issues reported by CTA WAVE, the biggest
   pain is ad insertion.
   ... There's a need to cope with different encodings, frame
   rates, etc.
   ... We tried to solve this in CTA WAVE by defining splicing
   ... because of the restrictions of MSE.
   ... If the requirements that MSE imposes could be relaxed, this
   could be made easier.

   Chris: Interesting, could you elaboarate a little on the MSE
   features that need to be relaxed?

   Ali: With many online services, ad content could come from
   another source than the original video content
   ... So the codec, frame rate, resolution, audio, etc, may be
   different to the main program.
   ... You want to have a seamless transition between the ad
   breaks and the original program.
   ... Also, most of the ad content is not encrypted,
   ... so there's a need to be able to switch between encrypted
   and unencrypted content.
   ... It's not straightforward to achieve a seamless transition.

   Chris: Thanks Ali. Any comments from others?

   Will: A bigger issue for the IG's work, is where this activity
   to be done?
   ... There needs to be a good home for MSE v2 discussion.

   Chris: I think that the IG is the right place to do this,
   ... to establishing use cases and requirements.
   ... But we do need to involve browser implementers as well.
   ... As Mark said, to understand the constraints with the
   current implementation architectures.

   Will: We can put requirements together, but the real aim is for
   the browser guys to also agree.
   ... So we need people from all 4 major browser engines
   ... We should focus on that, without browser vendors on board
   we would fail.

   Chris: I was hoping the right people would join today, I did
   invite them.
   ... But, you're right, we have to have the right contacts.

   Mark: We have discussed with browser people, and they do agree
   with our requirements.
   ... But the M&E IG is an IG, so we can't write specs ourselves,
   ... we can only write requirements.
   ... On the other hand, the WICG can write specs and get
   ... This was agreed for both MSE/EME v2 specs, so I think that
   is the right place,
   ... and the M&E IG can prioritize our requirements as a series
   of incremental projects.
   ... A WG could later take the results and make the draft into a
   spec, e.g., and updated MSE.
   ... In the M&E IG have a lot of experience, and can collaborate
   with the WICG
   ... and get some implementations.
   ... I think that could be the procedure we should take.

   Chris: As an example, here are some proposals for changes to
   EME from Netflix:


     [11] https://discourse.wicg.io/t/proposal-further-work-on-encrypted-media-extensions/2623

   Chris: All the browser vendors are signed up with WICG, so they
   don't have to do an IPR review

   Mark: This is a good example, there are 3 items there:
   ... Persistent Usage Record, HDCP detection, Encryption scheme
   capability detection.
   ... Each one would go to a separate repo.
   ... So another thread in the WICG Discourse for MSE v2 would
   make sense.

   Chris: I think it first requires us to have some conversation
   with the browser guys,
   ... to explain the changes we're thinking about, so they're
   already aware before it gets to WICG.
   ... I do agree that it's critical to make progress on these
   ... We should review our submitted requirements, and prepare to
   submit them to Discourse.
   ... We could draft explainer documents here, using the IG's
   GitHub and link to those from the posts we make to the WICG
   ... It requires somebody to initiate that discussion.


   Will: Silence means our agreement :)

   Chris: Would anyone take the lead?

   Mark: Maybe a TF of the IG is not the right place.
   ... We can individually/directly input to the discussion by the
   ... I myself am joining the Discourse would encourage people to

   Chris: Right. Chris Wilson explained us the WICG's work during
   TPAC 2017
   ... Starting a thread there in Discourse is the right approach.
   ... Individuals could use their own GitHub repos, or there's
   the M&E IG GitHub repo to host our explainer document for each

   Will: So there's nothing about MSE in the WICG discourse yet?

   Chris: That's right, so far only EME.
   ... So maybe this is a good time to bring our requirements,
   ... and create a separate thread about MSE.

   Will: Also there's currently no incubation itself happening on
   MSE or EME?
   ... How to start a new incubation flow?

   Chris: I don't think anything can happen automatically,
   ... posting to Discourse may be enough, or may need offline
   discussions with browser vendors.

   Mark: There is a MSE related group in WICG, actually, Media
   Playback Quality.
   ... It's transitioned to an incubation project.


     [12] https://github.com/WICG/media-playback-quality/graphs/contributors

   Mark: Looks like it's still active.

   Chris: It would be great if someone could kick off our
   ... but we're short on time, so we don't have to decide now.
   ... We can discuss offline or on the mailing list.
   ... Given the discussion today, it's good timing to restart the
   discussion on MSE v2.
   ... any other points for today?



Summary of Action Items

Summary of Resolutions

   [End of minutes]

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Received on Wednesday, 4 April 2018 13:38:12 UTC