TV Control API CG

17 Mar 2015


See also: IRC log


Bin, Kaz, Daniel, Chris, Paul, Alex


Summary of TV Developer Meetup in Tokyo

Daniel: We had a 2 day developer meetup, looking at the TV API
... from a Hybridcast and TV API point of view
... We looked at things in Hybridcast not supported by the TV API
... Firstly, the triggered interactive overlay. Could this be split into two requirements: a trigger requirement, and an overlay requirement
... There could be two kinds of triggers, one with a pre-defined time, and one that is generated live
... For those with pre-defined times, could the in-band resource track spec be used?

<ddavis> http://www.w3.org/2014/05/28-webtv-minutes.html#item05

Bin: There can be relative time stamps encoded in the stream for triggering events
... The service provider can signal events, say every 10 minutes

Paul: There is also an alarm clock API

Daniel: Can out of band triggers be supported by server sent events?

<ddavis> https://www.w3.org/community/tvapi/wiki/Main_Page/Requirements_Mapping

Daniel: Hybridcast does not have a channel change event, as the application is closed on changing channel

Paul: Hybridcast and HbbTV are essentially channel-bound, so changing channel discards the interactive environment, to be replaced with a new one.
... With the Open IPTV Forum specs, the application persists, this is described in the application lifecycle model in the DAE

Daniel: The group was wondering whether the TV control API should converge these two approaches

Paul: The issue of a security model was raised on the mailing list, and there are privacy concerns too.

Daniel: We discussed using watermark fingerprint triggers for synchronising alternate streams.

Bin: With the supplemental triggers, these are optional, if present they should be surfaced by the API
... We would have to define the content type and data structures for these triggers, to identify these as trigger metadata
... Some fields are mandatory, such those controlling the as start time and end time/duration of the trigger

<ddavis> Type: video/x-iptvf-broadcast

Daniel: It would help to write down more of this detail in the requirements

<ddavis> <param name="video" value="arib://<original_network_id>.<transport_stream_id>.<service_id>[;<content_id>] [.<event_id>]/<component_tag>[;<channel_id>]">

<ddavis> http://www.w3.org/TR/mediacapture-streams/#idl-def-MediaStream

Daniel: Regarding integration with HTML5 audio and video elements, Hybridcast a specific content-type, with parameters not available in the media stream

Paul: There is also a different state machine, when comparing HTML5 media with OIPF
... Looking at combining the W3C specs, we've found pausing live TV in a media element would require reinitialising the media element
... Chris suggested maybe allowing buffering with MediaStreams, but do we define that or put this to that group

Daniel: Emergency notifications are implemented by a separate system, EWS, not within Hybridcast

<aldafu> Zakim: aacc is me

Daniel: There is an earthquake prediction service, which may need to be triggered differently

Paul: In the US there is a classification, different alerts have different priorities

Daniel: Regarding the EPG, we have a getProgrammes method in the mapping table, which takes an options object
... our API should allow more filtering options, such as by type of content (movies, sport)
... also, get EPG by channel
... the duration option is confusing, as its the time range for the search, maybe we should change this to endTime?

Paul: There are lots of ways to search, so with TV Anytime, we have attribute pairings, more schema-less to allow more flexible data models

Daniel: The general view was to allow more ways to search for programmes

<ddavis> https://w3c.github.io/tvapi/spec/#h-tvprogram-interface

Daniel: The TVProgram interface, should there be both a short description and a long description, is it a satellite or terrestrial programme.
... The getAudioLanguages and getSubtitleLanguages methods were felt to be too restrictive. There can be alternate commentaries but in the same language.
... An API like getAudioTracks might be more flexible, similar for subtitles: getSubtitleTracks
... The satellite/terrestrial could be added to the TVChannelType enum
... The isFree flag on the TVChannel could be added to the TVProgramme object, for free channels that contain some paid programmes
... Regarding parental control, this could be done at the programme or at the system level, we may need to clarify our requirements
... We'll share our notes from the meeting

Paul: Did the group identify anything missing?

Daniel: Maybe more device information, with properties such as manufacturer, but we need to identify requirements.

Bin: Which group is working on the in band tracks?

<ddavis> https://www.w3.org/community/inbandtracks/

<ddavis> http://dev.w3.org/html5/html-sourcing-inband-tracks/

Paul: This is looking at mappings from ISDB, ATSC etc to tracks associated with a video element

Bin: I have an interest in the encoding mechanism, for example, a raw A/V stream from the studio, how do we add the triggers and encode them within the stream. Which is the easiest way to do this during encoding?
... The dataCue can provide an abstraction over the underlying transport method

Paul: HbbTV defines stream events. There's a method addStreamEventListener. How it's encoded in the transport stream would be specified by DVB

Daniel: One other comment, more for the multi device timing comnunity group: HTML5 needs a more accurate way to reference the timeline, e.g., for ad insertion. for example, the timeupdate event is only generated every 250ms
... That's all our feedback, we had a good useful discussion today.

Review of action items

<Bin_Hu> http://www.w3.org/community/tvapi/track/actions/open

<ddavis> ACTION: ddavis to share wiki page containing feedback from Japan TV dev meetup [recorded in http://www.w3.org/2015/03/17-tvapi-minutes.html#action01]

<trackbot> Created ACTION-28 - Share wiki page containing feedback from japan tv dev meetup [on Daniel Davis - due 2015-03-24].

Alex: with action 23, the feedback and discussion about action 24 is related to this, in particular the background task for recording

Bin: So we can close action 23
... Paul and Chris have reported their findings for actions 24 and 25, on recording and timeshifting

<kaz> action-23?

<trackbot> action-23 -- Alexander Futász to Email the mailing list regarding the recording.series requirement and proposed solutions -- due 2015-02-24 -- CLOSED

<trackbot> http://www.w3.org/community/tvapi/track/actions/23

<kaz> action-24?

<trackbot> action-24 -- Paul Higgs to Look at the media capture and streams api and compare against our recording and timeshifting requirements -- due 2015-04-14 -- OPEN

<trackbot> http://www.w3.org/community/tvapi/track/actions/24

<kaz> action-25?

<trackbot> action-25 -- Chris Needham to Look at the timeshifting requirements and the html video element -- due 2015-03-17 -- OPEN

<trackbot> http://www.w3.org/community/tvapi/track/actions/25

Paul: We need to ensure our API meets regulatory requirements regarding background workers, as TV devices go into standby mode
... It would be useful to see some examples of how the various APIs fit together

<Paul_Higgs> what I call the alarm clock API is http://www.w3.org/2012/sysapps/web-alarms/

<Paul_Higgs> sorry, I have a hard stop now - I think this call is just scheduled for 1 hour!

Bin: For action 25 (time shifting), we can do some more investigation, look again at our requirements, also we should understand the rationale for preventing buffering of MediaStreams. We should do this before proposing any changes.

<scribe> ACTION: Chris to look further into timeshifting and MediaStream API rationale [recorded in http://www.w3.org/2015/03/17-tvapi-minutes.html#action02]

<trackbot> Created ACTION-29 - Look further into timeshifting and mediastream api rationale [on Chris Needham - due 2015-03-24].

Bin: we'll leave actions 26 and 27 open, and hopefully report on these next time

<kaz> action-26?

<trackbot> action-26 -- Bin Hu to Contact sean and add emergency alert requirements to the spec -- due 2015-02-24 -- OPEN

<trackbot> http://www.w3.org/community/tvapi/track/actions/26

<kaz> action-27?

<trackbot> action-27 -- Bin Hu to Work on triggered interactive overlay requirements -- due 2015-02-24 -- OPEN

<trackbot> http://www.w3.org/community/tvapi/track/actions/27

<kaz> [ adjourned ]

Summary of Action Items

[NEW] ACTION: Chris to look further into timeshifting and MediaStream API rationale [recorded in http://www.w3.org/2015/03/17-tvapi-minutes.html#action02]
[NEW] ACTION: ddavis to share wiki page containing feedback from Japan TV dev meetup [recorded in http://www.w3.org/2015/03/17-tvapi-minutes.html#action01]
[End of minutes]

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$Date: 2015/04/02 16:01:22 $