- From: Kazuyuki Ashimura <ashimura@w3.org>
- Date: Wed, 26 Aug 2015 18:25:27 +0900
- To: Chris Needham <chris.needham@bbc.co.uk>
- Cc: "public-tvapi@w3.org" <public-tvapi@w3.org>
- Message-ID: <CAJ8iq9VF1RqpYFQnj9nWVDYqexEBHTYQ35SHuv7XOZyaagpTGA@mail.gmail.com>
Thanks a lot, Chris!!! Kazuyuki On Wed, Aug 26, 2015 at 6:14 PM, Chris Needham <chris.needham@bbc.co.uk> wrote: > Hi all, > > I've taken a look at the MPTF requirements [1] in more detail. Thanks Kaz > for the suggestion to look at these, there's certainly useful information > there. > > I haven't yet updated our Technical Requirement page [2], as I thought I'd > share the information here for discussion first. I'll be happy to update > the wiki if you think the changes I suggest below are OK. > > The Design Goals section in [1] mentions security: > > > A conforming specification needs to address the security concerns > > of end-users, authors, distributors and device manufacturers by > > recommending appropriate security policies and programming behavior. > > A conforming specification must also consider the distribution and > > deployment security requirements as they relate to authors and vendors. > > I don't think we've discussed security requirements as far as I know. One > concern I have is that an API that allows any web page to discover the list > of TV channels available, and the list of scheduled recordings, can be used > for fingerprinting, so impacts end-user privacy. Malicious web content > could also manipulate the scheduled recordings. > > I think this is something we'll need to consider as we move towards an > initial stable specification. I believe W3C has published some guidance for > spec authors, but I don't have the correct link to hand. I think it would > be useful to look at existing W3C specifications to see the approach taken > there, as well as the security aspects of the OIPF DAE. > > I suggest adding a new Security Requirements section, to say that our spec > shall conform to the published guidance for security and user privacy, and > then review our work from this point of view. > > The MPTF requirements document follows with the list of numbered > requirements: > > R1. Combined Main + Description Audio Track > > > Playing descriptive audio tracks, which come in two forms: > > * Description pre-mixed with main audio (e.g. USA, Canada) > > * Description not mixed with main audio (e.g. Europe) > > This requirement resulted in a change to the categories returned by > AudioTrack.kind() and VideoTrack.kind(). > > I think the requirement to support alternate streams is covered in > [trigger.sources], but our spec doesn't mention the use of AudioTrack and > VideoTrack. Maybe this is more an issue of API design than requirements - > our Technical Requirement page has a section "Integration with HTML <video> > and <audio> Elements" where we could add this level of detail if needed. > > R2. Key Metadata Types > > > An ability to distinguish specific types of metadata should be added > > so that key metadata types can be handled appropriately by a User Agent. > > The MPTF document did not identify any gaps, so I think no change is > needed here. > > R3. Handling of In-band Tracks > > > Playing in-band multiplexed media streams (e.g. broadcast > > television, live events and recorded movies) with track elements > > that come and go over time (e.g. secondary audio, subtitles in > > different languages, application signaling and content ratings.) > > Here, I suggest a couple of changes: > > Modify [trigger.types.caption] to add "in all available languages". > > Add a new requirement [trigger.sources.notifications] The API shall be > able to notify web apps when the the set of available tracks (audio, video, > subtitles etc.) changes, i.e., when tracks are added and removed. > > In practice, if we're using the AudioTrack and VideoTrack APIs, these > generate events when the set of available tracks changes. > > R4. Content Authorization Parameters > > > A method for securely informing web content of a media item's content > > rating or other authorization parameters should be developed. This should > > be delivered when the media is loaded and whenever the authorization > > parameters change. > > This is covered in our parental control and CAS requirements, but not the > part about changes to the authorization parameters. > > This raises questions such as what should happen if a live stream is being > displayed and the programme content changes such that authorization is > required to view. Should the browser stop media playback if user > authorization has not been given, or is this an application-level > responsibility? > > I suggest adding the following requirement: > > [parental.notification] The API shall be able to notify web apps of > changes in the protection status of the programme content, e.g., when age > restrictions are applicable. > > R5. Content Authorization Failure > > > A method for securely informing web content that a media item > > could not be played due to an authorization failure and the > > reason for the authorization failure. > > As far as I can tell this isn't covered in our requirements, so I suggest > adding: > > [parental.authorization] The API shall provide a method for informing the > web app that a media item could not be played due to an authorization > failure and the reason for the authorization failure. > > and > > [cas.authorization] The API shall provide a method for informing the web > app that a media item could not be played due to an authorization failure > and the reason for the authorization failure. > > R6. Adaptive Bit Rate Format Support > R7. Additional Media Parameters > R8. Additional Media Feedback and Errors > > These requirements concern adaptive bitrate playback, so aren't directly > applicable to the TV Control API, as they are covered by Media Source > Extensions for web-based media delivery (although some of the requirements > must be handled by an application-level adaptive streaming client). > > R9. Security and Digital Rights Management Identification > R10. Content Protection Parameters > R11. Content Protection Feedback and Errors > > These requirements concern content protection and DRM, which I believe are > covered by our own CAS requirements, but I suggest it would be useful if > someone else who has more time could look at these. > > Best regards, > > Chris > > [1] http://www.w3.org/2011/webtv/wiki/MPTF/MPTF_Requirements > [2] http://www.w3.org/community/tvapi/wiki/Main_Page/Technical_Requirement > > ________________________________________ > From: Kazuyuki Ashimura [ashimura@w3.org] > Sent: 30 June 2015 14:12 > To: public-tvapi@w3.org > Subject: ACTION-30: Skim the work done by the media pipeline tf > > Hi Bin and group, > > Based on my action item (ACTION-30): > http://www.w3.org/community/tvapi/track/actions/30 > > I've skimmed the Requirements document generated by the Media Pipeline > TF of the Web and TV IG at: > http://www.w3.org/2011/webtv/wiki/MPTF/MPTF_Requirements > > There are the following 11 requirements in the document, and I think > this could be a good check list for our requiremnts document at: > https://www.w3.org/community/tvapi/wiki/Main_Page/Technical_Requirement > > and the table at: > https://www.w3.org/community/tvapi/wiki/Main_Page/Requirements_Mapping > > Delivery of Television Services: > -------------------------------- > - R1. Combined "Main + Description" Audio Track > - R2. Key Metadata Types > - R3. Handling of In-band Tracks > - R4. Content Authorization Parameters > - R5. Content Authorization Failure > > Adaptive Streaming of Media Content: > ------------------------------------ > - R6. Adaptive Bit Rate Format Support > - R7. Additional Media Parameters > - R8. Additional Media Feedback and Errors > > Content Security and Digital Rights Management: > ----------------------------------------------- > - R9. Security and Digital Rights Management Identification > - R10. Content Protection Parameters > - R11. Content Protection Feedback and Errors > > Also I think it would be useful for us to revisit the Media Accessibility > User Requirements: > http://www.w3.org/TR/2014/WD-media-accessibility-reqs-20140814/ > > For example, we might want to consider how to handle: > - described video > - text video description > - extended video descriptions > - clean audio > > Thanks, > > Kazuyuki > -- Kaz Ashimura, W3C Staff Contact for Auto, TV, MMI, Voice and Geo Tel: +81 3 3516 2504
Received on Wednesday, 26 August 2015 09:26:39 UTC