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Bullet chatting questions (was RE: Bullet chatting interchange format was: W3C M&E IG conference call: 7th January 2020)

From: Chris Needham <chris.needham@bbc.co.uk>
Date: Tue, 14 Jan 2020 10:56:04 +0000
To: Nigel Megitt <nigel.megitt@bbc.co.uk>, Pierre-Anthony Lemieux <pal@sandflow.com>, "public-web-and-tv@w3.org" <public-web-and-tv@w3.org>
Message-ID: <590FCC451AE69B47BFB798A89474BB366BA3EE0F@bgb01xud1006>

I'd like to add some further questions, regarding the details of the Bullet Chatting use case:

# Rendering behaviour

Looking at some examples on bilibili, I see the following behaviour for an on-demand video:

- Pausing the video also pauses the comment overlay
- Seeking back in the video removes all comments, and the comments then re-appear as the video starts to play again

Are you looking to standardise the rendering behaviour, such as this, or leave it to the web application to decide?

I recall discussion at TPAC where it was said that the rendering should be as if the comments were part of the video, which implies that the comments would always maintain their position based on the media timeline. If I pause the video then scrub backwards or forwards, I would also see the comments move in sync. Am I remembering correctly?

# Interchange format

Regarding the need for a standardised interchange format, would it help to look at some of the data formats currently in use?

# Live streams

In a typical bullet chatting implementation for live streams, are comments distributed to clients in real time, e.g., over a WebSocket connection, and displayed immediately when received, without being synchronized to the media timeline?

As each client may be at a different playback position on the media timeline, is any timing information used to ensure the comments are relevant to each viewer? For example, what happens if I'm watching the live stream but 5 minutes behind the most recent playback position?

# Accesibility

Accessibility is always an important consideration for any W3C specification work. Have you considered how to make the Bullet Chat comments accessible? This would be an issue with canvas based rendering, for example.



From: Nigel Megitt [nigel.megitt@bbc.co.uk]
Sent: 09 January 2020 18:27
To: Pierre-Anthony Lemieux; public-web-and-tv@w3.org
Subject: Re: Bullet chatting interchange format was: W3C M&E IG conference  call:  7th January 2020

Pierre, all,

I agree that it is important to consider Pierre's question below.

I would also ask an additional related question: is there a requirement for a common interchange format for bullet chats that works interoperably across multiple applications?

Kind regards,


´╗┐On 09/01/2020, 18:15, "Pierre-Anthony Lemieux" <pal@sandflow.com> wrote:

    Dear all,

    Per our call on Tuesday and looking at the bullet chatting use cases
    at [1], below are follow-up questions/observations.

    With the exception of perhaps the "Interactive wall" use case, the use
    cases seem to involve a web application (provided by the service
    provider) running in a user agent (web browser).

    Is that accurate?

    For use cases that involve a web application running in a user agent,
    it is not evident that an interchange format such as TTML or WebVTT is
    necessary: the web application can simply interact directly with the
    user agent using CSS, DOM, etc. to display the bullet chat -- without
    the need for an intermediary interchange format.

    What are the use cases that do not involve web application (provided
    by the service provider) running in a user agent?

    Documenting all use cases is critical to help select the right
    technical solution for the interchange format and/or API. For example,
    do some use cases involve players that do not have access to the web


    -- Pierre

    [1] https://w3c.github.io/danmaku/usecase.html

    On Tue, Dec 31, 2019 at 7:49 AM Chris Needham <chris.needham@bbc.co.uk> wrote:
    > When: 07 January 2020 15:00-16:00. (UTC) Dublin, Edinburgh, Lisbon, London
    > Where: Webex
    > *~*~*~*~*~*~*~*~*~*
    > Dear all,
    > The next Media & Entertainment Interest Group will be on Tuesday 7th January.
    > This call will focus on Bullet Chatting, where I hope we can make further progress towards identifying what new standards are needed to support this use case.
    > # Agenda
    > - Welcome
    > - Bullet Chatting Task Force [Song Xu, Chris]
    >   - Objectives: identifying what new standards are needed:
    >     - A new data interchange format, e.g., TTML/ WebVTT?
    >     - A new client/server API?
    >     - Changes to HTML?
    >   - See Use Cases [1] and API Proposal [2]
    > - AOB
    > # Date and time
    > Tuesday, January 7, 2020
    > 10:00 am | EST (New York, GMT-05:00) | 1 hour
    > https://www.timeanddate.com/worldclock/fixedtime.html?msg=Media-Entertainment-IG&iso=20200107T15&ah=1
    > # Connection details
    > https://lists.w3.org/Archives/Member/member-web-and-tv/2018Sep/0001.html (member-only link)
    > Kind regards,
    > Chris (Co-chair, W3C Media & Entertainment Interest Group)
    > [1] https://w3c.github.io/danmaku/usecase.html
    > [2] https://w3c.github.io/danmaku/api.html
Received on Tuesday, 14 January 2020 10:56:27 UTC

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