[Bug 20714] timestampOffset in live case

https://www.w3.org/Bugs/Public/show_bug.cgi?id=20714

Aaron Colwell <acolwell@chromium.org> changed:

           What    |Removed                     |Added
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                 CC|                            |acolwell@chromium.org

--- Comment #8 from Aaron Colwell <acolwell@chromium.org> ---
Hi Cyril,

If I understand correctly, I think you are bringing up several different
issues.

1. The default UI for streams that don't start at 0 is suboptimal.
2. There is no way to disable seeking.
3. Media data has to be parsed in JavaScript to force a 0 start time.

For items 1 & 2, I think you have competing requirements for display that may
be specific to your personal preferences for live controls. Like Adrian says,
custom UI controls can make it easier for you to control seeking and display
the timeline however you wish. In the case of live, it could be considered a
feature that you can seek back into the buffered data.

For item 3, you don't have to parse the data in JavaScript. You could do the
following to make the timeline start at 0 w/o parsing the data in JavaScript.

sourceBuffer.append(firstMediaSegment);
sourceBuffer.timestampOffset = -sourceBuffer.buffered.start(0);
sourceBuffer.remove(sourceBuffer.buffered.start(0),
sourceBuffer.buffered.end(0))
sourceBuffer.append(firstMediaSegment);

You only have to do this once at the beginning and it will make the timeline
start at 0. I think this will make the default UI look closer to what you want,
but the displayed time will be 0 based instead of starting at the join time.
I've used this trick with some internal MSE live demos I've written so I know
it works.

I would prefer to keep things as is for v1. I don't think what I propose here
will be too high of a burden for web developers. If it is then we'll use their
feedback to craft a solution for v2.

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Received on Wednesday, 30 January 2013 00:24:36 UTC