W3C home > Mailing lists > Public > public-media-capture@w3.org > October 2012

Re: meaning of pausing MediaStream, and when to set media.readystate to HAVE_ENOUGH_DATA

From: Robert O'Callahan <robert@ocallahan.org>
Date: Thu, 25 Oct 2012 11:39:13 +1300
Message-ID: <CAOp6jLZi44UagL-G2F01=UrGsGg12R-7YWumjCgGgCREY9jvMA@mail.gmail.com>
To: Wei Jia <wjia@google.com>
Cc: public-media-capture@w3.org
On Tue, Oct 23, 2012 at 1:02 PM, Wei Jia <wjia@google.com> wrote:

> I have 2 questions regarding MediaStream as media elements (
> http://www.w3.org/TR/mediacapture-streams/#mediastreams-as-media-elements
> ):
> 1. What's the meaning of pausing media stream? This is related to "The
> timeline does not increment when the MediaStream is paused" . Does
> "paused" means MediaStream not "enabled", or it refers to <video> pause?

In Gecko, pausing a <video> element whose source is a MediaStream forces
the MediaStream to pause.

This question comes from use case when MediaStream is displayed with
> <video>. When the display is resumed from <video> pause, should the
> currentTime jump by a large amount (the paused duration), or continue from
> where it paused?

In Gecko, it continues from where it paused.

2. When to set media.readystate to HAVE_ENOUGH_DATA?
> According to the spec, at loading stage, the user agent needs to
> immediately set the media.readystate to HAVE_ENOUGH_DATA. This will trigger
> loadedmetadata event as well. But at that time, the user agent might not
> have received any information about the videoWidth/videoHeight. Would it be
> good to change the sentence to "setting the media.readystate to
> HAVE_ENOUGH_DATA when appropriate"? This would allow user agent to
> set media.readystate to HAVE_ENOUGH_DATA when it receives the first video
> frame from media stream.

I think we should wait for some data to arrive before entering
HAVE_METADATA or HAVE_ENOUGH_DATA states. In Gecko, we currently fire
loadedmetadata as soon as a MediaStream is connected to the media element,
but delay loadeddata and canplaythrough until we actually have some data in
the stream. I think the latter behavior is good but we should fix
loadedmetadata to fire later, along with the other events.

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Received on Wednesday, 24 October 2012 22:39:43 UTC

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