[Bug 22135] New: Changing Source Buffers

https://www.w3.org/Bugs/Public/show_bug.cgi?id=22135

            Bug ID: 22135
           Summary: Changing Source Buffers
    Classification: Unclassified
           Product: HTML WG
           Version: unspecified
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Media Source Extensions
          Assignee: adrianba@microsoft.com
          Reporter: oipfjon@gmail.com
        QA Contact: public-html-bugzilla@w3.org
                CC: mike@w3.org, public-html-media@w3.org

The specification is unclear how an app can change SourceBuffer at a particular
time in a way that gives a good user experience. For example, changing
SourceBuffer at the time when audio changes codec from Dolby to HE-AAC or
vice-versa. Section 2.4.4 of MSE describes the situation as follows;

“If buffered for at least one object in activeSourceBuffers contains a
TimeRange that ends at the current playback position and does not have a range
covering the time immediately after the current position”

And concludes with

Playback is suspended at this point since the media element doesn't have enough
data to advance the media timeline.

We believe this would generate a “waiting” event on the video element which an
app could then use to modify the active source buffers to remove the
SourceBuffer used for Dolby audio and add a SourceBuffer for the HE-AAC audio
(or vice versa). This however is unlikely to give a good user experience,
particularly as video playback would also be paused at this time.

Please provide a means to change SourceBuffer at a particular time which will
give a better user experience than relying on a “waiting” event being fired, a
JS event handler being activated which then disables and enables AudioTracks.

NOTE: This issue arises from joint discussions between the Open IPTV Forum,
HbbTV and the UK DTG. These organizations originally sent a liaison statement
to the W3C Web & TV IG which is archived here;

https://lists.w3.org/Archives/Member/member-web-and-tv/2013Jan/0000.html (W3C
member only link)

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Received on Wednesday, 22 May 2013 14:11:11 UTC