[Bug 21302] New: Support for inserting adverts as non-fragmented MP4 files

https://www.w3.org/Bugs/Public/show_bug.cgi?id=21302

            Bug ID: 21302
           Summary: Support for inserting adverts as non-fragmented MP4
                    files
    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

This issue results from a joint meeting between the Open IPTV Forum, HbbTV and
the UK DTG. These organizations originally sent a liaison statement to the W3C
Web & TV IG:

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

The broadcasters in our groups have a preference to work with existing web
advertising solutions. We are told that a number of these deliver adverts as
non-fragmented MP4 files.

While we note the discussion in response to the email http://lists.w3.org
/Archives/Public/public-html-media/2013Feb/0070.html, we don't understand a
number of the reasons given for not supporting this. Here are comments on some
of the reasons given in the public email thread.

>Supporting non-fragmented files would require the UA to hold the whole file in memory which could be very problematic on memory constrained devices. 

The connected TVs and set-top boxes that are the primary target of our 3
organisations already support HTTP streaming of non-fragmented MP4 files
without having the whole file in memory.

>If the UA decides to garbage collect part of the presentation timeline to free up space for new appends it is not clear how the web application could reappend the garbage collected regions without appending the whole file again. The fragmented form allows the application to easily select the desired segment and reappend it. Applications can control the level of duplicate appending by adjusting the fragment size appropriately. 

As explained in W3C bugzilla #21299 the specification being rather unclear on
memory management and garbage collection. It's hard to react to this comment
based on what's currently in the specification.

>Non-fragmented files are so permissive about how they can store samples, there is no simple way to collect segments of the timeline w/o essentially exposing a random access file API.

In practise, the formatting of non-fragmented files must be constrained to be
playable on any kind of embedded device. These constraints don't seem to cause
particular problems in the industry.

>My expectation is that the web application using MSE will make sure that all the content it intends to use in a presentation is in fragmented format.

Fragmenting a 30s advert would seem to be unnecessary.

>In my opinion the ad's should just be remuxed to fragmented form as part of the ingest process. Tools like GPAC<http://gpac.wp.mines-telecom.fr/> make this super easy.

The broadcasters that we are working with have a requirement to be able to
re-use their existing web advertising infrastructure as-is. Any changes that
have to be made for a particular platform will either delay or reduce the
probability of them providing content to that platform.

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Received on Friday, 15 March 2013 09:02:02 UTC