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Re: Media Fragments in Opera

From: Philip Jägenstedt <philipj@opera.com>
Date: Wed, 20 Oct 2010 16:57:08 +0200
To: public-media-fragment@w3.org
Message-ID: <op.vkvqhiapsr6mfa@kirk>
On Wed, 20 Oct 2010 11:48:15 +0200, Conrad Parker <conrad@metadecks.org>  

> On 18 October 2010 17:55, Philip Jägenstedt <philipj@opera.com> wrote:
>> For those of you who were not at FOMS, here's a little FYI:
>> The first native browser implementation of Media Fragments was demoed at
>> FOMS, that is: something I hacked into Opera. This is not ready to  
>> ship, so
>> don't expect to see it in desktop Opera just yet. Here's some  
>> implementation
>> feedback:
>> About t:
>> * We should consider making the HH component optional. Most clips  
>> online are
>> less than an hour, and being able to say #t=9:23 would be useful.
>> * It's not clear to me what to do with the smpte formats. In our  
>> underlying
>> media framework (GStreamer) time is expressed in nanoseconds, so it  
>> doesn't
>> actually give any great precision that using 9 decimals. For now, I've  
>> not
>> added support for the smpte formats at all. Are there any existing
>> implementations or indications that anyone does want to implement it?
>> * The use case for 'clock' syntax is pretty clear, but AFAIK the time  
>> in UTC
>> isn't available in Ogg or WebM, so I'm not sure what to do with it.
>> (In short, I've only implemented the npt syntax.)
> I was thinking that the smpte formats would be useful for applications
> that need to address specific frames, such as web-based video editors.
> Humans may not find these formats so necessary. It may be the case
> that something like Metavid is already advanced enough to do
> frame-level editing.

My issue with this syntax is that the actual media frameworks that one  
inevitably uses to implement it don't support addressing frames like this,  
they simply deal in nanoseconds or similar. (This is true of at least  
GStreamer and DirectShow.) If using the SMPTE syntax doesn't, in practice,  
give you greater precision than using more decimals, is it worthwhile?

For video editing in the browser, I think that would best be built using  
the JavaScript API, possibly with some additions to allow frame- and  
sample-accurate offsets if that turns out to be a problem. It seems  
premature to try to solve the problem using MF.

Philip Jägenstedt
Core Developer
Opera Software
Received on Wednesday, 20 October 2010 14:57:52 UTC

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