W3C home > Mailing lists > Public > public-media-fragment@w3.org > February 2009

Re: Action-28: updated syntax document with time formats

From: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
Date: Thu, 5 Feb 2009 13:11:07 +1100
Message-ID: <2c0e02830902041811x5238335dn8ccadde13201c3c5@mail.gmail.com>
To: Conrad Parker <conrad@metadecks.org>
Cc: Media Fragment <public-media-fragment@w3.org>

On Thu, Feb 5, 2009 at 1:05 PM, Silvia Pfeiffer
<silviapfeiffer1@gmail.com> wrote:
> On Thu, Feb 5, 2009 at 11:39 AM, Conrad Parker <conrad@metadecks.org> wrote:
>> 2009/2/5 Silvia Pfeiffer <silviapfeiffer1@gmail.com>:
>>> I totally agree with not using a single colon as a separator. I just
>>> thought that it would make sense to specify in a URL which time scheme
>>> we are using (as we did in the temporal URIs). However, if there is
>>> already a widespread consensus on specifying time scheme changes by
>>> using different characters, then we may as well use that. I am only
>>> afraid that people will make mistakes easily.
>> In the avid cmx syntax as I understand it, the frame separator is not
>> used to signify which time scheme is used, but to signify which field
>> of an interlaced frame is used in an edit.
>> The syntax that Jack wrote on the wiki does include the timescheme
>> name (just as we have for temporal URIs).
> In the wiki, we distiguish between "smpte-25" | "smpte-30" | "smpte-30-drop".
> In the avid cmx syntax "presence of a period in the bottom of the
> separator indicates NON Drop frame timecode, and presences of the
> comma (dropping below the line ) indicates Drop Frame timecode". So,
> at least a part of the avid cmx syntax is about dealing with drop
> frame time code or not.

Actually ... it would be cool if we could ignore the drop-frame issue
in the time specification and put it into the timecode specification
in the same way that the avid cmx syntax does it. Then we can more
easily deal with all the different smpte sampling rates: "smpte-24" |
"smpte-25" | "smpte-30" | "smpte-50" | "smpte-60".

This is also feedback on the wiki page: we really need to allow the
other smpte sampling rates. At the time that we wrote the temporal URI
spec I was in conversation with the relevant people at SMPTE and they
insisted that professional content can come in any of these sampling
rates and we have to cover them all.

So, my suggestion is to follow Conrad's avid cmx syntax proposal (with
the change of moving the ":" frame separator to "::") and extending
our time schemes with the ones listed above. We do indeed want to make
sure the fragment URIs are usable for video editing over the Web in
future, including professional content.

Received on Thursday, 5 February 2009 02:11:43 UTC

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