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

From: Jack Jansen <Jack.Jansen@cwi.nl>
Date: Sat, 28 Feb 2009 00:27:21 +0100
Cc: Media Fragment <public-media-fragment@w3.org>
Message-Id: <1EC9953D-9838-4DF2-A30F-38BA101C6EC6@cwi.nl>
To: Conrad Parker <conrad@metadecks.org>
This sounds reasonable, on first reading. I'm slightly (but only  
slightly) disturbed by the fact that you can't create a railroad  
diagram for this, but I think that's also already the case for  
1:30:24:14 versus 1:30:24.6.

On  25-Feb-2009, at 12:49 , Conrad Parker wrote:

> Hi,
>
> Thanks, that is a good summary. I guess my main concern was that the  
> strict
> RTSP timecodes are not very succinct, and there might be an  
> expectation
> that times like "1:30" should work -- ie. to allow hours to be  
> optional.
>
> (I guess this is the reason that YouTube chose to use separators  
> h,m,s.
> "1h30m" and "1m30s" are succinct and unambiguous, but perhaps have  
> some
> i18n issues).
>
> I agree that '.' shouldn't be used to separate frames -- frames
> should be visually distinct from fractional seconds; so I'm leaning  
> towards
> the RTSP syntax, but perhaps it could allow shorter variants.
>
> Here's a new suggestion for a parsing rule to allow hours to be  
> optional:
>
> For the case of frame offsets, perhaps we could simply mandate that if
> frames are specified, then hours must also be specified. ie.
>
> 1:30 == 1m 30s
> 1:30:24 == 1h 30m 24s
> 1:30:24:14 == 1h 30m 24s 14f
>
> ie. if the timecode consists of exactly 3 colon-separated integers,  
> then
> it is interpreted as hh:mm:ss. I think this would be a fair  
> disambiguation
> because timecodes that include frame offsets are likely to be either
> generated by software or written by an advanced user -- someone who  
> actually
> cares about frame offsets is probably technically savvy enough to  
> realize
> that they need to write a full hh:mm:ss:ff timecode.
>
> For the case of fractional seconds, the presence of the decimal point
> makes the meaning clear already, so it's straightforward to make hours
> optional:
>
> 1:30 == 1m 30s
> 1:30.24 == 1m 30.24s
> 1:30:24 == 1h 30m 24s
> 1:30:24.5 == 1h 30m 24.5s
>
> Also IIRC the current draft allows just seconds to be specified:
>
> 30 == 30s
> 30.5 == 30.5s
> 150.5 == 2m 30.5s
>
> So, in summary I'm suggesting that we use the existing RTSP syntax  
> (option 1
> below), but allow more optional elements and pattern-match on the  
> number
> of colon-separated integers: ss, mm:ss, hh:mm:ss, hh:mm:ss:ff.
>
> cheers,
>
> Conrad.

--
Jack Jansen, <Jack.Jansen@cwi.nl>, http://www.cwi.nl/~jack
If I can't dance I don't want to be part of your revolution -- Emma  
Goldman
Received on Friday, 27 February 2009 23:28:26 GMT

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