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Re: Fractional Repeat counts?

From: Sjoerd Mullender <sjoerd@acm.org>
Date: Fri, 23 Jul 2004 08:49:44 +0200
Message-ID: <4100B508.1000709@acm.org>
To: navil@emuzed.com
Cc: www-smil@w3.org

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John Navil Joseph wrote:
|
| Hi,
|
| SMIL 2.0 supports fractional repeat counts (ex. repeatCount = "0.75").
|
| Consider the following example.
|
| ...
| <video src="video1.mpg4" region="Region1" repeatCount="0.75" />
| ...
|
| I suppose that the standard assumes that the intrinsic duration of
| "video1.mpg4"
| is available beforehand for this to work correctly. But on small hand
| held  embedded
| devices it may be very expensive to calculate the exact intrinsic
| duration  of the
| streams. (especially for elementary streams as that of MPEG4, AAC).
|
| How does the standard expect the SMIL players to deal with these
| situations in which
| the intrinsic duration of the media objects is simply "unknown"?

I quote from the standard, take special note of the last sentence:

"When repeatCount is specified, it is understood to represent a count of
iterations of simple duration. Each iteration of the simple duration may
be different, and so a simple multiplication of the repeatCount and a
given simple duration may not yield an accurate active duration. In the
case of a partial repeatCount and a simple duration that is not
resolved, the most recent simple duration should be multiplied by the
fractional part of the repeatCount to constrain the last simple
duration. If the last iteration of the simple duration otherwise ends
before this time, the repeatCount should be considered to be complete.
If a repeatCount is less than 1 and the simple duration is unresolved,
the repeatCount cannot be correctly respected, and will behave as though
a repeatCount of "1" were specified."

In other words, in this case the repeatCount is effectively ignored.

You can find this at
http://www.w3.org/TR/smil20/smil-timing.html#Timing-RepeatCountAndUnresolvedSimpleDur

- --
Sjoerd Mullender <sjoerd@acm.org>
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Received on Friday, 23 July 2004 02:50:07 UTC

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