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small notes about time and frames

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Christian Thaeter 2007-08-28 22:24:46 +02:00
parent e41059497f
commit 017e19c108
1 changed files with 15 additions and 2 deletions
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wiki/support_library.html
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@ -720,6 +720,19 @@ We use a common base class for all our application specific exceptions. These ex
* getting standardized error messages automatically
</pre>
</div>
<div title="FrameAndTime" modifier="CehTeh" modified="200708282024" created="200708261938" changecount="2">
<pre>! Framerates
Framerates are stored as rational numbers eg. 30000/1001 for NTSC, this representation allows highly precise integer calculations for frames and times.
! Frames
All calculations in cinelerra are based on frames which is a signed integer type. Together with a Framerate and a starting point, every frame can be exactly located.
! Time
Time is used only internally in cinelerra, every external representation of time will be converted to frames. Time has a precision of 1 microsecond and is stored in POSIX struct timeval. Time is always handled as absolute time, thus frame addresses map to absolute times, there is at worst a 1us precision jitter but no drift.
!! SMPTE and other Timecodes
will be added on demand, but be frame based, not time based</pre>
</div>
<div title="FullScreenPlugin" modifier="CehTeh" modified="200706110313" created="200607241016" tags="systemConfig lewcidExtension" server.type="file" server.host="file:///home/ct/.homepage/home.html" server.page.revision="200706110313">
<pre>/***
|Name|FullScreenPlugin|
@ -2360,7 +2373,7 @@ h1,h2,h3,h4,h5,h6 {
/*}}}*/
</pre>
</div>
<div title="SupportLibrary" modifier="MichaelPloujnikov" modified="200707160346" created="200707102314" changecount="6">
<div title="SupportLibrary" modifier="CehTeh" modified="200708261935" created="200707102314" changecount="8">
<pre>The Support Library contains all tools we need at various places, but by themselves don't defines a subsystem on their own.
These things are:
@ -2369,7 +2382,7 @@ These things are:
* a wrapper for POSIX Threads
** Thread creation joining and canceling
** Locking primitives like Condition variables and Mutexes
* [[Frame and Time handling and calculations|FrameAndTime]]
(... to be continued)
</pre>