Asynchronous Decompression in Final Cut Pro?
Asynchronous Decompression in Final Cut Pro?
- Subject: Asynchronous Decompression in Final Cut Pro?
- From: Andreas Wittenstein <email@hidden>
- Date: Mon, 4 Apr 2005 17:24:53 -0700
My real-time lossless SheerVideo codecs don't play back nearly as
quickly in Final Cut Pro as in QuickTime Player and other QuickTime
applications. On investigation, I see that whereas QuickTime Player
typically decompresses up to 30 HD frames concurrently when playing
back a SheerVideo clip on a dual 2GHz G5, Final Cut Pro always
decompresses a single frame at a time. Any ideas why? [I would hope a
$1000 Final Cut Pro application would have better real-time handling
than the freebie QuickTime Player or $30 QuickTime Player Pro.]
Details:
Each Sheer decompressor
• implements 'GetMPWorkFunction()', 'QueueStarting()', and
'QueueStopping()';
• delegates 'GetBaseMPWorkFunction()', 'Busy()', and
'FlushLastFrame()';
• sets the 'canAsync' flag in the
'ImageSubCodecDecompressCapabilities' structure in 'Initialize()' •
and 'Preflight()';
• sets the 'codecCanAsync' and 'codecCanAsyncWhen' flags in the
'flags' member of the 'CodecCapabilities' structure in 'Preflight()'.
What else does it take to persuade Final Cut Pro to call the Sheer
decoders asynchronously?
QuickTime Player 6.5 typically stacks up to 30 calls to a Sheer
decoder's 'BeginBand()' before the first 'DrawBand()' is completed and
'EndBand()' is called. Final Cut Pro 4.5 HD, in contrast, never calls
'BeginBand()' again until it's finished 'DrawBand()' and 'EndBand()'.
Thanks in advance for any help,
Andreas Wittenstein
BitJazz Inc.
http://www.bitjazz.com/sheervideo/
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