[PD] gem codec basic review

Max Neupert abonnements at revolwear.com
Mon Dec 24 14:28:52 CET 2007

hi andrew, list,

here is a test patch which shows quite some jitter. but jpeg  
compression and uncompressed alike. i'd like to hear from some gem  
pros what they think on how to minimize the jitter. also i wonder why  
the movie loops not always in the same speed - do i need a  
btw. this patch can be used to reduce the gem framerate automatically  
if the rendering is slower than the framrerate to avoid gem locking  
up the computer (thanks sven for that hint).
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Am 03.12.2007 um 08:11 schrieb Andrew Brouse:

> Hi Max,
> JPEG decompression should be very fast on any modern CPU, it is  
> however possible that at those frame sizes and 30 FPS, you may be  
> seeing some jitter. If you are at 30 FPS, try reducing it to 15 or  
> even 10 FPS and see what happens.
> cheers,
> Andrew
> -- 
> On Sun, 2 Dec 2007, Max Neupert wrote:
>> Am 02.12.2007 um 16:35 schrieb Andrew Brouse:
>>> If you want to do any scrubbing, varispeed or playing backwards  
>>> of the
>>> video, you need a CODEC which does not use temporal compression.
>>> Photo-JPEG is in fact a very good choice in this case and if  
>>> compressed at
>>> 320 X 240 you get a good balance of file-size, picture quality and
>>> processor load. JPEG 2000 should also be a good choice (supported by
>>> QuickTime and there are libraries which support it on Linux but  
>>> not sure
>>> if it will play in GEM).
>> hi andrew,
>> i wonder if the photo-jpeg compression does introduce a jitter in  
>> the decoding speed depending on the complexity of the content. gem  
>> would need a different time to decode each time a different frame  
>> is called.
>> i am working now with 1024x768 video compressed with 75% quality  
>> photojpeg and sometimes see lags in the decoding.. but maybe it's  
>> just my imagination.
>> max

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