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MPEG-4 SP/ASP Decoder: Reduced frame rate ->quality degradation

Question asked by AlexKates on Sep 30, 2010
Latest reply on Oct 6, 2010 by RatheeshMallaya

Hello,

 

We are using the ADI MPEG4 SP-ASP  Encoder project on the BF561 ezkit and have run across a mysterious result.

 

We can  capture just fine at 30 FPS, with a "scaling" of zero, at D1 resolution.  However, if we change the -r (frame rate) to something like lower, like  15 or 4, we get a terrible resolution and distortion of the image. If  we then provide a scaling parameter of 3, the resolution appears to be  correct for 352*288(PAL) and 352*240(NTSC).

 

But I want to be able to  capture at lower fps *with the same* resolution (D1). Is this a known  issue? Is there something I can do about it?

 

We have been working with the  encoder for a long time, so we are using Rev 2.2.0 and the test parameters we  have used for a PAL camera in example.cmd are:

 

mpeg4enc -i PPI -o ch5.m4v ch6.m4v  -w 640 352 -h 480 288 -r 15 -n 300 -b 768000 -S 3 -s 0 -t telem4.dat ;

 

Again, running this with -r 30 gives us the quality we expect, just not at the 15 fps framerate.

 

For reference, this is the module: http://www.analog.com/en/embedded-processing-dsp/blackfin/BF_MPEG-4_SP_ASP_DECODER_LIBRARY/processors/product.html

 

 

Thanks!

Alex

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