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Inaccurate PAL frame rates with BF561 EZ-Kit Lite/USB-LAN EZ-Extender

Question asked by AlexKates on Feb 3, 2011
Latest reply on Feb 11, 2011 by RatheeshMallaya

We have discovered that the video files captured on the Blackfin 561 EZ-Kit using the Analog Devices MPEG_4_SP/ASP_Encoder code do not have accurate frame rates.

 

We can tell this because we set a frame rate (say 17 fps) and capture for 30600 frames, which should be 30 minutes at 17 fps.Here is an example of the command used:

 

mpeg4enc -i PPI -o 9_PAL_17fps_7_30Min.m4v -n 30600 -b 4096000  -S 3 -r 17 -k 7 -d 0 -t pal.dat ;

 

30600 frames are captured. However, capturing an accurate clock shows that we have captured 32.55 minutes from beginning to end, which averages to 15.67 fps.

 

We are finding the most accurate frame rates to be 5 and 25 fps, and 14-17 fps are the worst.

 

We will be using this hardware and encoder (modified) with synced data measurements, so we are very concerned with getting a lot closer to the nominal frame rates.

 

What can you recommend for us to get this working properly?

 

Thanks,

Alex

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