[Mp4-tech] testing slice mode in jm98

[David Oskardmay]

Hello,
I have been testing the performance of the JM 9.8 reference encoder with 
various features enabled/disabled and I noticed a substantial quality 
degradation when I turned on slice mode with a fixed number of Mb's per 
slice.
Config details:  resolution: 640x480, 30 fps, high motion test video, 1Mbps
SliceMode = 1 (fixed #mb in slice)
SliceArgument = 40
All other slice options are off.
The artifacts during high motion periods are much worse with slice mode 
enabled than with it off.  Any idea why this is so?  Is this a possible bug? 
  Pilot error?
Thanks in advance for any info.
Best Regards,
david