Tlt resnet18 performance drop between .tlt inference and .engine

See Issue with image classification tutorial and testing with deepstream-app - #24 by Morganh

gst-launch-1.0 multifilesrc location=“/tmp/%d.jpg” caps=“image/jpeg,framerate=30/1” ! jpegdec ! x264enc ! avimux ! filesink location=“out.avi”

The avi file is better than mp4 file for inference.