gstavviddec posts incorrect latency

Submitted by Baby octopus

Link to original bug (#773084)

Description

gstavviddec is always posting single frame latency irrespective of B frames. Latency would certainly creep in for reordering B picture

Following sender and receiver pipeline can be used to demonstrate the issue

Sender:
gst-launch-1.0 videotestsrc ! video/x-raw,width=320,height=240 ! x264enc bframes=4 key-int-max=25 b-adapt=0 ! mpegtsmux ! udpsink host=10.0.90.1 port=8000

Receiver:
gst-launch-1.0 udpsrc port=8000 ! tsdemux ! h264parse ! avdec_h264 ! fakesink sync=1 --gst-debug=basesink:5

The latency seen at basesink at the receiver side is always a single frame latency(733ms - 700ms belongs to tsdemux)

Version: 1.9.90