vaapih264enc produces encoding errors in CBR and VBR mode for white areas at the bottom
Can be reproduced with this pipeline:
gst-launch-1.0 videotestsrc ! imagefreeze ! video/x-raw,width=1920,height=1080 ! vaapih264enc rate-control=cbr ! avdec_h264 ! xvimagesink
The last few rows in the bottom white rectangle blink grey/white. The same happens in VBR mode, although it takes a bit before it starts.
This happens with GStreamer 1.16.0 and 1.14.x. The avdec / xvimagesink parts can be replaced. I just use those to make sure that the issue is in the encoder, not the decoder.
It seems to happen if the height is a multiple of 8 but not of 16.
Sometimes, depending on the input data and in CBR mode, the bottom 8 rows are always grey instead of white and not blinking.