[Mp4-tech][H.264]Trace file format

[Xu Ke]

Dear experts,
Currently I am studying the trace file dumped out by decoder where I got confused about the format of trace file.For example:
1)
@203    Luma # c & tr.1s vlc=1 #c=0 #t1=0                           11  (  3)
@205    Luma # c & tr.1s vlc=0 #c=0 #t1=0                            1  (  1)
What's the meaning of "vlc=1" and "vlc=0" in the above description? Why the vlc values are not equal?
2)
@239    Luma lev (0,3) k=1 vlc=0                                     1  (  1)
What's the meaning of "lev(0,3)","k=1" in the above description?
I can see many "vlc=xxx" in the trace file,what does "vlc" here refer to?
Many thanks in advance!
Best regards,
XU Ke