The grammar and meaning of the ground truth files is as follows:

% the whole file
FILE -> FRAMELIST

% a list of frame descriptions
FRAMELIST -> FRAME
FRAMELIST -> FRAMELIST FRAME

% a frame description
FRAME -> frame NAME FID ibl IBLIST eibl gbl GBLIST egbl eframe

% a video sequence name
NAME -> character string with no blanks

% the frame number
FID -> an integer

% a list of individual boxes
IBLIST -> 
IBLIST -> IBLIST IB

% a list of group boxes
GBLIST -> 
GBLIST -> GBLIST GB

% an individual box description
IB -> ib IID IC IR IW IH IO IASL IFLAGL eib

  % individual box ID
  IID -> an integer

  % IR, IC - row and column of center of individual box
  IC -> an integer 
  IR -> an integer 

  % IH, IW - height and width of individual box
  IW -> an integer 
  IH -> an integer 
  
  % IO - main axis orientation [0..179] degrees
  IO -> an integer 

  % IASL - state flag list
  IASL ->  
  IASL -> IASL IAS
  IAS ->  ap		% appear
	| di		% disappear
	| o		% occluded
	| in		% inactive
	| ac		% active
	| wk		% walking
	| r		% running

  % IFLAGL - scenario flag list
  PROB -> a floating point probability in [0.0...1.0]
  IFLAGL -> 
  IFLAGL -> IFLAGL IFLAG
  IFLAG ->
	   f   PROB	% fighter role
	|  br  PROB	% browser role
	|  lv  PROB	% left victim role
	|  lg  PROB	% leaving group role
	|  wr  PROB	% walker role
	|  lo  PROB	% left object role
	|  m   PROB	% moving situation
	|  is  PROB	% insactive situation
	|  bsi PROB	% browsing situation
	|  bsc PROB	% browsing scenario
	|  im  PROB	% immobile scenario
	|  wg  PROB	% walking scenario
	|  dd  PROB	% drop down scenario
	|  pi  PROB	% immobile event

% a group box description
GB -> gb GID GC GR GW GH GO gibl GMEML egibl GASL GFLAGL egb

  % group box ID
  GID -> an integer

  % GR, GC - row and column of center of group box
  GC -> an integer 
  GR -> an integer 

  % GH, GW - height and width of group box
  GW -> an integer 
  GH -> an integer 
  
  % GO - main axis orientation [0..179] degrees
  GO -> an integer 

  % GMEML - List of group members
  GMEML -> 
  GMEML -> GMEML IID

  % GASL - group state flag list
  GASL ->  
  GASL -> GASL GAS
  GAS ->  ap		% appear
	| d		% disappear
	| i		% inactive
	| ac		% active
	| mo		% movement

  % GFLAGL - scenario flag list
  PROB -> a floating point probability in [0.0...1.0]
  GFLAGL -> 
  GFLAGL -> GFLAGL GFLAG
  GFLAG ->
	   f   PROB	% fighters role
	|  me  PROB	% meeters role
	|  w   PROB	% walkers role
	|  gf  PROB	% fighting situation
	|  gmo PROB	% moving situation
	|  gme PROB	% meeting situation
	|  s   PROB	% split up situation
	|  gi  PROB	% inactive situation
	|  glv PROB	% leaving victim situation
	|  glo PROB	% leaving object situation
	|  fsc PROB	% fighting scenario
	|  mes PROB	% meeting scenario
	|  ls  PROB	% leaving object scenario
	|  fst PROB	% fight start event
	|  fe  PROB	% fight end event
	|  fv  PROB	% left victim event