JSON File Structure
Each JSON file contains array of per-frame annotation data:
The first element in the array (“zero frame”) contains general metadata, while the rest of the elements contain data for frames 1...N (where N is the last frame).
The length of the root array is therefore N+1 elements.
Example:
Zero frame object format
version
string (“1.4”)
The version of the output format
file
string (e.g: “/video/072.mp4”)
Annotated video file name with relative path to its location at the time of annotation
frame_skip
Integer
In case frames were skipped, indicates
skipping step
original_frame
Integer
First frame index. In case that target movie was divided to parts, the number of the second part will be the last frame+1
part
Integer
Part Index, in case that target movie was divided into multiple parts. Starting from part 1.
attributes
Map <attrID, value>
Non-interpolated file attribute values
objects
List <ObjectPropertiesFrame()>
Ids and properties of all the annotated objects
in the video
Object Properties on frame 0
nm
string (examples: “0.1”,
“0.2”)
Unique object identifier
shape
string
One of the object shapes:
bBox poly multiline skeleton
bitmap
type
string
Object type id
parent
string
Identifier of the parent object (only present if
nested)
attributes
Map<attrId, value>
Non-interpolated object attribute values
Frame object format
attributes
Map <attrID, value>
Interpolated file attribute values on this frame
objects
List <ObjectPropertiesFrame()>
array of objects appearing on this frame
Object Properties
nm
string
Id of the object (string) Constructed by 2 or 3 numbers divided by “.”
x1
number
Left edge coordinate in pixel of the containing BB of
the object shape
y1
number
Top edge coordinate in pixels of the containing BB of
the object shape
x2
number
Right edge coordinate in pixels of the containing BB of
the object shape
y2
number
Bottom edge coordinate in pixels of the containing BB
of the object shape
path
• List <List<[x: float, y: float]>>
**For polygon and multiline in legacy export version)
• List <Point>
Shape outline path
Bitmaps may have holes and disjoint areas, and therefore bitmap outline is a bit more complicated: it consists of several closed path sections, and points are included in the bitmap according to the “even-odd” rule (This rule determines the "insideness" of a point on the canvas by drawing a ray from that point to infinity in any direction and counting the number of path segments from the given shape that the ray crosses. If this number is odd, the point is inside; if even, the point is outside).
**Note that in bitmap paths, points are not objects but arrays containing x coordinate as a 1st element and y coordinate as a 2nd element.
*** Bound box shape objects will have their vertexes in the following order (upper left, upper right, bottom right , bottom left)
If legacy export option is selected for polygon or multiline :
Objects with polygon and multiline shapes will have a single path represented by a collection of {x, y} points.
skeleton
Map <skeletonBoneId,
Point>
Map of skeleton points
attributes
Map <attrID, value>
Interpolated object attribute values on this frame
key
Boolean
true if this is a key instance of object shape
false if this
is interpolated instance of object shape
attr_key
Boolean
true if at least one object attribute has a key value on
this frame
Point
x
Float
point x coordinate
y
Float
point y coordinate
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