X-Git-Url: https://www.fleuret.org/cgi-bin/gitweb/gitweb.cgi?p=mtp.git;a=blobdiff_plain;f=README.txt;h=a20e23d50b30aec77c682079bcc7f39472fff5d7;hp=8c38d6844861d068e351322f54b48eb70eaf8a83;hb=7f847d18f82e92c8af842f50e0ea16fa66bf9584;hpb=f2f1701bfeb50ecb468489d58a59741400d1d791 diff --git a/README.txt b/README.txt index 8c38d68..a20e23d 100644 --- a/README.txt +++ b/README.txt @@ -1,33 +1,135 @@ -This is a very simple implementation of the KSP applied to -multi-target tracking. It is dubbed Multi-Tracked Path. -The two main classes are MTPGraph and Tracker. + Multi-Tracked Paths (MTP) + ------------------------- -MTPGraph allows to define a directed acyclic graph (DAG), to associate -a length to each of its edge (which can be negative), and to compute -the family of paths in this graph that minimize the sum of the length -of their edges. +* INTRODUCTION -Tracker allows +This is a very simple implementation of a variant of the k-shortest +paths algorithm (KSP) applied to multi-target tracking, as described +in - (1) to define a spatial topology composed of + J. Berclaz, E. Turetken, F. Fleuret, and P. Fua. Multiple Object + Tracking using K-Shortest Paths Optimization. IEEE Transactions on + Pattern Analysis and Machine Intelligence (TPAMI), 33(9):1806-1819, + 2011. + +This implementation is not the reference implementation used for the +experiments presented in this article. It uses a Dijkstra with a +Binary Heap for the min-queue, and not the optimal Fibonacci heap. + +* INSTALLATION + +This software should compile with any C++ compiler. Under a unix-like +environment, just execute + + make + ./mtp_example + +It will create a synthetic dummy example, save its description in +tracker.dat, and print the optimal detected trajectories. + +If you now execute + + ./mtp tracker.dat + +It will load the file tracker.dat saved by the previous command, run +the detection, save the detected trajectories in result.trj, and the +underlying graph with occupied edges in graph.dot. + +If you do have the graphviz set of tools installed, you can produce a +pdf from the latter with the dot command: + + dot < graph.dot -T pdf -o graph.pdf + +* IMPLEMENTATION + +The two main classes are MTPGraph and MTPTracker. + +The MTPGraph class contains a directed acyclic graph (DAG), with a +length for each edge -- which can be negative -- and has methods to +compute the family of paths in this graph that globally minimizes the +sum of edge lengths. + +If there are no path of negative length, this optimal family will be +empty, since the minimum total length you can achieve is zero. Note +that the procedure is similar to that of KSP, in the sense that the +family it computes eventually is globally optimal, even if the +computation is iterative. + +The MTPTracker is defined by + + (1) a spatial topology composed of - a number of locations - - the allowed motions between them (i.e. a Boolean flag for each - pair of locations) - - the entrances (a Boolean flag for each location) - - the exits (a Boolean flag for each location) - (2) to define a number of time steps + - the allowed motions between them (a Boolean flag for each pair + of locations from/to) + + - the entrances (a Boolean flag for each location and time step) + + - the exits (a Boolean flag for each location and time step) + + (2) a number of time steps + + (3) a detection score for every location and time, which stands for + + log( P(Y(l,t) = 1 | X) / P(Y(l,t) = 0 | X) ) + + where Y is the occupancy of location l at time t and X is the + available observation. + +From this setting, MTPTracker has methods to compute the best set of +disjoint trajectories consistent with the defined topology, which +maximizes the overall detection score (i.e. the sum of the detection +scores of the nodes visited by the trajectories). If no trajectory of +total positive detection score exists, this optimal set of +trajectories will be empty. + +The MTPTracker is a wrapper around the MTPGraph class. From the +defined spatial topology and number of time steps, it builds a graph +with one source, one sink, and two nodes per location and time. The +edges from the source or to the sink, or between these pairs of nodes, +are of length zero, and the edges between the two nodes of such a pair +have negative lengths, equal to the opposite of the corresponding +detection scores. This structure also ensures that the trajectories +computed by the MTPTracker will be node-disjoint, since the +trajectories computed by the MTPGraph are edge-disjoint. + +The file mtp_example.cc gives a very simple usage example of the +MTPTracker class by setting the tracker parameters dynamically, and +running the tracking. + +The tracker data file for MTPTracker::read has the following format, +where L is the number of locations and T is the number of time steps: + +---------------------------- snip snip ------------------------------- + int:L int:T + + bool:allowed_motion_from_1_to_1 ... bool:allowed_motion_from_1_to_L + ... + bool:allowed_motion_from_L_to_1 ... bool:allowed_motion_from_L_to_L + + bool:entrance_1_1 ... bool:entrance_1_L + ... + bool:entrance_T_1 ... bool:entrance_T_L + + bool:exit_1_1 ... bool:exit_1_L + ... + bool:exit_T_1 ... bool:exit_T_L - (3) to set for every location and time a detection score + float:detection_score_1_1 ... float:detection_score_1_L + ... + float:detection_score_T_1 ... float:detection_score_T_L +---------------------------- snip snip ------------------------------- -From this input, it computes the best set of disjoint trajectories -consistent with the topology, which maximizes the overall detection -score (i.e. the sum of the detection scores of the nodes visited by -the trajectories) +The method MTPTracker::write_trajectories writes first the number of +trajectories, followed by one line per trajectory with the following +structure -The file mtp.cc gives a very simple example. +---------------------------- snip snip ------------------------------- + int:traj_number int:entrance_time int:duration float:score int:location_1 ... int:location_duration +---------------------------- snip snip ------------------------------- +-- François Fleuret -August 2012 +December 2012