X-Git-Url: https://fleuret.org/cgi-bin/gitweb/gitweb.cgi?p=mtp.git;a=blobdiff_plain;f=README.txt;h=807f567f0803072d0e39a42bb3759dd6263ac360;hp=708fea63fa8f92a5b9a3a0ad266739070d87fe06;hb=22e800d663bb7a6b03ba6735fef54bf12c6cd2b5;hpb=f248d9481cd0338053cb38a18eb3898042c126d3 diff --git a/README.txt b/README.txt index 708fea6..807f567 100644 --- a/README.txt +++ b/README.txt @@ -1,16 +1,43 @@ + Multi-Tracked Paths (MTP) + ------------------------- + * INTRODUCTION -This is a very simple implementation of a variant of KSP applied to -multi-target tracking dubbed "Multi-Tracked Paths" (MTP). +This is a very simple implementation of a variant of the k-shortest +paths algorithm (KSP) applied to multi-target tracking, as described +in + + 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 does not require any +library, and uses a Dijkstra with a Binary Heap for the min-queue, +instead of a Fibonacci heap. + +This software package includes three commands: -It works with negative edge length and stops when it can not find any -path of negative total length, instead of fixing the total number of -paths to a constant K. + - mtp is the generic command to use in practice. It takes tracking + parameters as input, and prints the tracked trajectories as + output. The format for these parameters is given at the bottom of + this documentation. + + - mtp_example creates a tracking toy example, and runs the tracking + algorithm on it. It gives an example of how to use MTPTracker on a + configuration produced dynamically, and produces a test input file + for the mtp command. + + - mtp_stress_test creates a larger problem with a lot of noise and + multiple trajectories, to check the behavior of the code under + slightly more complex situations. * INSTALLATION -This source code should compile with any C++ compiler. Just execute +This software should compile with any C++ compiler. Under a unix-like +environment, just execute make ./mtp_example @@ -20,12 +47,14 @@ tracker.dat, and print the optimal detected trajectories. If you now execute - ./mtp tracker.dat + ./mtp --verbose --trajectory-file result.trj --graph-file graph.dot 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. -It will load the tracker.dat example, run the detection, save the -detected trajectories in result.trj, and the underlying graph with -occupied edges in graph.dot. You can produce a pdf from the latter -with the dot command from graphviz: +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 @@ -33,70 +62,91 @@ with the dot command from graphviz: The two main classes are MTPGraph and MTPTracker. -The MTPGraph class stores a directed acyclic graph (DAG), with a -length for each edge -- which can be negative -- and can compute the -family of paths in this graph that minimizes the sum of edge lengths. +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. -This means that it will iteratively add paths as long as it can find -some with negative length. If there are no such path, it will compute -no path at all. 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. +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 class allows +The MTPTracker takes as input - (1) to define a spatial topology composed of + (1) a number of locations and a number of time steps - - 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) a spatial topology composed of - (2) to define a number of time steps + - the allowed motions between them (a Boolean flag for each pair + of locations from/to) - (3) to set for every location and time a detection score, which - should be equal to log(P(Y = 1 | X)/P(Y = 0 | X)) where Y stands - for the location occupancy and X for the observations. + - the entrances (a Boolean flag for each location and time step) -From this setting, 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 exits (a Boolean flag for each location and time step) -The MTPTracker class uses the MTPGraph. From the definition of the -spatial topology, it builds a graph with one source, one sink, and two -nodes per location and time. This structure ensures the trajectories -computed by the tracker to be node-disjoint by forcing the paths -computed by the MTPGraph to be edge-disjoint. + (3) a detection score for every location and time, which stands for -The edges from the source or to the sink, or between these pairs, are -of length zero, and the edge between the two nodes of such a pair has -a length equal to the opposite of the detection score. + log( P(Y(l,t) = 1 | X) / P(Y(l,t) = 0 | X) ) -The file mtp.cc gives a very simple usage example of the MTPTracker -class. + where Y is the occupancy of location l at time t and X is the + available observation. Hence, this score is negative on locations + where the probability that the location is occupied is close to + 0, and positive when it is close to 1. -The tracker data file one can read with MTPTracker::read has the -following format (with L the number of locations and T the number of -time steps): +From this parameters, the MTPTracker can 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). In particular, if no +trajectory of total positive detection score exists, this optimal set +of trajectories is empty. + +An MTPTracker is a wrapper around an MTPGraph. 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 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 ------------------------------- -L T + int:L int:T -allowed_motion_from_1_to_1 ... allowed_motion_from_1_to_L -... -allowed_motion_from_L_to_1 ... allowed_motion_from_L_to_L + 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 -is_an_entrance_1 ... is_an_entrance_L + bool:entrance_1_1 ... bool:entrance_1_L + ... + bool:entrance_T_1 ... bool:entrance_T_L -is_an_exit_1 ... is_an_exit_L + bool:exit_1_1 ... bool:exit_1_L + ... + bool:exit_T_1 ... bool:exit_T_L -detection_score_1_1 ... detection_score_1_L -... -detection_score_T_1 ... detection_score_T_L + float:detection_score_1_1 ... float:detection_score_1_L + ... + float:detection_score_T_1 ... float:detection_score_T_L +---------------------------- snip snip ------------------------------- + +The method MTPTracker::write_trajectories writes first the number of +trajectories, followed by one line per trajectory with the following +structure + +---------------------------- snip snip ------------------------------- + int:traj_number int:entrance_time int:duration float:score int:location_1 ... int:location_duration ---------------------------- snip snip ------------------------------- -- François Fleuret -August 2012 +January 2013