person tracker demo error

[hdmetor]

In th run.lua I obtain the following error:

==> processing options
==> load modules
==> downloading dataset
==> creating a new dataset from raw files:
ffmpeg -i INRIAPerson/bg.m4v -r 30 -t 10 -map 0:v:0 -s 142x80 -qscale 1 path/to/torch-demos/person-detector/scratch/bg.m4v_30fps_142x80_10s_c0_sk0_png/frame-%06d.png 2> /dev/null
Using frames in path/to/torch-demos/person-detector/scratch/bg.m4v_30fps_142x80_10s_c0_sk0_png/frame-%06d.png
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
image.load

loads an image into a torch.Tensor

> usage:
image.load(
    string                              -- path to file
    [number]                            -- force destination depth: 1 | 3
    [string]                            -- type: byte | float | double
)