A method of operation of a data collection system comprising a scan engine, the scan engine comprising: a two-dimensional image sensor having a field-of-view, and which in operation captures a sequence of frames of two-dimensional images; a set of image processor circuitry, the set of image processor circuitry communicatively coupled to the two-dimensional image sensor to receive at least some of the frames of two-dimensional images therefrom, and which in operation logically associates a respective identifier with each of the frames of two-dimensional images, the respective identifier which uniquely identifies the respective frame of the two-dimensional images for other ones of the frames of two-dimensional images in the sequence of frames of two-dimensional images; a set of decoding processor circuitry, the set of decoding processor circuitry directly or indirectly communicatively coupled to the two-dimensional image sensor to receive at least some of the frames of two-dimensional images therefrom, and which in operation decodes a number of machine-readable symbols represented in the frames of two-dimensional images; a first output interface, the first output interface communicatively coupled to the set of image processor circuitry to provide, therefrom, a set of the frames of two-dimensional images with the respective identifiers; and a second output interface, the second output interface communicatively coupled to the set of decoding processor circuitry to provide, therefrom, information decoded from machine-readable symbols by the set of decoding processor circuitry, in parallel with the stream of the frames of two-dimensional images with the respective identifiers, the method being characterised in that to logically associate a respective identifier with each of the frames of two-dimensional images, the set of image processor circuitry inserts the respective identifier into each of the frames of two-dimensional images, or inserts a respective frame identifier into each of the frames of two-dimensional images, or inserts a respective time stamp into each of the frames of two-dimensional images, or modifies a number of pixels within each of the frames, or encodes the respective identifier into optical black pixels for each frame. a two-dimensional image sensor having a field-of-view, and which in operation captures a sequence of frames of two-dimensional images; a set of image processor circuitry, the set of image processor circuitry communicatively coupled to the two-dimensional image sensor to receive at least some of the frames of two-dimensional images therefrom, and which in operation logically associates a respective identifier with each of the frames of two-dimensional images, the respective identifier which uniquely identifies the respective frame of the two-dimensional images for other ones of the frames of two-dimensional images in the sequence of frames of two-dimensional images; a set of decoding processor circuitry, the set of decoding processor circuitry directly or indirectly communicatively coupled to the two-dimensional image sensor to receive at least some of the frames of two-dimensional images therefrom, and which in operation decodes a number of machine-readable symbols represented in the frames of two-dimensional images; a first output interface, the first output interface communicatively coupled to the set of image processor circuitry to provide, therefrom, a set of the frames of two-dimensional images with the respective identifiers; and a second output interface, the second output interface communicatively coupled to the set of decoding processor circuitry to provide, therefrom, information decoded from machine-readable symbols by the set of decoding processor circuitry, in parallel with the stream of the frames of two-dimensional images with the respective identifiers, the method being characterised in that to logically associate a respective identifier with each of the frames of two-dimensional images, the set of image processor circuitry inserts the respective identifier into each of the frames of two-dimensional images, or inserts a respective frame identifier into each of the frames of two-dimensional images, or inserts a respective time stamp into each of the frames of two-dimensional images, or modifies a number of pixels within each of the frames, or encodes the respective identifier into optical black pixels for each frame.