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[[File:TBD.png|thumb|center|600px|<div id="fig1"></div>Fig. 1: Typical scenario of utilization]]
Streaming capability is used to monitor the production line remotely. Under normal operation, this is enough for the human operators to get an overview of the line while it is working. For this purpose, a simple low-frame-rate video stream (25 fps or something) over a local area network does the job.
The most interesting functionality is related to recording capability, however. As shown in the previous image, the production line is governed by a Programmable Logic Controller (PLC), which is interfaced to several actuators and sensors. Of course, the line may be subject to different kinds of faults. The most severe—for instance, a major mechanical failure—can lead to the automatic stop of the line. Thanks to the aforementioned sensors, the PLC is aware of such faulty conditions. In the occurrence of these eventssituations, it raises an alarm signal directed to the video recording system. Whenever an alarm is detected, the recording system stores saves (on a mass persistent storage device ) high-frame-rate footage showing what happened right before and right after the alarm event. This footage will be used later on for post-mortem analysis. In other words, automation Automation engineers and maintenance personnel can leverage afterwards this fine-grained sequence of frames to analyze in detail the framed scene around the occurrence of the alarm event moment, searching for its root cause (this process is also referred to as ''post-mortem analysis'').
===Alarm mode===
During normal operation, the high-frame-rate stream (indicated by the red flow in the previous picture) is stored in a buffer in RAM memory.
==Software implementation==
[[#fig1|Figure 1]] shows also a simplified block diagram of the application software architecture that was developed to implement this solution. The application is a multi-threaded program. The high-level business logic is coded in a finite state machine (FSM), which interacts with the threads. Each thread takes care of a particular task. For instance, T1 acquires the frames from the image sensor, stores them into the alarm buffer, and passes them to the thread T4 after a down rate conversion (low-frame-rate stream is denoted in green). T4 is responsible for creating a compressed video stream to be transmitted over the local network. The application also integrates a web interface that allows to supervise and control the recording/streaming system. For example, it can be used to enable/disable the alarm recording functionality and to read statistical information.
Alarm buffer's size is related to the size of the time window surrounding the alarm event, as depicted in the previous image.
which, in turn, enters "alarm mode." This mode is used to
===Alarm recordings===
==Future work==