Filtergraph documentation

The previous post introduced my plan of creating a filter graph library to make it easy to integrate different audio/video systems.

This post will contain design notes on the filter graph library for my own reference.

Notes:

• I will specify a precise terminology to make it simple to talk about the various parts of the system. 
• I will use some "plumber" analogies as a basis for my terminology.
• I will use boost::signal for propagating events about changes to the graph structure as well as the flow of data through the graph.
• I will separate the concerns of graph structure from the concerns about data passing through the graph so that the filter graph code may be used to build graphs that can handle buffers of any kind.

Filtergraph terminology illustration

Terminology:

• Graph: A system of one or more nodes linked together.
• Node: A single component in the graph.
• Pad: A connection point on a node which can be connected to exactly one other pad on another node. Can be either an input or an output.
• Source: A node that has only output pad(s) and no input pads.
• Sink: A node that has only input pad(s) and no output pads.
• Filter: A node that has both input and output pad(s)
• Connection: A link from an output pad of one node to an input pad of another node.
• Pump: A node that determines the flow of control throughout the graph. When a node pushing data from node(s) connected to its output(s) or by pulling data from node(s) connected to its input(s) is said to ac as a pump. Usually there is a single source or sink in the graph acting as pump.
• Simple: A node with only one input pad and/or one output pad is said to be simple. This makes it possible to talk about such things as "simple sink", or "simple filter pump".
• Buffer: A piece of data traveling though the graph. For video the content of the buffer usually corresponds to one frame of video. For audio, it usually corresponds to a certain length of time in audio samples.

Power and electronics schematic

I made a first sketch for the power and electronics diagram for DEVOL.

DEVOL power and electronics schematic

In essence the robot will rely on a 12V lead battery as the main source of power. A small gasoline powered generator will serve as a means to keeping this battery charged when in the field.

Power will be distributed from the battery via two separate regulators, a delicate and stable regulator for controllers and logic and a more robust and protecting  regulator for the power-hungry actuator motors.

The system is kept modular so that the different components such as visual input, strategic planning and real-time control may be handled by a separate computer (I suspect that especially the vision part will require a rather powerful computer).

The actuators are connected to a serial bus that distributes commands for each actuator from the real-time controller. Power is distributed along a separate power rail.

Visual input is provided by a calibrated stereo pair (two Logitech 9000 Pro) and another "long range" camera (Logitech 9000 Pro with mounted tele-lens). The whole camera rig is supposed to be put on a pan-tilt rig, guarded from the elements by a glass/plastic dome.

For audio, a hand-held zoom H1 stereo recorder, which provides high quality, low latency sound card and high quality microphones requiring very little power. It also has a third input where I intend to plug in a "long range" so called "shotgun microphone".

This is the first draft, expect drastic changes!