Base class for kernel functioanlities access from the driver classes. More...
Inherited by CDriverContext.
Public Member Functions | |
| virtual | ~IDriverContext (void) |
| Destructor. | |
| virtual OpenViBE::Kernel::ILogManager & | getLogManager (void) const =0 |
| Gets the kernel Log Manager. More... | |
| virtual OpenViBE::Kernel::IConfigurationManager & | getConfigurationManager (void) const =0 |
| Gets the kernel Configuration Manager. More... | |
| virtual OpenViBE::boolean | isConnected (void) const =0 |
| Gets connection status. More... | |
| virtual OpenViBE::boolean | isStarted (void) const =0 |
| Gets acquisition status. More... | |
| virtual OpenViBE::boolean | isImpedanceCheckRequested (void) const =0 |
| Checks if impedance check is required (when available) More... | |
| virtual OpenViBE::int64 | getDriftSampleCount (void) const =0 |
| Gets drift sample count. More... | |
| virtual OpenViBE::int64 | getDriftToleranceSampleCount (void) const =0 |
| Gets the drift sample count tolerance. More... | |
| virtual OpenViBE::int64 | getSuggestedDriftCorrectionSampleCount (void) const =0 |
| Gets the suggested drift correction sample count. More... | |
| virtual OpenViBE::boolean | correctDriftSampleCount (OpenViBE::int64 i64SampleCount)=0 |
| Corrects a drifting device. More... | |
| virtual OpenViBE::boolean | setInnerLatencySampleCount (OpenViBE::int64 i64SampleCount)=0 |
| Sets a fixed latency due to the driver implementation and / or hardware. More... | |
| virtual OpenViBE::int64 | getInnerLatencySampleCount (void) const =0 |
| Gets the fixed latency due to the driver implementation and / or hardware. More... | |
| virtual OpenViBE::boolean | updateImpedance (const OpenViBE::uint32 ui32ChannelIndex, const OpenViBE::float64 f64Impedance)=0 |
| Updates impedance for a specific channel. More... | |
Detailed Description
Base class for kernel functioanlities access from the driver classes.
- Date
- 2009-10-12
- See also
- IDriver
Member Function Documentation
|
pure virtual |
Gets the kernel Log Manager.
- Returns
- the kernel Log Manager
- See also
- OpenViBE::Kernel::ILogManager
Referenced by IDriverContext::~IDriverContext().
|
pure virtual |
Gets the kernel Configuration Manager.
- Returns
- the kernel Configuration Manager
Referenced by IDriverContext::~IDriverContext().
|
pure virtual |
Gets connection status.
- Returns
- true if the driver is connected
- false if the driver is not connected
- See also
- isStarted
Referenced by IDriverContext::~IDriverContext().
|
pure virtual |
Gets acquisition status.
- Returns
- true if acquisition is started
- false if acquisition is stoped
- See also
- isConnected
Referenced by IDriverContext::~IDriverContext().
|
pure virtual |
Checks if impedance check is required (when available)
- Returns
- true if impedance check is required
- false if impedance check is not required
It is up to the driver to check whether impedance check is required by the acquisition server or not. If this test is required, then the driver should perform impedance measures while initialized but not yet started.
Referenced by IDriverContext::~IDriverContext().
|
pure virtual |
Gets drift sample count.
- Returns
- the drift sample count
- See also
- correctDriftSampleCount
This function returns the difference between the theorical number of samples this driver should have sent so far and the number of samples it actually sent. This drift sample count is computed by the acquisition server and can be used to correct a drifting device behavior.
- Note
- If this number is less than 0 then samples are missing
- If this number if more than 0 then there are too much samples
- If this number is exactly 0 then the driver sent the exact number of samples it had to send
Referenced by IDriverContext::~IDriverContext().
|
pure virtual |
Gets the drift sample count tolerance.
- Returns
- the drift sample count tolerance
Gets the tolerance configured for the acquisition server. This tolerance is present to avoid numerous corrections on a drift value that would oscillate in a small range around 0. In such case, a correction in a way would probably turn in a correction in the opposite way a few seconds later, resulting in crap measurements because of irregular but valid source.
If the actual drift is in the [-tolerance +tolerance] range, better don't correct it.
Referenced by IDriverContext::~IDriverContext().
|
pure virtual |
Gets the suggested drift correction sample count.
- Returns
- the suggested drift correction sample count
In case you don't want to manage how much samples should be used to correct the drift, you could simply use this function. The algorithm used to compute the returned value should be considered as undefined. This computation could change over time and versions of OpenViBE. That means the driver should not make any assumption on the way of computing the actual value returned by this function.
Referenced by IDriverContext::~IDriverContext().
|
pure virtual |
Corrects a drifting device.
- Returns
- true in case of success
- false in case of error
Some devices don't sent the number of samples they promised to while requesting sampling rate. This can be for multiple reasons but the most probable one is that the device does not have its internal clock synchronized with the internal computer clock. OpenViBE data being dated with a start / end time, it is important for synchronisation purpose that all the theorical number of samples per second is preserved.
In case the difference between the theorical number of samples this driver should have sent so far and the number of samples it actually sent becomes too big, this function helps to correct the drifting, removing or adding dummy samples. In a strict signal processing point of view those samples can't be considered as valid. However, this is the only way to guarantee that the timings are preserved.
- Note
- Passing a negative value removes samples
- Passing a positive value adds samples
- Passing 0 does nothing
- This function can be called several times if needed but does not change what getDriftSampleCount returns until the next IDriver::loop execution
- Warning
- Please be careful when calling this function. Consider the fact that there could be some drifting in the device and ths OS-level driver itself, or even in the communication pipeline to the prorprietary acquisition software. As an OpenViBE driver developer, you should allow an arbitrary small drifting (which range depends of the actual driver you are creating).
Referenced by IDriverContext::~IDriverContext().
|
pure virtual |
Sets a fixed latency due to the driver implementation and / or hardware.
- Parameters
-
i64SampleCount [in] : the number of samples for the inner latency
- Returns
- true in case of success
- false in case of error
Some drivers / hardware devices implement processes that delay the overall acquisition stream. Such processes include for instance sample buffering or temporal filtering. The delay induced by these processes can not be known by the acquisition server in a generic way and are usually not provided by the device manufacturer. An intelligent setup based on hardware tagging could however induce a fair estimate of this latency so that it can be injected in the drift correction process. Driver developers will generally not have to care about this feature. However, if it is important to have neurophysiologically relevant measures (more particularly on ERPs) and it is know that the driver and / or hardware has a latency, this latency compensation can be injected in the drift correction process using the aforementionned function.
- Note
- Passing a positive value supposes the driver / hardware induce a delay which shall be corrected
- Passing a negative value supposes the driver / hardware is able to predict and send future measures before they actually get measured (probably not recommended)
- Passing 0 supposes both the driver and hardware are ideals and send samples immediately to the acquisition server as they happen on the scalp
- Default configuration supposes both the driver and hardware are ideal, thus sets the inner latency to 0
- See also
- getInnerLatencySampleCount
Referenced by IDriverContext::~IDriverContext().
|
pure virtual |
Gets the fixed latency due to the driver implementation and / or hardware.
- Returns
- The inner latency of the driver in sample count
- See also
- setInnerLatencySampleCount
Referenced by IDriverContext::~IDriverContext().
|
pure virtual |
Updates impedance for a specific channel.
- Parameters
-
ui32ChannelIndex [in] : the index of the channel should be updated f64Impedance [in] : the impedance of the specified channel (in ohm)
- Returns
- true in case of success.
- false in case of error.
This can be used during initialization phase to check if impedances are correct. This function should be connected while the driver is initialized and not started.
If f64Impedance is -1, then the impedance is considered as "unknown / measuring" If f64Impedance is -2, then the impedance is considered as "unknown / not available" If f64Impedance is any other negative value, then the impedance is considered as "unknown"
Referenced by IDriverContext::~IDriverContext().
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