type TSignalRateConverter = class(TSignal);
Changes the sampling frequency by any integer or rational factor.
The output sampling frequency is f_(s,out) = Factor* f_(s,in), so a continuous tone at f_0 keeps its absolute frequency in Hz while its normalised frequency f_0/f_s becomes f_0/(Factor* f_s). The aliasing-free band reaches up to min(f_(s,in),f_(s,out))/2.
This component makes use of TSignalDecimator, TSignalInterpolator
and TBandlimitedInterpolator for fast (real time) rate conversion. The quality of the rate conversion depends upon the floating point precision. With single precision no more then 80dB SNR (Signal to noise ratio) can be obtained. Double precision allows SNR up to 180 dB. The limiting factor is the quality of the bandlimited interpolation. Bandlimited interpolation is used only, if the factor is not an integer power of two. Bandlimited interpolation with SNR of 80dB requires about 5x more CPU then simple power of two interpolation. Very high SNR up to 160dB may increase the required processing power by further 3x. (which may no longer be real time)
If explicit multi-rate filtering is desired the TSignalFilter component should be used where the UpSample and DownSample factors and filter type can be defined explicitely.
Properties
| Name | Type | Description |
|---|---|---|
| Active | Boolean | Set active to false to suppress the propagation of the Pull request and the subsequent call to the Update method. |
| AudioSignal | Boolean | Enable when the signal processed is Audio signal. |
| BandWidth | Double | Return the bandwidth of the signal. |
| BandwidthH | Double | Returns the upper bandwidth edge of the signal. |
| BandwidthL | Double | Returns the lower bandwidth edge of the signal. |
| BlockAssign | Boolean | Block streaming of specific properties when storing only a "template". |
| ChannelCount | Integer | Get or set the number of channels multiplexed in the data property. |
| Complex | Boolean | Set this property to true, to request computation using complex numbers. |
| Continuous | Boolean | If True, the component will pass on the udpate request to the connected component. |
| Data | TVec | Stores the result of the processing. |
| Dt | Double | Time between two consecutive samples. |
| EditorActive | Boolean | Returns True, if the component editor is displayed. |
| Factor | Double | Factor by which to change the sampling frequency of the signal connected to the Input property. |
| FilterDelay | Double | Returns the filter delay in number of samples of the final sampling frequency. |
| FloatPrecision | TMtxFloatPrecision | Set this property to request computation in 32bit/64bit precision with real/complex numbers. |
| FloatPrecisionLock | Boolean | Set this property to true to lock changes to FloatPrecision property. |
| HalfBand | Boolean | The bandwidth will be halved during downsampling. |
| HzRes | Double | Frequency resolution obtained, if an FFT algorithm would be run on the data. |
| Input | TAnalysis | Connector property to obtain a pointer to the TSignal component holding the data to be processed. |
| IsDouble | Boolean | Set this property to false, to request computation in 32bit floating point precision, 64bit, if true. |
| Item | Double | Default property to access values of a real signal. |
| ItemNumber | Integer | Number to label the object when it is an item in the List. |
| Length | Integer | Get or set the length of the signal in samples. |
| Marks | TMarkList | Stores the time stamps and amplitude of selected samples. |
| MaxAmplt | Double | Stores the maximum amplitude of the signal found by the MinMax method. |
| MaxX | Double | Use the MaxX property to store the time stamp (in seconds) of the right most sample. |
| MinAmplt | Double | Stores the minimum amplitude of the signal found by the MinMax method. |
| MinX | Double | Use the MinX property to store the time stamp of the left-most sample. |
| OnAfterUpdate | TNotifyEvent | The event is triggered after the call to the Update method. |
| OnBeforeUpdate | TNotifyEvent | The event is triggered just before the call to the Update method. |
| OnDisplayUpdate | TNotifyEvent | The event is triggered after the OnAfterUpdate event. Use this event to update any associated charts or graphs or result tables. |
| OnGetInput | TNotifyEvent | If the Input property is not assigned, the component will call OnGetInput. |
| OnNotifyUpdate | TNotifyEvent | The event is called after a call to InternalUpdate, OnAfterUpdate and OnDisplayUpdate from within the Update method. |
| OnParameterUpdate | TNotifyEvent | The event is triggered when ParamUpdate method is called. The ParamUpdate method is usually called by component editors when a value was changed by the user and the editor was "Live". |
| PipeState | TPipeState | Returns the state of the pipe after the last update. |
| Reference | TReferenceList | Stores a list of components that have to be notified, when this component is destroyed. |
| Ripple | Double | Defines the ripple of the passband and of the stopband of the FIR lowpass filter used for interpolation. |
| SamplingFrequency | Double | Defines the sampling frequency of the signal. |
| SamplingTime | Double | The length of the signal in seconds. |
| ScaleFactor | Double | Additional scaling factor which is applied without extra performance cost. |
| SuspendNotifyUpdate | Boolean | Set this property to True, to prevent calling OnNotifyUpdate from the Update Method. |
| TransBW | Double | Defines the width of the transition band of the FIR filter used for interpolation/decimation. |
| UsesInputs | Boolean | Set it to True to indicate, that valid signals will be connected to the Input or Inputs properties. |
Methods
| Name | Description |
|---|---|
| AllowStreaming | Returns the negatated value of BlockAssign. |
| Append | Appends Sample to the end of the signal. |
| Assign | Assign values of all published properties from Source. |
| AssignTemplate | Assign values of "template-like" published properties from Source. |
| Copy | Copies signal Data and sampling frequency information. |
| Crest | Compute the CREST parameter. |
| EditorClass | To be overriden in descendanr classses. |
| Initialize | Initializes filtering structures after Factor and other properties have been set. |
| InputsDirty | If all Inputs[i] are dirty the function returns true. |
| InternalPull | When called, the method will pass Update requests recursively to all connected objects. |
| Invalidate | Notifies all connected components that this component has fresh data. |
| LoadFromStream | Load the component from Src stream. |
| LoadTemplateFromFile | Load a template from file. |
| LoadTemplateFromStream | Load a template from stream. |
| MarksToStrings | Convert marks to strings. |
| MinMax | Find minimum and maximum amplitude and store the result in the MinAmplt and MaxAmplt properties. |
| ParamUpdate | The method can be assigned to some other component even handler, as a notification that a parameter has changed and that Self should consider a recalculation. |
| Peak | Find the maximum deviation of the signal from its mean value. |
| PipeReset | Recursively processes all connected components backward and calls Reset method. |
| Pull | Request recalculation of the entire chain of all connected components. |
| PullUntilEnd | Calls Pull until pipeEnd is returned. |
| Reset | Reset all delay lines. |
| SaveTemplateToFile | Save template to file. |
| SaveTemplateToStream | Save template to stream. |
| SaveToStream | Save the component to Dst stream. |
| Size | Assign the size of the signal from Src. |
| Update | Request recalculation of the data and place the result in Self. |
| UpdateNotify | Call this method only, if SuspendNotifyUpdate is True. |
| ValuesToStrings | Convert values to strings. |