public:user_software:cr-tools:datareader

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public:user_software:cr-tools:datareader [2011-10-18 11:56] – created Lars Bahrenpublic:user_software:cr-tools:datareader [2017-03-08 15:27] (current) – external edit 127.0.0.1
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     * [[#Performance]]     * [[#Performance]]
   * [[#Development]]   * [[#Development]]
 +  * [[#Usage with C/C++ code]]
  
 ==== Overview ==== ==== Overview ====
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 The [[lopesdoxy>classDataReader.html|DataReader]] handles progression through the data volume via a set of [[DataIterator]] objects, providing //N// positions for //N// data streams. These stream- and position pointers allow a variety of access schemes: The [[lopesdoxy>classDataReader.html|DataReader]] handles progression through the data volume via a set of [[DataIterator]] objects, providing //N// positions for //N// data streams. These stream- and position pointers allow a variety of access schemes:
   * Access to the same segment in multiple streams, e.g. when reading raw data recorded with the //LOFAR ITS//.   * Access to the same segment in multiple streams, e.g. when reading raw data recorded with the //LOFAR ITS//.
-{{software:packages:lopes-tools:tools:DataReader stream navigation 01.png?300|DataReader stream navigation, example 1}}+{{DataReader stream navigation 01.png?300|DataReader stream navigation, example 1}}
   * Access to different segments in multiple streams   * Access to different segments in multiple streams
-{{software:packages:lopes-tools:tools:DataReader stream navigation 02.png?300|DataReader stream navigation, example 2}}+{{DataReader stream navigation 02.png?300|DataReader stream navigation, example 2}}
   * Access to different segments withhin a single stream, e.g. when reading data from a [[lopesdoxy>classLopesEvent.html|LopesEvent]] file.   * Access to different segments withhin a single stream, e.g. when reading data from a [[lopesdoxy>classLopesEvent.html|LopesEvent]] file.
-{{software:packages:lopes-tools:tools:DataReader stream navigation 03.png?300|DataReader stream navigation, example 3}}+{{DataReader stream navigation 03.png?300|DataReader stream navigation, example 3}}
  
 === Data flow === === Data flow ===
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 The figure below illustrates the data flow inside the DataReader: The figure below illustrates the data flow inside the DataReader:
  
-{{software:packages:lopes-tools:tools:DataReader data flow.png?550|Data flow inside the DataReader}}+{{DataReader data flow.png?550|Data flow inside the DataReader}}
  
 There is the option to insert a [[.Hanning Filter|Hanning Filter]] step before performing the Fourier transform; this can be used to reduce the sidelobes in the frequency domain, originating from cutting out a block of data (which is equivalent to the multiplication of the data with a box function).  There is the option to insert a [[.Hanning Filter|Hanning Filter]] step before performing the Fourier transform; this can be used to reduce the sidelobes in the frequency domain, originating from cutting out a block of data (which is equivalent to the multiplication of the data with a box function). 
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 ==== Internal data initialization ==== ==== Internal data initialization ====
  
-{{software:packages:lopes-tools:modules:datareader_init_sequence.png?550}}+{{datareader_init_sequence.png?550}}
  
-===== Usage =====+==== Usage with C/C++ code ====
  
-==== ... with C/C++ code ==== +  - Creation of a new DataReader object: <code cpp>
- +
-=== Usage within an application === +
- +
-<code cpp>+
 #include <lopes/IO/DataReader.h> #include <lopes/IO/DataReader.h>
 #include <lopes/Data/LopesEvent.h> #include <lopes/Data/LopesEvent.h>
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 LopesEvent *le = new LopesEvent (eventfile,      // location the LopesEvent file LopesEvent *le = new LopesEvent (eventfile,      // location the LopesEvent file
                                  blocksize,      // nof. samples per block of data                                  blocksize,      // nof. samples per block of data
-                                 adc2voltage,    // conversion weights: ADC values to voltages [optional] +                                 adc2voltage,    // conversion weights [optional] 
-                                 fft2calfft);    // calibration weights: raw to calibrated FFT [optional]+                                 fft2calfft);    // calibration weights [optional]
 dr = le; dr = le;
- +</code> With the conversion arrays optional you can even use the simpler construction method: <code cpp> 
-// processing of the data+LopesEvent *le = new LopesEvent (eventfile,      // location the LopesEvent file 
 +                                 blocksize)      // nof. samples per block of data 
 +</code> 
 +  - Reading in data for processing: <code cpp>
 for (int block(0); block<nofBlocks; block++) { for (int block(0); block<nofBlocks; block++) {
   fft = dr->fft();   fft = dr->fft();
 } }
 </code> </code>
- +  - Data selection: Selection of frequency channels and antennas can be performed directly within the DataReader, e.g. <code cpp>
-With the conversion arrays optional you can even use the simpler construction method +
-<code cpp> +
-LopesEvent *le = new LopesEvent (eventfile,      // location the LopesEvent file +
-                                 blocksize)      // nof. samples per block of data +
-</code> +
- +
-=== Data selection === +
- +
-Selection of frequency channels and antennas can be performed directly within the DataReader, e.g.  +
-<code cpp>+
     dr->setSelectedChannels (selection);     dr->setSelectedChannels (selection);
-</code> +</code> where ''selection'' is an array of boolians of length ''fftLength''.
-where ''selection'' is an array of boolians of length ''fftLength''.+
  
-{{software:packages:lopes-tools:tools:.datareader_-_channel_selection.png?550|Selection of frequency channels in the FFT}}+{{datareader_-_channel_selection.png?550|Selection of frequency channels in the FFT}}
  
 +\\
 +----
 +<- [[public:user software:User Software]] • [[public:user software:CR-Tools]]
  • Last modified: 2011-10-18 11:56
  • by Lars Bahren