Various EEG File Formats and ConventionsDocumented by Paul Bourke
NeuroScan EEG File FormatsApril 1997, updated September 1997The following documents the file structure for continuous EEG files as created by SCAN version 4 (the files are still reported as version 3 as the format hasn't changed). Experience has shown that many (most) of the fields are not filled out correctly by the software. In particular, the best way to work out the number of samples is
Average EEG To calculate the expected number of samples from the file size
Sample code to convert average files to ascii, avg2ascii.c sethead.h The following is my version of the "sethead.h" file, designed to make implementations on other machines easier, namely "other-endian" machines. Note that character fields are single byte, longs are 4 bytes, floats are 4 bytes IEEE format, short ints are 2 bytes.
typedef struct { /* Electrode structure ------------------- */
char lab[10]; /* Electrode label - last bye contains NULL */
char reference; /* Reference electrode number */
char skip; /* Skip electrode flag ON=1 OFF=0 */
char reject; /* Artifact reject flag */
char display; /* Display flag for 'STACK' display */
char bad; /* Bad electrode flag */
unsigned short int n; /* Number of observations */
char avg_reference; /* Average reference status */
char ClipAdd; /* Automatically add to clipboard */
float x_coord; /* X screen coord. for 'TOP' display */
float y_coord; /* Y screen coord. for 'TOP' display */
float veog_wt; /* VEOG correction weight */
float veog_std; /* VEOG std dev. for weight */
float snr; /* signal-to-noise statistic */
float heog_wt; /* HEOG Correction weight */
float heog_std; /* HEOG Std dev. for weight */
short int baseline; /* Baseline correction value in raw ad units*/
char Filtered; /* Toggel indicating file has be filtered */
char Fsp; /* Extra data */
float aux1_wt; /* AUX1 Correction weight */
float aux1_std; /* AUX1 Std dev. for weight */
float sensitivity; /* electrode sensitivity */
char Gain; /* Amplifier gain */
char HiPass; /* Hi Pass value */
char LoPass; /* Lo Pass value */
unsigned char Page; /* Display page */
unsigned char Size; /* Electrode window display size */
unsigned char Impedance; /* Impedance test */
unsigned char PhysicalChnl; /* Physical channel used */
char Rectify; /* Free space */
float calib; /* Calibration factor */
} ELECTLOC;
typedef struct{
char rev[20]; /* Revision string */
char type; /* File type AVG=1, EEG=0 */
char id[20]; /* Patient ID */
char oper[20]; /* Operator ID */
char doctor[20]; /* Doctor ID */
char referral[20]; /* Referral ID */
char hospital[20]; /* Hospital ID */
char patient[20]; /* Patient name */
short int age; /* Patient Age */
char sex; /* Patient Sex Male='M', Female='F' */
char hand; /* Handedness Mixed='M',Rt='R', lft='L' */
char med[20]; /* Medications */
char classif[20]; /* Classification */
char state[20]; /* Patient wakefulness */
char label[20]; /* Session label */
char date[10]; /* Session date string */
char time[12]; /* Session time strin */
float mean_age; /* Mean age (Group files only) */
float stdev; /* Std dev of age (Group files only) */
short int n; /* Number in group file */
char compfile[38]; /* Path and name of comparison file */
float SpectWinComp; /* Spectral window compensation factor */
float MeanAccuracy; /* Average respose accuracy */
float MeanLatency; /* Average response latency */
char sortfile[46]; /* Path and name of sort file */
long NumEvents; /* Number of events in eventable */
char compoper; /* Operation used in comparison */
char avgmode; /* Set during online averaging */
char review; /* Set during review of EEG data */
short unsigned nsweeps; /* Number of expected sweeps */
short unsigned compsweeps; /* Number of actual sweeps */
short unsigned acceptcnt; /* Number of accepted sweeps */
short unsigned rejectcnt; /* Number of rejected sweeps */
short unsigned pnts; /* Number of points per waveform */
short unsigned nchannels; /* Number of active channels */
short unsigned avgupdate; /* Frequency of average update */
char domain; /* Acquisition domain TIME=0, FREQ=1 */
char variance; /* Variance data included flag */
unsigned short rate; /* D-to-A rate */
double scale; /* scale factor for calibration */
char veogcorrect; /* VEOG corrected flag */
char heogcorrect; /* HEOG corrected flag */
char aux1correct; /* AUX1 corrected flag */
char aux2correct; /* AUX2 corrected flag */
float veogtrig; /* VEOG trigger percentage */
float heogtrig; /* HEOG trigger percentage */
float aux1trig; /* AUX1 trigger percentage */
float aux2trig; /* AUX2 trigger percentage */
short int heogchnl; /* HEOG channel number */
short int veogchnl; /* VEOG channel number */
short int aux1chnl; /* AUX1 channel number */
short int aux2chnl; /* AUX2 channel number */
char veogdir; /* VEOG trigger direction flag */
char heogdir; /* HEOG trigger direction flag */
char aux1dir; /* AUX1 trigger direction flag */
char aux2dir; /* AUX2 trigger direction flag */
short int veog_n; /* Number of points per VEOG waveform */
short int heog_n; /* Number of points per HEOG waveform */
short int aux1_n; /* Number of points per AUX1 waveform */
short int aux2_n; /* Number of points per AUX2 waveform */
short int veogmaxcnt; /* Number of observations per point - VEOG */
short int heogmaxcnt; /* Number of observations per point - HEOG */
short int aux1maxcnt; /* Number of observations per point - AUX1 */
short int aux2maxcnt; /* Number of observations per point - AUX2 */
char veogmethod; /* Method used to correct VEOG */
char heogmethod; /* Method used to correct HEOG */
char aux1method; /* Method used to correct AUX1 */
char aux2method; /* Method used to correct AUX2 */
float AmpSensitivity; /* External Amplifier gain */
char LowPass; /* Toggle for Amp Low pass filter */
char HighPass; /* Toggle for Amp High pass filter */
char Notch; /* Toggle for Amp Notch state */
char AutoClipAdd; /* AutoAdd on clip */
char baseline; /* Baseline correct flag */
float offstart; /* Start point for baseline correction */
float offstop; /* Stop point for baseline correction */
char reject; /* Auto reject flag */
float rejstart; /* Auto reject start point */
float rejstop; /* Auto reject stop point */
float rejmin; /* Auto reject minimum value */
float rejmax; /* Auto reject maximum value */
char trigtype; /* Trigger type */
float trigval; /* Trigger value */
char trigchnl; /* Trigger channel */
short int trigmask; /* Wait value for LPT port */
float trigisi; /* Interstimulus interval (INT trigger) */
float trigmin; /* Min trigger out voltage (start of pulse)*/
float trigmax; /* Max trigger out voltage (during pulse) */
char trigdir; /* Duration of trigger out pulse */
char Autoscale; /* Autoscale on average */
short int n2; /* Number in group 2 (MANOVA) */
char dir; /* Negative display up or down */
float dispmin; /* Display minimum (Yaxis) */
float dispmax; /* Display maximum (Yaxis) */
float xmin; /* X axis minimum (epoch start in sec) */
float xmax; /* X axis maximum (epoch stop in sec) */
float AutoMin; /* Autoscale minimum */
float AutoMax; /* Autoscale maximum */
float zmin; /* Z axis minimum - Not currently used */
float zmax; /* Z axis maximum - Not currently used */
float lowcut; /* Archival value - low cut on external amp*/
float highcut; /* Archival value - Hi cut on external amp */
char common; /* Common mode rejection flag */
char savemode; /* Save mode EEG AVG or BOTH */
char manmode; /* Manual rejection of incomming data */
char ref[10]; /* Label for reference electode */
char Rectify; /* Rectification on external channel */
float DisplayXmin; /* Minimun for X-axis display */
float DisplayXmax; /* Maximum for X-axis display */
char phase; /* flag for phase computation */
char screen[16]; /* Screen overlay path name */
short int CalMode; /* Calibration mode */
short int CalMethod; /* Calibration method */
short int CalUpdate; /* Calibration update rate */
short int CalBaseline; /* Baseline correction during cal */
short int CalSweeps; /* Number of calibration sweeps */
float CalAttenuator; /* Attenuator value for calibration */
float CalPulseVolt; /* Voltage for calibration pulse */
float CalPulseStart; /* Start time for pulse */
float CalPulseStop; /* Stop time for pulse */
float CalFreq; /* Sweep frequency */
char taskfile[34]; /* Task file name */
char seqfile[34]; /* Sequence file path name */
char SpectMethod; /* Spectral method */
char SpectScaling; /* Scaling employed */
char SpectWindow; /* Window employed */
float SpectWinLength; /* Length of window % */
char SpectOrder; /* Order of Filter for Max Entropy method */
char NotchFilter; /* Notch Filter in or out */
char unused[11]; /* Free space */
short FspStopMethod; /* FSP - Stoping mode */
short FspStopMode; /* FSP - Stoping mode */
float FspFValue; /* FSP - F value to stop terminate */
short int FspPoint; /* FSP - Single point location */
short int FspBlockSize; /* FSP - block size for averaging */
unsigned short FspP1; /* FSP - Start of window */
unsigned short FspP2; /* FSP - Stop of window */
float FspAlpha; /* FSP - Alpha value */
float FspNoise; /* FSP - Signal to ratio value */
short int FspV1; /* FSP - degrees of freedom */
char montage[40]; /* Montage file path name */
char EventFile[40]; /* Event file path name */
float fratio; /* Correction factor for spectral array */
char minor_rev; /* Current minor revision */
short int eegupdate; /* How often incomming eeg is refreshed */
char compressed; /* Data compression flag */
float xscale; /* X position for scale box - Not used */
float yscale; /* Y position for scale box - Not used */
float xsize; /* Waveform size X direction */
float ysize; /* Waveform size Y direction */
char ACmode; /* Set SYNAP into AC mode */
unsigned char CommonChnl; /* Channel for common waveform */
char Xtics; /* Scale tool- 'tic' flag in X direction */
char Xrange; /* Scale tool- range (ms,sec,Hz) flag X dir*/
char Ytics; /* Scale tool- 'tic' flag in Y direction */
char Yrange; /* Scale tool- range (uV, V) flag Y dir */
float XScaleValue; /* Scale tool- value for X dir */
float XScaleInterval; /* Scale tool- interval between tics X dir */
float YScaleValue; /* Scale tool- value for Y dir */
float YScaleInterval; /* Scale tool- interval between tics Y dir */
float ScaleToolX1; /* Scale tool- upper left hand screen pos */
float ScaleToolY1; /* Scale tool- upper left hand screen pos */
float ScaleToolX2; /* Scale tool- lower right hand screen pos */
float ScaleToolY2; /* Scale tool- lower right hand screen pos */
short int port; /* Port address for external triggering */
long NumSamples; /* Number of samples in continous file */
char FilterFlag; /* Indicates that file has been filtered */
float LowCutoff; /* Low frequency cutoff */
short int LowPoles; /* Number of poles */
float HighCutoff; /* High frequency cutoff */
short int HighPoles; /* High cutoff number of poles */
char FilterType; /* Bandpass=0 Notch=1 Highpass=2 Lowpass=3 */
char FilterDomain; /* Frequency=0 Time=1 */
char SnrFlag; /* SNR computation flag */
char CoherenceFlag; /* Coherence has been computed */
char ContinousType; /* Method used to capture events in *.cnt */
long EventTablePos; /* Position of event table */
float ContinousSeconds; /* Number of seconds to displayed per page */
long ChannelOffset; /* Block size of one channel in SYNAMPS */
char AutoCorrectFlag; /* Autocorrect of DC values */
unsigned char DCThreshold; /* Auto correct of DC level */
} SETUP;
typedef struct {
char Teeg; /* Either 1 or 2 */
long Size; /* Total length of all the events */
long Offset; /* Hopefully always 0 */
} TEEG;
typedef struct {
unsigned short StimType; /* range 0-65535 */
unsigned char KeyBoard; /* range 0-11 corresponding to fcn keys +1 */
char KeyPad_Accept; /* 0->3 range 0-15 bit coded response pad */
/* 4->7 values 0xd=Accept 0xc=Reject */
long Offset; /* file offset of event */
} EVENT1;
typedef struct{
unsigned short StimType; /* range 0-65535 */
unsigned char KeyBoard; /* range 0-11 corresponding to fcn keys +1 */
char KeyPad_Accept; /* 0->3 range 0-15 bit coded response pad */
/* 4->7 values 0xd=Accept 0xc=Reject */
long Offset; /* file offset of event */
short Type;
short Code;
float Latency;
char EpochEvent;
char Accept2;
char Accuracy;
} EVENT2;
Electrode position as used by Brain Dynamics Laboratory, 1996/1997
Westmead EEG file formatAugust 1997The following describes the important aspects of the EEG data files from the Department of Medical Physics and Cognitive Neuroscience Unit, Westmead Hospital, Westmead, NSW 2145, Australia. The files consist a ID line followed by a header followed by the actual data section. The ID and header is ascii/readable text while the EEG data is binary, simply a series of 2 byte signed ints (usually referred to in C as "short int"). Note that while the files have an ASCII header they must be FTPed or otherwise transferred in binary mode to preserve the EEG data part. While the mixed ASCII/BINARY nature makes dealing with these files a bit awkward at times, it is often convenient to browse the header using a text editor or just using "more".
Basic C source code that takes a Westmead EEG file and converts it into an ascii file is given here: westmead2ascii.c. It can be readily modified and used as the basis of a converter to meet you specific needs. Electrode positions as used by Westmead Hospital, 1995 -> 1999.
ASCII format for EEG signalsSeptember 1997The file consists of two header lines followed by the data. The first header line has 4 constants, the number of channels, the sampling frequency (Hz), the number of events, and the number of samples. The second header line consists of the column names for the data that follows. If the data is raw EEG signals then the columns should be the electrode names. The first two columns of the data section are predefined, they are the sample number and the event code. The remaining columns contain the samples from each channel (electrode).
Note:
The first few representative lines of such a file might look like this:
62 500 0 1000 sample event FP1 FPZ FP2 F3A F4A F7 F5 F3 F1 FZ F2 F4 F6 F8 C5A C3A . . . 0 0 -1746 -1717 -1716 -1710 -1676 -1528 -1738 -1493 -1736 -1324 -1432 . . . 1 0 -1962 -1891 -1988 -1864 -1717 -1663 -1853 -1583 -1746 -1378 -1505 . . . 2 0 -2112 -1952 -2128 -1936 -1688 -1748 -1867 -1612 -1786 -1394 -1548 . . . 3 0 -2063 -1857 -2032 -1853 -1600 -1694 -1774 -1547 -1802 -1373 -1535 . . . 4 0 -1767 -1595 -1697 -1551 -1438 -1433 -1552 -1406 -1688 -1296 -1437 . . . 5 0 -1315 -1222 -1229 -1128 -1219 -1032 -1196 -1176 -1430 -1172 -1281 . . . 6 0 -898 -887 -822 -802 -1062 -683 -838 -976 -1144 -1067 -1148 -1139 . . . 7 0 -757 -799 -692 -772 -1042 -571 -676 -940 -1051 -1079 -1143 -1147 . . . : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : :
Electrocap CoordinatesCompiled by Per LineJanuary 1997
 International 10-20 electrode position standard.
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