Improve examples, fix typos

Author: tstenner

examples/CMakeLists.txt

@@ -36,6 +36,7 @@ addlslexample(ReceiveDataInChunks cpp)
 addlslexample(ReceiveDataSimple cpp)
 addlslexample(ReceiveStringMarkers cpp)
 addlslexample(ReceiveStringMarkersC c)
+addlslexample(SendData cpp)
 addlslexample(SendDataC c)
 addlslexample(SendDataInChunks cpp)
 addlslexample(SendDataSimple cpp)

examples/ReceiveDataC.c

@@ -5,21 +5,28 @@
  * Example program that demonstrates how to resolve a specific stream on the lab network and how to
  * connect to it in order to receive data.
  */
+#define NCHANS 8
+
 
 int main(int argc, char *argv[]) {
 
 	unsigned k, t;		 /* channel index */
 	lsl_streaminfo info; /* the streaminfo returned by the resolve call */
 	lsl_inlet inlet;	 /* a stream inlet to get samples from */
 	int errcode;		 /* error code (lsl_lost_error or timeouts) */
-	float cursample[8];	 /* array to hold our current sample */
+	float cursample[NCHANS]; /* array to hold our current sample */
 	double timestamp;	 /* time stamp of the current sample (in sender time) */
 
 	/* resolve the stream of interest (result array: info, array capacity: 1 element, type shall be
 	 * EEG, resolve at least 1 stream, wait forever if necessary) */
 	printf("Now waiting for an EEG stream...\n");
 	lsl_resolve_byprop(&info, 1, "type", "EEG", 1, LSL_FOREVER);
 
+	/* These next two variables aren't used for anything in this example.
+	 * They simply demonstrate how to use streaminfo getters. */
+	lsl_channel_format_t fmt = lsl_get_channel_format(info);
+	double srate = lsl_get_nominal_srate(info);
+
 	/* make an inlet to read data from the stream (buffer max. 300 seconds of data, no preference
 	 * regarding chunking, automatic recovery enabled) */
 	inlet = lsl_create_inlet(info, 300, LSL_NO_PREFERENCE, 1);
@@ -33,9 +40,10 @@ int main(int argc, char *argv[]) {
 	for (t = 0; t < 100000000; t++) {
 		/* get the next sample form the inlet (read into cursample, 8 values, wait forever if
 		 * necessary) and return the timestamp if we got something */
-		timestamp = lsl_pull_sample_f(inlet, cursample, 8, LSL_FOREVER, &errcode);
+		timestamp = lsl_pull_sample_f(inlet, cursample, NCHANS, LSL_FOREVER, &errcode);
 
 		/* print the data */
+		printf("%.2f", timestamp);
 		for (k = 0; k < 8; ++k) printf("\t%.2f", cursample[k]);
 		printf("\n");
 	}

examples/ReceiveDataInChunks.cpp

@@ -8,14 +8,21 @@
 int main(int argc, char **argv) {
 	std::cout << "ReceiveDataInChunks" << std::endl;
 	std::cout << "ReceiveDataInChunks StreamName max_buflen flush" << std::endl;
+	std::cout << "- max_buffered -- duration in sec (or x100 samples if samplerate is 0) to buffer "
+				 "in the receiver"
+			  << std::endl;
+	std::cout
+		<< "- flush -- set non-zero to flush data instead of pulling; useful for testing throughput"
+		<< std::endl;
 
 	try {
 
 		std::string name{argc > 1 ? argv[1] : "MyAudioStream"};
-		int32_t max_buflen = argc > 2 ? std::stol(argv[2]) : 360;
+		double max_buffered = argc > 2 ? std::stod(argv[2]) : 360.;
 		bool flush = argc > 3;
 		// resolve the stream of interest & make an inlet
-		lsl::stream_inlet inlet(lsl::resolve_stream("name", name).at(0), max_buflen);
+		lsl::stream_info inlet_info = lsl::resolve_stream("name", name).at(0);
+		lsl::stream_inlet inlet(inlet_info, max_buffered);
 
 		// Use set_postprocessing to get the timestamps in a common base clock.
 		// Do not use if this application will record timestamps to disk -- it is better to 

examples/ReceiveDataSimple.cpp

@@ -1,3 +1,4 @@
+#include <iostream>
 #include <lsl_cpp.h>
 #include <vector>
 
@@ -16,7 +17,10 @@ int main(int argc, char **argv) {
 
 	// receive data & time stamps forever (not displaying them here)
 	std::vector<float> sample;
-	while (true) inlet.pull_sample(sample);
+	while (true) {
+		double timestamp = inlet.pull_sample(sample);
+		std::cout << timestamp << "\t" << sample[0] << "\t" << sample[1] << "..." << std::endl;
+	}
 
 	return 0;
 }

examples/SendData.cpp

@@ -1,8 +1,9 @@
 #include "lsl_cpp.h"
+#include <array>
+#include <chrono>
 #include <iostream>
 #include <stdlib.h>
-#include <time.h>
-using namespace std;
+#include <thread>
 
 /**
  * This example program offers an 8-channel stream, float-formatted, that resembles EEG data.
@@ -16,54 +17,73 @@ using namespace std;
 const char *channels[] = {"C3", "C4", "Cz", "FPz", "POz", "CPz", "O1", "O2"};
 
 int main(int argc, char *argv[]) {
-	string name, type;
-	if (argc != 3) {
-		cout << "This opens a stream under some user-defined name and with a user-defined content "
-				"type."
-			 << endl;
-		cout << "Please enter the stream name and the stream type (e.g. \"BioSemi EEG\" (without "
-				"the quotes)):"
-			 << endl;
-		cin >> name >> type;
+	std::string name, type;
+	if (argc < 3) {
+		std::cout
+			<< "This opens a stream under some user-defined name and with a user-defined content "
+			   "type."
+			<< std::endl;
+		std::cout << "SendData Name Type [n_channels=8] [srate=100] [max_buffered=360]"
+				  << std::endl;
+		std::cout
+			<< "Please enter the stream name and the stream type (e.g. \"BioSemi EEG\" (without "
+			   "the quotes)):"
+			<< std::endl;
+		std::cin >> name >> type;
 	} else {
 		name = argv[1];
 		type = argv[2];
 	}
+	int n_channels = argc > 3 ? std::stol(argv[3]) : 8;
+	n_channels = n_channels < 8 ? 8 : n_channels;
+	int samplingrate = argc > 4 ? std::stol(argv[4]) : 100;
+	int max_buffered = argc > 5 ? std::stol(argv[5]) : 360;
 
 	try {
 
 		// make a new stream_info (100 Hz)
-		lsl::stream_info info(name, type, 8, 100, lsl::cf_float32, string(name) += type);
+		lsl::stream_info info(
+			name, type, n_channels, samplingrate, lsl::cf_float32, std::string(name) += type);
 
 		// add some description fields
-		info.desc().append_child_value("manufacturer", "BioSemi");
+		info.desc().append_child_value("manufacturer", "LSL");
 		lsl::xml_element chns = info.desc().append_child("channels");
-		for (int k = 0; k < 8; k++)
+		for (int k = 0; k < n_channels; k++)
 			chns.append_child("channel")
-				.append_child_value("label", channels[k])
+				.append_child_value("label", k < 8 ? channels[k] : "Chan-" + std::to_string(k + 1))
 				.append_child_value("unit", "microvolts")
-				.append_child_value("type", "EEG");
+				.append_child_value("type", type);
 
 		// make a new outlet
-		lsl::stream_outlet outlet(info);
+		lsl::stream_outlet outlet(info, 0, max_buffered);
+		std::vector<float> sample(n_channels, 0.0);
+
+		// Your device might have its own timer. Or you can decide how often to poll
+		//  your device, as we do here.
+		int32_t sample_dur_us = 1000000 / (samplingrate > 0 ? samplingrate : 100);
+		auto t_start = std::chrono::high_resolution_clock::now();
+		auto next_sample_time = t_start;
 
 		// send data forever
-		cout << "Now sending data... " << endl;
+		std::cout << "Now sending data... " << std::endl;
 		double starttime = ((double)clock()) / CLOCKS_PER_SEC;
 		for (unsigned t = 0;; t++) {
-
-			// wait a bit and create random data
-			while (((double)clock()) / CLOCKS_PER_SEC < starttime + t * 0.01)
-				;
-			float sample[8];
+			// Create random data for the first 8 channels.
 			for (int c = 0; c < 8; c++) sample[c] = (float)((rand() % 1500) / 500.0 - 1.5);
+			// For the remaining channels, fill them with a sample counter (wraps at 1M).
+			std::fill(sample.begin() + 8, sample.end(), t % 1000000);
+
+			// Wait until the next expected sample time.
+			next_sample_time += std::chrono::microseconds(sample_dur_us);
+			std::this_thread::sleep_until(next_sample_time);
 
 			// send the sample
+			std::cout << sample[0] << "\t" << sample[8] << std::endl;
 			outlet.push_sample(sample);
 		}
 
-	} catch (std::exception &e) { cerr << "Got an exception: " << e.what() << endl; }
-	cout << "Press any key to exit. " << endl;
-	cin.get();
+	} catch (std::exception &e) { std::cerr << "Got an exception: " << e.what() << std::endl; }
+	std::cout << "Press any key to exit. " << std::endl;
+	std::cin.get();
 	return 0;
 }

examples/SendDataInChunks.cpp

@@ -44,9 +44,11 @@ struct fake_device {
 		pattern.reserve(pattern_samples * n_channels);
 		for (auto sample_ix = 0; sample_ix < pattern_samples; ++sample_ix) {
 			for (auto chan_ix = 0; chan_ix < n_channels; ++chan_ix) {
+				// sin(2*pi*f*t), where f cycles from 1 Hz to Nyquist: srate / 2
+				double f = (chan_ix + 1) % (int)(srate / 2);
 				pattern.emplace_back(
 					offset_0 + chan_ix * offset_step +
-					magnitude * static_cast<int16_t>(sin(M_PI * chan_ix * sample_ix / n_channels)));
+					magnitude * static_cast<int16_t>(sin(2 * M_PI * f * sample_ix / srate)));
 			}
 		}
 		last_time = std::chrono::steady_clock::now();
@@ -64,15 +66,15 @@ struct fake_device {
 		return output;
 	}
 
-	std::size_t get_data(std::vector<int16_t> &buffer) {
+	std::size_t get_data(std::vector<int16_t> &buffer, bool nodata = false) {
 		auto now = std::chrono::steady_clock::now();
 		auto elapsed_nano =
 			std::chrono::duration_cast<std::chrono::nanoseconds>(now - last_time).count();
 		int64_t elapsed_samples = std::size_t(elapsed_nano * srate * 1e-9); // truncate OK.
 		elapsed_samples = std::min(elapsed_samples, (int64_t)(buffer.size() / n_channels));
-		if (false) {
+		if (nodata) {
 			// The fastest but no patterns.
-			memset(&buffer[0], 23, buffer.size() * sizeof buffer[0]);
+			// memset(&buffer[0], 23, buffer.size() * sizeof buffer[0]);
 		} else {
 			std::size_t end_sample = head + elapsed_samples;
 			std::size_t nowrap_samples = std::min(pattern_samples - head, elapsed_samples);
@@ -96,24 +98,28 @@ int main(int argc, char **argv) {
 	std::string name{argc > 1 ? argv[1] : "MyAudioStream"}, type{argc > 2 ? argv[2] : "Audio"};
 	int samplingrate = argc > 3 ? std::stol(argv[3]) : 44100;  // Here we specify srate, but typically this would come from the device.
 	int n_channels = argc > 4 ? std::stol(argv[4]) : 2;        // Here we specify n_chans, but typically this would come from theh device.
-	int32_t max_buffered = argc > 5 ? std::stol(argv[5]) : 360;
+	double max_buffered = argc > 5 ? std::stod(argv[5]) : 360.;
 	int32_t chunk_rate = argc > 6 ? std::stol(argv[6]) : 10;  // Chunks per second.
 	int32_t chunk_samples = samplingrate > 0 ? std::max((samplingrate / chunk_rate), 1) : 100;  // Samples per chunk.
 	int32_t chunk_duration = 1000 / chunk_rate;  // Milliseconds per chunk
 
 	try {
 		// Prepare the LSL stream.
-		lsl::stream_info info(name, type, n_channels, samplingrate, lsl::cf_int16);
-		lsl::stream_outlet outlet(info, 0, max_buffered);
+		lsl::stream_info info(
+			name, type, n_channels, samplingrate, lsl::cf_int16, "example-SendDataInChunks");
 		lsl::xml_element desc = info.desc();
 		desc.append_child_value("manufacturer", "LSL");
 		lsl::xml_element chns = desc.append_child("channels");
 		for (int c = 0; c < n_channels; c++) {
 			lsl::xml_element chn = chns.append_child("channel");
 			chn.append_child_value("label", "Chan-" + std::to_string(c));
 			chn.append_child_value("unit", "microvolts");
-			chn.append_child_value("type", "EEG");
+			chn.append_child_value("type", type);
 		}
+		int32_t buf_samples = max_buffered * samplingrate;
+		lsl::stream_outlet outlet(info, chunk_samples, buf_samples);
+		info = outlet.info(); // Refresh info with whatever the outlet captured.
+		std::cout << "Stream UID: " << info.uid() << std::endl;
 
 		// Create a connection to our device.
 		fake_device my_device(n_channels, (float)samplingrate);
@@ -126,7 +132,8 @@ int main(int argc, char **argv) {
 
 		// Your device might have its own timer. Or you can decide how often to poll
 		//  your device, as we do here.
-		auto next_chunk_time = std::chrono::high_resolution_clock::now();
+		auto t_start = std::chrono::high_resolution_clock::now();
+		auto next_chunk_time = t_start;
 		for (unsigned c = 0;; c++) {
 			// wait a bit
 			next_chunk_time += std::chrono::milliseconds(chunk_duration);
@@ -137,9 +144,10 @@ int main(int argc, char **argv) {
 
 			// send it to the outlet. push_chunk_multiplexed is one of the more complicated approaches.
 			//  other push_chunk methods are easier but slightly slower.
-			outlet.push_chunk_multiplexed(chunk_buffer.data(), returned_samples * n_channels, 0.0, true);
+			double ts = lsl::local_clock();
+			outlet.push_chunk_multiplexed(
+				chunk_buffer.data(), returned_samples * n_channels, ts, true);
 		}
-
 	} catch (std::exception &e) { std::cerr << "Got an exception: " << e.what() << std::endl; }
 	std::cout << "Press any key to exit. " << std::endl;
 	std::cin.get();

include/lsl_cpp.h

@@ -499,7 +499,7 @@ class stream_outlet {
 	}
 
 	/** Push a pointer to raw numeric data as one sample into the outlet.
-	 * This is the lowest-level function; performns no checking whatsoever. Can not be used for
+	 * This is the lowest-level function; performs no checking whatsoever. Cannot be used for
 	 * variable-size / string-formatted channels.
 	 * @param sample A pointer to the raw sample data to push.
 	 * @param timestamp Optionally the capture time of the sample, in agreement with local_clock();

src/tcp_server.h

@@ -63,12 +63,13 @@ class tcp_server : public std::enable_shared_from_this<tcp_server> {
 	 * Initiate teardown of IO processes.
 	 *
 	 * The actual teardown will be performed by the IO thread that runs the operations of
-	 * thisserver.
+	 * this server.
 	 */
 	void end_serving();
 
 private:
 	friend class client_session;
+
 	/// Start accepting a new connection.
 	void accept_next_connection();