X-Git-Url: https://git.sesse.net/?p=pitch;a=blobdiff_plain;f=linux_audio.cpp;fp=linux_audio.cpp;h=b76909e7588fa2048bfa6b7ba8bf2e0abb257847;hp=0000000000000000000000000000000000000000;hb=14e6df5b242c72acc44cf8f68a56ee35dd5c43cf;hpb=46e9a2072aecb33f37aadf36ad783639b3877ce8

diff --git a/linux_audio.cpp b/linux_audio.cpp
new file mode 100644
index 0000000..b76909e
--- /dev/null
+++ b/linux_audio.cpp
@@ -0,0 +1,82 @@
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <math.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <sys/ioctl.h>
+#include <linux/soundcard.h>
+
+#include "linux_audio.h"
+
+int get_dsp_fd(int sample_rate, int fft_length, int overlap)
+{
+	int fd = open("/dev/dsp", O_RDWR);
+	if (fd == -1) {
+		perror("/dev/dsp");
+		exit(1);
+	}
+	
+	ioctl(3, SNDCTL_DSP_RESET, 0);
+	
+	int fmt = AFMT_S16_LE;   // FIXME
+	ioctl(fd, SNDCTL_DSP_SETFMT, &fmt);
+
+	int chan = 1;
+	ioctl(fd, SOUND_PCM_WRITE_CHANNELS, &chan);
+	
+	int rate = sample_rate;
+	ioctl(fd, SOUND_PCM_WRITE_RATE, &rate);
+
+	int max_fragments = 2;
+	int frag_shift = ffs(fft_length / overlap) - 1;
+	int fragments = (max_fragments << 16) | frag_shift;
+        ioctl(fd, SNDCTL_DSP_SETFRAGMENT, &fragments);
+	
+	ioctl(3, SNDCTL_DSP_SYNC, 0);
+	
+	return fd;
+}
+
+#if 1
+void read_chunk(int fd, short *in, unsigned num_samples)
+{
+	int ret;
+
+	ret = read(fd, in, num_samples * sizeof(short));
+	if (ret == 0) {
+		printf("EOF\n");
+		exit(0);
+	}
+
+	if (ret != int(num_samples * sizeof(short))) {
+		// blah
+		perror("read");
+		exit(1);
+	}
+}
+#else
+// make a pure 440hz sine for testing
+void read_chunk(int fd, short *in, unsigned num_samples)
+{
+	static double theta = 0.0;
+	for (unsigned i = 0; i < num_samples; ++i) {
+		in[i] = 32768.0 * cos(theta);
+		theta += 2.0 * M_PI * 440.0 / double(SAMPLE_RATE);
+	}
+}
+#endif
+
+void write_sine(int dsp_fd, double freq, unsigned num_samples, unsigned sample_rate) 
+{
+	static double theta = 0.0;
+	short buf[num_samples];
+	
+	for (unsigned i = 0; i < num_samples; ++i) {
+		buf[i] = short(cos(theta) * 16384.0);
+		theta += 2.0 * M_PI * freq / double(sample_rate);
+	}
+
+	write(dsp_fd, buf, num_samples * sizeof(short));
+}
+