Replace Javax Sound with direct alsa access

jni/nv_alsa/build.sh

@@ -0,0 +1,4 @@
+rm *.o libnv_alsa.so
+gcc -I $JAVA_HOME/include -I $JAVA_HOME/include/linux -I /opt/vc/include -I/opt/vc/include/interface/vcos/pthreads -I/opt/vc/include/interface/vmcs_host/linux -I ./inc -fPIC -L. -c *.c
+gcc -shared -Wl,-soname,libnv_alsa.so -Wl,--no-undefined -o libnv_alsa.so *.o -L. -lasound
+rm *.o

jni/nv_alsa/nv_alsa.c

@@ -0,0 +1,54 @@
+/* Use the newer ALSA API */
+#define ALSA_PCM_NEW_HW_PARAMS_API
+
+/* All of the ALSA library API is defined
+ * in this header */
+#include <alsa/asoundlib.h>
+
+snd_pcm_t *handle;
+
+int nv_alsa_init(unsigned int channelCount, unsigned int sampleRate) {
+	int rc;
+	snd_pcm_hw_params_t *params;
+	int dir;
+	
+	/* Open PCM device for playback. */
+	if ((rc = snd_pcm_open(&handle, "default", SND_PCM_STREAM_PLAYBACK, 0)) != 0)
+		return rc;
+	
+	snd_pcm_hw_params_alloca(&params);
+	snd_pcm_hw_params_any(handle, params);
+	
+	snd_pcm_hw_params_set_access(handle, params, SND_PCM_ACCESS_RW_INTERLEAVED);
+	snd_pcm_hw_params_set_format(handle, params, SND_PCM_FORMAT_S16_LE);
+	snd_pcm_hw_params_set_channels(handle, params, channelCount);
+	snd_pcm_hw_params_set_rate_near(handle, params, &sampleRate, &dir);
+	
+	snd_pcm_uframes_t frames = 32;
+	snd_pcm_hw_params_set_period_size_near(handle, params, &frames, &dir);
+	
+	if ((rc = snd_pcm_hw_params(handle, params)) != 0)
+		return rc;
+}
+
+int nv_alsa_play(const unsigned char* indata, int data_len) {
+	int frames = data_len/4; /* 2 bytes/sample, 2 channels */
+	int rc = snd_pcm_writei(handle, indata, frames);
+	if (rc == -EPIPE) {
+		/* EPIPE means underrun */
+		fprintf(stderr, "underrun occurred\n");
+		snd_pcm_prepare(handle);
+	} else if (rc < 0) {
+		fprintf(stderr,
+			"error from writei: %s\n",
+			snd_strerror(rc));
+	} else if (rc != (int) frames) {
+		fprintf(stderr,
+			"short write, write %d frames\n", rc);
+	}	
+}
+
+int nv_alsa_close(void) {
+	snd_pcm_drain(handle);
+	snd_pcm_close(handle);
+}

jni/nv_alsa/nv_alsa.h

@@ -0,0 +1,5 @@
+#include <jni.h>
+
+int nv_alsa_init(unsigned int channelCount, unsigned int sampleRate);
+int nv_alsa_play(unsigned char* indata, int inlen);
+void nv_alsa_close(void);

jni/nv_alsa/nv_alsa_jni.c

@@ -0,0 +1,36 @@
+#include "nv_alsa.h"
+
+#include <stdlib.h>
+#include <jni.h>
+
+// This function must be called before
+// any other decoding functions
+JNIEXPORT jint JNICALL
+Java_com_limelight_binding_audio_AlsaAudio_init(JNIEnv *env, jobject this, jint channelCount, jint sampleRate)
+{
+	return nv_alsa_init(channelCount, sampleRate);
+}
+
+JNIEXPORT void JNICALL
+Java_com_limelight_binding_audio_AlsaAudio_close(JNIEnv *env, jobject this)
+{
+	nv_alsa_close();
+}
+
+JNIEXPORT jint JNICALL
+Java_com_limelight_binding_audio_AlsaAudio_play(
+	JNIEnv *env, jobject this, // JNI parameters
+	jbyteArray indata, jint inoff, jint inlen)
+{
+	jint ret;
+	jbyte* jni_input_data;
+
+	jni_input_data = (*env)->GetByteArrayElements(env, indata, 0);
+
+	ret = nv_alsa_play(&jni_input_data[inoff], inlen);
+
+	// The input data isn't changed so it can be safely aborted
+	(*env)->ReleaseByteArrayElements(env, indata, jni_input_data, JNI_ABORT);
+	
+	return ret;
+}