音頻壓縮工具——Speex的使用

在Android開發中，需要錄音併發送到對方設備上。這時問題來了，手機常會是GPRS、3G等方式上網，所以節省流量是非常關鍵的，使用Speex來壓縮音頻文件，可以將音頻壓文件小數倍。

1.去Speex官網下載最新Speex源碼。

2.創建一個新的應用（我創建的應用名爲Audio），並創建一個jni目錄（$project/jni）。

3.把speex源碼目錄下的libspeex和include目錄及其子目錄文件全部拷貝到$project/jni目錄下（$project/jni/libspeex and $project/jni/include）。

4.在jni目錄下新增Android.mk文件，編輯內容如下

LOCAL_PATH := $(call my-dir)


include $(CLEAR_VARS)
 
LOCAL_MODULE    := libspeex
LOCAL_CFLAGS = -DFIXED_POINT -DUSE_KISS_FFT -DEXPORT="" -UHAVE_CONFIG_H
LOCAL_C_INCLUDES := $(LOCAL_PATH)/include
 
LOCAL_SRC_FILES :=  \
./speex_jni.cpp \
./libspeex/bits.c \
./libspeex/buffer.c \
./libspeex/cb_search.c \
./libspeex/exc_10_16_table.c \
./libspeex/exc_10_32_table.c \
./libspeex/exc_20_32_table.c \
./libspeex/exc_5_256_table.c \
./libspeex/exc_5_64_table.c \
./libspeex/exc_8_128_table.c \
./libspeex/fftwrap.c \
./libspeex/filterbank.c \
./libspeex/filters.c \
./libspeex/gain_table.c \
./libspeex/gain_table_lbr.c \
./libspeex/hexc_10_32_table.c \
./libspeex/hexc_table.c \
./libspeex/high_lsp_tables.c \
./libspeex/jitter.c \
./libspeex/kiss_fft.c \
./libspeex/kiss_fftr.c \
./libspeex/lpc.c \
./libspeex/lsp.c \
./libspeex/lsp_tables_nb.c \
./libspeex/ltp.c \
./libspeex/mdf.c \
./libspeex/modes.c \
./libspeex/modes_wb.c \
./libspeex/nb_celp.c \
./libspeex/preprocess.c \
./libspeex/quant_lsp.c \
./libspeex/resample.c \
./libspeex/sb_celp.c \
./libspeex/scal.c \
./libspeex/smallft.c \
./libspeex/speex.c \
./libspeex/speex_callbacks.c \
./libspeex/speex_header.c \
./libspeex/stereo.c \
./libspeex/vbr.c \
./libspeex/vq.c \
./libspeex/window.c
 
include $(BUILD_SHARED_LIBRARY)

5.在jni目錄下新增Application.mk文件，編輯內容如下

APP_ABI := armeabi armeabi-v7a

6.在$project/jni/include/speex/目錄下新增speex_config_types.h文件，編輯內容如下

#ifndef __SPEEX_TYPES_H__
#define __SPEEX_TYPES_H__
typedef short spx_int16_t;
typedef unsigned short spx_uint16_t;
typedef int spx_int32_t;
typedef unsigned int spx_uint32_t;
#endif

7.創建JNI包裝類speex_jni.cpp，用來調用Speex中的C代碼函數，編輯內容如下

#include <jni.h>

#include <string.h>
#include <unistd.h>

#include <speex/speex.h>

static int codec_open = 0;

static int dec_frame_size;
static int enc_frame_size;

static SpeexBits ebits, dbits;
void *enc_state;
void *dec_state;

static JavaVM *gJavaVM;

extern "C"
JNIEXPORT jint JNICALL Java_com_audio_Speex_open
  (JNIEnv *env, jobject obj, jint compression) {
	int tmp;

	if (codec_open++ != 0)
		return (jint)0;

	speex_bits_init(&ebits);
	speex_bits_init(&dbits);

	enc_state = speex_encoder_init(&speex_nb_mode);
	dec_state = speex_decoder_init(&speex_nb_mode);
	tmp = compression;
	speex_encoder_ctl(enc_state, SPEEX_SET_QUALITY, &tmp);
	speex_encoder_ctl(enc_state, SPEEX_GET_FRAME_SIZE, &enc_frame_size);
	speex_decoder_ctl(dec_state, SPEEX_GET_FRAME_SIZE, &dec_frame_size);

	return (jint)0;
}

extern "C"
JNIEXPORT jint Java_com_audio_Speex_encode
    (JNIEnv *env, jobject obj, jshortArray lin, jint offset, jbyteArray encoded, jint size) {

        jshort buffer[enc_frame_size];
        jbyte output_buffer[enc_frame_size];
	int nsamples = (size-1)/enc_frame_size + 1;
	int i, tot_bytes = 0;

	if (!codec_open)
		return 0;

	speex_bits_reset(&ebits);

	for (i = 0; i < nsamples; i++) {
		env->GetShortArrayRegion(lin, offset + i*enc_frame_size, enc_frame_size, buffer);
		speex_encode_int(enc_state, buffer, &ebits);
	}
	//env->GetShortArrayRegion(lin, offset, enc_frame_size, buffer);
	//speex_encode_int(enc_state, buffer, &ebits);

	tot_bytes = speex_bits_write(&ebits, (char *)output_buffer,
				     enc_frame_size);
	env->SetByteArrayRegion(encoded, 0, tot_bytes,
				output_buffer);

        return (jint)tot_bytes;
}

extern "C"
JNIEXPORT jint JNICALL Java_com_audio_Speex_decode
    (JNIEnv *env, jobject obj, jbyteArray encoded, jshortArray lin, jint size) {

        jbyte buffer[dec_frame_size];
        jshort output_buffer[dec_frame_size];
        jsize encoded_length = size;

	if (!codec_open)
		return 0;

	env->GetByteArrayRegion(encoded, 0, encoded_length, buffer);
	speex_bits_read_from(&dbits, (char *)buffer, encoded_length);
	speex_decode_int(dec_state, &dbits, output_buffer);
	env->SetShortArrayRegion(lin, 0, dec_frame_size,
				 output_buffer);

	return (jint)dec_frame_size;
}

extern "C"
JNIEXPORT jint JNICALL Java_com_audio_getFrameSize
    (JNIEnv *env, jobject obj) {

	if (!codec_open)
		return 0;
	return (jint)enc_frame_size;

}

extern "C"
JNIEXPORT void JNICALL Java_com_audio_Speex_close
    (JNIEnv *env, jobject obj) {

	if (--codec_open != 0)
		return;

	speex_bits_destroy(&ebits);
	speex_bits_destroy(&dbits);
	speex_decoder_destroy(dec_state);
	speex_encoder_destroy(enc_state);
}

8.在Java層創建Speex工具類，內容如下

package com.audio;

class Speex  {

	/* quality
	 * 1 : 4kbps (very noticeable artifacts, usually intelligible)
	 * 2 : 6kbps (very noticeable artifacts, good intelligibility)
	 * 4 : 8kbps (noticeable artifacts sometimes)
	 * 6 : 11kpbs (artifacts usually only noticeable with headphones)
	 * 8 : 15kbps (artifacts not usually noticeable)
	 */
	private static final int DEFAULT_COMPRESSION = 8;

	Speex() {
	}

	public void init() {
		load();	
		open(DEFAULT_COMPRESSION);
	}
	
	private void load() {
		try {
			System.loadLibrary("speex");
		} catch (Throwable e) {
			e.printStackTrace();
		}

	}

	public native int open(int compression);
	public native int getFrameSize();
	public native int decode(byte encoded[], short lin[], int size);
	public native int encode(short lin[], int offset, byte encoded[], int size);
	public native void close();
	
}

9.打開cygwin工具，切換到項目目錄（我項目是在F:\workspace\Audio），輸入$NDK/ndk-build

cygwin工具的安裝與配置，可以看這篇文章——使用NDK與環境搭建

會在項目中生成libs目錄和libspeex.so文件，這就是Speex類中System.loadLibrary("speex");代碼引用的，系統會根據操作系統由"speex"找到對應的動態庫libspeex.so，Windows下是.dll文件，linux下是.so文件。

當前，我的項目結構如下圖

可以從android-recorder下載代碼作爲參考

我自己做了一個語音SDK，大家可以下載使用：http://download.csdn.net/detail/chenfeng0104/6549675