音频压缩工具——Speex的使用

在Android开发中，需要录音并发送到对方设备上。这时问题来了，手机常会是GPRS、3G等方式上网，所以节省流量是非常关键的，使用Speex来压缩音频文件，可以将音频压文件小数倍。

1.去Speex官网下载最新Speex源码。

2.创建一个新的应用（我创建的应用名为Audio），并创建一个jni目录（$project/jni）。

3.把speex源码目录下的libspeex和include目录及其子目录文件全部拷贝到$project/jni目录下（$project/jni/libspeex and $project/jni/include）。

4.在jni目录下新增Android.mk文件，编辑内容如下

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目录下新增Application.mk文件，编辑内容如下

APP_ABI := armeabi armeabi-v7a

6.在 $project/jni/include/speex/目录下新增speex_config_types.h文件，编辑内容如下

#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.创建JNI包装类speex_jni.cpp，用来调用Speex中的C代码函数，编辑内容如下

#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层创建Speex工具类，内容如下

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.打开cygwin工具，切换到项目目录（我项目是在F:\workspace\Audio），输入$NDK/ndk-build

cygwin工具的安装与配置，可以看这篇文章——使用NDK与环境搭建

会在项目中生成libs目录和libspeex.so文件，这就是Speex类中System.loadLibrary("speex");代码引用的，系统会根据操作系统由"speex"找到对应的动态库libspeex.so，Windows下是.dll文件，linux下是.so文件。

当前，我的项目结构如下图

可以从android-recorder下载代码作为参考