FFMPEG 之音频解码及AudioTrack播放音频

一、实现原理

使用FFMPEG解码音频文件，然后调用AudioTrack播放解码文件

二、实现

1、导入ffmpeg的头文件，以及so文件



2、创建native方法，以及AudioTrack对象

PlayerControl.java

package com.xiaofan.testffmpeg2;
import android.media.AudioFormat;
import android.media.AudioManager;
import android.media.AudioTrack;

public class PlayerControl {
public native void sound(String input, String output);

/**
* @param sampleRateInHz 当前 声音的频率
* @param channelsNB 声道个数
* @return
*/
public AudioTrack createAudioTrack(int sampleRateInHz,int channelsNB) {

int audioFormat = AudioFormat.ENCODING_PCM_16BIT;
//声道布局，默认设置立体声
int channelConfig;
if(channelsNB==1){
channelConfig = AudioFormat.CHANNEL_OUT_MONO;
}else if(channelsNB==2){
channelConfig = AudioFormat.CHANNEL_OUT_STEREO;
}else {
channelConfig = AudioFormat.CHANNEL_OUT_STEREO;
}
int bufferSizeInBytes = AudioTrack.getMinBufferSize(sampleRateInHz, channelConfig, audioFormat);

AudioTrack audioTrack = new AudioTrack(AudioManager.STREAM_MUSIC,
sampleRateInHz, channelConfig,
audioFormat, bufferSizeInBytes,
AudioTrack.MODE_STREAM);

return audioTrack;
}

static {
System.loadLibrary("avutil-54");
System.loadLibrary("swresample-1");
System.loadLibrary("avcodec-56");
System.loadLibrary("avformat-56");
System.loadLibrary("swscale-3");
System.loadLibrary("postproc-53");
System.loadLibrary("avfilter-5");
System.loadLibrary("avdevice-56");
System.loadLibrary("native-lib");
}
}

3、CMake文件编写

cmake_minimum_required(VERSION 3.4.1)

add_library(native-lib
SHARED
src/main/cpp/native-lib.c )
find_library(log-lib
log )

add_library(libavcodec-56
SHARED
IMPORTED)

set_target_properties(libavcodec-56
PROPERTIES IMPORTED_LOCATION
${CMAKE_CURRENT_SOURCE_DIR}/src/main/jniLibs/armeabi/libavcodec-56.so)

add_library(libavdevice-56
SHARED
IMPORTED)
set_target_properties(libavdevice-56
PROPERTIES IMPORTED_LOCATION
${CMAKE_CURRENT_SOURCE_DIR}/src/main/jniLibs/armeabi/libavdevice-56.so)

add_library(libavfilter-5
SHARED
IMPORTED)
set_target_properties(libavfilter-5
PROPERTIES IMPORTED_LOCATION
${CMAKE_CURRENT_SOURCE_DIR}/src/main/jniLibs/armeabi/libavfilter-5.so)

add_library(libavformat-56
SHARED
IMPORTED)
set_target_properties(libavformat-56
PROPERTIES IMPORTED_LOCATION
${CMAKE_CURRENT_SOURCE_DIR}/src/main/jniLibs/armeabi/libavformat-56.so)
add_library(libavutil-54
SHARED
IMPORTED)
set_target_properties(libavutil-54
PROPERTIES IMPORTED_LOCATION
${CMAKE_CURRENT_SOURCE_DIR}/src/main/jniLibs/armeabi/libavutil-54.so)
add_library(libpostproc-53
SHARED
IMPORTED)
set_target_properties(libpostproc-53
PROPERTIES IMPORTED_LOCATION
${CMAKE_CURRENT_SOURCE_DIR}/src/main/jniLibs/armeabi/libpostproc-53.so)

add_library(libswresample-1
SHARED
IMPORTED)
set_target_properties(libswresample-1
PROPERTIES IMPORTED_LOCATION
${CMAKE_CURRENT_SOURCE_DIR}/src/main/jniLibs/armeabi/libswresample-1.so)
add_library(libswscale-3
SHARED
IMPORTED)
set_target_properties(libswscale-3
PROPERTIES IMPORTED_LOCATION
${CMAKE_CURRENT_SOURCE_DIR}/src/main/jniLibs/armeabi/libswscale-3.so)

target_link_libraries(  native-lib
libavcodec-56
libavdevice-56
libavfilter-5
libavformat-56
libavutil-54
libpostproc-53
libswresample-1
libswscale-3
${log-lib} )

4、使用javah命令生成头文件

5、编写解压以及播放流程

native-lib.c

#include "com_xiaofan_testffmpeg2_PlayerControl.h"
#include <android/log.h>
#include <stdio.h>
#include <stdlib.h>
#include <android/native_window.h>
#include <android/native_window_jni.h>

#define LOGI(FORMAT, ...) __android_log_print(ANDROID_LOG_INFO,"wanxiaofan",FORMAT,##__VA_ARGS__);
#define LOGE(FORMAT, ...) __android_log_print(ANDROID_LOG_ERROR,"wanxiaofan",FORMAT,##__VA_ARGS__);
//封装格式
#include "include/ffmpeg/libavformat/avformat.h"
//解码
#include "include/ffmpeg/libavcodec/avcodec.h"
//缩放
#include "include/ffmpeg/libswscale/swscale.h"
#include "include/ffmpeg/libavutil/avutil.h"
#include "include/ffmpeg/libavutil/frame.h"
//重采样
#include "include/ffmpeg/libswresample/swresample.h"
#include <unistd.h>

JNIEXPORT void JNICALL Java_com_xiaofan_testffmpeg2_PlayerControl_sound
(JNIEnv *env, jobject jobj, jstring jstr_input, jstring jstr_output) {
const char *input_cstr = (*env)->GetStringUTFChars(env, jstr_input, NULL);
const char *output_cstr = (*env)->GetStringUTFChars(env, jstr_output, NULL);
//注册组件
av_register_all();
AVFormatContext *pFormatCtx = avformat_alloc_context();
//打开音频文件
if (avformat_open_input(&pFormatCtx, input_cstr, NULL, NULL) != 0) {
LOGE("%s", "无法打开音频文件！");
return;
}
//获取输入文件信息
if (avformat_find_stream_info(pFormatCtx, NULL) < 0) {
LOGE("%s", "无法获取输入文件信息！");
return;
}
//    获取音频流索引位置
int i = 0, audio_stream_idx = -1;
for (; i < pFormatCtx->nb_streams; ++i) {
if (pFormatCtx->streams[i]->codec->codec_type == AVMEDIA_TYPE_AUDIO) {
audio_stream_idx = i;
break;
}
}
//    获取解码器
AVCodecContext *codeCtx = pFormatCtx->streams[audio_stream_idx]->codec;
AVCodec *codec = avcodec_find_decoder(codeCtx->codec_id);
if (codec == NULL) {
LOGE("%s", "无法获取解码器");
return;
}
//    打开解码器
if (avcodec_open2(codeCtx, codec, NULL) < 0) {
LOGE("%s", "无法打开解码器");
return;
}

//压缩数据
AVPacket *packet = av_malloc(sizeof(AVPacket));
//解压缩数据
AVFrame *frame = av_frame_alloc();
//同一音频采样格式与采样率，把frame->16bit PCM,采样率默认用44.1kHZ
SwrContext *swrCtx = swr_alloc();//开辟空间
//设置选项  start
//输入的采样格式
enum AVSampleFormat in_sample_fmt = codeCtx->sample_fmt;
//输出的采样格式16bit PCM
enum AVSampleFormat out_sample_fmt = AV_SAMPLE_FMT_S16;
//输入采样率
int in_sample_rate = codeCtx->sample_rate;
//输出采样率  44100
int out_sample_rate = in_sample_rate;
//获取输入的声道布局
/**
*根据声道个数获取默认的声道布局（2个声道，默认立体声）
*/
//int64_t  in_ch_layout=av_get_default_channel_layout(codeCtx->channels);
int64_t in_ch_layout = codeCtx->channel_layout;
//获取输出的声道布局(默认立体声)
int64_t out_ch_layout = AV_CH_LAYOUT_STEREO;
swr_alloc_set_opts(swrCtx,
out_ch_layout, out_sample_fmt, out_sample_rate,
in_ch_layout, in_sample_fmt, in_sample_rate,
0, NULL);
//输出的声道个数
int out_channel_nb = av_get_channel_layout_nb_channels(out_ch_layout);

//设置选项end

//jni start
//获取AudioTrack对象
jclass jcls = (*env)->GetObjectClass(env, jobj);
jmethodID create_audio_track_mid = (*env)->GetMethodID(env, jcls, "createAudioTrack",
"(II)Landroid/media/AudioTrack;");

jobject audio_track = (*env)->CallObjectMethod(env, jobj, create_audio_track_mid,
out_sample_rate, codeCtx->channels);

//    调用AudioTrack.play方法
jclass audio_track_class = (*env)->GetObjectClass(env, audio_track);
jmethodID audio_track_play_mid = (*env)->GetMethodID(env, audio_track_class, "play", "()V");

(*env)->CallVoidMethod(env, audio_track, audio_track_play_mid);
//调用AudioTrack.write
jmethodID audio_track_write_mid = (*env)->GetMethodID(env, audio_track_class, "write",
"([BII)I");
//    jni end

swr_init(swrCtx);

//    不断读取压缩数据
uint8_t *out_buffer = (uint8_t *) av_malloc(2 * 44100);//保存的就是 16bit PCM  44.1kHZ的数据
FILE *fp_pcm = fopen(output_cstr, "wb");
int got_frame = 0, index = 0, ret;
while (av_read_frame(pFormatCtx, packet) >= 0) {
//解码音频类型的packet
if (packet->stream_index == audio_stream_idx) {
//解码
ret = avcodec_decode_audio4(codeCtx, frame, &got_frame, packet);
if (ret < 0) {
LOGE("%s", "解码完成");
}
//解码一帧成功
if (got_frame > 0) {
LOGI("解码：%d", index++);
swr_convert(swrCtx, &out_buffer, 2 * 44100, frame->data, frame->nb_samples);
//获取sample的size
int out_buffer_size = av_samples_get_buffer_size(NULL,
out_channel_nb,
frame->nb_samples,
out_sample_fmt, 1);
//out_buffer缓冲数据，转成byte数组
jbyteArray data_array = (*env)->NewByteArray(env, out_buffer_size);
jbyte *sample_byte = (*env)->GetByteArrayElements(env, data_array, NULL);
//赋值
memcpy(sample_byte, out_buffer, out_buffer_size);
//同步
(*env)->ReleaseByteArrayElements(env, data_array, sample_byte, 0);
//将pcm的数据写入AudioTrack
//            fwrite(out_buffer, 1, out_buffer_size, fp_pcm);
//byte[] audioData, int offsetInBytes, int sizeInBytes
(*env)->CallIntMethod(env, audio_track, audio_track_write_mid, data_array, 0,
out_buffer_size);
//释放局部引用
(*env)->DeleteLocalRef(env, data_array);
usleep(1000 * 16);
}

av_free_packet(packet);
}
}
//释放资源
fclose(fp_pcm);
av_frame_free(&frame);
av_free(out_buffer);
swr_free(&swrCtx);
avcodec_close(codeCtx);
avformat_close_input(&pFormatCtx);
(*env)->ReleaseStringUTFChars(env, jstr_input, input_cstr);
(*env)->ReleaseStringUTFChars(env, jstr_output, output_cstr);
}

6、在Activity中正常调用就行，然后就能实现播放

注意：

在AS中使用javap -s命令得到方法签名需到debug目录下，且方法改变了之后需要编译debug中的文件才会改变