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