Android NDK开发之旅 目录

前言

基于Android NDK开发之旅34--FFmpeg音频解码这篇文章，我们已经学会音频解码基本过程。

音频播放有两种方法：FFmpeg+AudioTrack(Android自带的播放工具) 、FFmpeg+OpenSL ES。

这篇文章就通过FFmpeg+AudioTrack方式对音频解码的文件进行播放操作。

1.Java中 jni声明

package com.haocai.ffmpegtest.util;

import android.view.Surface;

public class VideoPlayer {

    //音频播放
    public native void audioPlayer(String input);

    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("myffmpeg");
    }


}

2.定义播放?？锳udioTrack

package com.haocai.ffmpegtest.util;

import android.media.AudioFormat;
import android.media.AudioManager;
import android.media.AudioTrack;
import android.util.Log;

/**
 * Created by Xionghu on 2017/12/12.
 * Desc:
 */

public class AudioUtil {

    //Todo 生成JNI签名后删除 该声明
    //Todo 该声明 来源于 audioTrack.write()
    public int write(byte[] audioData, int offsetInBytes, int sizeInBytes) {
        return 0;
    }

    /**
     * 创建一个AudioTrack对象，用于播放
     * @return
     */
    public AudioTrack createAudioTrack(int sampleRateInHz, int nb_channels){
        Log.i("AudioUtil", "nb_channels:"+nb_channels);
        Log.i("AudioUtil", "sampleRateInHz:"+sampleRateInHz);
        //固定格式的音频码流
        int audioFormat = AudioFormat.ENCODING_PCM_16BIT;

        //声道个数 影响声道的布局
        int channelConfig;
        if(nb_channels == 1){
            channelConfig = android.media.AudioFormat.CHANNEL_OUT_MONO;
        }else if(nb_channels == 2){
            channelConfig = android.media.AudioFormat.CHANNEL_OUT_STEREO;
        }else{
            channelConfig = android.media.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);
        //audioTrack.write()
        return audioTrack;
    }

}

3.获取播放模块AudioTrack相关方法的签名

3.1Build ->Rebuild Project 得到编译文件classes

3.2通过javap得到方法的签名

Windows 命令模式下

D:\>CD D:\AndroidProject\FFmpegTest\app\build\intermediates\classes\debug

D:\AndroidProject\FFmpegTest\app\build\intermediates\classes\debug> javap -s -p com.haocai.ffmpegtest.util.AudioUtil
Compiled from "AudioUtil.java"
public class com.haocai.ffmpegtest.util.AudioUtil {
  public com.haocai.ffmpegtest.util.AudioUtil();
    descriptor: ()V

  public int write(byte[], int, int);
    descriptor: ([BII)I

  public android.media.AudioTrack createAudioTrack(int, int);
    descriptor: (II)Landroid/media/AudioTrack;
}

获取签名

4.编写音频解码播放功能

ffmpeg_voicer.c

#include <com_haocai_ffmpegtest_util_VideoPlayer.h>
#include <android/log.h>
#include <android/native_window_jni.h>
#include <android/native_window.h>
#include <unistd.h>
#include <stdlib.h>
//解码
#include "include/libavcodec/avcodec.h"
//封装格式处理
#include "include/libavformat/avformat.h"
//像素处理
#include "include/libswscale/swscale.h"
//重采样
#include "include/libswresample/swresample.h"


#define  LOG_TAG    "ffmpegandroidplayer"
#define  LOGI(FORMAT,...) __android_log_print(ANDROID_LOG_INFO,LOG_TAG,FORMAT,##__VA_ARGS__);
#define  LOGE(FORMAT,...) __android_log_print(ANDROID_LOG_ERROR,LOG_TAG,FORMAT,##__VA_ARGS__);
#define  LOGD(FORMAT,...)  __android_log_print(ANDROID_LOG_DEBUG, LOG_TAG,FORMAT, ##__VA_ARGS__)

//音频解码 采样率 新版版可达48000 * 4
#define MAX_AUDIO_FRME_SIZE  2 * 44100


//音频播放
JNIEXPORT void JNICALL Java_com_haocai_ffmpegtest_util_VideoPlayer_audioPlayer
(JNIEnv *env, jobject jobj, jstring input_jstr) {
    const char* input_cstr = (*env)->GetStringUTFChars(env, input_jstr, NULL);
    LOGI("%s", "init");
    //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) {
        LOGI("%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) {
        LOGI("%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;
        }
    }
    if (audio_stream_idx == -1)
    {
        LOGI("%s", "找不到音频流");
        return;
    }
    //获取解码器
    AVCodecContext *pCodeCtx = pFormatCtx->streams[audio_stream_idx]->codec;
    AVCodec *codec = avcodec_find_decoder(pCodeCtx->codec_id);
    if (codec == NULL) {
        LOGI("%s", "无法获取加码器");
        return;
    }
    //打开解码器
    if (avcodec_open2(pCodeCtx, codec, NULL) < 0) {
        LOGI("%s", "无法打开解码器");
        return;
    }

    //压缩数据
    AVPacket *packet = (AVPacket *)av_malloc(sizeof(AVPacket));
    //解压缩数据
    AVFrame *frame = av_frame_alloc();
    //frame->16bit  44100 PCM 统一音频采样格式与采样率
    SwrContext *swrCtx = swr_alloc();

    //输入采样率格式
    enum AVSampleFormat in_sample_fmt = pCodeCtx->sample_fmt;
    //输出采样率格式16bit PCM
    enum AVSampleFormat out_sample_fmt = AV_SAMPLE_FMT_S16;
    //输入采样率
    int in_sample_rate = pCodeCtx->sample_rate;
    //输出采样率
    int out_sample_rate = 44100;
    //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)
    //av_get_default_channel_layout(pCodeCtx->channels);
    uint64_t in_ch_layout = pCodeCtx->channel_layout;
    //输出的声道布局
    uint64_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);


    swr_init(swrCtx);

    //获取输入输出的声道个数
    int out_channel_nb = av_get_channel_layout_nb_channels(out_ch_layout);
    LOGI("out_count:%d", out_channel_nb);

     //jclass  player_class = (*env)->GetObjectClass(env,jobj);

    jclass cls = (*env)->FindClass(env, "com/haocai/ffmpegtest/util/AudioUtil");
     //jmethodID
    jmethodID  constructor_mid= (*env)->GetMethodID(env, cls,"<init>","()V");

    //实例化一个AudioUtil对象(可以在constructor_mid后加参)
    jobject audioutil_obj =  (*env)->NewObject(env, cls, constructor_mid);   //类似于AudioUtil audioutil =new AudioUtil();

    //AudioTrack对象
    jmethodID create_audio_track_mid =(*env)->GetMethodID(env,cls,"createAudioTrack","(II)Landroid/media/AudioTrack;");
    jobject audio_track = (*env)->CallObjectMethod(env,audioutil_obj,create_audio_track_mid,out_sample_rate,out_channel_nb);

    //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);

    //AudioTrack.write
    jmethodID audio_track_write_mid =  (*env)->GetMethodID(env,audio_track_class,"write","([BII)I");

    //16bit 44100 PCM 数据
    uint8_t *out_buffer = (uint8_t *)av_malloc(MAX_AUDIO_FRME_SIZE);

    int got_frame = 0, framecount = 0, ret;
    //6.一帧一帧读取压缩的音频数据AVPacket
    while (av_read_frame(pFormatCtx, packet) >= 0) {
        //解码音频类型的Packet，  packet 有可能是音频数据流 有可能是视频数据流
        if (packet->stream_index == audio_stream_idx) {
            //解码
            ret = avcodec_decode_audio4(pCodeCtx, frame, &got_frame, packet);

            if (ret < 0) {
                LOGI("%s", "解码完成");
                break;
            }
            //非0，正在解码
            if (got_frame > 0) {
                LOGI("解码：%d", framecount++);
                swr_convert(swrCtx, &out_buffer, MAX_AUDIO_FRME_SIZE, (const uint8_t **)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 缓冲区数据，转换成byte数组
                jbyteArray audio_sample_array =  (*env)->NewByteArray(env,out_buffer_size);

                jbyte* sample_byte = (*env)->GetByteArrayElements(env,audio_sample_array,NULL);

                 //将out_buffer的数据复制到sample_byte
                 memcpy(sample_byte,out_buffer,out_buffer_size);

                 //同步数据 同时释放sample_byte
                 (*env)->ReleaseByteArrayElements(env,audio_sample_array,sample_byte,0);

                //AudioTrack.write PCM数据
                 (*env)->CallIntMethod(env,audio_track,audio_track_write_mid,audio_sample_array,0,out_buffer_size);

                 //释放局部引用  否则报错JNI ERROR (app bug): local reference table overflow (max=512)
                 (*env)->DeleteLocalRef(env,audio_sample_array);
                usleep(1000 * 16); //16ms
            }
        }
        av_free_packet(packet);
    }
    av_frame_free(&frame);
    av_free(out_buffer);
    swr_free(&swrCtx);
    avcodec_close(pCodeCtx);
    avformat_close_input(&pFormatCtx);

    (*env)->ReleaseStringUTFChars(env, input_jstr, input_cstr);


}

5.调用音频播放功能

   /**
     * 音频解码
     */
    public void audioPlayer(){
        /**
         * 1.播放视频文件中的音频
         */
    //   String input = new File(Environment.getExternalStorageDirectory(),"告白气球.avi").getAbsolutePath();

        /**
         * 2.播放音频文件中的音频
         */
        String input = new File(Environment.getExternalStorageDirectory(),"说散就散.mp3").getAbsolutePath();
        VideoPlayer player = new VideoPlayer();
        player.audioPlayer(input);
        Log.d("Main","正在播放");
    }
}

6.调用音频播放功能

Log输出

I/ffmpegandroidplayer: init
I/ffmpegandroidplayer: out_count:2
I/AudioUtil: nb_channels:2
I/AudioUtil: sampleRateInHz:44100
I/ffmpegandroidplayer: 解码：0
I/ffmpegandroidplayer: 解码：1
I/ffmpegandroidplayer: 解码：2
I/ffmpegandroidplayer: 解码：3
I/ffmpegandroidplayer: 解码：4
太多省略......

至此，音频播放功能已完成。

源码下载

Github：https://github.com/kpioneer123/FFmpegTest

特别感谢：

动脑学院Jason