Android 音视频深入 十四 FFmpeg与OpenSL ES 播放mp3音乐，能暂停（附源码

Posted 2020-10-25

项目地址
https://github.com/979451341/FFmpegOpenslES

这次说的是FFmpeg解码mp3，数据给OpenSL ES播放，并且能够暂停。
1.创建引擎

slCreateEngine(&engineObject,0,NULL,0,NULL,NULL);//创建引擎
(*engineObject)->Realize(engineObject,SL_BOOLEAN_FALSE);//实现engineObject接口对象
(*engineObject)->GetInterface(engineObject,SL_IID_ENGINE,&engineEngine);//通过引擎调用接口初始化SLEngineItf

2.创建混音器

(*engineEngine)->CreateOutputMix(engineEngine,&outputMixObject,0,0,0);//用引擎对象创建混音器接口对象
(*outputMixObject)->Realize(outputMixObject,SL_BOOLEAN_FALSE);//实现混音器接口对象
SLresult   sLresult = (*outputMixObject)->GetInterface(outputMixObject,SL_IID_ENVIRONMENTALREVERB,&outputMixEnvironmentalReverb);//利用混音器实例对象接口初始化具体的混音器对象
//设置
if (SL_RESULT_SUCCESS == sLresult) {
    (*outputMixEnvironmentalReverb)->
            SetEnvironmentalReverbProperties(outputMixEnvironmentalReverb, &settings);
}

3.FFmpeg解码mp3准备工作

av_register_all();
char *input = "/storage/emulated/0/pauseRecordDemo/video/a.mp3";
pFormatCtx = avformat_alloc_context();
LOGE("Lujng %s",input);
LOGE("xxx %p",pFormatCtx);
int error;
char buf[] = "";
//打开视频地址并获取里面的内容(解封装)
if (error = avformat_open_input(&pFormatCtx, input, NULL, NULL) < 0) {
    av_strerror(error, buf, 1024);
    // LOGE("%s" ,inputPath)
    LOGE("Couldn‘t open file %s: %d(%s)", input, error, buf);
    // LOGE("%d",error)
    LOGE("打开视频失败")
}
//3.获取视频信息
if(avformat_find_stream_info(pFormatCtx,NULL) < 0){
    LOGE("%s","获取视频信息失败");
    return -1;
}

int i=0;
for (int i = 0; i < pFormatCtx->nb_streams; ++i) {
    if (pFormatCtx->streams[i]->codec->codec_type == AVMEDIA_TYPE_AUDIO) {
        LOGE("  找到音频id %d", pFormatCtx->streams[i]->codec->codec_type);
        audio_stream_idx=i;
        break;
    }
}

// mp3的解码器

// 获取音频编解码器
pCodecCtx=pFormatCtx->streams[audio_stream_idx]->codec;
LOGE("获取视频编码器上下文 %p ",pCodecCtx);

pCodex = avcodec_find_decoder(pCodecCtx->codec_id);
LOGE("获取视频编码 %p",pCodex);

if (avcodec_open2(pCodecCtx, pCodex, NULL)<0) {
}
packet = (AVPacket *)av_malloc(sizeof(AVPacket));

// av_init_packet(packet);
// 音频数据

frame = av_frame_alloc();

// mp3 里面所包含的编码格式 转换成 pcm SwcContext
swrContext = swr_alloc();

int length=0;
int got_frame;

// 441002
out_buffer = (uint8_t ) av_malloc(44100 * 2);
uint64_t out_ch_layout=AV_CH_LAYOUT_STEREO;
// 输出采样位数 16位
enum AVSampleFormat out_formart=AV_SAMPLE_FMT_S16;
//输出的采样率必须与输入相同
int out_sample_rate = pCodecCtx->sample_rate;

swr_alloc_set_opts(swrContext, out_ch_layout, out_formart, out_sample_rate,
                   pCodecCtx->channel_layout, pCodecCtx->sample_fmt, pCodecCtx->sample_rate, 0,
                   NULL);

swr_init(swrContext);

// 获取通道数 2
out_channer_nb = av_get_channel_layout_nb_channels(AV_CH_LAYOUT_STEREO);
rate = pCodecCtx->sample_rate;
channel = pCodecCtx->channels;

4.缓存队列设置

int rate;
int channels;
createFFmpeg(&rate,&channels);
LOGE("RATE %d",rate);
LOGE("channels %d",channels);
/*
 * typedef struct SLDataLocator_androidBufferQueue_ {
SLuint32    locatorType;//缓冲区队列类型
SLuint32    numBuffers;//buffer位数

} */

SLDataLocator_AndroidBufferQueue android_queue = {SL_DATALOCATOR_ANDROIDSIMPLEBUFFERQUEUE,2};
/**
typedef struct SLDataFormat_PCM_ {
    SLuint32         formatType;  pcm
    SLuint32         numChannels;  通道数
    SLuint32         samplesPerSec;  采样率
    SLuint32         bitsPerSample;  采样位数
    SLuint32         containerSize;  包含位数
    SLuint32         channelMask;     立体声
    SLuint32        endianness;    end标志位
} SLDataFormat_PCM;
 */
SLDataFormat_PCM pcm = {SL_DATAFORMAT_PCM,channels,rate*1000
        ,SL_PCMSAMPLEFORMAT_FIXED_16
        ,SL_PCMSAMPLEFORMAT_FIXED_16
        ,SL_SPEAKER_FRONT_LEFT|SL_SPEAKER_FRONT_RIGHT,SL_BYTEORDER_LITTLEENDIAN};

/*
 * typedef struct SLDataSource_ {
        void *pLocator;//缓冲区队列
        void *pFormat;//数据样式,配置信息
    } SLDataSource;
 * */
SLDataSource dataSource = {&android_queue,&pcm};

SLDataLocator_OutputMix slDataLocator_outputMix={SL_DATALOCATOR_OUTPUTMIX,outputMixObject};

SLDataSink slDataSink = {&slDataLocator_outputMix,NULL};

const SLInterfaceID ids[3]={SL_IID_BUFFERQUEUE,SL_IID_EFFECTSEND,SL_IID_VOLUME};
const SLboolean req[3]={SL_BOOLEAN_FALSE,SL_BOOLEAN_FALSE,SL_BOOLEAN_FALSE};

/*
 * SLresult (*CreateAudioPlayer) (
    SLEngineItf self,
    SLObjectItf * pPlayer,
    SLDataSource *pAudiosrc,//数据设置
    SLDataSink *pAudioSnk,//关联混音器
    SLuint32 numInterfaces,
    const SLInterfaceID * pInterfaceIds,
    const SLboolean * pInterfaceRequired
);
 * */
LOGE("执行到此处")
(*engineEngine)->CreateAudioPlayer(engineEngine,&audioplayer,&dataSource,&slDataSink,3,ids,req);
(*audioplayer)->Realize(audioplayer,SL_BOOLEAN_FALSE);
LOGE("执行到此处2")
(*audioplayer)->GetInterface(audioplayer,SL_IID_PLAY,&slPlayItf);//初始化播放器
//注册缓冲区,通过缓冲区里面 的数据进行播放
(*audioplayer)->GetInterface(audioplayer,SL_IID_BUFFERQUEUE,&slBufferQueueItf);
//设置回调接口
(*slBufferQueueItf)->RegisterCallback(slBufferQueueItf,getQueueCallBack,NULL);

最后还要给这个缓存回调函数赋予参数，这个回调函数主要负责提供FFmpeg解码出的数据

//开始播放
getQueueCallBack(slBufferQueueItf,NULL);

我们再来看看这个函数说的啥，靠Enqueue函数把数据放入队列里，这个数据则是从getPcm函数得到的

void getQueueCallBack(SLAndroidSimpleBufferQueueItf slBufferQueueItf, void context){
buffersize=0;
getPcm(&buffer,&buffersize);
if(buffer!=NULL&&buffersize!=0){
//将得到的数据加入到队列中
(slBufferQueueItf)->Enqueue(slBufferQueueItf,buffer,buffersize);
}
}

这个FFmpeg解码mp3得到Pcm数据，这个主要是每解码出一个packet数据，就跳出循环，将数据给上层函数压入队列，当队列的数据读取完了，又会调用getQueueCallBack函数再来获取FFmpeg解码出的pcm数据

int getPcm(void *pcm,size_t pcm_size){
int frameCount=0;
int got_frame;
while (av_read_frame(pFormatCtx, packet) >= 0) {
if (packet->stream_index == audio_stream_idx) {
// 解码 mp3 编码格式frame----pcm frame
avcodec_decode_audio4(pCodecCtx, frame, &got_frame, packet);
if (got_frame) {
LOGE("解码");
/**

• int swr_convert(struct SwrContext s, uint8_t out, int out_count,
  const uint8_t in , int in_count);
  /
  swr_convert(swrContext, &out_buffer, 44100 * 2, (const uint8_t *) frame->data, frame->nb_samples);
  // 缓冲区的大小
  int size = av_samples_get_buffer_size(NULL, out_channer_nb, frame->nb_samples,
  AV_SAMPLE_FMT_S16, 1);
  pcm = out_buffer;
  *pcm_size = size;
  break;
  }
  }
  }
  return 0;
  }

5.播放音乐

(*slPlayItf)->SetPlayState(slPlayItf,SL_PLAYSTATE_PLAYING);

6.暂停音乐

(*slPlayItf)->SetPlayState(slPlayItf, SL_PLAYSTATE_PAUSED);

7.释放资源

首先释放关于OpenSL ES的实体

if(audioplayer!=NULL){
    (*audioplayer)->Destroy(audioplayer);
    audioplayer=NULL;
    slBufferQueueItf=NULL;
    slPlayItf=NULL;
}
if(outputMixObject!=NULL){
    (*outputMixObject)->Destroy(outputMixObject);
    outputMixObject=NULL;
    outputMixEnvironmentalReverb=NULL;
}
if(engineObject!=NULL){
    (*engineObject)->Destroy(engineObject);
    engineObject=NULL;
    engineEngine=NULL;
}

然后释放FFmpeg占用的资源

av_free_packet(packet);
av_free(out_buffer);
av_frame_free(&frame);
swr_free(&swrContext);
avcodec_close(pCodecCtx);
avformat_close_input(&pFormatCtx);