Android 音视频学习基础--1.7 Android最简单的

vs代码下载链接：
https://pan.baidu.com/s/1c2dIuYk 密码：ld4b

/* 
 *最简单的基于FFmpeg的音频播放器
 *Simplest FFmpeg Audio Player
 *Communication University of China / Digital TV Technology
 *http://blog.csdn.net/leixiaohua1020
 *
 *本程序实现了音频的解码和播放。
 *
 */
#include <stdlib.h>
#include <string.h>
extern "C"
{
#include "libavcodec/avcodec.h"
#include "libavformat/avformat.h"
#include "libswresample/swresample.h"
//SDL
#include "sdl/SDL.h"
#include "sdl/SDL_thread.h"
};
#include "decoder.h"

//#define _WAVE_

//全局变量---------------------
    static  Uint8  *audio_chunk; 
    static  Uint32  audio_len; 
    static  Uint8  *audio_pos; 
//-----------------
    /*  The audio function callback takes the following parameters: 
    stream: A pointer to the audio buffer to be filled 
    len: The length (in bytes) of the audio buffer (这是固定的4096？)
    回调函数
    注意：mp3为什么播放不顺畅？
    len=4096;audio_len=4608;两个相差512！为了这512，还得再调用一次回调函数。。。
    m4a,aac就不存在此问题(都是4096)！
    */ 
    void  fill_audio(void *udata,Uint8 *stream,int len){ 
        /*  Only  play  if  we  have  data  left  */ 
    if(audio_len==0) 
            return; 
        /*  Mix  as  much  data  as  possible  */ 
    len=(len>audio_len?audio_len:len); 
    SDL_MixAudio(stream,audio_pos,len,SDL_MIX_MAXVOLUME);
    audio_pos += len; 
    audio_len -= len; 
    } 
//-----------------


int decode_audio(char* no_use)
{
    AVFormatContext *pFormatCtx;
    int             i, audioStream;
    AVCodecContext  *pCodecCtx;
    AVCodec         *pCodec;


    
    char url[300]={0};
    strcpy(url,no_use);

    av_register_all();
    //支持网络流输入ff
    avformat_network_init();
    //初始化
    pFormatCtx = avformat_alloc_context();
    //打开
    if(avformat_open_input(&pFormatCtx,url,NULL,NULL)!=0){
        printf("Couldn't open input stream.\n");
        return -1;
    }
    // Retrieve stream information
    if(av_find_stream_info(pFormatCtx)<0)
    {
        printf("Couldn't find stream information.\n");
        return -1;
    }
    // Dump valid information onto standard error
    av_dump_format(pFormatCtx, 0, url, false);

    // Find the first audio stream
    audioStream=-1;
    for(i=0; i < pFormatCtx->nb_streams; i++)
        if(pFormatCtx->streams[i]->codec->codec_type==AVMEDIA_TYPE_AUDIO)
        {
            audioStream=i;
            break;
        }

    if(audioStream==-1)
    {
        printf("Didn't find a audio stream.\n");
        return -1;
    }

    // Get a pointer to the codec context for the audio stream
    pCodecCtx=pFormatCtx->streams[audioStream]->codec;

    // Find the decoder for the audio stream
    pCodec=avcodec_find_decoder(pCodecCtx->codec_id);
    if(pCodec==NULL)
    {
        printf("Codec not found.\n");
        return -1;
    }

    // Open codec
    if(avcodec_open2(pCodecCtx, pCodec,NULL)<0)
    {
        printf("Could not open codec.\n");
        return -1;
    }

    FILE *pFile;
#ifdef _WAVE_
    pFile=fopen("output.wav", "wb");
    fseek(pFile, 44, SEEK_SET); //预留文件头的位置
#else
    pFile=fopen("output1.pcm", "wb");
#endif

    AVPacket *packet=(AVPacket *)malloc(sizeof(AVPacket));
    av_init_packet(packet);

    AVFrame *pFrame;
    pFrame=avcodec_alloc_frame();
    //输出音频数据大小，一定小于输出内存。
    int out_linesize;
    //输出内存大小
    int out_buffer_size=av_samples_get_buffer_size(&out_linesize, pCodecCtx->channels,pCodecCtx->frame_size,pCodecCtx->sample_fmt, 1);
    uint8_t *out_buffer=new uint8_t[out_buffer_size];
    //---------SDL--------------------------------------
    //初始化
    if(SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_TIMER)) {  
        printf( "Could not initialize SDL - %s\n", SDL_GetError()); 
        exit(1);
    }

    //结构体，包含PCM数据的相关信息
    SDL_AudioSpec wanted_spec;
    wanted_spec.freq = pCodecCtx->sample_rate; 
    wanted_spec.format = AUDIO_S16SYS; 
    wanted_spec.channels = pCodecCtx->channels; 
    wanted_spec.silence = 0; 
    //wanted_spec.samples = 1024; //播放AAC，M4a，缓冲区的大小
    wanted_spec.samples = 1152; //播放MP3，WMA时候用
    wanted_spec.callback = fill_audio; 
    wanted_spec.userdata = pCodecCtx; 

    if (SDL_OpenAudio(&wanted_spec, NULL)<0)//步骤（2）打开音频设备 
    { 
        printf("can't open audio.\n"); 
        return 0; 
    } 
    //-----------------------------------------------------
    printf("Bitrate:\t %3d\n", pFormatCtx->bit_rate);
    printf("Decoder Name:\t %s\n", pCodecCtx->codec->long_name);
    printf("Channels:\t %d\n", pCodecCtx->channels);
    printf("Sample per Second\t %d \n", pCodecCtx->sample_rate);

    uint32_t ret,len = 0;
    int got_picture;
    int index = 0;
    struct SwrContext *au_convert_ctx;
    au_convert_ctx = swr_alloc();
    au_convert_ctx=swr_alloc_set_opts(au_convert_ctx,AV_CH_LAYOUT_STEREO, AV_SAMPLE_FMT_S16, 44100,
        pCodecCtx->channel_layout,pCodecCtx->sample_fmt , pCodecCtx->sample_rate,0, NULL);
    swr_init(au_convert_ctx);
    while(av_read_frame(pFormatCtx, packet)>=0)
    {
        if(packet->stream_index==audioStream)
        {

            ret = avcodec_decode_audio4( pCodecCtx, pFrame,&got_picture, packet);
            if ( ret < 0 ) 
            {
                printf("Error in decoding audio frame.\n");
                exit(0);
            }
            if ( got_picture > 0 )
            {
#if 1
                swr_convert(au_convert_ctx,&out_buffer, out_linesize,(const uint8_t **)pFrame->data , pFrame->nb_samples);

                printf("index:%5d\t pts %5d\n", index,packet->pts);
#endif
                //直接写入
#if 1
                fwrite(out_buffer, 1, out_linesize, pFile);
#endif
                index++;
            }
#if 1
            //---------------------------------------
            //printf("begin....\n"); 
            //设置音频数据缓冲,PCM数据
            audio_chunk = (Uint8 *) out_buffer; 
            //设置音频数据长度
            audio_len = out_linesize;
            audio_len = 4096;
            //播放mp3的时候改为audio_len = 4096
            //则会比较流畅，但是声音会变调！MP3一帧长度4608
            //使用一次回调函数（4096字节缓冲）播放不完，所以还要使用一次回调函数，导致播放缓慢。。。
            //设置初始播放位置
            audio_pos = audio_chunk;
            //回放音频数据 
            SDL_PauseAudio(0);
            //printf("don't close, audio playing...\n"); 
            while(audio_len>0)//等待直到音频数据播放完毕! 
                SDL_Delay(1); 
            //---------------------------------------
#endif
        }
        av_free_packet(packet);
    }

#ifdef _WAVE_
    fseek(pFile, 0, SEEK_SET);
    struct WAVE_HEADER wh;

    memcpy(wh.header.RiffID, "RIFF", 4);
    wh.header.RiffSize = 36 + len;
    memcpy(wh.header.RiffFormat, "WAVE", 4);

    memcpy(wh.format.FmtID, "fmt ", 4);
    wh.format.FmtSize = 16;
    wh.format.wavFormat.FormatTag = 1;
    wh.format.wavFormat.Channels = pCodecCtx->channels;
    wh.format.wavFormat.SamplesRate = pCodecCtx->sample_rate;
    wh.format.wavFormat.BitsPerSample = 16;
    calformat(wh.format.wavFormat); //Calculate AvgBytesRate and BlockAlign

    memcpy(wh.data.DataID, "data", 4);
    wh.data.DataSize = len;

    fwrite(&wh, 1, sizeof(wh), pFile);
#endif
    SDL_CloseAudio();//关闭音频设备 
    // Close file
    fclose(pFile);
    // Close the codec
    avcodec_close(pCodecCtx);
    // Close the video file
    av_close_input_file(pFormatCtx);

    return 0;
}

Android 音视频学习基础--1.1 音视频基础知识
Android 音视频学习基础--1.2 需要认识的一些工具
Android 音视频学习基础--1.3 主流的开源项目
Android 音视频学习基础--1.4 ffmpeg pcm输出
Android 音视频学习基础--1.5 ffmpeg yuv输出
Android 音视频学习基础--1.6 ffmpeg 简单视频播放器
Android 音视频学习基础--1.7 Android最简单的音频播放器
Android 音视频学习基础--1.8 Android最简单的音频播放器
Android 音视频学习基础--1.9 Android最简单的视频播放器
Android 音视频学习基础--1.10 Android自制简单音视频播放器