1.7 Android最简单的音频播放器

/*
*最简单的基于FFmpeg的音频播放器
*Simplest FFmpeg Audio Player
*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;
}