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/* *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; }
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