ffmpeg内存读取音频数据转码后发送到海思AI-」AO

前两节 “从内存中读取数据” “将数据输出到内存” 转载自博客https://blog.csdn.net/leixiaohua1020/article/details/12980423/

从内存中读取数据

ffmpeg一般情况下支持打开一个本地文件，例如“C:\test.avi”

或者是一个流媒体协议的URL，例如“rtmp://222.31.64.208/vod/test.flv”

其打开文件的函数是avformat_open_input()，直接将文件路径或者流媒体URL的字符串传递给该函数就可以了。

但其是否支持从内存中读取数据呢？这个问题困扰了我很长时间。当时在做项目的时候，通过Winpcap抓取网络上的RTP包，打算直接送给ffmpeg进行解码。一直没能找到合适的方法。因为抓取的数据包是存在内存中的，所以无法传递给avformat_open_input()函数其路径（根本没有路径= =）。当然也可以将抓取的数据报存成文件，然后用ffmpeg打开这个文件，但是这样的话，程序的就太难控制了。

后来经过分析ffmpeg的源代码，发现其竟然是可以从内存中读取数据的，代码很简单，如下所示：

AVFormatContext *ic = NULL; ic = avformat_alloc_context(); unsigned char * iobuffer=(unsigned char *)av_malloc(32768); AVIOContext *avio =avio_alloc_context(iobuffer, 32768,0,NULL,fill_iobuffer,NULL,NULL); ic->pb=avio; err = avformat_open_input(&ic, "nothing", NULL, NULL);

关键要在avformat_open_input()之前初始化一个AVIOContext，而且将原本的AVFormatContext的指针pb（AVIOContext类型）指向这个自行初始化AVIOContext。当自行指定了AVIOContext之后，avformat_open_input()里面的URL参数就不起作用了。示例代码开辟了一块空间iobuffer作为AVIOContext的缓存。 fill_iobuffer则是将数据读取至iobuffer的回调函数。fill_iobuffer()形式（参数，返回值）是固定的，是一个回调函数，如下所示（只是个例子，具体怎么读取数据可以自行设计）。示例中回调函数将文件中的内容通过fread()读入内存。

//读取数据的回调函数------------------------- //AVIOContext使用的回调函数！ //注意：返回值是读取的字节数 //手动初始化AVIOContext只需要两个东西：内容来源的buffer，和读取这个Buffer到FFmpeg中的函数 //回调函数，功能就是：把buf_size字节数据送入buf即可 //第一个参数(void *opaque)一般情况下可以不用 int fill_iobuffer(void * opaque,uint8_t *buf, int bufsize){ if(!feof(fp_open)){ int true_size=fread(buf,1,buf_size,fp_open); return true_size; }else{ return -1; } }

整体结构大致如下：

FILE *fp_open; int fill_iobuffer(void *opaque, uint8_t *buf, int buf_size){ ... } int main(){ ... fp_open=fopen("test.h264","rb+"); AVFormatContext *ic = NULL; ic = avformat_alloc_context(); unsigned char * iobuffer=(unsigned char *)av_malloc(32768); AVIOContext *avio =avio_alloc_context(iobuffer, 32768,0,NULL,fill_iobuffer,NULL,NULL); ic->pb=avio; err = avformat_open_input(&ic, "nothing", NULL, NULL); ...//解码 }

将数据输出到内存

和从内存中读取数据类似，ffmpeg也可以将处理后的数据输出到内存。

回调函数如下示例，可以将输出到内存的数据写入到文件中。

//写文件的回调函数 int write_buffer(void *opaque, uint8_t *buf, int buf_size){ if(!feof(fp_write)){ int true_size=fwrite(buf,1,buf_size,fp_write); return true_size; }else{ return -1; } }

主函数如下所示。

FILE *fp_write; int write_buffer(void *opaque, uint8_t *buf, int buf_size){ ... } main(){ ... fp_write=fopen("src01.h264","wb+"); //输出文件 ... AVFormatContext* ofmt_ctx=NULL; avformat_alloc_output_context2(&ofmt_ctx, NULL, "h264", NULL); unsigned char* outbuffer=(unsigned char*)av_malloc(32768); AVIOContext *avio_out =avio_alloc_context(outbuffer, 32768,0,NULL,NULL,write_buffer,NULL); ofmt_ctx->pb=avio_out; ofmt_ctx->flags=AVFMT_FLAG_CUSTOM_IO; ... }

从内存读取数据到ffmpeg转码

新建AVFormatContext容器并构建AVIOContext AVFormatContext* _fmt_ctx = NULL; AVIOContext *avio = NULL; int readSize = 1152*8; unsigned char * iobuffer = NULL; fp_open=fopen(filename,"r"); _fmt_ctx = avformat_alloc_context(); iobuffer=(unsigned char *)av_malloc(readSize); avio =avio_alloc_context(iobuffer, readSize,0,(void *)this,CInputCodeChn::fill_iobuffer,NULL,NULL); //新建读取线程往iobuffer中填充数据，下面检测code应该会用到 _fmt_ctx->pb = avio; _fmt_ctx->flags=AVFMT_FLAG_CUSTOM_IO; ret = avformat_open_input(&_fmt_ctx, "", NULL, NULL); if (ret < 0) { printf("CInputCodeChn: failed to call avformat_open_input\n"); exit(1); } 编写发送接口 //从内存中读取buf数据传入长度size int CInputCodeChn::sendAudioBuffer(char* buf, int size) { if((buf == NULL) && (size <= 0) ) { return -1; } pPbuf = memPbuf_alloc(PBUF_RAW,size,PBUF_RAM); if(pPbuf == NULL) { return -1; } pthread_mutex_lock(&mutex_pbuf); memcpy(pPbuf->payload,buf,size); pPbuf->tot_len = size; //将数据压入发送队列链表 m_rawFrameList.push_back(pPbuf); pthread_mutex_unlock(&mutex_pbuf); return size; }

新建一个线程不断地对网络流进行读取缓存将数据存储到m_rawFrameList队列中

在fill_iobuffer中对缓存队列进行读取并填充buf static int fill_iobuffer(void *opaque, uint8_t *buf, int buf_size) { struct memPbuf *pStreamFrame = NULL; CInputCodeChn *inputCodeChn = (CInputCodeChn *)opaque; int true_size = 0; /*if(!feof(inputCodeChn->fp_open)){ //从内部构建的缓存中去读 int true_size=fread(buf,1,buf_size,inputCodeChn->fp_open); //usleep(10*1000); if(true_size == 0) { printf("read file size = 0 +++++++++++++++++++++++++++\n"); } return true_size; } else { return -1; }*/ while(1){ pthread_mutex_lock(&inputCodeChn->mutex_pbuf); if(inputCodeChn->m_rawFrameList.size() > 0) { pStreamFrame = (struct memPbuf *)inputCodeChn->m_rawFrameList.front(); if (NULL == pStreamFrame) { printf( "new pStreamFrame fail\n"); } else { inputCodeChn->m_rawFrameList.pop_front(); } //填充buf memcpy(buf,pStreamFrame->payload,pStreamFrame->tot_len); true_size = pStreamFrame->tot_len; inputCodeChn->memPbuf_free(pStreamFrame); pthread_mutex_unlock(&inputCodeChn->mutex_pbuf); return true_size; }else{ pthread_mutex_unlock(&inputCodeChn->mutex_pbuf); av_usleep(10*1000); continue; } } pthread_mutex_unlock(&inputCodeChn->mutex_pbuf); return 0; } 接收解码后的数据 bool CInputCodeChn::ReciverThreadProc() { AVFrame* pFrame = av_frame_alloc(); AVPacket packet; av_init_packet(&packet); struct timeval now; int got_sound; while (_state == PREPARED) { } while (_state == RUNNING) { packet.data = NULL; packet.size = 0; if (av_read_frame(_fmt_ctx, &packet) < 0) { printf("there is no context mic \n"); break; } if (packet.stream_index == _index_audio) { if (avcodec_decode_audio4(_fmt_ctx->streams[_index_audio]->codec, pFrame, &got_sound, &packet) < 0) { printf("fail to avcodec_decode_audio4 \n"); break; } av_free_packet(&packet); if (!got_sound) { continue; } //处理解码后的数据帧pFrame } } av_frame_free(&pFrame); return true; }

读取编码后的帧缓存发送到海思音频接口

构建编码器上下文 fp_open=fopen(fileName,"wb+"); ret = avformat_alloc_output_context2(&_fmt_ctx_out, NULL, "wav", NULL); if (ret < 0) { printf("Mixer: failed to call avformat_alloc_output_context2\n"); return -1; } AVStream* stream_a = NULL; stream_a = avformat_new_stream(_fmt_ctx_out, NULL); if (stream_a == NULL) { printf("Mixer: failed to call avformat_new_stream\n"); return -1; } _index_a_out = 0; stream_a->codec->codec_type = AVMEDIA_TYPE_AUDIO; codec_aac = NULL; codec_aac = avcodec_find_encoder(AV_CODEC_ID_PCM_S16LE); if (codec_aac == NULL) { printf("Mixer: failed to call avcodec_find_encoder ++++\n"); return -1; } stream_a->codec->codec = codec_aac; stream_a->codec->sample_rate = 44100; stream_a->codec->channels = 1; stream_a->codec->channel_layout = av_get_default_channel_layout(1); stream_a->codec->sample_fmt = codec_aac->sample_fmts[0]; stream_a->codec->bit_rate = 32000; stream_a->codec->time_base.num = 1; stream_a->codec->time_base.den = stream_a->codec->sample_rate; stream_a->codec->codec_tag = 0; if (_fmt_ctx_out->oformat->flags & AVFMT_GLOBALHEADER) stream_a->codec->flags |= CODEC_FLAG_GLOBAL_HEADER; if (avcodec_open2(stream_a->codec, stream_a->codec->codec, NULL) < 0) { printf("Mixer: failed to call avcodec_open2\n"); return -1; } unsigned char* outbuffer=(unsigned char*)av_malloc(4608); AVIOContext *avio_out =avio_alloc_context(outbuffer,4608,1,fp_open,NULL,CAmixFilter::write_buffer,NULL); _fmt_ctx_out->pb=avio_out; _fmt_ctx_out->flags=AVFMT_FLAG_CUSTOM_IO; //write_buffer里发送编码后的wav数据到海思接口 /* if (!(_fmt_ctx_out->oformat->flags & AVFMT_NOFILE)) { printf("avio_open AVFMT_NOFILE\n"); if (avio_open(&_fmt_ctx_out->pb, NULL, AVIO_FLAG_WRITE) < 0) { printf("Mixer: failed to call avio_open\n"); return -1; } }*/ printf("avio_open1 \n"); if (avformat_write_header(_fmt_ctx_out, NULL) < 0) { printf("Mixer: failed to call avformat_write_header\n"); return -1; } bool b = (!_fmt_ctx_out->streams[0]->time_base.num && _fmt_ctx_out->streams[0]->codec->time_base.num); av_dump_format(_fmt_ctx_out, _index_a_out, NULL, 1); 构建write_buffer 发送函数 static int write_buffer(void *opaque, uint8_t *buf, int buf_size){ HI_S32 s32Ret; AUDIO_STREAM_S stAudioStream; /* FILE* fpopen = (FILE*)opaque; if(!feof(fpopen)){ int true_size=fwrite(buf,1,buf_size,fpopen); return true_size; }else{ return -1; }*/ if(buf_size > 0) { stAudioStream.pStream = buf; stAudioStream.u32Len = buf_size; //发送到海思ADEC进行播放adec->ao s32Ret = HI_MPI_ADEC_SendStream(0, &stAudioStream, HI_TRUE); if(HI_SUCCESS != s32Ret) { printf("%s: HI_MPI_ADEC_SendStream(%d) failed with %#x!\n",\ __FUNCTION__, 0, s32Ret); return 0; } return buf_size; } }