# FFmpeg-iOS的H.264解码 语言：zh-CN 原文：[FFmpeg-iOS的H.264解码]() 中文：[中文 HTML]() English: [English HTML]() 发布于: 2017-07-11T00:00:00+08:00 内容更新于: 2026-10-23T00:00:00+08:00 署名：[Bison]() 从导入 FFmpeg-iOS 与配置头文件搜索路径开始，梳理打开媒体、查找视频流、初始化解码器、读取数据包和释放资源的 H.264 解码流程，并提供封装示例。 原文署名 Bison，保留原发布时的内容。 **阅读前** 这是 2015–2017 年间的技术记录，本次整理未重新运行验证示例。原文发表于 2017 年，包含 av\_register\_all、avcodec\_decode\_video 等旧版 FFmpeg 接口。 本文的 av\_register\_all、avcodec\_decode\_video2 等调用属于原文使用的旧接口。阅读时可以先理清解封装、找到视频流、解码和释放资源的顺序；在当前 FFmpeg 中实现解码，应对照 send/receive API，分别处理送入数据与循环取帧。旧工程未重新编译。 - [FFmpeg：send/receive 编解码 API]() 阅读说明补充于 2026-10-23 历史配图暂不可用，[保留原图地址]()供查阅。 新建工程，导入由[Mac编译ffmpeg获取FFmpeg-iOS]()编译好的`FFmpeg-iOS`，然后导入系统依赖的库 ``` AudioToolbox.framework CoreMedia.framework VideoToolbox.framework libiconv.tbd libbz2.tbd libz.tbd ``` 编译的时候报错： ‘libavcodec/avcodec.h’ file not found ，修改Header search paths 里的路径： ``` $(PROJECT_DIR)/FFmpeg-iOS/include ``` 然后导入头文件 ``` /*----------------解码必须导入-----------------*/ #import "avformat.h" #include #include #include #include /*-------------------------------------------*/ ``` 运行一下项目不报错的话，就可以开始解码渲染之旅了。下面我们先从解码开始； ### h.264解码 ffmpeg对视频文件进行解码的大致流程： 1.注册所有容器格式和CODEC: av\_register\_all() ``` static dispatch_once_t onceToken; dispatch_once(&onceToken, ^{ av_register_all(); }); ``` 2.打开文件: av\_open\_input\_file() ``` pFormatContext = avformat_alloc_context(); NSString *fileName = [[NSBundle mainBundle] pathForResource:@"zjd.h264" ofType:nil]; if (fileName == nil) { NSLog(@"Couldn't open file:%@",fileName); return; } //[1]函数调用成功之后处理过的AVFormatContext结构体;[2]打开的视音频流的URL;[3]强制指定AVFormatContext中AVInputFormat的。这个参数一般情况下可以设置为NULL，这样FFmpeg可以自动检测AVInputFormat;[4]附加的一些选项，一般情况下可以设置为NULL。) if (avformat_open_input(&pFormatContext, [fileName cStringUsingEncoding:NSASCIIStringEncoding], NULL, NULL) != 0) { NSLog(@"无法打开文件"); return; } ``` 3.从文件中提取流信息: av\_find\_stream\_info() ``` if (avformat_find_stream_info(pFormatContext, NULL) < 0) { NSLog(@"无法提取流信息"); return; } ``` 4.穷举所有的流，查找其中种类为CODEC\_TYPE\_VIDEO ``` int videoStream = -1; for (int i = 0; i < pFormatContext -> nb_streams; i++) { if (pFormatContext -> streams[i] -> codec -> codec_type == AVMEDIA_TYPE_VIDEO) { videoStream = i; } } if (videoStream == -1) { NSLog(@"Didn't find a video stream."); return; } ``` 5.查找对应的解码器: avcodec\_find\_decoder() ``` pCodecCtx = pFormatContext->streams[videoStream]->codec; AVCodec *pCodec = avcodec_find_decoder(AV_CODEC_ID_H264); if (pCodec == NULL) { NSLog(@"pVideoCodec not found."); return NO; } ``` 6.打开编解码器: avcodec\_open() ``` avcodec_open2(pCodecCtx, pCodec, NULL); ``` 7.为解码帧分配内存: avcodec\_alloc\_frame() ``` pFrame = av_frame_alloc(); ``` 8.不停地从码流中提取中帧数据: av\_read\_frame() ``` AVPacket packet; av_init_packet(&packet); if (av_read_frame(pFormatContext, &packet) >= 0) {//已经读取到了数据 }else{//没读取到数据 } ``` 9.判断帧的类型，对于视频帧调用: avcodec\_decode\_video() ``` //作用是解码一帧视频数据。输入一个压缩编码的结构体AVPacket，输出一个解码后的结构体AVFrame avcodec_decode_video2(pCodecCtx, pFrame, &frameFinished, &packet); av_free_packet(&packet); if (frameFinished) //解码成功 { } ``` 10.解码完后，释放解码器: avcodec\_close() ``` avcodec_close() ``` 11.关闭输入文件:av\_close\_input\_file() ``` av_close_input_file() ``` 最后封装的代码如下 ``` /*input_str 输入的文件路径 *output_str 输出的文件路径 *return 解码后的信息 */ #pragma mark - 基于FFmpeg的视频解码器 - (NSString *)decoder:(NSString *)input_str output_str:(NSString *)output_str{ AVFormatContext *pFormatCtx; int i, videoindex; AVCodecContext *pCodecCtx; AVCodec *pCodec; AVFrame *pFrame,*pFrameYUV; uint8_t *out_buffer; AVPacket *packet; int y_size; int ret, got_picture; struct SwsContext *img_convert_ctx; FILE *fp_yuv; int frame_cnt; clock_t time_start, time_finish; double time_duration = 0.0; char input_str_full[500]={0}; char output_str_full[500]={0}; char info[1000]={0}; // NSString *input_str= [NSString stringWithFormat:@"resource.bundle/sintel.mov"]; // NSString *output_str= [NSString stringWithFormat:@"resource.bundle/test.yuv"]; NSString *input_nsstr=[[[NSBundle mainBundle]resourcePath] stringByAppendingPathComponent:input_str]; NSString *output_nsstr=[[[NSBundle mainBundle]resourcePath] stringByAppendingPathComponent:output_str]; sprintf(input_str_full,"%s",[input_nsstr UTF8String]); sprintf(output_str_full,"%s",[output_nsstr UTF8String]); printf("Input Path:%s\n",input_str_full); printf("Output Path:%s\n",output_str_full); //注册编解码器 av_register_all(); //打开网络流 avformat_network_init(); //初始化AVFormatContext pFormatCtx = avformat_alloc_context(); if(avformat_open_input(&pFormatCtx,input_str_full,NULL,NULL)!=0){ printf("Couldn't open input stream.\n"); return nil; } if(avformat_find_stream_info(pFormatCtx,NULL)<0){ printf("Couldn't find stream information.\n"); return nil; } videoindex=-1; for(i=0; inb_streams; i++) if(pFormatCtx->streams[i]->codecpar->codec_type==AVMEDIA_TYPE_VIDEO){ videoindex=i; break; } if(videoindex==-1){ printf("Couldn't find a video stream.\n"); return nil; } pCodecCtx = avcodec_alloc_context3(NULL); if (pCodecCtx == NULL) { printf("Could not allocate AVCodecContext\n"); return nil; } avcodec_parameters_to_context(pCodecCtx, pFormatCtx->streams[videoindex]->codecpar); pCodec = avcodec_find_decoder(pCodecCtx->codec_id); //指向AVCodec的指针.查找解码器 if(pCodec==NULL){ printf("Couldn't find Codec.\n"); return nil; } if(avcodec_open2(pCodecCtx, pCodec,NULL)<0){ printf("Couldn't open codec.\n"); return nil; } pFrame=av_frame_alloc(); pFrameYUV=av_frame_alloc(); out_buffer=(unsigned char *)av_malloc(av_image_get_buffer_size(AV_PIX_FMT_YUV420P, pCodecCtx->width, pCodecCtx->height,1)); av_image_fill_arrays(pFrameYUV->data, pFrameYUV->linesize,out_buffer, AV_PIX_FMT_YUV420P,pCodecCtx->width, pCodecCtx->height,1); packet=(AVPacket *)av_malloc(sizeof(AVPacket)); img_convert_ctx = sws_getContext(pCodecCtx->width, pCodecCtx->height, pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height, AV_PIX_FMT_YUV420P, SWS_BICUBIC, NULL, NULL, NULL); sprintf(info, "[Input ]%s\n", [input_str UTF8String]); sprintf(info, "%s[Output ]%s\n",info,[output_str UTF8String]); sprintf(info, "%s[Format ]%s\n",info, pFormatCtx->iformat->name); sprintf(info, "%s[Codec ]%s\n",info, pCodecCtx->codec->name); sprintf(info, "%s[Resolution]%dx%d\n",info, pCodecCtx->width,pCodecCtx->height); fp_yuv=fopen(output_str_full,"wb+"); if(fp_yuv==NULL){ printf("Cannot open output file.\n"); return nil; } frame_cnt=0; time_start = clock(); while(av_read_frame(pFormatCtx, packet)>=0){ if(packet->stream_index==videoindex){ ret = avcodec_decode_video2(pCodecCtx, pFrame, &got_picture, packet); if(ret < 0){ printf("Decode Error.\n"); return nil; } if(got_picture){ sws_scale(img_convert_ctx, (const uint8_t* const*)pFrame->data, pFrame->linesize, 0, pCodecCtx->height, pFrameYUV->data, pFrameYUV->linesize); y_size=pCodecCtx->width*pCodecCtx->height; fwrite(pFrameYUV->data[0],1,y_size,fp_yuv); //Y fwrite(pFrameYUV->data[1],1,y_size/4,fp_yuv); //U fwrite(pFrameYUV->data[2],1,y_size/4,fp_yuv); //V //Output info char pictype_str[10]={0}; switch(pFrame->pict_type){ case AV_PICTURE_TYPE_I:sprintf(pictype_str,"I");break; case AV_PICTURE_TYPE_P:sprintf(pictype_str,"P");break; case AV_PICTURE_TYPE_B:sprintf(pictype_str,"B");break; default:sprintf(pictype_str,"Other");break; } printf("Frame Index: %5d. Type:%s\n",frame_cnt,pictype_str); frame_cnt++; } } av_packet_unref(packet); } //flush decoder //FIX: Flush Frames remained in Codec while (1) { ret = avcodec_decode_video2(pCodecCtx, pFrame, &got_picture, packet); if (ret < 0) break; if (!got_picture) break; sws_scale(img_convert_ctx, (const uint8_t* const*)pFrame->data, pFrame->linesize, 0, pCodecCtx->height, pFrameYUV->data, pFrameYUV->linesize); int y_size=pCodecCtx->width*pCodecCtx->height; fwrite(pFrameYUV->data[0],1,y_size,fp_yuv); //Y fwrite(pFrameYUV->data[1],1,y_size/4,fp_yuv); //U fwrite(pFrameYUV->data[2],1,y_size/4,fp_yuv); //V //Output info char pictype_str[10]={0}; switch(pFrame->pict_type){ case AV_PICTURE_TYPE_I:sprintf(pictype_str,"I");break; case AV_PICTURE_TYPE_P:sprintf(pictype_str,"P");break; case AV_PICTURE_TYPE_B:sprintf(pictype_str,"B");break; default:sprintf(pictype_str,"Other");break; } printf("Frame Index: %5d. Type:%s\n",frame_cnt,pictype_str); frame_cnt++; } time_finish = clock(); time_duration=(double)(time_finish - time_start); sprintf(info, "%s[Time ]%fus\n",info,time_duration); sprintf(info, "%s[Count ]%d\n",info,frame_cnt); sws_freeContext(img_convert_ctx); fclose(fp_yuv); av_frame_free(&pFrameYUV); av_frame_free(&pFrame); avcodec_close(pCodecCtx); avformat_close_input(&pFormatCtx); NSString * info_ns = [NSString stringWithFormat:@"%s", info]; // NSLog(@"解码后的信息%@",info_ns); NSLog(@"文件输出路径%@",output_nsstr); return info_ns; } ``` 参考资料：[雷神的ffmpeg解码]() [LBffmpegDemo下载地址](); --- 好文推荐：[菜鸟程序员2015年年终总结]()