使用FFMPEG5.0和SDL2.0编写视频简单播放器

使用ffmpeg5.0和SDL1.2（操作系统原本安装了这个版本，所以想先用这个库调试看看），编写视频播放器daemon时，视频卡在第一帧会报错：

测试例程如下：

int B_Play_Openfile(const char* szFilePath)
{int iRet = 0;int iVideo_index = 0;char szError[128] = {0};unsigned char *out_buffer = NULL;AVFormatContext *FormatContext = avformat_alloc_context();     /* 媒体文件句柄 */AVCodec *Video_Codec = NULL;                                   /* 解码器句柄 */AVCodecContext *Video_CodecContext = NULL;                      /* 解码器上下文 */AVFrame *Video_Frame = NULL;                                   /* 帧缓存 */AVFrame *YUV_Frame = NULL;                                        /* YUV帧 */                                  AVPacket *Video_Packet = NULL;if (szFilePath == NULL){B_LOG("illegal file path\r\n");return -1;}else{B_LOG("B_Play_Openfile, Path[%s]\r\n", szFilePath);}/* 打开一个输入流并读取头部 */iRet = avformat_open_input(&FormatContext, szFilePath, NULL, NULL);if (iRet != 0){av_strerror(iRet, szError, sizeof(szError));B_LOG("avformat_open_input fail, Ret[%d], Err[%s]\r\n", iRet, szError);return iRet;}/* 读取媒体文件的数据包以获取流信息 */iRet = avformat_find_stream_info(FormatContext, NULL);if (iRet < 0){av_strerror(iRet, szError, sizeof(szError));B_LOG("avformat_open_input fail, Ret[%d], Err[%s]\r\n", iRet, szError);avformat_close_input(&FormatContext);return iRet;}/* 查找视频码流索引 */iVideo_index = av_find_best_stream(FormatContext, AVMEDIA_TYPE_VIDEO, -1, -1, NULL, 0);if (AVERROR_STREAM_NOT_FOUND == iVideo_index){/* 未找到视频流 */B_LOG("av_find_best_stream not found video stream\r\n");avformat_close_input(&FormatContext);return -1;}else if (AVERROR_DECODER_NOT_FOUND == iVideo_index){/* 找到视频流，但是没找到解码器 */B_LOG("av_find_best_stream streams were found but no decoder\r\n");avformat_close_input(&FormatContext);return -1;}/* 查找解码器 */Video_Codec = avcodec_find_decoder(FormatContext->streams[iVideo_index]->codecpar->codec_id);if (NULL == Video_Codec){B_LOG("avcodec_find_decoder fail\r\n");avformat_close_input(&FormatContext);return -1;}/* 创建解码器上下文(为Video_CodecContext申请内存空间) */Video_CodecContext = avcodec_alloc_context3(Video_Codec);if (NULL == Video_CodecContext){B_LOG("avcodec_alloc_context3 fail\r\n");avformat_close_input(&FormatContext);return -1;}/* 预初始化解码器上下文(从FormatContext->streams[iVideo_index]->codecpar获取解码器的有关参数,并填充至Video_CodecContext) */iRet = avcodec_parameters_to_context(Video_CodecContext, FormatContext->streams[iVideo_index]->codecpar);if (iRet < 0){av_strerror(iRet, szError, sizeof(szError));B_LOG("avcodec_parameters_to_context fail, Ret[%d], Err[%s]\r\n", iRet, szError);avformat_close_input(&FormatContext);return iRet;}/* 打开解码器上下文 */iRet = avcodec_open2(Video_CodecContext, Video_Codec, NULL);if (iRet != 0){av_strerror(iRet, szError, sizeof(szError));B_LOG("avcodec_open2 fail, Ret[%d], Err[%s]\r\n", iRet, szError);avformat_close_input(&FormatContext);return iRet;}/* 申请帧缓存 */Video_Frame = av_frame_alloc();if (NULL == Video_Frame){B_LOG("av_frame_alloc fail,\r\n");avformat_close_input(&FormatContext);return iRet;}YUV_Frame = av_frame_alloc();if (NULL == YUV_Frame){B_LOG("av_frame_alloc fail,\r\n");avformat_close_input(&FormatContext);return iRet;}struct SwsContext *img_convert_ctx;int Video_H = 0;                                                /* 视频高 */int Video_W = 0;                                              /* 视频宽 */SDL_Surface *screen; SDL_VideoInfo *vi;SDL_Overlay *bmp; SDL_Rect rect;int got_picture;iRet = SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_TIMER);if (iRet != 0){B_LOG("SDL_Init fail, Ret[%d]\r\n", iRet);avformat_close_input(&FormatContext);return iRet;}Video_H = Video_CodecContext->width;Video_W = Video_CodecContext->height;screen = SDL_SetVideoMode(Video_W, Video_H, 0, 0);if (screen == NULL){B_LOG("SDL_SetVideoMode fail, Ret[%d]\r\n", iRet);avformat_close_input(&FormatContext);return iRet;}bmp = SDL_CreateYUVOverlay(Video_CodecContext->width, Video_CodecContext->height,SDL_YV12_OVERLAY, screen); rect.x = 0;    rect.y = 0;    rect.w = Video_W;    rect.h = Video_H; Video_Packet = (AVPacket *)av_malloc(sizeof(AVPacket));av_dump_format(FormatContext, 0, szFilePath, 0);SDL_WM_SetCaption("B_Play",NULL);img_convert_ctx = sws_getContext(Video_CodecContext->width, Video_CodecContext->height, Video_CodecContext->pix_fmt, Video_CodecContext->width, Video_CodecContext->height, AV_PIX_FMT_YUV420P, SWS_BICUBIC, NULL, NULL, NULL); B_LOG("1111111");while(av_read_frame(FormatContext, Video_Packet)>=0){B_LOG("2222222");if(Video_Packet->stream_index==iVideo_index){//Decodeavcodec_send_packet(Video_CodecContext, Video_Packet);got_picture = avcodec_receive_frame(Video_CodecContext, Video_Frame);if(got_picture){SDL_LockYUVOverlay(bmp);YUV_Frame->data[0]=bmp->pixels[0];YUV_Frame->data[1]=bmp->pixels[2];YUV_Frame->data[2]=bmp->pixels[1];     YUV_Frame->linesize[0]=bmp->pitches[0];YUV_Frame->linesize[1]=bmp->pitches[2];   YUV_Frame->linesize[2]=bmp->pitches[1];sws_scale(img_convert_ctx, (const uint8_t* const*)Video_Frame->data, Video_Frame->linesize, 0, Video_CodecContext->height, YUV_Frame->data, YUV_Frame->linesize);SDL_UnlockYUVOverlay(bmp); SDL_DisplayYUVOverlay(bmp, &rect); //Delay 40msSDL_Delay(40);}}av_packet_unref(Video_Packet);}B_LOG("3333333333\n");while (1) {B_LOG("4444444444\n");avcodec_send_packet(Video_CodecContext, Video_Packet);got_picture = avcodec_receive_frame(Video_CodecContext, Video_Frame);if (got_picture)break;sws_scale(img_convert_ctx, (const uint8_t* const*)Video_Frame->data, Video_Frame->linesize, 0, Video_CodecContext->height, YUV_Frame->data, YUV_Frame->linesize);SDL_LockYUVOverlay(bmp);YUV_Frame->data[0]=bmp->pixels[0];YUV_Frame->data[1]=bmp->pixels[2];YUV_Frame->data[2]=bmp->pixels[1];     YUV_Frame->linesize[0]=bmp->pitches[0];YUV_Frame->linesize[1]=bmp->pitches[2];   YUV_Frame->linesize[2]=bmp->pitches[1];SDL_UnlockYUVOverlay(bmp); SDL_DisplayYUVOverlay(bmp, &rect); //Delay 40msSDL_Delay(40);}sws_freeContext(img_convert_ctx);SDL_Quit();//av_free(out_buffer);av_free(YUV_Frame);avcodec_close(Video_CodecContext);avformat_close_input(&FormatContext);return 0;
}

当时对这个问题的理解不是很深刻，不过上网查了一下资料发现别人FFMPEG高版本但是搭配SDL2.0使用的，于是想着先用SDL2.0试试看。不过后面发现这个报错原因是自己代码写的有点问题（avcodec_receive_frame的返回值判断上写反了导致处理视频帧处没有进入。。。）

安装SDL2.0：

sudo apt-get install libsdl2-2.0
sudo apt-get install libsdl2-dev

安装完成后重新编译工程，发现有这么多报错：

原因是SDL1.2和2.0接口发生了比较大的差异，具体可以参看：https://blog.csdn.net/chaoswiming/article/details/46788707
根据SDL2.0接口重新编码后，还是会有编译报错：

这种问题一般是和库版本或是编译配置有关，于是我重新下了一份SDL源码，编译了一边，并且在自己过程的makefille里面链上了静态库：

这个时候会有这种报错：

看来是编译存在问题，修改makefile：

最终解决了SDL2.0的编译问题。

最后调试例程如下：

int B_Play_Openfile(const char* szFilePath)
{int iRet = 0;int iVideo_index = 0;char szError[128] = {0};unsigned char *out_buffer = NULL;AVFormatContext *FormatContext = avformat_alloc_context();     /* 濯掍綋鏂囦欢鍙ユ焺 */AVCodec *Video_Codec = NULL;                                    /* 瑙ｇ爜鍣ㄥ彞鏌?*/AVCodecContext *Video_CodecContext = NULL;                     /* 瑙ｇ爜鍣ㄤ笂涓嬫枃 */AVFrame *Video_Frame = NULL;                                 /* 甯х紦瀛?*/AVFrame *YUV_Frame = NULL;                                       /* YUV甯?*/                                  AVPacket *Video_Packet = NULL;int ret, got_picture;if (szFilePath == NULL){B_LOG("illegal file path\r\n");return -1;}else{B_LOG(">>>>>>>>>>>>>>>>>>>>>>>>>>>B_Play_Openfile, Path[%s]\r\n", szFilePath);}/* 鎵撳紑涓€涓緭鍏ユ祦骞惰鍙栧ご閮?*/iRet = avformat_open_input(&FormatContext, szFilePath, NULL, NULL);if (iRet != 0){av_strerror(iRet, szError, sizeof(szError));B_LOG("avformat_open_input fail, Ret[%d], Err[%s]\r\n", iRet, szError);return iRet;}/* 璇诲彇濯掍綋鏂囦欢鐨勬暟鎹寘浠ヨ幏鍙栨祦淇℃伅 */iRet = avformat_find_stream_info(FormatContext, NULL);if (iRet < 0){av_strerror(iRet, szError, sizeof(szError));B_LOG("avformat_open_input fail, Ret[%d], Err[%s]\r\n", iRet, szError);avformat_close_input(&FormatContext);return iRet;}/* 鏌ユ壘瑙嗛鐮佹祦绱㈠紩 */iVideo_index = av_find_best_stream(FormatContext, AVMEDIA_TYPE_VIDEO, -1, -1, NULL, 0);if (AVERROR_STREAM_NOT_FOUND == iVideo_index){/* 鏈壘鍒拌棰戞祦 */B_LOG("av_find_best_stream not found video stream\r\n");avformat_close_input(&FormatContext);return -1;}else if (AVERROR_DECODER_NOT_FOUND == iVideo_index){/* 鎵惧埌瑙嗛娴侊紝浣嗘槸娌℃壘鍒拌В鐮佸櫒 */B_LOG("av_find_best_stream streams were found but no decoder\r\n");avformat_close_input(&FormatContext);return -1;}/* 鏌ユ壘瑙ｇ爜鍣?*/Video_Codec = avcodec_find_decoder(FormatContext->streams[iVideo_index]->codecpar->codec_id);if (NULL == Video_Codec){B_LOG("avcodec_find_decoder fail\r\n");avformat_close_input(&FormatContext);return -1;}/* 鍒涘缓瑙ｇ爜鍣ㄤ笂涓嬫枃(涓篤ideo_CodecContext鐢宠鍐呭瓨绌洪棿) */Video_CodecContext = avcodec_alloc_context3(Video_Codec);if (NULL == Video_CodecContext){B_LOG("avcodec_alloc_context3 fail\r\n");avformat_close_input(&FormatContext);return -1;}/* 棰勫垵濮嬪寲瑙ｇ爜鍣ㄤ笂涓嬫枃(浠嶧ormatContext->streams[iVideo_index]->codecpar鑾峰彇瑙ｇ爜鍣ㄧ殑鏈夊叧鍙傛暟,骞跺～鍏呰嚦Video_CodecContext) */iRet = avcodec_parameters_to_context(Video_CodecContext, FormatContext->streams[iVideo_index]->codecpar);if (iRet < 0){av_strerror(iRet, szError, sizeof(szError));B_LOG("avcodec_parameters_to_context fail, Ret[%d], Err[%s]\r\n", iRet, szError);avformat_close_input(&FormatContext);return iRet;}/* 鎵撳紑瑙ｇ爜鍣ㄤ笂涓嬫枃 */iRet = avcodec_open2(Video_CodecContext, Video_Codec, NULL);if (iRet != 0){av_strerror(iRet, szError, sizeof(szError));B_LOG("avcodec_open2 fail, Ret[%d], Err[%s]\r\n", iRet, szError);avformat_close_input(&FormatContext);return iRet;}/* 鐢宠甯х紦瀛?*/Video_Frame = av_frame_alloc();if (NULL == Video_Frame){B_LOG("av_frame_alloc fail,\r\n");avformat_close_input(&FormatContext);return iRet;}YUV_Frame = av_frame_alloc();if (NULL == YUV_Frame){B_LOG("av_frame_alloc fail,\r\n");avformat_close_input(&FormatContext);return iRet;}
#ifdef SDL2_0int Video_H = 0;                                              /* 瑙嗛楂?*/int Video_W = 0;out_buffer=(unsigned char *)av_malloc(av_image_get_buffer_size(AV_PIX_FMT_YUV420P,  Video_CodecContext->width, Video_CodecContext->height,1));if (NULL == out_buffer){B_LOG("av_malloc fail,\r\n");avformat_close_input(&FormatContext);return iRet;}struct SwsContext *img_convert_ctx;av_image_fill_arrays(YUV_Frame->data, YUV_Frame->linesize,out_buffer, AV_PIX_FMT_YUV420P,Video_CodecContext->width, Video_CodecContext->height,1);Video_Packet = (AVPacket *)av_malloc(sizeof(AVPacket));av_dump_format(FormatContext, 0, szFilePath, 0);img_convert_ctx = sws_getContext(Video_CodecContext->width, Video_CodecContext->height, Video_CodecContext->pix_fmt, Video_CodecContext->width, Video_CodecContext->height, AV_PIX_FMT_YUV420P, SWS_BICUBIC, NULL, NULL, NULL);iRet = SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_TIMER);if (iRet != 0){B_LOG("SDL_Init fail, Ret[%d]\r\n", iRet);avformat_close_input(&FormatContext);return iRet;}Video_W = Video_CodecContext->width;Video_H = Video_CodecContext->height;SDL_Window *screen = SDL_CreateWindow("B_Play", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, Video_W, Video_H, SDL_WINDOW_OPENGL);if(!screen) {  B_LOG("SDL: could not create window - exiting:%s\n",SDL_GetError());  return -1;}SDL_Renderer *sdlRenderer = SDL_CreateRenderer(screen, -1, 0);  SDL_Texture *sdlTexture = SDL_CreateTexture(sdlRenderer, SDL_PIXELFORMAT_IYUV, SDL_TEXTUREACCESS_STREAMING,Video_CodecContext->width,Video_CodecContext->height);  SDL_Rect sdlRect;sdlRect.x=0;sdlRect.y=0;sdlRect.w=Video_W;sdlRect.h=Video_H;while(av_read_frame(FormatContext, Video_Packet)>=0){if(Video_Packet->stream_index==iVideo_index){//iRet = avcodec_decode_video2(Video_CodecContext, Video_Frame, &got_picture, Video_Packet);avcodec_send_packet(Video_CodecContext, Video_Packet);got_picture = avcodec_receive_frame(Video_CodecContext, Video_Frame);if(!got_picture){sws_scale(img_convert_ctx, (const unsigned char* const*)Video_Frame->data, Video_Frame->linesize, 0, Video_CodecContext->height, YUV_Frame->data, YUV_Frame->linesize);SDL_UpdateYUVTexture(sdlTexture, &sdlRect,YUV_Frame->data[0], YUV_Frame->linesize[0],YUV_Frame->data[1], YUV_Frame->linesize[1],YUV_Frame->data[2], YUV_Frame->linesize[2]);SDL_RenderClear( sdlRenderer );  SDL_RenderCopy( sdlRenderer, sdlTexture,  NULL, &sdlRect);  SDL_RenderPresent( sdlRenderer );  SDL_Delay(40);}}av_packet_unref(Video_Packet);}while (1) {//ret = avcodec_decode_video2(Video_CodecContext, Video_Frame, &got_picture, Video_Packet);avcodec_send_packet(Video_CodecContext, Video_Packet);got_picture = avcodec_receive_frame(Video_CodecContext, Video_Frame);if (!got_picture)break;sws_scale(img_convert_ctx, (const unsigned char* const*)Video_Frame->data, Video_Frame->linesize, 0, Video_CodecContext->height, YUV_Frame->data, YUV_Frame->linesize);SDL_UpdateTexture( sdlTexture, &sdlRect, YUV_Frame->data[0], YUV_Frame->linesize[0] );  SDL_RenderClear( sdlRenderer );  SDL_RenderCopy( sdlRenderer, sdlTexture,  NULL, &sdlRect);  SDL_RenderPresent( sdlRenderer );  SDL_Delay(40);}sws_freeContext(img_convert_ctx);SDL_Quit();av_frame_free(&YUV_Frame);av_frame_free(&Video_Frame);avcodec_close(Video_CodecContext);avformat_close_input(&FormatContext);#elsestruct SwsContext *img_convert_ctx;int Video_H = 0;                                                /* 瑙嗛楂?*/int Video_W = 0;                                             /* 瑙嗛瀹?*/SDL_Surface *screen; SDL_VideoInfo *vi;SDL_Overlay *bmp; SDL_Rect rect;int got_picture;iRet = SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_TIMER);if (iRet != 0){B_LOG("SDL_Init fail, Ret[%d]\r\n", iRet);avformat_close_input(&FormatContext);return iRet;}Video_H = Video_CodecContext->width;Video_W = Video_CodecContext->height;screen = SDL_SetVideoMode(Video_W, Video_H, 0, 0);if (screen == NULL){B_LOG("SDL_SetVideoMode fail, Ret[%d]\r\n", iRet);avformat_close_input(&FormatContext);return iRet;}bmp = SDL_CreateYUVOverlay(Video_CodecContext->width, Video_CodecContext->height,SDL_YV12_OVERLAY, screen); rect.x = 0;    rect.y = 0;    rect.w = Video_W;    rect.h = Video_H; Video_Packet = (AVPacket *)av_malloc(sizeof(AVPacket));av_dump_format(FormatContext, 0, szFilePath, 0);SDL_WM_SetCaption("B_Play",NULL);img_convert_ctx = sws_getContext(Video_CodecContext->width, Video_CodecContext->height, Video_CodecContext->pix_fmt, Video_CodecContext->width, Video_CodecContext->height, AV_PIX_FMT_YUV420P, SWS_BICUBIC, NULL, NULL, NULL); B_LOG("1111111");while(av_read_frame(FormatContext, Video_Packet)>=0){B_LOG("2222222");if(Video_Packet->stream_index==iVideo_index){//Decodeavcodec_send_packet(Video_CodecContext, Video_Packet);got_picture = avcodec_receive_frame(Video_CodecContext, Video_Frame);if(!got_picture){SDL_LockYUVOverlay(bmp);YUV_Frame->data[0]=bmp->pixels[0];YUV_Frame->data[1]=bmp->pixels[2];YUV_Frame->data[2]=bmp->pixels[1];     YUV_Frame->linesize[0]=bmp->pitches[0];YUV_Frame->linesize[1]=bmp->pitches[2];   YUV_Frame->linesize[2]=bmp->pitches[1];sws_scale(img_convert_ctx, (const uint8_t* const*)Video_Frame->data, Video_Frame->linesize, 0, Video_CodecContext->height, YUV_Frame->data, YUV_Frame->linesize);SDL_UnlockYUVOverlay(bmp); SDL_DisplayYUVOverlay(bmp, &rect); //Delay 40msSDL_Delay(40);}}av_packet_unref(Video_Packet);}B_LOG("3333333333\n");while (1) {B_LOG("4444444444\n");avcodec_send_packet(Video_CodecContext, Video_Packet);got_picture = avcodec_receive_frame(Video_CodecContext, Video_Frame);if (got_picture)break;sws_scale(img_convert_ctx, (const uint8_t* const*)Video_Frame->data, Video_Frame->linesize, 0, Video_CodecContext->height, YUV_Frame->data, YUV_Frame->linesize);SDL_LockYUVOverlay(bmp);YUV_Frame->data[0]=bmp->pixels[0];YUV_Frame->data[1]=bmp->pixels[2];YUV_Frame->data[2]=bmp->pixels[1];     YUV_Frame->linesize[0]=bmp->pitches[0];YUV_Frame->linesize[1]=bmp->pitches[2];   YUV_Frame->linesize[2]=bmp->pitches[1];SDL_UnlockYUVOverlay(bmp); SDL_DisplayYUVOverlay(bmp, &rect); //Delay 40msSDL_Delay(40);}sws_freeContext(img_convert_ctx);SDL_Quit();//av_free(out_buffer);av_free(YUV_Frame);avcodec_close(Video_CodecContext);avformat_close_input(&FormatContext);
#endifreturn 0;
}

运行进程时发现出来的窗口是一片绿色的：

后面检查了一下代码，问题出在avcodec_receive_frame这个接口上面，通过查看注释发现，该接口成功获取到帧后返回值置为0，测试例程这个地方写反了

后面将if (got_picture)改成if (!got_picture)后视频流可以成功推送到屏幕上：