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问题:
So I've been trying to go through the following tutorial on ffmpeg: http://dranger.com/ffmpeg/tutorial02.html
However, when I try to compile using gcc, I get the following output:
root:/Users/mbrodeur/Downloads/HACKATHON CONTENT/Tutorials-> gcc -o tutorial02 tutorial02.c -lavutil -lavformat -lavcodec -lz -lavutil -lm -lswscale -D_THREAD_SAFE -lSDL2 tutorial02.c: In function ‘main’: tutorial02.c:41: error: ‘SDL_Overlay’ undeclared (first use in this function) tutorial02.c:41: error: (Each undeclared identifier is reported only once tutorial02.c:41: error: for each function it appears in.) tutorial02.c:41: error: ‘bmp’ undeclared (first use in this function) tutorial02.c:98: warning: assignment makes pointer from integer without a cast tutorial02.c:110: error: ‘SDL_YV12_OVERLAY’ undeclared (first use in this function)
Now, I read that SDL_Overlay is no longer used in SDL2, so therein lies the problem. I've been poking around, but can't seem to find anything helpful. Is there a replacement for SDL_Overlay? Is it necessary?
SDL_Overlay is used in the following context:
SDL_Overlay *bmp; bmp = SDL_CreateYUVOverlay(pCodecCtx->width, pCodecCtx->height, SDL_YV12_OVERLAY, screen);
回答1:
Try SDL_CreateTexture() with a YUV pixel format that matches the layout and planar-ity of your decoded frames.
Or use libswscale to convert ffmpeg's YUV buffers to RGB.
EDIT: SDL2 >= 2.0.1 has SDL_UpdateYUVTexture() for updating planar YUV textures so you don't have to manually coalesce libav's buffers any more.
回答2:
I have updated the tutorial to work with SDL 2.0.1. It replaces SDL_Overlay with SDL_Texture in YV12 format.
int main(int argc, char *argv[]) { AVFormatContext *pFormatCtx = NULL; int videoStream; unsigned i; AVCodecContext *pCodecCtxOrig = NULL; AVCodecContext *pCodecCtx = NULL; AVCodec *pCodec = NULL; AVFrame *pFrame = NULL; AVPacket packet; int frameFinished; struct SwsContext *sws_ctx = NULL; SDL_Event event; SDL_Window *screen; SDL_Renderer *renderer; SDL_Texture *texture; Uint8 *yPlane, *uPlane, *vPlane; size_t yPlaneSz, uvPlaneSz; int uvPitch; if (argc \n"); exit(1); } // Register all formats and codecs av_register_all(); if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_TIMER)) { fprintf(stderr, "Could not initialize SDL - %s\n", SDL_GetError()); exit(1); } // Open video file if (avformat_open_input(&pFormatCtx, argv[1], NULL, NULL) != 0) return -1; // Couldn't open file // Retrieve stream information if (avformat_find_stream_info(pFormatCtx, NULL) nb_streams; i++) if (pFormatCtx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO) { videoStream = i; break; } if (videoStream == -1) return -1; // Didn't find a video stream // Get a pointer to the codec context for the video stream pCodecCtxOrig = pFormatCtx->streams[videoStream]->codec; // Find the decoder for the video stream pCodec = avcodec_find_decoder(pCodecCtxOrig->codec_id); if (pCodec == NULL) { fprintf(stderr, "Unsupported codec!\n"); return -1; // Codec not found } // Copy context pCodecCtx = avcodec_alloc_context3(pCodec); if (avcodec_copy_context(pCodecCtx, pCodecCtxOrig) != 0) { fprintf(stderr, "Couldn't copy codec context"); return -1; // Error copying codec context } // Open codec if (avcodec_open2(pCodecCtx, pCodec, NULL) width, pCodecCtx->height, 0 ); if (!screen) { fprintf(stderr, "SDL: could not create window - exiting\n"); exit(1); } renderer = SDL_CreateRenderer(screen, -1, 0); if (!renderer) { fprintf(stderr, "SDL: could not create renderer - exiting\n"); exit(1); } // Allocate a place to put our YUV image on that screen texture = SDL_CreateTexture( renderer, SDL_PIXELFORMAT_YV12, SDL_TEXTUREACCESS_STREAMING, pCodecCtx->width, pCodecCtx->height ); if (!texture) { fprintf(stderr, "SDL: could not create texture - exiting\n"); exit(1); } // initialize SWS context for software scaling sws_ctx = sws_getContext(pCodecCtx->width, pCodecCtx->height, pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height, PIX_FMT_YUV420P, SWS_BILINEAR, NULL, NULL, NULL); // set up YV12 pixel array (12 bits per pixel) yPlaneSz = pCodecCtx->width * pCodecCtx->height; uvPlaneSz = pCodecCtx->width * pCodecCtx->height / 4; yPlane = (Uint8*)malloc(yPlaneSz); uPlane = (Uint8*)malloc(uvPlaneSz); vPlane = (Uint8*)malloc(uvPlaneSz); if (!yPlane || !uPlane || !vPlane) { fprintf(stderr, "Could not allocate pixel buffers - exiting\n"); exit(1); } uvPitch = pCodecCtx->width / 2; while (av_read_frame(pFormatCtx, &packet) >= 0) { // Is this a packet from the video stream? if (packet.stream_index == videoStream) { // Decode video frame avcodec_decode_video2(pCodecCtx, pFrame, &frameFinished, &packet); // Did we get a video frame? if (frameFinished) { AVPicture pict; pict.data[0] = yPlane; pict.data[1] = uPlane; pict.data[2] = vPlane; pict.linesize[0] = pCodecCtx->width; pict.linesize[1] = uvPitch; pict.linesize[2] = uvPitch; // Convert the image into YUV format that SDL uses sws_scale(sws_ctx, (uint8_t const * const *) pFrame->data, pFrame->linesize, 0, pCodecCtx->height, pict.data, pict.linesize); SDL_UpdateYUVTexture( texture, NULL, yPlane, pCodecCtx->width, uPlane, uvPitch, vPlane, uvPitch ); SDL_RenderClear(renderer); SDL_RenderCopy(renderer, texture, NULL, NULL); SDL_RenderPresent(renderer); } } // Free the packet that was allocated by av_read_frame av_free_packet(&packet); SDL_PollEvent(&event); switch (event.type) { case SDL_QUIT: SDL_DestroyTexture(texture); SDL_DestroyRenderer(renderer); SDL_DestroyWindow(screen); SDL_Quit(); exit(0); break; default: break; } } // Free the YUV frame av_frame_free(&pFrame); free(yPlane); free(uPlane); free(vPlane); // Close the codec avcodec_close(pCodecCtx); avcodec_close(pCodecCtxOrig); // Close the video file avformat_close_input(&pFormatCtx); return 0; }
回答3:
I got this problem too. I used SDL 1.2 since I didn't know how to replace SDL_Overlay in SDL2.0. If you are on Mac 10.10, you can use this patch http://www.emaculation.com/doku.php/compiling_sheepshaver_basilisk#tidbits
patch Then in /src/video/x11/SDL_x11sym.h, replace line 168 and 169 to this
SDL_X11_SYM(int,_XData32,(Display *dpy,register _Xconst long *data,unsigned len),(dpy,data,len),return) SDL_X11_SYM(void,_XRead32,(Display *dpy,register long *data,long len),(dpy,data,len), return)
It worked with me.
回答4:
The tutorial https://github.com/chelyaev/ffmpeg-tutorial links against SDL1 http://www.libsdl.org/download-1.2.php and they should have mentioned it(or they did and I haven't seen it).All works perfectly with SDL1.
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