c - SDL2.0 Alternative for SDL_Overlay

Question

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);

Answer 1

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 < 2) {
        fprintf(stderr, "Usage: test <file>
");
        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
", 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) < 0)
        return -1; // Couldn't find stream information

    // Dump information about file onto standard error
    av_dump_format(pFormatCtx, 0, argv[1], 0);

    // Find the first video stream
    videoStream = -1;
    for (i = 0; i < pFormatCtx->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!
");
        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) < 0)
        return -1; // Could not open codec

    // Allocate video frame
    pFrame = av_frame_alloc();

    // Make a screen to put our video
    screen = SDL_CreateWindow(
            "FFmpeg Tutorial",
            SDL_WINDOWPOS_UNDEFINED,
            SDL_WINDOWPOS_UNDEFINED,
            pCodecCtx->width,
            pCodecCtx->height,
            0
        );

    if (!screen) {
        fprintf(stderr, "SDL: could not create window - exiting
");
        exit(1);
    }

    renderer = SDL_CreateRenderer(screen, -1, 0);
    if (!renderer) {
        fprintf(stderr, "SDL: could not create renderer - exiting
");
        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
");
        exit(1);
    }

    // initialize SWS context for software scaling
    sws_ctx = sws_getContext(pCodecCtx->width, pCodecCtx->height,
            pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height,
            AV_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
");
        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;
}