YUV <-> RGB by ffmpeg

vf_rgb.c

    // Convert from YUV to RGB
    struct SwsContext *sws_ctx = NULL;
    sws_ctx =
      sws_getContext
      (
        inlink->w,
        inlink->h,
        inlink->format,
        outlink->w,
        outlink->h,
        AV_PIX_FMT_RGB24,
        SWS_BILINEAR,NULL,NULL,NULL
      );
    uint8_t *prgb24 = calloc(3 * inlink->w * inlink->h, sizeof(uint8_t));
    uint8_t *rgb24[1] = { prgb24 };
    int rgb24_stride[1] = { 3 * inlink->w };
    sws_scale(sws_ctx, in->data, in->linesize, 0, inlink->h, rgb24, rgb24_stride);
    if (!out) {
        av_frame_free(&in);
        return AVERROR(ENOMEM);
    }
    av_frame_copy_props(out, in);
    // Put 0 to all red byte
    for (i = 0; i < inlink->w * inlink->h; i++ )
    {
        rgb24[0][i * 3] = 0;
    }

    // Convert from RGB to YUV
    sws_ctx = sws_getContext(
            inlink->w,
            inlink->h,
            AV_PIX_FMT_RGB24,
            outlink->w,
            outlink->h,
            AV_PIX_FMT_YUV420P,
            SWS_BILINEAR, NULL, NULL, NULL
            );
    sws_scale(sws_ctx, rgb24, rgb24_stride, 0, inlink->h, out->data, out->linesize);

    free(prgb24);