使用FFMPEG將屏幕截圖編碼爲視頻

Question

我試圖從屏幕獲取像素，並使用ffmpeg將屏幕截圖編碼爲視頻。我見過幾個例子，但他們要麼假設你已經有了像素數據，要麼使用圖像文件輸入。這似乎是我是否使用sws_scale（）或不包括在我看過的例子中，或者我是在類型化一個HBITMAP或RGBQUAD *它告訴我圖像的src數據是壞的並且正在編碼一個空白圖像而不是截圖。有什麼我在這裏失蹤？

AVCodec* codec; 
AVCodecContext* c = NULL; 
AVFrame* inpic; 
uint8_t* outbuf, *picture_buf; 
int i, out_size, size, outbuf_size; 
HBITMAP hBmp; 
//int x,y; 

avcodec_register_all(); 

printf("Video encoding\n"); 

// Find the mpeg1 video encoder 
codec = avcodec_find_encoder(CODEC_ID_H264); 
if (!codec) { 
    fprintf(stderr, "Codec not found\n"); 
    exit(1); 
} 
else printf("H264 codec found\n"); 

c = avcodec_alloc_context3(codec); 
inpic = avcodec_alloc_frame(); 

c->bit_rate = 400000; 
c->width = screenWidth;          // resolution must be a multiple of two 
c->height = screenHeight; 
c->time_base.num = 1; 
c->time_base.den = 25; 
c->gop_size = 10;           // emit one intra frame every ten frames 
c->max_b_frames=1; 
c->pix_fmt = PIX_FMT_YUV420P; 
c->codec_id = CODEC_ID_H264; 
//c->codec_type = AVMEDIA_TYPE_VIDEO; 

//av_opt_set(c->priv_data, "preset", "slow", 0); 
//printf("Setting presets to slow for performance\n"); 

// Open the encoder 
if (avcodec_open2(c, codec,NULL) < 0) { 
    fprintf(stderr, "Could not open codec\n"); 
    exit(1); 
} 
else printf("H264 codec opened\n"); 

outbuf_size = 100000 + 12*c->width*c->height;   // alloc image and output buffer 
//outbuf_size = 100000; 
outbuf = static_cast<uint8_t *>(malloc(outbuf_size)); 
size = c->width * c->height; 
picture_buf = static_cast<uint8_t*>(malloc((size*3)/2)); 
printf("Setting buffer size to: %d\n",outbuf_size); 

FILE* f = fopen("example.mpg","wb"); 
if(!f) printf("x - Cannot open video file for writing\n"); 
else printf("Opened video file for writing\n"); 

/*inpic->data[0] = picture_buf; 
inpic->data[1] = inpic->data[0] + size; 
inpic->data[2] = inpic->data[1] + size/4; 
inpic->linesize[0] = c->width; 
inpic->linesize[1] = c->width/2; 
inpic->linesize[2] = c->width/2;*/ 


//int x,y; 
// encode 1 second of video 
for(i=0;i<c->time_base.den;i++) { 
    fflush(stdout); 


    HWND hDesktopWnd = GetDesktopWindow(); 
    HDC hDesktopDC = GetDC(hDesktopWnd); 
    HDC hCaptureDC = CreateCompatibleDC(hDesktopDC); 
    hBmp = CreateCompatibleBitmap(GetDC(0), screenWidth, screenHeight); 
    SelectObject(hCaptureDC, hBmp); 
    BitBlt(hCaptureDC, 0, 0, screenWidth, screenHeight, hDesktopDC, 0, 0, SRCCOPY|CAPTUREBLT); 
    BITMAPINFO bmi = {0}; 
    bmi.bmiHeader.biSize = sizeof(bmi.bmiHeader); 
    bmi.bmiHeader.biWidth = screenWidth; 
    bmi.bmiHeader.biHeight = screenHeight; 
    bmi.bmiHeader.biPlanes = 1; 
    bmi.bmiHeader.biBitCount = 32; 
    bmi.bmiHeader.biCompression = BI_RGB; 
    RGBQUAD *pPixels = new RGBQUAD[screenWidth*screenHeight]; 
    GetDIBits(hCaptureDC,hBmp,0,screenHeight,pPixels,&bmi,DIB_RGB_COLORS); 

inpic->pts = (float) i * (1000.0/(float)(c->time_base.den))*90; 
    avpicture_fill((AVPicture*)inpic, (uint8_t*)pPixels, PIX_FMT_BGR32, c->width, c->height);     // Fill picture with image 
    av_image_alloc(inpic->data, inpic->linesize, c->width, c->height, c->pix_fmt, 1); 
    //printf("Allocated frame\n"); 
    //SaveBMPFile(L"screenshot.bmp",hBmp,hDc,screenWidth,screenHeight); 
    ReleaseDC(hDesktopWnd,hDesktopDC); 
    DeleteDC(hCaptureDC); 
    DeleteObject(hBmp); 

    // encode the image 
    out_size = avcodec_encode_video(c, outbuf, outbuf_size, inpic); 
    printf("Encoding frame %3d (size=%5d)\n", i, out_size); 
    fwrite(outbuf, 1, out_size, f); 
} 

// get the delayed frames 
for(; out_size; i++) { 
    fflush(stdout); 

    out_size = avcodec_encode_video(c, outbuf, outbuf_size, NULL); 
    printf("Writing frame %3d (size=%5d)\n", i, out_size); 
    fwrite(outbuf, 1, out_size, f); 
} 

// add sequence end code to have a real mpeg file 
outbuf[0] = 0x00; 
outbuf[1] = 0x00; 
outbuf[2] = 0x01; 
outbuf[3] = 0xb7; 
fwrite(outbuf, 1, 4, f); 
fclose(f); 
free(picture_buf); 
free(outbuf); 

avcodec_close(c); 
av_free(c); 
av_free(inpic); 
printf("Closed codec and Freed\n"); 

Answer 1

我設法讓它在相當多的試驗和錯誤之後工作。填充後我正在分配圖像，這是第一個問題。第二個問題是屏幕截圖沒有正確創建，應該作爲COLORREF *而不是RGBQUAD。

AVCodec* codec; 
AVCodecContext* c = NULL; 
uint8_t* outbuf; 
int i, out_size, outbuf_size; 

avcodec_register_all();         // mandatory to register ffmpeg functions 

printf("Video encoding\n"); 

codec = avcodec_find_encoder(CODEC_ID_H264);   // finding the H264 encoder 
if (!codec) { 
    fprintf(stderr, "Codec not found\n"); 
    exit(1); 
} 
else printf("H264 codec found\n"); 

c = avcodec_alloc_context3(codec); 
c->bit_rate = 400000; 
c->width = 1280;          // resolution must be a multiple of two (1280x720),(1900x1080),(720x480) 
c->height = 720; 
c->time_base.num = 1;         // framerate numerator 
c->time_base.den = 25;         // framerate denominator 
c->gop_size = 10;          // emit one intra frame every ten frames 
c->max_b_frames = 1;         // maximum number of b-frames between non b-frames 
c->keyint_min = 1;          // minimum GOP size 
c->i_quant_factor = (float)0.71;      // qscale factor between P and I frames 
c->b_frame_strategy = 20;        ///// find out exactly what this does 
c->qcompress = (float)0.6;        ///// find out exactly what this does 
c->qmin = 20;           // minimum quantizer 
c->qmax = 51;           // maximum quantizer 
c->max_qdiff = 4;          // maximum quantizer difference between frames 
c->refs = 4;           // number of reference frames 
c->trellis = 1;           // trellis RD Quantization 
c->pix_fmt = PIX_FMT_YUV420P;       // universal pixel format for video encoding 
c->codec_id = CODEC_ID_H264; 
c->codec_type = AVMEDIA_TYPE_VIDEO; 

if (avcodec_open2(c, codec,NULL) < 0) { 
    fprintf(stderr, "Could not open codec\n");   // opening the codec 
    exit(1); 
} 
else printf("H264 codec opened\n"); 

outbuf_size = 100000 + c->width*c->height*(32>>3);  // allocate output buffer 
outbuf = static_cast<uint8_t *>(malloc(outbuf_size)); 
printf("Setting buffer size to: %d\n",outbuf_size); 

FILE* f = fopen("example.mpg","wb");     // opening video file for writing 
if(!f) printf("x - Cannot open video file for writing\n"); 
else printf("Opened video file for writing\n"); 

// encode video 
for(i=0;i<STREAM_FRAME_RATE*STREAM_DURATION;i++) { 
    fflush(stdout); 

    screenCap();                        // taking screenshot 

    int nbytes = avpicture_get_size(PIX_FMT_YUV420P, c->width, c->height);          // allocating outbuffer 
    uint8_t* outbuffer = (uint8_t*)av_malloc(nbytes*sizeof(uint8_t)); 

    AVFrame* inpic = avcodec_alloc_frame();                  // mandatory frame allocation 
    AVFrame* outpic = avcodec_alloc_frame(); 

    outpic->pts = (int64_t)((float)i * (1000.0/((float)(c->time_base.den))) * 90);        // setting frame pts 
    avpicture_fill((AVPicture*)inpic, (uint8_t*)pPixels, PIX_FMT_RGB32, c->width, c->height);     // fill image with input screenshot 
    avpicture_fill((AVPicture*)outpic, outbuffer, PIX_FMT_YUV420P, c->width, c->height);      // clear output picture for buffer copy 
    av_image_alloc(outpic->data, outpic->linesize, c->width, c->height, c->pix_fmt, 1); 

    inpic->data[0] += inpic->linesize[0]*(screenHeight-1);              // flipping frame 
    inpic->linesize[0] = -inpic->linesize[0];                 // flipping frame 

    struct SwsContext* fooContext = sws_getContext(screenWidth, screenHeight, PIX_FMT_RGB32, c->width, c->height, PIX_FMT_YUV420P, SWS_FAST_BILINEAR, NULL, NULL, NULL); 
    sws_scale(fooContext, inpic->data, inpic->linesize, 0, c->height, outpic->data, outpic->linesize);   // converting frame size and format 

    out_size = avcodec_encode_video(c, outbuf, outbuf_size, outpic);           // encoding video 
    printf("Encoding frame %3d (size=%5d)\n", i, out_size); 
    fwrite(outbuf, 1, out_size, f); 

    delete [] pPixels;                       // freeing memory 
    av_free(outbuffer);  
    av_free(inpic); 
    av_free(outpic); 
} 

for(; out_size; i++) { 
    fflush(stdout); 

    out_size = avcodec_encode_video(c, outbuf, outbuf_size, NULL);            // encode the delayed frames 
    printf("Writing frame %3d (size=%5d)\n", i, out_size); 
    fwrite(outbuf, 1, out_size, f); 
} 

outbuf[0] = 0x00; 
outbuf[1] = 0x00;                        // add sequence end code to have a real mpeg file 
outbuf[2] = 0x01; 
outbuf[3] = 0xb7; 
fwrite(outbuf, 1, 4, f); 
fclose(f); 

avcodec_close(c);                        // freeing memory 
free(outbuf); 
av_free(c); 
printf("Closed codec and Freed\n");