FFmpeg doesn't use GPU - windows

Question

I got the latest version binaries of ffmpeg from here. When I examine CPU and GPU usages when I play a video by its ffplay, I see that GPU is used during play. Not much using of CPU also indicates it. But when I get the latest version sources from the original site, I can't use GPU. To clarify, I include a player test program I wrote until now. When I uncomment the line which includes avcodec_find_decoder_by_name("h264_cuvid"), I get error -1. The error happens in avcodec_open2 with the description of Operation not permitted.
CString format(const char *fmt, ...)
{
va_list ap;
va_start(ap, fmt);
char buf[512];
vsnprintf(buf, sizeof(buf), fmt, ap);
va_end(ap);
return buf;
}
int CplayerDlg::play()
{
FILE *fp = fopen("video_files/1010.brf", "rb");
if (!fp)
{
AfxMessageBox("can't open video file");
return -1;
}
RecordFrame frame;
RecordHeader hdr;
fread(&frame, sizeof(frame), 1, fp);
if (frame.frameType != FRAME_TYPE_HEADER)
{
AfxMessageBox("record file doesn't begin with header");
return -1;
}
fread(&hdr, sizeof(hdr), 1, fp);
GetDlgItem(IDC_DIM)->SetWindowText(format("%dx%d", hdr.width, hdr.height));
GetDlgItem(IDC_CODEC_ID)->SetWindowText(format("%d", hdr.codecId));
GetDlgItem(IDC_PIXEL_FORMAT)->SetWindowText(format("%d", hdr.pixelFormat));
GetDlgItem(IDC_TIMEBASE)->SetWindowText(format("%d/%d", hdr.timebaseNum, hdr.timebaseDen));
AVCodec *pCodec;
#if 0
#define CHECK(decoder)\
pCodec = avcodec_find_decoder_by_name(#decoder);\
AfxMessageBox(pCodec ? #decoder " found" : "can't find " #decoder);
CHECK(h264_cuvid);
#undef CHECK
#endif
pCodec = avcodec_find_decoder(AV_CODEC_ID_H264);
//pCodec = avcodec_find_decoder_by_name("h264_cuvid");
if (!pCodec)
{
AfxMessageBox("can't find h264 decoder");
return -1;
}
AVCodecContext *pCodecContext = avcodec_alloc_context3(pCodec);
if (!pCodecContext)
{
AfxMessageBox("can't allocate codec context");
return -1;
}
#if 0
// enumerating available codecs
//av_register_all();
avcodec_register_all();
AVCodec *current_codec = av_codec_next(NULL);
while (current_codec != NULL)
{
TRACE("%s\n", current_codec->name);
current_codec = av_codec_next(current_codec);
}
#endif
int err = avcodec_open2(pCodecContext, pCodec, NULL);
if (err != 0)
{
char buf[AV_ERROR_MAX_STRING_SIZE];
av_make_error_string(buf, AV_ERROR_MAX_STRING_SIZE, err);
char buf2[AV_ERROR_MAX_STRING_SIZE];
sprintf(buf2, "%d (%x): %s\n", err, err, buf);
AfxMessageBox(buf2);
return -1;
}
AfxMessageBox("operation completed successfully");
fclose(fp);
return 0;
}