I have a GoPro Hero 3+ (Black) which is connected to a video capture card (AverMedia Game Broadcaster HD). I simply want to get the video stream in OpenCV. With a Logitech Webcam there are no problems. The used code is below.
VideoCapture cap;
cap.open(0);
waitKey(300);
//cap.set(CV_CAP_PROP_FRAME_WIDTH, 1280);
//cap.set(CV_CAP_PROP_FRAME_HEIGHT, 720);
if (cap.isOpened()){
cout << "Cam identified" << endl;
}
namedWindow("dst", 1);
while (1){
Mat frame;
if (!cap.read(frame)) {
std::cout << "Unable to read frame from video stream" << std::endl;
continue;
}
imshow("dst", frame);
[...]
}
With the GoPro the following happens: OpenCV is able to open the VideoCapture ("Cam identified") but can't read any frames (just a gray screen and the output: "Unable to read frame from video stream"). I also checked this with frame.empty();.
I know that the video capture card works correct because Unity opens a WebCamTexture with the GoPro stream without any issues. I read about codec problems in OpenCv and so I already tried to compile OpenCV with FFMPEG support. Now the recorded MP4-Videos of the GoPro can be displayed but the stream still doesn't work.
I use OpenCV 2.48, Windows 7 and Visual Studio 2013.
EDIT: Here is the code of libVLC solution:
struct ctx
{
uint8_t* pixeldata;
std::mutex imagemutex;
};
static void display(void *data, void *id);
static void unlock(void *data, void *id, void *const *p_pixels);
static void *lock(void *data, void **p_pixels);
struct ctx ctx;
libvlc_instance_t *inst;
libvlc_media_player_t *mp;
libvlc_media_t *m;
int main(int argc, char* argv[])
{
ctx.pixeldata = new uint8_t[1280 * 720 * 3];
char const *vlc_argv[] =
{
"-vvv",
"--no-audio", /* skip any audio track */
"--no-xlib", /* tell VLC to not use Xlib */
};
int vlc_argc = sizeof(vlc_argv) / sizeof(*vlc_argv);
inst = libvlc_new(vlc_argc, vlc_argv);
const char *options[] =
{
":dshow-vdev=AVerMedia HD Capture",
":dshow-adev=none",
//":dshow-size=1280x720",
":dshow-fps=24",
":dshow-chroma=YUY2",
":dshow-video-input=1",
":dshow-video-output=1",
":dshow-aspect-ratio=16\:9",
":live-caching=80",
NULL
};
m = libvlc_media_new_location(inst, "dshow://");
for (const char **opt = options; *opt; opt++)
libvlc_media_add_option(m, *opt);
mp = libvlc_media_player_new_from_media(m);
libvlc_media_release(m);
libvlc_video_set_callbacks(mp, lock, unlock, display, &ctx);
libvlc_video_set_format(mp, "RV24", 1280, 720, 1280 * 3);
libvlc_media_player_play(mp);
namedWindow("all", 1);
Mat frame(720, 1280, CV_8UC3);
while (1){
ctx.imagemutex.lock();
memcpy(gesamt.data, ctx.pixeldata, 1280 * 720 * sizeof(uint8_t) * 3);
ctx.imagemutex.unlock();
imshow("all", gesamt);
if (waitKey(30) == 27) //wait for 'esc' key press for 30ms. If 'esc' key is pressed, break loop
{
cout << "esc key is pressed by user" << endl;
break;
}
}
libvlc_media_player_stop(mp);
libvlc_media_player_release(mp);
libvlc_release(inst);
delete[] ctx.pixeldata;
return 0;
}
void display(void *data, void *id){
(void)data;
assert(id == NULL);
}
void unlock(void *data, void *id, void *const *p_pixels){
struct ctx *ctx = (struct ctx*)data;
ctx->imagemutex.unlock();
assert(id == NULL);
}
void *lock(void *data, void **p_pixels){
struct ctx *ctx = (struct ctx*)data;
ctx->imagemutex.lock();
*p_pixels = ctx->pixeldata;
return NULL;
}
I've had the same issues trying to stream a Sony action cam through an Avermedia capture card. One quick fix seems to be using DVDrive, which makes your capture card output look like a webcam. I've had success using this as a workaround.
来源:https://stackoverflow.com/questions/23345286/opencv-and-gopro-empty-frames-in-videocapture-stream