opencv关于视频添加滚动条的问题 一样的程序 为什么结构不一样呢！奇怪极了(4)

#include "highgui.h"

int g_slider_position = 0;
CvCapture* g_capture = NULL;

void onTrackbarSlide(int pos)
{
cvSetCaptureProperty(g_capture, CV_CAP_PROP_POS_FRAMES,pos);
}

int main()
{
cvNamedWindow("example",CV_WINDOW_AUTOSIZE);
g_capture = cvCreateFileCapture("I:\\资料\\opencv相关资料\\OpenCV教程\\图像与视频\\video.long.mjpg.avi");
int frames = (int)cvGetCaptureProperty(g_capture,CV_CAP_PROP_FRAME_COUNT);
//int frameRate = (int)cvGetCaptureProperty(g_capture,CV_CAP_PROP_FPS);

if(frames!=0)
cvCreateTrackbar("position","example", &g_slider_position, frames, onTrackbarSlide);

IplImage* frame;
for(g_slider_position=0;g_slider_position<frames;g_slider_position++)
{
frame = cvQueryFrame(g_capture);
if(!frame)     break;
cvShowImage("example", frame);
char c = cvWaitKey(33);
cvSetTrackbarPos("position","example", g_slider_position);
onTrackbarSlide(g_slider_position);
if(c == 27)    break;
}
cvReleaseCapture(&g_capture);
cvDestroyWindow("example");
}

#include "highgui.h"

int g_slider_position = 0;
CvCapture* g_capture   =NULL;
void onTrackbarSlide(int pos)
{
cvSetCaptureProperty(g_capture,CV_CAP_PROP_POS_FRAMES,pos);
}

int main()
{
cvNamedWindow("example",CV_WINDOW_AUTOSIZE);
g_capture = cvCreateFileCapture("I:\\资料\\opencv相关资料\\OpenCV教程\\图像与视频\\video.long.mjpg.avi");
int frames=(int)cvGetCaptureProperty(g_capture,CV_CAP_PROP_FRAME_COUNT);
//int frameRate = (int)cvGetCaptureProperty(g_capture,CV_CAP_PROP_FPS);
if(frames!=0)
cvCreateTrackbar("position","exapmle", &g_slider_position, frames, onTrackbarSlide);

IplImage * frame;
for(g_slider_position=0;g_slider_position<frames;g_slider_position++)
{
frame = cvQueryFrame(g_capture);
if(!frame) break;
cvShowImage("example",frame);
char c = cvWaitKey(33);
cvSetTrackbarPos("position","example",g_slider_position);
onTrackbarSlide(g_slider_position);
if(c==27)  break;
}
cvReleaseCapture(&g_capture);
cvDestroyWindow("example");

}