josh/WebcamTracker
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requesting and memory-mapping a buffer

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git-svn-id: svn://anubis/misc/WebcamTracker@121 bd8a9e45-a331-0410-811e-c64571078777
This commit is contained in:
josh 2009-08-07 23:06:58 +00:00
parent ca070c2d8c
commit 96eb602808
2 changed files with 76 additions and 20 deletions
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94
WebcamTracker.cc
View File

@ -5,6 +5,9 @@
#include <stdlib.h> /* exit() */
#include <sys/ioctl.h> /* ioctl() */
#include <libv4lconvert.h>
#include <unistd.h>
#include <sys/mman.h> /* mmap() */
#include <errno.h>
#include <iostream>
#include "WebcamTracker.h"
using namespace std;
@ -23,26 +26,61 @@ WebcamTracker::WebcamTracker(const char * device)
m_open = true;
struct v4l2_capability cap;
ioctl(m_fd, VIDIOC_QUERYCAP, &cap);
#define check_cap(x) do { \
if (cap.capabilities & (x)) \
cout << " cap: " << #x << endl; \
} while (0)
check_cap(V4L2_CAP_VIDEO_CAPTURE);
check_cap(V4L2_CAP_VIDEO_OUTPUT);
check_cap(V4L2_CAP_VIDEO_OVERLAY);
check_cap(V4L2_CAP_VBI_CAPTURE);
check_cap(V4L2_CAP_VBI_OUTPUT);
check_cap(V4L2_CAP_SLICED_VBI_CAPTURE);
check_cap(V4L2_CAP_SLICED_VBI_OUTPUT);
check_cap(V4L2_CAP_RDS_CAPTURE);
check_cap(V4L2_CAP_VIDEO_OUTPUT_OVERLAY);
check_cap(V4L2_CAP_TUNER);
check_cap(V4L2_CAP_AUDIO);
check_cap(V4L2_CAP_RADIO);
check_cap(V4L2_CAP_READWRITE);
check_cap(V4L2_CAP_ASYNCIO);
check_cap(V4L2_CAP_STREAMING);
int ret = ioctl(m_fd, VIDIOC_QUERYCAP, &cap);
if (ret != 0)
{
cerr << "VIDIOC_QUERYCAP ioctl failed: " << ret << endl;
}
if (!(cap.capabilities & V4L2_CAP_VIDEO_CAPTURE))
{
cerr << "Warning: V4L2_CAP_VIDEO_CAPTURE not supported!" << endl;
}
v4l2_requestbuffers reqbuf;
reqbuf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
reqbuf.count = 1;
reqbuf.memory = V4L2_MEMORY_MMAP;
ret = ioctl(m_fd, VIDIOC_REQBUFS, &reqbuf);
if (ret != 0)
{
cerr << "VIDIOC_REQBUFS ioctl failed: returned " << ret
<< ", errno " << errno;
if (errno == EBUSY)
cerr << " (EBUSY)";
if (errno == EINVAL)
cerr << " (EINVAL)";
cerr << endl;
}
struct v4l2_buffer buf;
buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
buf.index = 0;
ret = ioctl(m_fd, VIDIOC_QUERYBUF, &buf);
if (ret != 0)
{
cerr << "VIDIOC_QUERYBUF ioctl failed: returned " << ret
<< ", errno: " << errno;
if (errno == EINVAL)
cerr << " (EINVAL)";
cerr << endl;
}
m_vidbuflen = buf.length;
m_vidbuf = mmap(NULL, buf.length, PROT_READ | PROT_WRITE, MAP_SHARED,
m_fd, buf.m.offset);
if (m_vidbuf == MAP_FAILED)
{
cerr << "mmap() failed: errno " << errno;
if (errno == EBADF)
cerr << " (EBADF)";
if (errno == EACCES)
cerr << " (EACCES)";
if (errno == EINVAL)
cerr << " (EINVAL)";
if (errno == ENOMEM)
cerr << " (ENOMEM)";
cerr << endl;
}
}
else
{
@ -54,6 +92,22 @@ WebcamTracker::~WebcamTracker()
{
if (m_open)
{
munmap(m_vidbuf, m_vidbuflen);
v4l2_requestbuffers reqbuf;
reqbuf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
reqbuf.count = 0;
reqbuf.memory = V4L2_MEMORY_MMAP;
int ret = ioctl(m_fd, VIDIOC_REQBUFS, &reqbuf);
if (ret != 0)
{
cerr << "~WebcamTracker(): VIDIOC_REQBUFS ioctl failed: "
<< ret << endl;
if (errno == EBUSY)
cerr << "EBUSY" << endl;
if (errno == EINVAL)
cerr << "EINVAL" << endl;
}
close(m_fd);
}
}

2
WebcamTracker.h
View File

@ -14,6 +14,8 @@ class WebcamTracker
~WebcamTracker();
protected:
void * m_vidbuf;
int m_vidbuflen;
bool m_open;
int m_fd;
};