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Added GetFPS and SetFPS functions #32

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Added GetFPS and SetFPS functions #32

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47 changes: 47 additions & 0 deletions v4l2.go
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@ package webcam
import (
"bytes"
"encoding/binary"
"fmt"
"unsafe"

"github.com/blackjack/webcam/ioctl"
Expand Down Expand Up @@ -75,6 +76,8 @@ var (
VIDIOC_QUERYBUF = ioctl.IoRW(uintptr('V'), 9, unsafe.Sizeof(v4l2_buffer{}))
VIDIOC_QBUF = ioctl.IoRW(uintptr('V'), 15, unsafe.Sizeof(v4l2_buffer{}))
VIDIOC_DQBUF = ioctl.IoRW(uintptr('V'), 17, unsafe.Sizeof(v4l2_buffer{}))
VIDIOC_G_PARM = ioctl.IoRW(uintptr('V'), 21, unsafe.Sizeof(v4l2_streamparm{}))
VIDIOC_S_PARM = ioctl.IoRW(uintptr('V'), 22, unsafe.Sizeof(v4l2_streamparm{}))
VIDIOC_G_CTRL = ioctl.IoRW(uintptr('V'), 27, unsafe.Sizeof(v4l2_control{}))
VIDIOC_S_CTRL = ioctl.IoRW(uintptr('V'), 28, unsafe.Sizeof(v4l2_control{}))
VIDIOC_QUERYCTRL = ioctl.IoRW(uintptr('V'), 36, unsafe.Sizeof(v4l2_queryctrl{}))
Expand Down Expand Up @@ -203,6 +206,26 @@ type v4l2_control struct {
value int32
}

type v4l2_fract struct {
numerator uint32
denominator uint32
}

type v4l2_streamparm_union struct {
capability uint32
output_mode uint32
time_per_frame v4l2_fract
extended_mode uint32
buffers uint32
reserved [4]uint32
data [200 - (10 * unsafe.Sizeof(uint32(0)))]byte
}

type v4l2_streamparm struct {
_type uint32
union v4l2_streamparm_union
}

func checkCapabilities(fd uintptr) (supportsVideoCapture bool, supportsVideoStreaming bool, err error) {

caps := &v4l2_capability{}
Expand Down Expand Up @@ -471,6 +494,30 @@ func setControl(fd uintptr, id uint32, val int32) error {
return ioctl.Ioctl(fd, VIDIOC_S_CTRL, uintptr(unsafe.Pointer(ctrl)))
}

func getFps(fd uintptr) (int32, error) {
param := &v4l2_streamparm{}
param._type = V4L2_BUF_TYPE_VIDEO_CAPTURE

err := ioctl.Ioctl(fd, VIDIOC_G_PARM, uintptr(unsafe.Pointer(param)))
if err != nil {
return 0, err
}
tf := param.union.time_per_frame
if tf.denominator == 0 || tf.numerator == 0 {
return 0, fmt.Errorf("Frames per second: invalid (%d/%d)", tf.denominator, tf.numerator)
}
return int32(tf.denominator / tf.numerator), nil
}

func setFps(fd uintptr, fps uint32) error {
param := &v4l2_streamparm{}
param._type = V4L2_BUF_TYPE_VIDEO_CAPTURE
param.union.time_per_frame.numerator = 1000
param.union.time_per_frame.denominator = fps * 1000

return ioctl.Ioctl(fd, VIDIOC_S_PARM, uintptr(unsafe.Pointer(param)))
}

func queryControls(fd uintptr) []control {
controls := []control{}
var err error
Expand Down
10 changes: 10 additions & 0 deletions webcam.go
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Original file line number Diff line number Diff line change
Expand Up @@ -153,6 +153,16 @@ func (w *Webcam) SetControl(id ControlID, value int32) error {
return setControl(w.fd, uint32(id), value)
}

// Get the FPS.
func (w *Webcam) GetFps() (int32, error) {
return getFps(w.fd)
}

// Set FPS
func (w *Webcam) SetFps(fps int32) error {
return setFps(w.fd, uint32(fps))
}

// Start streaming process
func (w *Webcam) StartStreaming() error {
if w.streaming {
Expand Down