Skip to content

Commit

Permalink
Add functions to set and get framerate (#48)
Browse files Browse the repository at this point in the history
- Mostly taken from #32.
  • Loading branch information
f-fl0 authored Mar 29, 2022
1 parent 10ed912 commit ba06470
Show file tree
Hide file tree
Showing 2 changed files with 58 additions and 1 deletion.
46 changes: 46 additions & 0 deletions v4l2.go
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 @@ -466,6 +489,29 @@ func setControl(fd uintptr, id uint32, val int32) error {
return ioctl.Ioctl(fd, VIDIOC_S_CTRL, uintptr(unsafe.Pointer(ctrl)))
}

func getFramerate(fd uintptr) (float32, 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("Invalid framerate (%d/%d)", tf.denominator, tf.numerator)
}
return float32(tf.denominator) / float32(tf.numerator), nil
}

func setFramerate(fd uintptr, num, denom uint32) error {
param := &v4l2_streamparm{}
param._type = V4L2_BUF_TYPE_VIDEO_CAPTURE
param.union.time_per_frame.numerator = num
param.union.time_per_frame.denominator = denom
return ioctl.Ioctl(fd, VIDIOC_S_PARM, uintptr(unsafe.Pointer(param)))
}

func queryControls(fd uintptr) []control {
controls := []control{}
var err error
Expand Down
13 changes: 12 additions & 1 deletion webcam.go
Original file line number Diff line number Diff line change
Expand Up @@ -5,9 +5,10 @@ package webcam

import (
"errors"
"golang.org/x/sys/unix"
"reflect"
"unsafe"

"golang.org/x/sys/unix"
)

// Webcam object
Expand Down Expand Up @@ -153,6 +154,16 @@ func (w *Webcam) SetControl(id ControlID, value int32) error {
return setControl(w.fd, uint32(id), value)
}

// Get the framerate.
func (w *Webcam) GetFramerate() (float32, error) {
return getFramerate(w.fd)
}

// Set FPS
func (w *Webcam) SetFramerate(fps float32) error {
return setFramerate(w.fd, 1000, uint32(1000*(fps)))
}

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

0 comments on commit ba06470

Please sign in to comment.