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stream_param.go
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stream_param.go
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package v4l2
// #include <linux/videodev2.h>
import "C"
import (
"fmt"
"unsafe"
)
// Flags for capability and capture mode fields
// See https://linuxtv.org/downloads/v4l-dvb-apis/userspace-api/v4l/vidioc-g-parm.html#parm-flags
// See https://elixir.bootlin.com/linux/latest/source/include/uapi/linux/videodev2.h#L1214
type StreamParamFlag = uint32
const (
StreamParamModeHighQuality StreamParamFlag = C.V4L2_MODE_HIGHQUALITY
StreamParamTimePerFrame StreamParamFlag = C.V4L2_CAP_TIMEPERFRAME
)
// StreamParam (v4l2_streamparam)
// https://linuxtv.org/downloads/v4l-dvb-apis/userspace-api/v4l/vidioc-g-parm.html#c.V4L.v4l2_streamparm
// See https://elixir.bootlin.com/linux/latest/source/include/uapi/linux/videodev2.h#L2362
type StreamParam struct {
Type IOType
Capture CaptureParam
Output OutputParam
}
// CaptureParam (v4l2_captureparm)
// https://linuxtv.org/downloads/v4l-dvb-apis/userspace-api/v4l/vidioc-g-parm.html#c.V4L.v4l2_captureparm
// See https://elixir.bootlin.com/linux/latest/source/include/uapi/linux/videodev2.h#L1205
type CaptureParam struct {
Capability StreamParamFlag
CaptureMode StreamParamFlag
TimePerFrame Fract
ExtendedMode uint32
ReadBuffers uint32
_ [4]uint32
}
// OutputParam (v4l2_outputparm)
// https://linuxtv.org/downloads/v4l-dvb-apis/userspace-api/v4l/vidioc-g-parm.html#c.V4L.v4l2_outputparm
// See https://elixir.bootlin.com/linux/latest/source/include/uapi/linux/videodev2.h#L1228
type OutputParam struct {
Capability StreamParamFlag
CaptureMode StreamParamFlag
TimePerFrame Fract
ExtendedMode uint32
WriteBuffers uint32
_ [4]uint32
}
// GetStreamParam returns streaming parameters for the driver (v4l2_streamparm).
// https://linuxtv.org/downloads/v4l-dvb-apis/userspace-api/v4l/vidioc-g-parm.html
// See https://elixir.bootlin.com/linux/latest/source/include/uapi/linux/videodev2.h#L2362
func GetStreamParam(fd uintptr, bufType BufType) (StreamParam, error) {
var v4l2Param C.struct_v4l2_streamparm
v4l2Param._type = C.uint(bufType)
if err := send(fd, C.VIDIOC_G_PARM, uintptr(unsafe.Pointer(&v4l2Param))); err != nil {
return StreamParam{}, fmt.Errorf("stream param: %w", err)
}
capture := *(*CaptureParam)(unsafe.Pointer(&v4l2Param.parm[0]))
output := *(*OutputParam)(unsafe.Pointer(uintptr(unsafe.Pointer(&v4l2Param.parm[0])) + unsafe.Sizeof(C.struct_v4l2_captureparm{})))
return StreamParam{
Type: BufTypeVideoCapture,
Capture: capture,
Output: output,
}, nil
}
func SetStreamParam(fd uintptr, bufType BufType, param StreamParam) error {
var v4l2Parm C.struct_v4l2_streamparm
v4l2Parm._type = C.uint(bufType)
if bufType == BufTypeVideoCapture {
*(*C.struct_v4l2_captureparm)(unsafe.Pointer(&v4l2Parm.parm[0])) = *(*C.struct_v4l2_captureparm)(unsafe.Pointer(¶m.Capture))
}
if bufType == BufTypeVideoOutput {
*(*C.struct_v4l2_outputparm)(unsafe.Pointer(uintptr(unsafe.Pointer(&v4l2Parm.parm[0])) + unsafe.Sizeof(v4l2Parm.parm[0]))) =
*(*C.struct_v4l2_outputparm)(unsafe.Pointer(¶m.Output))
}
if err := send(fd, C.VIDIOC_S_PARM, uintptr(unsafe.Pointer(&v4l2Parm))); err != nil {
return fmt.Errorf("stream param: %w", err)
}
return nil
}