// Start streaming process
func (w *Webcam) StartStreaming() error {
buf_count := C.uint32_t(256)
res, err := C.mmapRequestBuffers(C.int(w.fd), &buf_count)
if res < 0 {
return err
}
if uint32(buf_count) < 2 {
return errors.New("Insufficient buffer memory")
}
w.buffers = make([]buffer, uint32(buf_count))
for index, buf := range w.buffers {
var length C.uint32_t
var start unsafe.Pointer
res, err := C.mmapQueryBuffer(C.int(w.fd), C.uint32_t(index), &length, &start)
if res < 0 {
if err != nil {
return err
} else {
return errors.New("Failed to map memory")
}
}
buf.start = start
buf.length = uint32(length)
w.buffers[index] = buf
}
for index, _ := range w.buffers {
res, err = C.mmapEnqueueBuffer(C.int(w.fd), C.uint32_t(index))
if res < 0 {
return errors.New("Failed to enqueue buffer")
}
}
res, err = C.startStreaming(C.int(w.fd))
if res < 0 {
return err
}
return nil
}
// Read a single frame from the webcam
// If frame cannot be read at the moment
// function will return empty array
func (w *Webcam) ReadFrame() ([]byte, error) {
var index C.uint32_t
var length C.uint32_t
res, err := C.mmapDequeueBuffer(C.int(w.fd), &index, &length)
if res < 0 {
return nil, err
} else if res > 0 {
return nil, nil
}
buffer := w.buffers[int(index)]
result := C.GoBytes(buffer.start, C.int(length))
res, err = C.mmapEnqueueBuffer(C.int(w.fd), index)
if res < 0 {
return result, err
} else {
return result, nil
}
}
