Re: how to make qbuf
Lamarque Vieira Souza <[email protected]>
| Newsgroups | gmane.comp.video.video4linux |
|---|---|
| Message-ID | <[email protected]> |
Em Tuesday 07 July 2009, 서정민 escreveu: > Hi. Hi, > I'm making V4l2 device driver for mplayer. mplayer already implements v4l2 specification, you do not need to implement a driver for it. > But > It's too difficult to understand V4l2 driver internal structure. > > I can't understand how to use VIDIOC_QBUF, VIDIOC_DQBUF ioctl and 'struct > videobuf_queue' VIDIOC_QBUF queues a buffer (struct v4l2_buffer) to a buffer list managed by the device driver (usually a kernel module). The driver fills the buffer with needed information (image data, compression type, etc) and the application must use VIDIOC_DQBUF to get the filled buffer from the device driver's buffer list. Applications, such as mplayer must use VIDIOC_QBUF and VIDIOC_DQBUF. videobuf_queue is used by the device driver (kernel space) to manage the buffer list. If you are creating/changing an application (mplayer) you do not need to know about videobuf_queue. If you are creating a device driver for a capture device (webcam, etc) in kernel space then using videobuf_queue will make your life easier. > Why does v4l2 driver need to use 'videobuf_queue'? videobuf_queue is not mandatory but it will make it easier to manage video frames and implement some needed ioctls in the device driver. > Please. tell me v4l2 driver internal operation. You can read more bout v4l2 here http://v4l2spec.bytesex.org/spec- single/v4l2.html > Thanks. > -- > video4linux-list mailing list > Unsubscribe mailto:[email protected]?subject=unsubscribe > https://www.redhat.com/mailman/listinfo/video4linux-list -- Lamarque V. Souza http://www.geographicguide.com/brazil.htm Linux User #57137 - http://counter.li.org/ -- video4linux-list mailing list Unsubscribe mailto:[email protected]?subject=unsubscribe https://www.redhat.com/mailman/listinfo/video4linux-list