Hello Xie,
I'm not sure which camera interface driver you are using, but it seems
to be camera interface driver's problem. Let me guess, are you using
pxa camera interface driver from Marvell?(proprietary but not in up
stream kernel)
It just looks like that camera interface driver is not returning
proper data in dqbuf.
And one more thing. I prefer to use byteused rather than length in
buf. because as far as I know the size of preview data from camera is
in byte unit which we need to copy to memory. But it should be
possible to use length, I guess..
Cheers,
Nate
On Mon, Jun 8, 2009 at 11:05 AM, xie<yili.xie@xxxxxxxxx> wrote:
> Dear all ~~
>
> I have met a issue when I used the mmap method for previewing . I just
> used the standard code as spec to get the image data :
> status_t CameraHardwareProwave::V4l2Camera::v4l2CaptureMainloop()
> {
> LOG_FUNCTION_NAME
> int rt ;
> unsigned int i ;
> fd_set fds ;
> struct timeval tv ;
> struct v4l2_buffer buf ;
>
> for(;;){
> FD_ZERO(&fds) ;
> FD_SET(v4l2Fd, &fds) ;
> //now the time is long ,just for debug
> tv.tv_sec = 2 ;
> tv.tv_usec = 0 ;
>
> rt = select(v4l2Fd + 1, &fds, NULL, NULL, &tv) ;
> LOGD("The value of select return : %d\n", rt) ;
>
> /********** for debug
> if(V4L2_NOERROR != v4l2ReadFrame()){
> LOGE("READ ERROR") ;
> }
> ***********/
>
> if(-1 == rt){
> LOGE("there is something wrong in select function(select)") ;
> //no defined error manage
> return V4L2_IOCTL_ERROR ;
> }
> if(0 == rt){
> LOGE("wait for data timeout in select") ;
> return V4L2_TIMEOUT ;
> }
>
> memset(&buf, 0, sizeof(buf)) ;
> buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE ;
> buf.memory = V4L2_MEMORY_MMAP ;
> if(-1 == ioctl(v4l2Fd, VIDIOC_DQBUF, &buf)){
> LOGE("there is something wrong in dequeue buffer(VIDIOC_DQBUF)") ;
> return V4L2_IOCTL_ERROR ;
> }
>
> assert(i < n_buf) ;
> LOGE("buf.index 0buf.length = %d %d \n", buf.index , buf.length) ;
> memcpy((mCameraProwave->getPreviewHeap())->base(),
> v4l2Buffer[buf.index].start, buf.length) ;
> if(-1 == ioctl(v4l2Fd, VIDIOC_QBUF, &buf)){
> LOGE("there is something wrong in enqueue buffer(VIDIOC_QBUF)") ;
> return V4L2_IOCTL_ERROR ;
> }
> //break ; //i don't know whether the break is needed ;
>
> }
> return V4L2_NOERROR ;
> }
>
> when executed the VIDIOC_DQBUF IOCTL,the return value was right, but the
> value of buf.length would always be zero. Then I used the read()
> function to read raw data in the file handle for debug, and I can get
> the raw data. Anybody have met this issue before ? Who can give me some
> advices or tell me what is wrong , thanks a lot ~
>
>
--
=
DongSoo, Nathaniel Kim
Engineer
Mobile S/W Platform Lab.
Digital Media & Communications R&D Centre
Samsung Electronics CO., LTD.
e-mail : dongsoo.kim@xxxxxxxxx
dongsoo45.kim@xxxxxxxxxxx
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