Re: [libdc1394-devel] dc1394_dma_setup_format7_capture() & QUERY_FROM_CAMERA

[Damien D. <d.d...@te...>]

Hi Ralf,

On Fri, 2003-09-05 at 22:02, Ralf Ebeling wrote:
> Hi,
>=20
> one of our customers run into trouble when using the function
> dc1394_dma_setup_format7_capture() and QUERY_FROM_CAMERA as a
> parameter. He wrote his own software and didn't use Coriander...
>=20
> >  dc1394_dma_setup_format7_capture(handle,
> >           /* node */                   node,
> >           /* channel */                0,
> >           /* capture mode */           MODE_FORMAT7_4,
> >           /* speed */                  SPEED_400,
> >           /* bytes per packet */       (unsigned int)QUERY_FROM_CAMERA,
> >           /* left */                   (unsigned int)QUERY_FROM_CAMERA,
> >           /* top */                    (unsigned int)QUERY_FROM_CAMERA,
> >           /* width */                  (unsigned int)QUERY_FROM_CAMERA,
> >           /* height */                 (unsigned int)QUERY_FROM_CAMERA,
> >           /* DMA buffers */            DMA_BUFFERS,
> > 	                                     &camera_);
>=20
> If QUERY_FROM_CAMERA is used the function reads the format7 register
> IMAGE_SIZE, IMAGE_POSITION and BytesPerPackage. As stated by the IIDC
> spec 1.30 these register are initialized with 0x0.

I checked 1.30 and could not find this initialization requirement. Which
page contains this information?

> If someone didn't write valid values to the above mentioned registers,
> capturing images could fail...

Indeed...=20

> I would suggest:
> - to read IMAGE_SIZE_INQ
> - to set IMAGE_SIZE to IMAGE_SIZE_INQ, if IMAGE_POSITION is 0 or
>   to calculate an adequate value, if IMAGE_POSITION is not 0

I have patched libdc to handle this 0x0 init value: if the value is zero
the maximum size is used (taking the image position into account).

> - to read MaxBytesPerPacket after setting size and position (be-
>   cause it depends on the size and color coding)
> - to set BytesPerPackets to MaxBytesPerPacket, if BytesPerPacket
>   is 0 and to validate BytesPerPacket if it was set by the user

Reading back the code I think we already do that in the switch statement
at line 453 of dc1394_format7.c.

Cheers,

Damien
--=20
  _    Damien Douxchamps
 (=B0-   PhD Student / Research Assistant
 //\   Image Processing Group, Telecom Laboratory, UCL, Belgium
 V_/_  http://www.tele.ucl.ac.be/MEMBERS/Douxchamps_Damien_e.html