Camera stream formats
The AF51 camera will stream images down the USB cable in a format selectable by the
user via interaction with the USB 2.0 microcontroller interface. The user may select to get
either raw images in the YUYV format (this results in slower frame rates ranging from a
maximum of 3 to 25 FPS depending on the frame resolution but higher quality images
best suited for scientific applications) or the compressed MJPEG format (this yields
images at a maximum of 30 FPS at all resolutions so is best suited to capturing or
previewing live HD video but with each image having a degree of image compression
artefact).
The complete list of available formats and resolutions are shown in table 3.3.
Resolutions
(WxH)
Aspect
Ratio
Max. FPS
YUYV
Max. FPS
MJPEG
Also Called
Pan
Tilt
Zoom
320 x 240
4:3
25
30
QVGA
Yes (Z) Yes (Z) Yes (3)
424 x 240
16:9*
25
30
WQVGA
Yes
Yes
Yes (2)
640 x 360
16:9
25
30
nHD
Yes
No
No
640 x 480
4:3
25
30
VGA
No
No
No
848 x 480
16:9*
15
30
WVGA
Yes
Yes
No
960 x 540
16:9
10
30
qHD
Yes
Yes
No
1280 x 720 16:9
10
30
HD 720p
Yes
No
No
1280 x 960 4:3
10
30
SXGA-
No
No
No
1920 x 1080 16:9
5
30
Full HD 1080p
No
No
No
2560 x 1440 16:9
3
30
QHD 2K 1440p
Yes
Yes
No
2592 x 1944 4:3
3
30
5 MP
No
No
No
Table 3.3 Available camera stream formats for the AF51. Also shown is the compatibility of each format with
the (digital) Pan, Tilt and Zoom controls of the camera. * These are the closest approximations to 16:9
aspect ratio that maintain modulo 16 compatibility (i.e. each dimension pixel count is exactly divisible by 16).
This is important because encoding frames into a streaming format is done by breaking the frames down
into blocks of 4x4 or 16x16 pixels. In the above names Q can stand for ‘quarter’ (meaning 4 times fewer
pixels) or ‘quad’ (meaning 4 times more pixels) and ‘q’ stands for ‘quarter’ (qHD has a quarter the number of
pixels as 1080p Full HD); W indicates the wide version of a format. nHD stands for ninth HD because it has
9 times fewer pixels than 1080p Full HD. VGA refers to the Video Graphics Array standard of 640x480
pixels, SXGA- refers to an unofficial terminology to indicate a slightly lower resolution version of the Super
eXtended Graphics Array standard (the original SXGA is 1280x1024). Sometimes QHD is also referred to
as ‘2.5 K’. The QHD (quad HD) terminology refers to the fact that it has 4 times the number of pixels as
‘standard’ HD (720p) resolution. The Pan, tilt and Zoom entries show which of these functions are available
at each resolution. ‘Yes (3)’ means all 3 steps of zoom can be done, ‘Yes (2)’ means only two steps of zoom
can be done. ‘Yes (Z)’ means pan or tilt will work only when zoomed in.
OptArc AF51 Camera Page 33 of 99 User Guide v1.02