1. Overview[edit | edit source]
Yavta stands for "Yet Another V4L2 Test Application". This is a test application based on V4L2 Linux® kernel interface that allows testing, debugging and controlling camera subsystem.
2. How to use Yavta[edit | edit source]
/usr/sbin # yavta --help
Usage: yavta [options] device
Supported options:
-c, --capture[=nframes] Capture frames
-C, --check-overrun Verify dequeued frames for buffer overrun
-d, --delay Delay (in ms) before requeuing buffers
-D, --display Display frames
-f, --format format Set the video format
-F, --file[=name] Read/write frames from/to disk
For video capture devices, the first '#' character in the file name is
expanded to the frame sequence number. The default file name is
'frame-#.bin'.
-h, --help Show this help screen
-i, --input input Select the video input
-I, --fill-frames Fill frames with check pattern before queuing them
-l, --list-controls List available controls
-n, --nbufs n Set the number of video buffers
-p, --pause Pause before starting the video stream
-q, --quality n MJPEG quality (0-100)
-r, --get-control ctrl Get control 'ctrl'
-R, --realtime=[priority] Enable realtime RR scheduling
-s, --size WxH Set the frame size
-t, --time-per-frame num/denom Set the time per frame (eg. 1/25 = 25 fps)
-u, --userptr Use the user pointers streaming method
-w, --set-control 'ctrl value' Set control 'ctrl' to 'value'
--enum-formats Enumerate formats
--enum-inputs Enumerate inputs
--no-query Don't query capabilities on open
--offset User pointer buffer offset from page start
--requeue-last Requeue the last buffers before streamoff
--skip n Skip the first n frames
--sleep-forever Sleep forever after configuring the device
--stride value Line stride in bytes
3. Examples[edit | edit source]
- Getting supported controls/formats/resolutions:
yavta -l --enum-formats --enum-inputs /dev/video0
Device /dev/video0 opened.
Device `STM32 Camera Memory Interface' on `platform:dcmi' is a video capture device.
--- Image Processing Controls (class 0x009f0001) ---
control 0x009f0903 `Test Pattern' min 0 max 1 step 1 default 0 current 1.
1 control found.
- Available formats:
Format 0: RGB565 (50424752)
Type: Video capture (1)
Name: 16-bit RGB 5-6-5
Frame size: 640x480 ()
Frame size: 320x240 ()
Frame size: 160x120 ()
- Available inputs:
Input 0: Camera.
Video format: RGB565 (50424752) 160x120 (stride 320) buffer size 38400
- Capturing 10 frames on the disk (default format/resolution):
yavta -F /dev/video0 --capture=10
/usr/sbin # yavta -F /dev/video0 --capture=10 Device /dev/video0 opened. Device `STM32 Camera Memory Interface' on `platform:dcmi' is a video capture device. Video format: RGB565 (50424752) 160x120 (stride 320) buffer size 38400 8 buffers requested. length: 38400 offset: 0 Buffer 0 mapped at address 0xc0710000. length: 38400 offset: 40960 Buffer 1 mapped at address 0xc0720000. length: 38400 offset: 81920 Buffer 2 mapped at address 0xc0730000. length: 38400 offset: 122880 Buffer 3 mapped at address 0xc0740000. length: 38400 offset: 163840 Buffer 4 mapped at address 0xc0750000. length: 38400 offset: 204800 Buffer 5 mapped at address 0xc0760000. length: 38400 offset: 245760 Buffer 6 mapped at address 0xc0770000. length: 38400 offset: 286720 Buffer 7 mapped at address 0xc0780000. 0 (0) [-] 0 38400 bytes 1378.374325 1378.374535 17.819 fps 1 (1) [-] 1 38400 bytes 1378.407623 1378.407822 30.032 fps 2 (2) [-] 2 38400 bytes 1378.440939 1378.441111 30.016 fps 3 (3) [-] 3 38400 bytes 1378.474288 1378.474450 29.986 fps 4 (4) [-] 4 38400 bytes 1378.507624 1378.507827 29.998 fps 5 (5) [-] 5 38400 bytes 1378.540989 1378.541196 29.972 fps 6 (6) [-] 6 38400 bytes 1378.574288 1378.574489 30.031 fps 7 (7) [-] 7 38400 bytes 1378.607624 1378.607827 29.998 fps 8 (0) [-] 8 38400 bytes 1378.640959 1378.641162 29.999 fps 9 (1) [-] 9 38400 bytes 1378.674288 1378.674488 30.004 fps Captured 10 frames in 0.356282 seconds (28.067590 fps, 1077795.461669 B/s).