Writeback driver support for DM8168
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RidgeRun provides support for the DM816x writeback driver. This driver is used to access the OSD and blended video and graphics images out of the hardware compositor.
You can think of the DM816x writeback driver as giving you the ability to do a screen shot of the currently displayed video frame overlayed with the QT or other OSD text and graphics. Some people think of the writeback driver as giving you the ability to do a video screen capture, similar to the way some programs run on a personal computer. No matter how you choose to think of the writeback driver, it gives you access to each video frame with the OSD overlayed on top.
Writeback driver
The DM816x SoC supports a feedback data path (which is called writeback) in DVO1, as shown in the TI DM818x diagram.
To manage the stream of video frames coming from the writeback path, we add an extra video device /dev/video7. So, your system is ready to capture using V4L2 and you will be able to capture from both VIP0 and VIP1 video input nodes and from the writeback path. If the V4L2 display driver is enabled, the video nodes would have the following map:
/dev/video0 → Capture VIP 0 Port A /dev/video1 → Display 0 /dev/video2 → Display 1 /dev/video3 → Display 2 /dev/video4 → Capture VIP 0 Port B /dev/video5 → Capture VIP 1 Port A /dev/video6 → Capture VIP 1 Port B /dev/video7 → Capture SC5 WB2
If you are not using the V4L2 display driver, you need to use this mapping instead:
/dev/video0 → Capture VIP 0 Port A /dev/video1 → Capture VIP 0 Port B /dev/video2 → Capture VIP 1 Port A /dev/video3 → Capture VIP 1 Port B /dev/video4 → Capture SC5 WB2
Enabling the writeback driver
To enable the writeback driver, run make config and select:
--> Proprietary software
- Enable Writeback driver support
Then run make and make install as usual. Now, your SDK is ready to capture data from the writeback path.
In order to use the writeback driver we need to display something on DVO1 (HDMI). If you are thinking about using DVO2, you need to tie DVO2 and DVO1 and then use the writeback driver:
insmod just in the EVM insmod lib/modules/2.6.37-ridgerun/kernel/drivers/video/ti81xx/sii9022a/sii9022a.ko echo 0 > /sys/devices/platform/vpss/graphics0/enabled echo 0 > /sys/devices/platform/vpss/display0/enabled echo 0 > /sys/devices/platform/vpss/display1/enabled echo 5 > /sys/devices/platform/vpss/system/tiedvencs echo 2:hdmi,dvo2 > /sys/devices/platform/vpss/graphics0/nodes echo vcompmux:hdmi,dvo2 > /sys/devices/platform/vpss/video0/nodes echo 1 > /sys/devices/platform/vpss/display0/enabled echo 1 > /sys/devices/platform/vpss/display1/enabled echo 1 > /sys/devices/platform/vpss/graphics0/enabled
GStreamer pipelines
Snapshot pipeline
gst-launch -e v4l2src device=/dev/video7 num-buffers=1 always-copy=false queue-size=8 ! 'video/x-raw-yuv,format=(fourcc)YUY2,width=1920,height=1080,framerate=(fraction)60/1' ! omxbufferalloc \ numBuffers=10 ! queue ! ffmpegcolorspace ! jpegenc ! jifmux ! filesink location=writeback.jpeg
Videotestsrc with writeback pipeline
gst-launch videotestsrc ! "video/x-raw-yuv, format=(fourcc)NV12, width=1920, height=1080, framerate=60/1, buffer-count-requested=4" ! omx_mdeiscaler name=d d.src_00 ! 'video/x-raw-yuv, \ width=(int)1920, height=(int)1080' ! v4l2sink sync=false device=/dev/video1 d.src_01 ! fakesink silent=true -v &
V42 source with writeback pipeline
gst-launch -e v4l2src device=/dev/video7 num-buffers=1 always-copy=false queue-size=8 ! 'video/x-raw-yuv,format=(fourcc)YUY2,width=1920,height=1080,framerate=(fraction)60/1' ! rrbufferalloc \ numBuffers=10 ! queue ! ffmpegcolorspace ! jpegenc ! jifmux ! filesink location=writeback.jpeg
RTSP streaming V4L2 source with writeback pipeline
gst-launch v4l2src device=/dev/video7 always-copy=false queue-size=8 ! 'video/x-raw-yuv, format=(fourcc)YUY2, width=1920, height=1080, framerate=(fraction)30/1, buffer-count-requested=10' ! \ omxbufferalloc numBuffers=10 ! omx_noisefilter ! gstperf ! omx_h264enc output-buffers=10 input-buffers=10 i-period=30 force-idr-period=90 bitrate=5000000 ! rr_h264parser singleNalu=true \ ! video/x-h264, mapping=/stream1 ! rtspsink name=sink service=554
In the host side, you can use vlc or the next pipeline:
IPADDR=10.251.101.114 gst-launch-0.10 rtspsrc location=rtsp://$IPADDR:/stream1 ! rtph264depay ! queue ! ffdec_h264 ! fpsdisplaysink sync=false
It is important to mention that the output on the writeback path is in YUY2 format. So, we use the omx_noisefilter to convert the image from YUY2 to NV12.
RTSP streaming, video test source with writeback pipeline
Videotestsrc + Writeback + RTSP
gst-launch v4l2src device=/dev/video7 always-copy=false queue-size=8 ! 'video/x-raw-yuv, format=(fourcc)YUY2, width=1920, height=1080, framerate=(fraction)30/1, buffer-count-requested=10' ! \ omxbufferalloc numBuffers=10 ! omx_noisefilter ! omx_h264enc output-buffers=10 input-buffers=10 i-period=30 force-idr-period=90 bitrate=5000000 ! rr_h264parser singleNalu=true ! \ video/x-h264, mapping=/stream1 ! rtspsink name=sink service=554 videotestsrc ! "video/x-raw-yuv, format=(fourcc)NV12, width=1920, height=1080, framerate=15/1, buffer-count-requested=4" ! \ omx_mdeiscaler name=d d.src_00 ! 'video/x-raw-yuv, width=(int)1920, height=(int)1080' ! v4l2sink sync=false device=/dev/video1 d.src_01 ! fakesink silent=true -v
In the host side, you can use vlc or the next pipeline (remember to change the ip address):
IPADDR=10.251.101.114 gst-launch-0.10 rtspsrc location=rtsp://$IPADDR:/stream1 ! rtph264depay ! queue ! ffdec_h264 ! fpsdisplaysink sync=false
Triple capture with writeback pipeline
Capture two 1080p@60fps and one 1080p@60fsp writeback.
gst-launch -e v4l2src device=/dev/video0 always-copy=false queue-size=8 ! 'video/x-raw-yuv,format=(fourcc)NV12,width=1920,height=1080,framerate=(fraction)60/1' ! omxbufferalloc \ numBuffers=10 ! gstperf ! fakesink v4l2src device=/dev/video5 always-copy=false queue-size=8 ! 'video/x-raw-yuv,format=(fourcc)NV12,width=1920,height=1080,framerate=(fraction)60/1' ! \ omxbufferalloc numBuffers=10 ! gstperf ! fakesink v4l2src device=/dev/video7 always-copy=false queue-size=8 ! 'video/x-raw-yuv,format=(fourcc)NV12,width=1920, \ height=1080,framerate=(fraction)60/1' ! omxbufferalloc numBuffers=10 ! gstperf ! fakesink
Triple capture with writeback pipeline with display
Capture two 1080p@60fps and one 1080p@60fps writeback capture with two displays 1080 and one HDMI component output.
gst-launch -e v4l2src device=/dev/video0 always-copy=false queue-size=8 ! 'video/x-raw-yuv,format=(fourcc)YUY2,width=1920,height=1080,framerate=(fraction)60/1' ! omxbufferalloc \ numBuffers=10 ! gstperf ! v4l2sink sync=false device=/dev/video1 sync=false v4l2src device=/dev/video5 always-copy=false queue-size=8 ! 'video/x-raw-yuv,format=(fourcc)YUY2, \ width=1920,height=1080,framerate=(fraction)60/1' ! omxbufferalloc numBuffers=10 ! gstperf ! v4l2sink sync=false device=/dev/video2 v4l2src device=/dev/video7 always-copy=false queue-size=8 ! \ 'video/x-raw-yuv,format=(fourcc)YUY2,width=1920,height=1080,framerate=(fraction)60/1' ! omxbufferalloc numBuffers=10 ! gstperf ! fakesink
Same functionality but displaying writeback with low latency.
gst-launch -e v4l2src device=/dev/video0 always-copy=false queue-size=8 ! 'video/x-raw-yuv,format=(fourcc)YUY2,width=1920,height=1080,framerate=(fraction)60/1' ! omxbufferalloc \ numBuffers=10 ! gstperf ! v4l2sink sync=false device=/dev/video1 sync=false v4l2src device=/dev/video7 always-copy=false queue-size=8 ! 'video/x-raw-yuv,format=(fourcc)YUY2, \ width=1920,height=1080,framerate=(fraction)60/1' ! omxbufferalloc numBuffers=10 ! gstperf ! v4l2sink enable-last-buffer=false sync=false device=/dev/video2 v4l2src device=/dev/video5 \ always-copy=false queue-size=8 ! 'video/x-raw-yuv,format=(fourcc)YUY2,width=1920,height=1080,framerate=(fraction)60/1' ! omxbufferalloc numBuffers=10 ! gstperf ! fakesink
Capture 2x1080p@60fps + 1x1080p@60fps Writeback capture + 2 display 1080 - component, HDMI + RTSP
gst-launch -e v4l2src device=/dev/video0 always-copy=false queue-size=8 ! 'video/x-raw-yuv,format=(fourcc)YUY2,width=1920,height=1080,framerate=(fraction)60/1' ! omxbufferalloc \ numBuffers=10 !gstperf ! v4l2sink sync=false device=/dev/video1 sync=false v4l2src device=/dev/video5 always-copy=false queue-size=8 ! 'video/x-raw-yuv,format=(fourcc)YUY2, \ width=1920,height=1080,framerate=(fraction)60/1' ! omxbufferalloc numBuffers=10 ! gstperf ! v4l2sink sync=false device=/dev/video2 v4l2src device=/dev/video7 always-copy=false \ queue-size=8 ! 'video/x-raw-yuv,format=(fourcc)YUY2,width=1920,height=1080,framerate=(fraction)60/1' ! omxbufferalloc numBuffers=10 ! gstperf ! omx_noisefilter ! omx_h264enc \ output-buffers=10 input-buffers=10 i-period=30 force-idr-period=90 bitrate=5000000 ! rr_h264parser singleNalu=true ! video/x-h264, mapping=/stream1 ! rtspsink name=sink service=554
In the host side, you can use vlc or the next pipeline (remember to change the ip address):
gst-launch-0.10 rtspsrc location=rtsp://10.251.101.114:/stream1 ! rtph264depay ! queue ! ffdec_h264 ! fpsdisplaysink sync=false
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