Can't make v4l2grab_h264 to work properly

[brainstormi]

Hi...
I'm trying to get v4l2grab_h264 to capture desktop and stream it with v4l2rtspstreamserver (running in Pi3B/osmc/kodi) without luck, maybe I'm not using it correctly. I created a loopback device with:

sudo modprobe v4l2loopback video_nr=10
v4l2grab_h264 -vv /dev/video10 

and stream it with:

v4l2rtspserver -vv /dev/video10

I'm trying to reproduce it with VLC (rtsp://ip:8554/unicast) without luck. Most of the times remains there forver without displaying anything and from time to time it displays a static image of the desktop with the bottom of the screem totally distorted.

I tried to do the same using raspidisp driver from uv4l project and v4l2compress_omx with a lot more luck, making easy to connect 90% of the times and when it does it plays smoothly the desktop with some artifacts, but I'll open a different issue about it.

I played with v4l2grab_h264 write API (-w) and v4l2rtspserver (-r and -w) in all combinations possible without success.

Below the logs from v4l2grab_h264 and v4l2rtsp from the initial example, frame sizes are already suspicious:

v4l2grab_h264 output
https://pastebin.com/5LSD4Mi8

v4l2rtspserver -vv /dev/video10
https://pastebin.com/CUP10iVE

Regards,

[brainstormi]

Playing a movie in full screen v4l2grab_h264 shows in the log frame sizes more logical, and in VLC you see the screen is updated more frequently although totally garbled, full of artifacts:

[DEBUG] src/v4l2grab_h264.cpp:188
Writing frame size:65536
[DEBUG] src/v4l2grab_h264.cpp:188
Writing frame size:65536
[DEBUG] src/v4l2grab_h264.cpp:188
Writing frame size:11412
[WARN] src/v4l2grab_h264.cpp:184
fwrite: Error emptying buffer:4294967295!=54068
[DEBUG] src/v4l2grab_h264.cpp:188
Writing frame size:1605
[DEBUG] src/v4l2grab_h264.cpp:188
Writing frame size:44765
[DEBUG] src/v4l2grab_h264.cpp:188
Writing frame size:46676
[DEBUG] src/v4l2grab_h264.cpp:188
Writing frame size:48937
[DEBUG] src/v4l2grab_h264.cpp:188
Writing frame size:13390

[mpromonet]

Hi,
This commit 79af898#diff-7a50a337891585a439948f5e4f0959f5 should help.
Best Regards,
Michel.

[brainstormi]

A lot better now!!. Now it's possible to connect to RTSP stream without hassle and it shows the live desktop with the similar artifacts issues reported when using raspidisp driver #28 .
The issue now is that it's not possible to stream a movie in fullscreen. For example when trying to do it with kodi, v4l2grab_h264 just freeze when starting the movie or just a few seconds later (5-10 seconds), always. This doesn't happen with uv4l driver and v4l2compress_omx or _h264.
There is no error in the output console, it just stops. Only way to resume it is killing the process and launching it again:

[DEBUG] src/v4l2grab_h264.cpp:183
Writing frame size:5266
[DEBUG] src/v4l2grab_h264.cpp:183
Writing frame size:55524
[DEBUG] src/v4l2grab_h264.cpp:183
Writing frame size:38644
[DEBUG] src/v4l2grab_h264.cpp:183
Writing frame size:21844
[DEBUG] src/v4l2grab_h264.cpp:183

[brainstormi]

Great!. Your last commit seems to have fixed the streaming issues with the grabber, including displaying movies in full screen.
There is a minor issue, also present in raspidisp. In both cases if you configure Kodi, to sync screen refresh rate with movie when it starts/stops, kills the grabber with the following error:

[DEBUG] src/v4l2grab_h264.cpp:183
v4l2grab_h264: src/v4l2grab_h264.cpp:46: int take_snapshot(void*, DISPMANX_DISPLAY_HANDLE_T, DISPMANX_RESOURCE_HANDLE_T, DISPMANX_MODEINFO_T, VC_RECT_T*, DISPMANX_TRANSFORM_T): Assertion `ret == 0' failed.
	Writing frame size:753Abortado

The only program I tested using the same dispmanx API that manages properly this scenario is dispmanx_vncserver, in particular this fork: https://github.com/patrikolausson/dispmanx_vnc, but taking a look at it, I could understand that a change of resolution could cause an issue with vc_dispmanx_snapshot(display,resource,transform) because the resource created has change its size, but not with refresh rate.