Supported dynamic resolution change by DV timings & ioctl() timeout #164

mdevaev · 2018-09-12T04:12:24Z

input_uvc had two problems:

It hangs if you disconnect the camera cable (or HDMI cable from capture board) while mjpg-streamer was running on ioctl(VIDIOC_DQBUF). I added select() befure this syscall and now mjpg streamer closes after timeout (5 sec. by default). It can be changed by option -timeout.
When using video capture devices, it is possible to change the resolution spontaneously when changing the source. I added support of DV timings events and now mjpg-streamer don't hang on changing source disconnecting/connecting cable - it changes resolution automatically and and continues streaming. This behavior may be enabled by -dv_timings.

Both these changes are necessary for work Auvidea B101 board:
https://auvidea.com/b101-hdmi-to-csi-2-bridge-15-pin-fpc/

This is a very promising device for video processing. It's officially supports by Raspberry Pi team:
https://www.raspberrypi.org/forums/viewtopic.php?f=38&t=120702

May I ask you to take this patch as soon as possible? It is necessary for the open-source IP-KVM project that I develop. In addition, it will be very useful to everyone who uses devices that are disconnected from the PC.

Example for B101:

mjpg_streamer -i 'input_uvc.so -d /dev/video0 -u -n -timeout 1 -dv_timings' -o 'output_http.so -l 0.0.0.0 -p 8082'
MJPG Streamer Version.: 2.0
 i: Using V4L2 device.: /dev/video0
 i: Desired Resolution: 640 x 480
 i: Frames Per Second.: -1
 i: Format............: UYVY
 i: JPEG Quality......: 80
 i: TV-Norm...........: DEFAULT
 i: QUERY_DV_TIMINGS returned 640x480 pixclk 25200000
 o: www-folder-path......: disabled
 o: HTTP TCP port........: 8082
 o: HTTP Listen Address..: 0.0.0.0
 o: username:password....: disabled
 o: commands.............: enabled
# -------------------- hdmi cable disconnected
 i: select() timeout
 i: select() timeout
 i: select() timeout
 i: select() timeout
 i: select() timeout
 i: select() timeout
 i: select() timeout
 i: select() timeout
 i: select() timeout
 i: select() timeout
 i: select() timeout
# -------------------- connected hd source, streaming...
 i: QUERY_DV_TIMINGS returned 1920x1080 pixclk 148500000
# -------------------- hdmi cable disconnected
 i: select() timeout
 i: select() timeout
 i: select() timeout
 i: select() timeout
 i: select() timeout
# -------------------- connected old PC, streaming...
 i: QUERY_DV_TIMINGS returned 640x480 pixclk 25200000

PS: Sorry for my English.

input_uvc had two problems: 1) It hangs if you disconnect the camera cable (or HDMI cable from capture board) while mjpg-streamer was running on ioctl(VIDIOC_DQBUF). I added select() befure this syscall and now mjpg streamer closes after timeout (5 sec. by default). It can be changed by option -timeout. 2) When using video capture devices, it is possible to change the resolution spontaneously when changing the source. I added support of DV timings events and now mjpg-streamer don't hang on changing source disconnecting/connecting cable - it changes resolution automatically and and continues streaming. Both these changes are necessary for work Auvidea B101 board: https://auvidea.com/b101-hdmi-to-csi-2-bridge-15-pin-fpc/ This is a very promising device for video processing. It's officially supports by Raspberry Pi team: https://www.raspberrypi.org/forums/viewtopic.php?f=38&t=120702

mdevaev · 2018-09-12T04:52:59Z

Also my patch fixes segfault on IN_CMD_RESOLUTION.
When changing the resolution from smaller to larger the image did not fit into framebuffer.

jacksonliam

Thanks for this, resolution switching is something I've wanted for a while and I'm sure people will find the timeout useful.

However, I'm hoping you can disable the timeout by default, because some people might not want mjpg streamer to quit or may want it to wait a really long time.

mjpg-streamer-experimental/plugins/input_uvc/input_uvc.c

jacksonliam · 2018-09-12T07:46:41Z

mjpg-streamer-experimental/plugins/input_uvc/input_uvc.c

@@ -74,6 +74,8 @@ static unsigned int every = 1;
 static int wantTimestamp = 0;
 static struct timeval timestamp;
 static int softfps = -1;
+static unsigned int timeout = 5;


Can timeout be disabled by default? To keep current behaviour.

The current behaviour is totally broken. You don't have any way to know that something went wrong while the program is running. If the connection to device is broken it will never be restored and the fd will be "dead". Mjpg-streamer will hang forever and you do not know why. If you have a timeout, at least you can restart the program.

For example, if mjpg-streamer works inside the camera firmware, the self-monitoring will restart stream in case of a problem if you have this timeout. With old behavior this is impossible, mjpg-streamer will remain frozen and broken.

Do you really want to keep this behavior?

OpenCV uses the same logic for V4L: https://github.com/opencv/opencv/blob/b39cd06249213220e802bb64260727711d9fc98c/modules/videoio/src/cap_libv4l.cpp#L1170

mjpg-streamer-experimental/plugins/input_uvc/input_uvc.c

jacksonliam · 2018-09-12T07:51:02Z

mjpg-streamer-experimental/plugins/input_uvc/input_uvc.c

+            pthread_mutex_unlock(&pglobal->in[pcontext->id].db);
+        }
+
+other_select_handlers:


Not crazy about the multiple gotos, but I guess this code not very well structured to start with and I can't see an quick way to fix it!

I think it's an old problem of this function. I didn't want to modify the existing code too much to get a giant patch because I saw that you are working on something in this function. I plan to investigate the automatic resolution change and continue to implement the best support for B101 and maybe I will have to refactor. It seems to me that it is better to make other PR.

I refactored this code and moved events processing into a separate function.

mdevaev · 2018-09-24T19:16:29Z

BTW I started my own streamer project. Now it supports multi-threaded compression, hardware compression on Raspberry Pi using OpenMAX and dynamic resolution change. I managed to get a much larger FPS than in mjpg-streamer. Perhaps you will find it useful for yourself :)
https://github.com/pi-kvm/ustreamer

jacksonliam · 2018-10-14T18:16:53Z

Thanks again!

minor improvements

09a9428

jacksonliam reviewed Sep 12, 2018

View reviewed changes

mdevaev added 3 commits September 12, 2018 14:00

review fixes

2d18dc7

small refactoring

55b1ea3

A more correct subscription to DV events that prevents possible hangs

856d237

jacksonliam merged commit 856d237 into jacksonliam:master Oct 14, 2018

jacksonliam mentioned this pull request Oct 21, 2018

MJPG-streamer stops streaming but no error found #100

Closed

KiillThemAll mentioned this pull request Apr 24, 2020

Video capture not supported by the device pikvm/ustreamer#18

Closed

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Supported dynamic resolution change by DV timings & ioctl() timeout #164

Supported dynamic resolution change by DV timings & ioctl() timeout #164

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Supported dynamic resolution change by DV timings & ioctl() timeout #164

Supported dynamic resolution change by DV timings & ioctl() timeout #164

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