#StackBounty: #linux #ffmpeg #video-streaming #latency #opencv Low latency video shared in local gigabit network using linux

Bounty: 50

For a robotics task we need to share the video (Webcam) live to about 6 or 7 users in the same room. OpenCV will be used on the clients to read the situation and send new tasks to the robots. Latency should not be much more than one second, the lower the better. What commands would you recommend for this?

We have one camera on a Linux host which wants to share the video to about 6 other units just some meters away.

I already experimented with different setups. While raw-video looks like perfectly latency free (local loopback, the issue is the amount of data), any compression suddenly ads about a second delay.
And how should we share this in the network. Is broadcasting the right approach? How can it be so hard, they are right next to each other.

Works locally, issues over the network.

#server
ffmpeg -f video4linux2 -r 10 -s 1280x720 -i /dev/video0 -c:v libx264 -preset veryfast -tune zerolatency -pix_fmt yuv420p -f mpegts - | socat - udp-sendto:192.168.0.255:12345,broadcast
#client
socat -u udp-recv:12345,reuseaddr - | vlc --live-caching=0 --network-caching=0 --file-caching=0 -

raw video – perfectly fine like this, video with many artefacts if sent over the network

ffmpeg -f video4linux2 -r 10 -s 1280x720 -i /dev/video0 -c:v rawvideo -f rawvideo -pix_fmt yuv420p - | vlc --demux rawvideo --rawvid-fps 10 --rawvid-width 1280 --rawvid-height 720 --rawvid-chroma I420 -

The technology used doesen’t matter, we do not care about network load either. Just want to use opencv on different clients using live data.


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#StackBounty: #linux #ubuntu #boot #grub Ubuntu/Windows 10 Dualboot – Grub missing

Bounty: 100

I previously installed a standalone copy of Windows 10 on my Microsoft Surfacebook. I intend to set up Ubuntu dual-boot alongside it. Unfortunately, after installation following these instructions, it seems that Windows still boots over Ubuntu — the GRUB loader is ignored?

I have tried the following:

  • Running boot repair from Live Ubuntu USB. This apparently runs and does some things, which prevents both Windows and Ubuntu from booting altogether — gets stuck with the Surfacebook loading animation, screen flashes, goes into UEFI.
  • Going into windows and trying to change the boot according to this post.
  • Installing Ubuntu by itself — for some reason, the GRUB refuses to show up, and no boot-repair operations are of any help.

Here is the info output of my boot-repair program: https://pastebin.com/N1J4H9eF

Here is a screenshot of GParted
screenshot of gparted for my SSD

Any help would be greatly appreciated. Been wrestling with this problem for more than a few days now, and just can’t figure it out… would prefer not to do backend development on Windows!


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#StackBounty: #windows #linux #database #mysql Automated mysql table duplication between servers, via SQL

Bounty: 50

The problem: I need to backup a few servers databases (sometimes a single table, other times all tables in the database) and also in once case replicate a database on a nightly basis.

So this is database to database copying. You may say, use mysql replication however I’m trying to achieve this without using mysql replication as I don’t always have access to configure this on remotely hosted servers.

To clarify, these are servers at different locations and not in the same location. I’m aware of many solutions when the tables exist in databases on the same server but options seem much more limited when this isn’t the scenario.

I need this to run on a schedule I can setup, say once a day in a totally automated fashion, copying and overwriting the target tables with the data from the source.

I’m aware through the research I’ve done of a windows commercial product that can do this (SQLyog) but I wanted to see if anyone knows of alternatives and maybe for Linux as well as Windows.


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#StackBounty: #linux #linux-kernel #drivers Trying to understand how Device Drivers work

Bounty: 100

I am trying to understand how Device Drivers work, based on what I know so far, a Device Driver is simply a “middle-man” between the Operating System and the Device. I have created the following diagram to show my understanding of Device Drivers:

enter image description here

Also, an Application cannot interact directly with a Device Driver, only the Operating System can do that (so for example, if an Application wants to print something, it “tells” the Operating System, and the Operating system tells the Device Driver).

Is my understanding correct? And is the concept of Device Drivers the same on Windows and macOS as it is on Linux?


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#StackBounty: #linux #package-management #gcc #slackware slackpkg cannot install gcc package

Bounty: 50

I’ve been using the current repository for a while, but recently I executed the traditional slackpkg update and now slackpkg cannot find the gcc package.

I’ve tried:

# slackpkg file-search gcc
[uninstalled] - gcc-7.1.0-x86_64-1
[uninstalled] - gcc-brig-7.1.0-x86_64-1
[  upgrade  ] - gcc-g++-5.4.0-x86_64-1

it is listening the packages but cannot be installed/upgraded using slackpkg install gcc or slackpkg upgrade gcc-g++

The mirror i’m using is: http://ftp.osuosl.org/.2/slackware/slackware64-current/

Any advice in this matter is welcome, thanks for reading


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#StackBounty: #windows #linux #database #mysql Automated mysql table duplication between servers

Bounty: 50

The problem: I need to backup a few servers databases (sometimes a single table, other times all tables in the database) and also in once case replicate a database on a nightly basis.

So this is database to database copying. You may say, use mysql replication however I’m trying to achieve this without using mysql replication as I don’t always have access to configure this on remotely hosted servers.

To clarify, these are servers at different locations and not in the same location. I’m aware of many solutions when the tables exist in databases on the same server but options seem much more limited when this isn’t the scenario.

I need this to run on a schedule I can setup, say once a day in a totally automated fashion, copying and overwriting the target tables with the data from the source.

I’m aware through the research I’ve done of a windows commercial product that can do this (SQLyog) but I wanted to see if anyone knows of alternatives and maybe for Linux as well as Windows.


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#StackBounty: #linux #bash #google-chrome-os #dash scripting : how to non interactively perform setreuid()/setregid() in a bash script …

Bounty: 50

I have a bash script started with cap_sys_admin,cap_setgid,cap_setuid+eip (which means those capabilities are inheritable), what is the command for becoming root without typing password (note this simply means using setreuid(0,0)) ?

The aim is to perform this while not being in developer mode, nor turning rootfs versification off. This mean I can’t call a wrapper I would have written myself nor I can use python or perl.
The script is started during the boot process.


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#StackBounty: #linux #kernel #time #uptime What is the right time when linux suffer drift time?

Bounty: 50

Supose that a linux server, at startup, report the following btime:

boot btime -> 1493875000

This server is virtualized inside a busy box and the I/O load is high, in spite of have ntp running, a month ago the report change:

last btime -> 1493875100

The system suffer a drift of “100” seconds. If the uptime is “2592000” seconds, what is the right btime? what of the following options is the right time?

1. boot btime + uptime
   1493875000 + 2592000 = 1496467000

2. boot btime + uptime + drift
   1493875000 + 2592000 + 100 = 1496467100

3. boot btime + uptime - drift
   1493875000 + 2592000 - 100 = 1496466900

4. last btime + uptime
   1493875100 + 2592000 = 1496467100

5. last btime + uptime + drift
   1493875100 + 2592000 + 100 = 1496467200

6. last btime + uptime - drift
   1493875100 + 2592000 - 100 = 1496467000


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#StackBounty: #linux #networking #fedora #networkmanager #pptp Fedora 25, pptp connects but not working, too many transferred packets

Bounty: 50

After update to Fedora 25 one of my PPTP connections strangely works. Remote net is not available.

It is connected, successfully get remote net IP address. While connected nothing is available in remote net, but internet works fine. After a few minutes connection breaks by itself.

I’ve noticed strange thing, while pptp connection is on there are too much TX packets transferred:

ppp0: flags=4305<UP,POINTOPOINT,RUNNING,NOARP,MULTICAST>  mtu 1400
        inet 192.168.1.96  netmask 255.255.255.255  destination ___.__.___.___
        ppp  txqueuelen 3  (Point-to-Point Protocol)
        RX packets 10  bytes 172 (172.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 9864041  bytes 5842982146 (5.4 GiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

In a 10-15 seconds it shows up to 5.4 GiB of packets. It grows very fast.

The same if firewalld is disabled.

I’m using Network-Manager to connect to pptp.

[root@c0rp ~]# lsb_release -a
LSB Version:    :core-4.1-amd64:core-4.1-noarch:cxx-4.1-amd64:cxx-4.1-noarch:desktop-4.1-amd64:desktop-4.1-noarch:languages-4.1-amd64:languages-4.1-noarch:printing-4.1-amd64:printing-4.1-noarch
Distributor ID: Fedora
Description:    Fedora release 25 (Twenty Five)
Release:    25
Codename:   TwentyFive
[root@c0rp ~]# uname -a
Linux c0rp 4.10.8-200.fc25.x86_64 #1 SMP Fri Mar 31 13:20:22 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux

Can someone help me to investigate the problem, please


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#StackBounty: #linux #multiple-monitors #gnome #gnome3 #gnome-shell How to set default display for new windows in Gnome 3

Bounty: 50

I have 2 displays, a monitor and a TV. The first one I use all the time and it has set as primary in Gnome settings, but a TV is turned on only when watching movies from a sofa. Mainly, everything is going as expected, but some apps opens at the TV which is turned off at the moment, thus, I have to turn it on and drag window to the monitor and it happens all the time with a certain apps, i.e. qBittorrent.

I spent a lot of time with Google but I failed to find a way to let all apps appear on primary display.


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