I have 2 webcams installed on my desktop - Intex USB 2.0 and Logitech Webcam C170. I am using libvlc .net wrapper and I want to stream the second webcam.
I am creating a playerStream using the given example -
VlcSinglePlayer playerStream = (VlcSinglePlayer)factory.CreatePlayer(new
PlayerOutput(":sout=#transcode{vcodec=h264,vb=256,fps=30,scale=1,acodec=none}:udp{mux=ts,dst=127.0.0.1:8080}"));
playerStream.SetMediaInput(new MediaInput(MediaInputType.UnparsedMrl,
"dshow://:dshow-vdev=\"Webcam C170\" :dshow-adev=none :live-caching=300 "));
The above code works but the stream I capture in VLC (udp://#:8080) is always from the first webcam (Intex USB 2.0) and not from the Logitech Webcam C170.
When I try using VLC from the command line everything works fine.
How can I fix this error?
Since it is always picking your first device VLC must not be aware of the device option you specified, so most likely there's an error in the syntax somewhere.
Are you simply missing a space after "dshow://"?
You have this:
playerStream.SetMediaInput(
new MediaInput(MediaInputType.UnparsedMrl,
"dshow://:dshow-vdev=\"Webcam C170\" :dshow-adev=none :live-caching=300"));
There should be a space after "dshow://" and before the following colon:
playerStream.SetMediaInput(
new MediaInput(MediaInputType.UnparsedMrl,
"dshow:// :dshow-vdev=\"Webcam C170\" :dshow-adev=none :live-caching=300"));
Sometimes it is necessary to use "--" syntax rather than ":", so this might be necessary instead:
playerStream.SetMediaInput(
new MediaInput(MediaInputType.UnparsedMrl,
"dshow:// --dshow-vdev=\"Webcam C170\" --dshow-adev=none --live-caching=300"));
If that still doesn't work, then you need to consult the documentation for how that MediaInputType.UnparsedMrl expects its arguments. In my own LibVLC bindings, here only "dshow://" would be considered the "MRL", and everything else would be options that must be passed separately and explicitly added to the media (it's a different API call under the covers).
Some options can (and in some cases need to) be passed when creating the LibVLC instance. For this library that would be something like this:
factory = new VlcMediaLibraryFactory (new string[] {
"--dshow-vdev=\"Webcam C170\"",
"--dshow-adev=none",
"--live-caching=300"});
Related
I installed ROS melodic version in Ubuntu 18.04.
I'm running a rosbag in the background to mock cameras in messages rostopics.
I set the camera names in rosparams and iterated through it to capture each camera topics.
I'm using message_filter ApproximateTimeSynchronizer to get time synchronized data as mentioned in the official documentation,
http://wiki.ros.org/message_filters
But most of the time the callback function to ApproximateTimeSynchronizer is not being called/is having delay. The code snippet I'm using is given below:
What am I doing wrong here?
def camera_callback(*args):
pass # Other logic comes here
rospy.init_node('my_listener', anonymous=True)
camera_object_data = []
for camera_name in rospy.get_param('/my/cameras'):
camera_object_data.append(message_filters.Subscriber(
'/{}/hd/camera_info'.format(camera_name), CameraInfo))
camera_object_data.append(message_filters.Subscriber(
'/{}/hd/image_color_rect'.format(camera_name), Image))
camera_object_data.append(message_filters.Subscriber(
'/{}/qhd/image_depth_rect'.format(camera_name), Image))
camera_object_data.append(message_filters.Subscriber(
'/{}/qhd/points'.format(camera_name), PointCloud2)
topic_list = [filter_obj for filter_obj in camera_object_data]
ts = message_filters.ApproximateTimeSynchronizer(topic_list, 10, 1, allow_headerless=True)
ts.registerCallback(camera_callback)
rospy.spin()
Looking at your code, it seems correct. There is, however, a trouble with perhaps bad timestamps and ergo this synchronizer as well, see http://wiki.ros.org/message_filters/ApproximateTime for algorithm assumptions.
My recommendation is to write a corresponding node that publishes empty versions of these four msgs all at the same time. If it's still not working in this perfect scenario, there is an issue with the code above. If it is working just fine, then you need to pay attention to the headers.
Given that you have it as a bag file, you can step through the msgs on the command line and observe the timestamps as well. (Can also step within python).
$ rosbag play --pause recorded1.bag # step through msgs by pressing 's'
On time-noisy msgs with small payloads, I've just written a node to listen to all these msgs, and republish them all with the latest time found on any of them (for sync'd logging to csv). Not optimal, but it should reveal where the issue lies.
I am working on new costume board based on (i. MX 6Solo6DualLite).and I use (TJA1100 100BASE-T1 PHY) for Automotive Ethernet..
please correct me if my questions don't make sense, or I am in the wrong way.
I want to write driver for this device.. and make sure that it works correctly.
1- I can make sure that the driver works properly in the U-boot step, Right? I mean no need to load Linux kernel, so I have just to add source code C driver in U-boot source code and compile it. I want to do this in U-boot step, so I can limit the numbers of files that initialise all peripheriques, and make it simple as possible since that U-boot can behave like (mini-Os)
2-I don't know how to write this driver (exactly..), so I am looking for the driver (source code) that initialise the Ethernet Controller in any other processor , and initialise another typeof ethernet phy, in order to get an idea and write a similar driver source code for I.MX6 and TJA1100,?
after this i think that i could maybe add some very basic file c For simple Protocol like ARP, for test purpose..
3- is this good idea writing driver code by inspiring from another driver code source?
4 - maybe, if you already have a driver for (i. MX 6Solo6DualLite and TJA1100 100BASE-T1 PHY) can you provide to me please... ?
for my second question i tried to extract from U-boot source code the C file that initialise Ethernet Controller in AM335x, and initialise LAN8710A phy,(in beaglebone black) in order to get an idea and write a similar driver source code but i couldn't found it .. i found network C file for protocol .... but that's disturp me i couldn't seperate them from the real C file that initialise ethernet controller and ethernent Phy .
http://www.denx.de/wiki/U-Boot/SourceCode
There is a driver published on the NXP forum:
https://community.nxp.com/thread/460767
It includes both some bare metal code that should be usable with U-Boot and a Linux driver.
I use VLC media player 1.1.9 on Ubuntu 11.04. I'm trying to experiment with lua extensions for VLC; so I've added the file test.lua in ~/.local/share/vlc/lua/extensions/, which has only these two lines:
fps="25.000"
frame_duration=1/tonumber(fps)
When I run vlc with verbose output for debugging, I get (edited to split on multiple lines:):
$ vlc --verbose 2
...
[0xa213874] lua generic warning: Error loading script
~/.local/share/vlc/lua/extensions/test.lua:
.../.local/share/vlc/lua/extensions/test.lua:2:
attempt to call global 'tonumber' (a nil value)
...
Now, as far as I know, tonumber as function is part of Lua5.1 proper (Lua 5.1 Reference Manual: tonumber) - and on my system:
$ locate --regex 'lua.*so.*' | head -4
/usr/lib/libipelua.so.7.0.10
/usr/lib/liblua5.1.so
/usr/lib/liblua5.1.so.0
/usr/lib/liblua5.1.so.0.0.0
... apparently I do have Lua 5.1 installed.
So, why do I get an error on using tonumber here - and how can I use this (and other) standard functions in a VLC lua extension properly?
Documentation is sparse for VLC Lua extensions to say the least but I did find an example in the github vlc repository here: https://github.com/videolan/vlc/blob/master/share/lua/extensions/VLSub.lua
Judging from that example it appears you need to supply some basic event functions for your addon for VLC to call into when certain events happen. Some of the obvious callback handlers I've noticed:
descriptor, this should return a table that contains fields describing your addon.
activate, this seems to get called when you activate it from view menubar.
deactivate, called when you deactivate the addon from view menubar.
plus a couple of other functions like close and input_change which you can guess what they're for.
From my brief testing done on VLC 2.0.8 under Win7 it appears VLC loads the lua extension using an empty sandbox environment. This is likely the reason you're getting nil for tonumber and I'm betting none of the other standard lua functions are accessible either when you try to perform computation at this global scope.
However, if I move that code into one of the event handling functions then all those standard functions are accessible again. For example:
function descriptor()
return
{
title = "Test Ext";
version = "0.1";
author = "";
shortdesc = "Testing Lua Extension";
capabilities = {};
description = "VLC Hello Test Addon";
}
end
function activate()
print "test activating"
local fps = tonumber "25.000"
local frame_duration = 1 / fps
print(frame_duration)
return true
end
-- ...
That prints out what you would expect in the console debug log. Now the documentation (what little there is) doesn't mention any of this but what's probably happening here is VLC is injecting the standard lua functions and vlc api table into the sandboxed environment when any of these event handlers get called. But during the extension loading phase, it is done in an empty sandbox environment which explains why all those lua function calls end up being nil when you try to use it at the outter most scope.
I recommend cloning the VLC source tree from github and then performing a grep on the C source that's embedding lua to see what VLC is really doing behind the scenes. Most of the relevant code will likely be here: https://github.com/videolan/vlc/tree/master/modules/lua
Probably some extension script installed in your system overwrites the function and the Lua interpreter instance is shared between all extension scripts, so you end up not being able to call the function if that script is called before yours.
As a quick workaround, Lua being dynamically typed, you can still do things like:
1 / "25.000"
and the string will be coerced to a number.
Alternatively, you can define a tonumber equivalent like:
string_to_num = function(s) return s + 0 end
This again relies on dynamic typing.
I'll be using window.postMessage("", "*", [transferableData]) to send data between two browser windows. However, I didn't find any straight answer on how to convert types into Transferables.
So, in order for me to start learning this, it would be great to know how to convert a simple String into an Transferable (ByteBuffer) and read it on the other side (the side that is getting the message with the data). This would help me solving my problem and learning about this concept.
IMPORTANT UPDATE:
This question led me here: Dart Language: printing reports
Transferable Objects are not yet implemented on Dart VM (http://dartbug.com/4149). That means, if you're running your application via Dartium (Dart VM) the other window will be receiving and processing the first argument of postMessage, and not the Transferable Object. However, JavaScript does the job: the object gets transfered and the original array, emptied.
import 'dart:convert';
var list = Utf8.encode('xxx');
var data = list is Uint8List ? list.buffer : new Uint8List.fromList(list).buffer;
to send the data using window.PostMessage use
window.postMessage({'data': data}, '*', [data]);
and read it on the receiver side like
var string = Utf8.decode(message.data['data']);
See also http://dartbug.com/19968 for the status of transferrables.
The recent Dart dev channel release already ships with Dartium 38.xxx as far as I know.
Here is a small test case for transferrables https://code.google.com/p/dart/source/browse/branches/bleeding_edge/dart/tests/html/transferables_test.dart
I am porting a C# program to Linux (using Mono). The only compatibility issues that MoMA has found were all related to printing: P/Invokes of functions from winspool.drv:
ClosePrinter
EndDocPrinter
EndPagePrinter
OpenPrinter
StartDocPrinter
StartPagePrinter
WritePrinter
These are all used in the same class, which prints files (which must be either PDF or PS) by wrapping them in PJL (to set the paper size/tray/orientation) and calling WritePrinter.
I'll need to rewrite this printing logic with non-Windows-specific code. A previous question refers to System.Drawing.Printing, but it seems to be way too low level. I don't want DrawString and DrawImage, I want "print this PostScript file". Is there functionality in Mono to do this?
I ended up using System.Diagnostics.Process to call the lp command.