Lowyat.NET: Latest topics by mystical zero

CCTV - Channel Hopping

mystical zero — Sun, 28 Jun 2009 20:58:45 +0800

I have been using the bundled cctv software (AverMedia EyesPro) in conjunction with my 4 channel dvr capture card for years now. But it is not without problems. Occasionally, the cpu usage would ramp up to the point of stalling. So, I installed the trial version of webcamXP -- an alternative. The problem is when viewing any 1 channel, that channel would intermittently switch to the next channel automatically and then it would switch back again. Sometimes, it would even switch back and forth continuously. Frustrated, I switched to Ubuntu and use the open-source Zoneminder. And, guess what? The same problem persists -- channel-hopping.

So, what do you think guys? I thought it would be a hardware issue. However, isn't it weird that I did not encounter the channel-hopping issue when using AverMedia EyesPro?

Note: I'm using a Brooktree BT878 chipset based DVR capture card.

Edited: Nvm. Got it to work somehow by messing with the video mode settings and using the right brooktree card values in /etc/modprobe.d/bttv.

Comp Architecture

mystical zero — Fri, 12 Jun 2009 22:26:10 +0800

Not sure if this is the right place to ask. Well, anyway... here goes...

As you have already know, system memory is segmented into text(or code) segment and data segment. And, the CPU's program counter(PC) will always be incremented by 4 after every clock cycle so that it would refer to the next instruction contained in the code segment. Since the PC keeps incrementing, wouldn't the PC point to the data segment in the event the PC exceeds the code segment boundary? Is there some sort of mechanism which would trigger the PC to point back to the first block of the code segment after reaching the boundary?

This question may seem peculiar to you. Anyway, pardon me as I just stumbled upon this question in my mind whilst I was reading about the fundamentals of the MIPS architecture.

Thanks in advance.

Sockets

mystical zero — Sat, 09 May 2009 15:55:52 +0800

From my previous experience on using UNIX Sockets, I know that it is impossible to bind 2 different processes on the same port. Running the first process followed by the second process will cause the second process to output an error.
Now, I'm given a task to analyse 2 simple VOIP programs - a sender and a receiver (using Windows Sockets). First, I was asked to change both the sender and receiver IP address to 127.0.0.1 and run the program on the same computer. The thing is the ports corresponding to the 2 processes are being bind to the same port which is 4321. To my surprise, there is no error when I ran them.
Confused, I fired up TCPView and this is what I got:

Notice the port used by VOIPSend.exe. It's 50550! Why isn't it 4321 as specified in the source code? Does Windows handle the error for me when I attempt to use the same port for both processes? For example, Windows detects that I'm trying to bind 4321 to 2 processes and automatically change the port to 50550. Does it work this way?

Below are snippets of source code for both programs:
VOIPSender:

» Click to show Spoiler - click again to hide... «

CODE

..
..
..
..
unsigned char buffer[1024];
unsigned long bytes_read = 0, bytes_written = 0;

WSADATA w; //Storage for WINSOCK information
SOCKET sd; //Socket descriptor
int receiver_length;
struct sockaddr_in receiver; //Details of the UDP receiver
struct sockaddr_in sender; //Details of the UDP sender

unsigned short port_number = 4321; //UDP Port number

/* RECEVIER IP ADDRESS - a1:a4 */
unsigned char a1 = 127,
a2 = 0,
a3 = 0,
a4 = 1;

/* SENDER IP ADDRESS (This computer) - b1:b4 */
unsigned char b1 = 127,
b2 = 0,
b3 = 0,
b4 = 1;

unsigned long packetsize = 256; //UDP packet datasize (bytes)

/* Start winsock version number 0x0101 */
WSAStartup(0x0101, &w);

/* Create a UDP socket */
sd = socket(AF_INET, //Using IPv4
SOCK_DGRAM, //UDP socket
IPPROTO_UDP);

/* Clear the memory used to store the receiver/sender information */
memset((void *)&receiver, '\0', sizeof(struct sockaddr_in));
memset((void *)&sender, '\0', sizeof(struct sockaddr_in));

/* Set the receiver parameters */
receiver.sin_family = AF_INET; //IPv4
receiver.sin_port = htons(port_number); //Convert data to 'network' byte order
receiver.sin_addr.S_un.S_un_b.s_b1 = a1;
receiver.sin_addr.S_un.S_un_b.s_b2 = a2; //Set the IP address
receiver.sin_addr.S_un.S_un_b.s_b3 = a3;
receiver.sin_addr.S_un.S_un_b.s_b4 = a4;

printf("Sending to receiver at %u.%u.%u.%u:%u\n\n", a1,a2,a3,a4,port_number);

/* Set the sender parameters (this computer) */
sender.sin_family = AF_INET;
sender.sin_port = htons(port_number);
sender.sin_addr.S_un.S_un_b.s_b1 = b1;
sender.sin_addr.S_un.S_un_b.s_b2 = b2;
sender.sin_addr.S_un.S_un_b.s_b3 = b3;
sender.sin_addr.S_un.S_un_b.s_b4 = b4;

printf("This sender is at %u.%u.%u.%u\n\n", b1,b2,b3,b4);

/* Bind the local information to the socket we made */
bind(sd, //Socket Descriptor
(struct sockaddr *)&sender, //Pointer to the sender information
sizeof(struct sockaddr_in));..
..
..
..

VOIPReceive:

» Click to show Spoiler - click again to hide... «

Any help will be much appreciated.

Link to library?

mystical zero — Fri, 26 Dec 2008 14:32:58 +0800

As all of us know, in creating a program in C, we would first write the code, compile it into an object file and then link the object file with the required libraries to produce the executable.
What I don't understand is why do we need to explicitly link the object file with the required libraries when we have already included the necessary header files in the source file?
Let's just say that i have a source file with the #include <math.h> directive. When compiling with gcc, why do I have to explicitly include the -lm parameter? Isn't the math function already defined in the header file? If so, why do I still need to link it with the maths library?

Suppress update notification

mystical zero — Mon, 03 Nov 2008 11:50:24 +0800

I've just patched a file from the kernel source tree and have recompiled the kernel. After installing the said kernel using the generated deb file, update-manager prompts me for an update even though the recompiled kernel and the one listed under update-manager have the same version number and abi number.

I've tried the "Lock Version" option in synaptic, hoping that the prompt would go away. But, to no avail. How can I stop the update notification?

If there's no any other way to do it, I guess I will have to forcefully change the deb version string to a higher number.

Edited:
Nvm. Got impatient and changed the version number. Problem solved.

Assign different memory address

mystical zero — Fri, 11 Jul 2008 01:26:17 +0800

I wanted to change an address where a pointer points to, to a completely different address. So I use delete on the pointer then assign it to new int, hoping it would change to another memory address. But it turns out the same. Before and after both return the same memory address. The code below is just an example on what i am trying to achieve but to no avail.

CODE

#include <iostream>

using namespace std;

int main() {

int *a = new int;

cout << "Address of pointer a is " << a << ".\n";

//Free to memory pool.
delete a;

//Assign a new address to pointer a.
a = new int;

cout << "Address of pointer a is now " << a << ".\n";

cin.get();

return 0;

}

How can I go about doing this? What methods can I use?

Thanks in advance.

Serious Facebook Privacy Flaw

mystical zero — Fri, 02 May 2008 17:18:29 +0800

QUOTE

The popular social networking site allows users to add a variety of applications to their profile.

But a malicious program, masquerading as a harmless application, could potentially harvest personal data.

Facebook says users should exercise caution when adding applications. By adding a malicious application, not only you but your friends could be exposed to ID fraud.

Source: http://news.bbc.co.uk/1/hi/programmes/clic...ine/7375772.stm

Video: http://news.bbc.co.uk/1/hi/technology/7376738.stm

Splitter. No effect?

mystical zero — Wed, 16 Jan 2008 22:15:09 +0800

Broadband provider
ISP/package: TMNet Streamyx 1Mbps package
Location: Kota Kemuning
Have you called your ISP's helpline?: Yes. But what they say is just that they are going to lodge a report. Blablabla...

Personal equipment
Modem: ZTE ZXDSL 831
Router: D-Link DI-634M
Firewall used: No Hardware Firewall. Only on NAT.

Problem details
First occurence of problem: Few weeks ago i guess.
Problem frequency: Always.

Problem description:
Well, to start off, it's a really weird problem.

Internet got disconnected when the phone is off-hook. Phone and fax buzzed. You guys must be thinking that i do not have a splitter at this point. But, the opposite is true. Everything was setup properly. One end of the splitter was connected to the phone jack on the wall. While, the other two ports on the other side of the splitter was connected to the ZTE modem and a HP all-in-one printer with fax respectively. As the HP all-in-one printer has an extra phone port for output, I connected the HP all-in-one printer to another conventional telephone.

What I've done to troubleshoot this problem:

Connect the fax/telephone directly to the phone jack on the wall. Phone and fax worked flawlessly. Phone has no buzzing sound. Was able to send outgoing fax.
I thought it must be a problem with the splitter. So i got a new one and tried it out. Failed.

So the question is even with a splitter, how can this happen?

Note that DSL and fax is under the same phone line.

Configuration layout:

Well, I don't see anything wrong with the configuration. If there's anything amiss, please do tell me.

Oh. And, by the way, I'm able to receive incoming fax. Weird, huh?

Any help will be appreciated.

Just couldn't obtain a LAN address

mystical zero — Fri, 22 Jun 2007 18:12:50 +0800

OS: Ubuntu 7.04
Connection type: Ethernet
Problem:
Network manager is always probing for an IP address. After waiting, it notifies me that "Connection has been established". But, I found out that the LAN IP isn't correct as it is 169.254.7.176. Initially, I disabled avahi and the matter worsens as network manager will never stop probing regardless of how long I've waited. Thus, I renabled avahi. I followed this guide but it works apparently. Not until a few days later, the problem came back. I repeated the steps from that guide, but this time, to no avail.

For extra information, this is my ifconfig:

» Click to show Spoiler - click again to hide... «

What I've tried but failed:

sudo killall dhclient
then
sudo dhclient
Reboot my router
Configured a static IP
Modify the DHCP leased table

Note that the problem doesn't occur on Windows Vista ̶ my secondary OS.

So, can anyone tell me a solution to this?

Any help will be greatly appreciated.

Problem -- display blur

mystical zero — Sun, 29 Apr 2007 14:30:18 +0800

Problem:
The problem haunted me ever since i installed Windows XP on my new rig. When i login into Windows XP, everything was blur. The fonts are not crisp and not sharp at all. The mouse cursor and icons are blur too. Basically, the whole GUI environment was blur. I thought it might have thing to do with the DVI connector. Thus, i tried using a D-SUB analog cable instead to connect my graphics card to my monitor. As i thought, the problem was gone. Everything is clear and vivid under Windows XP. However, i refused to admit that the problem was caused by the DVI connector. Therefore, i tried using DVI again. Although it is still the same as before, when i login into my second OS, which is Windows Vista, there's no problem. So, i doubt it is a problem with the DVI connector. Not willing to give up, i tried exploring the monitor's on-screen menu. From my observations, the resolution which was shown on the on-screen menu when i am on Windows XP is 1280x1024 75Hz. Well, how can that be? Since i am using a wide screen 19" monitor, shouldn't the resolution be 1440x900? What's weird is that even though the aspect ratio is different, the display doesn't stretch. And, after setting the display resolution to 1440x900 through the NVIDIA control panel, the monitor's on-screen menu still show the resolution as 1280x1024. Therefore, i guess this is the problem.

Just to add on, when i viewed my monitor's on-screen menu under Windows Vista, the resolution stated is 1440x900 60Hz which is normal. But, this leads to another problem. When i change the refresh rate to 75Hz via the NVIDIA control panel, the refresh rate stated on my monitor's on-screen menu is still 60Hz.

What i've done so far but failed:

Reinstall nvidia display driver.
Reinstall monitor's driver.
Use another DVI cable.

I'm out of ideas.

I'll be glad if you guys can give some suggestions on solving this problem.

Any help will be appreciated.

Problem installing Dlink g510 driver on ubuntu

mystical zero — Sat, 21 Apr 2007 23:31:10 +0800

I'm using ubuntu 7.04 and have trouble installing the driver for my Dlink DWL-G510 pci wireless card which is based on Ralink chipset.

Well, i followed the guide here. And, when i reach the step sh Configure. I got this error:

QUOTE

-------------------- Ralink RT61 Station Configuration --------------------

Linux kernel source directory [/usr/src/linux-2.6.20-15-generic]:

Linux source tree '/usr/src/linux-2.6.20-15-generic' is incomplete or missing!

Configuration failed

I have tried googling around for solution but there are none.

I'm glad if someone can tell me what causes this and how can i solve this.

Any help will be appreciated.

ARP table

mystical zero — Sun, 15 Apr 2007 23:35:52 +0800

QUOTE

Interface: 192.168.0.121 --- 0xb
Internet Address Physical Address Type
192.168.0.1 00-15-e9-d7-d7-5c dynamic
192.168.0.255 ff-ff-ff-ff-ff-ff static
224.0.0.22 01-00-5e-00-00-16 static
224.0.0.252 01-00-5e-00-00-fc static

Above are the entries obtained from my windows vista's arp table.

As most of us normally know, the arp table normally displays ip address within the LAN range in conjunction with the MAC address. But, there's something weird about my arp table above. Note the ip address i bolded. As an effort to get rid of the above bolded ip, i try using the arp -d command. Although successful, the bolded ip are being cache to the arp tables again when i connect to the LAN.

It is weird to have such ip outside my LAN range. Due to my curiosity, i did a whois lookup on the bolded ip. These are the outputs:

CODE

OrgName: Internet Assigned Numbers Authority
OrgID: IANA
Address: 4676 Admiralty Way, Suite 330
City: Marina del Rey
StateProv: CA
PostalCode: 90292-6695
Country: US

NetRange: 224.0.0.0 - 239.255.255.255
CIDR: 224.0.0.0/4
NetName: MCAST-NET
NetHandle: NET-224-0-0-0-1
Parent:
NetType: IANA Special Use
NameServer: FLAG.EP.NET
NameServer: STRUL.STUPI.SE
NameServer: NS.ISI.EDU
NameServer: NIC.NEAR.NET
Comment: This block is reserved for special purposes.
Comment: Please see RFC 3171 for additional information.
Comment:
RegDate: 1991-05-22
Updated: 2002-09-16

OrgAbuseHandle: IANA-IP-ARIN
OrgAbuseName: Internet Corporation for Assigned Names and Number
OrgAbusePhone: +1-310-301-5820
OrgAbuseEmail: *****@iana.org

OrgTechHandle: IANA-IP-ARIN
OrgTechName: Internet Corporation for Assigned Names and Number
OrgTechPhone: +1-310-301-5820
OrgTechEmail: *****@iana.org

Well, it looks legit at first as it originates from IANA.

Hmm....i was wondering why IANA's ip is listed in my arp table. Can someone enlighten me about this? Is my LAN being intrude by outsiders?

Any help will be appreciated.

About ClamAV

mystical zero — Sun, 04 Mar 2007 21:08:10 +0800

Anyone using ClamAV here? Well, i have a problem with it. I just don't understand why i couldn't get it updated.

Any ideas?

concern about choice of subjects

mystical zero — Mon, 08 Jan 2007 22:02:11 +0800

I am a mufy student studying in sunway university college. Although i am still having the orientation program now, i am quite concern about which additional subject i should take. And, i would like to take up the electrical and electronic engineering course in the future. Well, I have already picked 4 other subjects but i am not sure whether to take chemistry or computer science as my additional subject. Any advise?

ZA problem

mystical zero — Mon, 19 Jun 2006 22:53:30 +0800

Well, i am using ZA 6.5.714(the latest one). Been using it since ZA 5. Few days ago, i updated my ZA to 6.5.714. FYI, i am using ZA security suite. Since then, my ZA has been quite weird. It has been using enormous amount of physical and virtual memory. Initially, when i start my pc, ZA will just occupy approximately 30MB of physical memory and it will gradually increase as time passes . You can take a look at my screenshot below:

Guys, is this normal? And, any of you experiencing this problem? For my pc specs, refer to my sig.