MPEG-2 Video GOP Structure

If GOP structure is group of pictures behind a gop video header in side elementary header.

A GOP contains I frame, P frames, and B frames.

It follows a pattern. For example:

1.   GOP = 10 and b frame =2
        Encoding sequence: "I P B B P B B P B B"
        Display sequence: " I B B P B B P B B P "
 

2.   GOP = 30 and b frame =3
        Encoding sequence: " I  P B B B P B B B P B B B P B B B P B B B P B B B P B B B P  "
        Display sequence: " I B B B P B B B P B B B P B B B P B B B P B B B P B B B P P  "
       

Create image of flash drive / Memory card in linux.

Hi guys sometime we need to make image of memory card, pendrive or any flash device.
There is a tools in linux by which we can easily make images.

1. Insert memory card / flash drive in card reader or usb.
2. Now open terminal window using ("ctrl + alt + t" in ubuntu).
3. make a directory at desktop where we will save image by following commands:
• sudo mkdir ~/Desktop/backupImages
• cd ~/Desktop/backupImages
4. give command clear"dmesg"
• dmesg -C
• dmesg

• You will find result "attached scsi removable disk". Here "sdd" is found on my pc.
• Make sure you check on your computer. "Careful in this step to get your device name"

• Now give command to make image of your device
• sudo dd if=/dev/sdd of=myflashbackup.img
• now wait for few minutes depending upon size of flash drive.
• A new file is created named "myflashbackup.img".

Note: "if" is source and "of" is destination.

please post if having any query.

Linux Command Line

Basic Linux Commands

• ls            :       It Shows List of directories.
• mkdir      :        It make a directory at current path.
• cd              :       Changes current directory.
• ps              :        Shows list of process running.
• dmesg       :        Shows Debug messages.
• cp              :        Copy file or empty directory from source to destination.
• cp -rf         :        Copy directory with contents.
• clear          :        Clear terminal screen.
• cat              :        Concatenate and print (display) the content of files.
• chmod       :        Change access permissions.
• chown        :        Change file owner and group.
• ifconfig      :        Show networking information.
• mv              :       Move file/ directory.
• kill              :       Kill process by process ID.
• pkill            :       Kill process by its name.
• touch           :       Edit information details about file.
• vi                 :       Screen based vi editor is initiated.
• vim              :       Modified version of vi editor.
• whoami       :       Displays current user ID.

Linux Boot Process

Linux Boot Process

Basic Structural block diagram:

BIOS: 

• BIOS stands for Basic Input Output System.
• It is a small program that checks system integrity.
• It conducts first hardware checks.
• In personal computer it resides inside ROM chip populated on mother board.
• It checks for secondary memory availability.
• Finally it loads and execute MBR (Master Boot Record).

MBR:

• MBR stands for master Boot Record.
• It is located in first sector of  HDD or flash drive. "/dev/hda" or "/dev/sda".
• MBR is pretty small in size, less than 512 Bytes. It has following three components:
• Primary bootloader information in first   : 446 Bytes.
• partition table information                       :   64 Bytes.
• MBR validation check                              :     2 Bytes.
• It contains information about bootloader (here we consider GRUB), it simply load and executes GRUB.

GRUB:

• GRUB stands for Grand Unified Bootloader.
• It displays the list of all available kernel images in system. I has option to choose any one of them.
• GRUB has knowledge of Filesystem.
• Present in /etc/grub.conf or /boot/grub/grub.conf
• It loads kernel and initrd images.

Kernel:

• It is a core part of Operating System.
• It executes /sbin/init program file.
• It initiates initrd image.
• initrd stands for initial ramdisk.
• It is a temporary file system mounted until kernel is booted.
• initrd has basic device drivers for HDD, other hardware.
• Mounts root filesystem.

init: 

• It is very first program which executed by kernel after booting.
• It has PID =1.
• It has following runlevels:
• 0 :  halt
• 1 : Single user
• 2 : multi user
• 3 :
• 4 : unused
• 5 : multi user with full GUI.
• 6 : reboot

Introduction to Linux

Hi Guys,

Here we will study about linux OS comprehensively.

Introduction to Linux

What is Linux?

Linux is a operating system based on Unix like kernel. It was initially written by Linus Benedict Torvalds. Linux is written in c.

Why Linux?

• Source code is freely available.
• Large community uses Linux.
• Can be modified or customized.

Which Linux?

• Red hat.
• Fedora.
• Ubuntu.
• Mint, etc.

Linux Structure

Shells Available: 

• Ksh
• Csh
• Bsh
• Bash, etc.