17 FFmpeg Commands For Beginners

#1 Getting audio/video file information

ffmpeg -i video.mp4

(use -hide_banner flag to hide information such as version, configuration details, copyright notice, build and library options etc.)


#2 Converting video files into AVI

ffmpeg -i video.mp4 video.avi

(use -qscale 0 to preserve the quality of your source video file)


#3 understand comman Abbr
-i filename (i=Input)
-vn  Indicates that we have disabled video recording in the output file.
-ar  Set the audio frequency of the output file. The common values used are 22050, 44100, 48000 Hz.
-ac  Set the number of audio channels.
-ab  Indicates the audio bitrate.
-f  Output file format. In our case, it’s mp3 format.
-b:v 64k (-b:v video bitrate)
-r 24 (change the frame rate)
-vf video filter (vf video filter)
-af audio filter (af audio filter)
-an file name (No audio)
-sn file name (No sub-title)
-dn file name (No data-stream)



#4 Change resolution of video files

ffmpeg -i input.mp4 -filter:v scale=1280:720 -c:a copy output.mp4

#5 Compressing video files

ffmpeg -i input.mp4 -vf scale=1280:-1 -c:v libx264 -preset veryslow -crf 24 output.mp4

#6 Compressing Audio files

ffmpeg -i input.mp3 -ab 128 output.mp3

96kbps
112kbps
128kbps
160kbps
192kbps
256kbps
320kbps


#7 Removing audio stream from a media file

ffmpeg -i input.mp4 -an output.mp4

#8 Removing video stream from a media file

ffmpeg -i input.mp4 -vn output.mp3

#9 Cropping videos

ffmpeg -i input.mp4 -croptop 100 -cropbottom 100 -cropleft 300 -cropright 300 output.mp4

#12 Set the aspect ratio to video

ffmpeg -i input.mp4 -aspect 16:9 output.mp4

#13 Trim a media file using start and stop times

ffmpeg -i input.mp4 -ss 00:00:50 -codec copy -t 50 output.mp4

#14 Changing resolution and Reencoding

ffmpeg -i 1.mp4 -vf scale=1280:720 -acodec aac -vcodec libx264   NewFile.mp4 -hide_banner

#15 Joining multiple video parts into one

ffmpeg -f concat -i join.txt -c copy output.mp4

(join.txt will have path of all videos)


#16 Add subtitles to a video file

fmpeg -i input.mp4 -i subtitle_file.srt -map 0 -map 1 -c copy -c:v libx264 -crf 23 -preset veryfast output.mp4

#17 Increase video playback speed

ffmpeg -i inputvideo.mp4 -vf "setpts=0.5*PTS" outputvideo.mp4

Question: How to execute ssh command in PHP and get the results?

exec("ls",$o);
print_r($o);

Zend Framework 2 Session Management - Add Update Delete Session

Question: What is Zend Session?
A Session is a way to store information (in variables) to be used across multiple pages. It is mainly used to check for login information on browser and track the user activies. Zend Session is Zend libery for Session which helps to manage the session data.


Question: What is difference between Session Manager and Session Container?
Zend\Session\Container instances provide the primary API for manipulating session data. Containers are used to segregate all session data. Zend\Session\SessionManager, is a class that is responsible for all aspects of session management. It is used to initializes and configuration, storage and save handling.


Question: What is difference between Session Manager and Session Container and Session Config in One line each?
Container: The provides the core interface for managing session data.
SessionConfig: Handles setting for session config options.
SessionManager: Handles session management such as session start/exists/write/regenerate id/time-to-live/and destroy and session validation.


Question: Can you store session data in database?
Yes, we can.
For this we need to set the configuration like below:

use Zend\Db\TableGateway\TableGateway;
use Zend\Session\SaveHandler\DbTableGateway;
use Zend\Session\SaveHandler\DbTableGatewayOptions;
use Zend\Session\SessionManager;

$tableGateway = new TableGateway('session', $adapter); //this is table where session will store, you need to create the table and its model also.
$saveHandler  = new DbTableGateway($tableGateway, new DbTableGatewayOptions());
$manager      = new SessionManager();
$manager->setSaveHandler($saveHandler);

Question: How to set the Defualt Session Mangaer for Session Container?

use Zend\Session\Container;
use Zend\Session\SessionManager;

$manager = new SessionManager();
Container::setDefaultManager($manager);

Question: How to create session Object?

use Zend\Session\Container;
$sessionObj = new Container('sessinName');

Question: How to set Session value?

$sessionObj->offsetSet('email', 'email@domain.com');

Question: How to get Session value?

$sessionObj->offsetGet('email');

Question: How to check Session value exist OR Not?

$sessionObj->offsetExists('email');

Question: How to unset the session value?

$sessionObj->offsetUnset('email');

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3. How to install Zend Framework 2 in windows.

FCM push notification example

Question: What is FCM Messages?
Full form of FCM is Firebase Cloud Messaging.
FCM is a cross-platform messaging solution that lets you reliably deliver messages to android and IOS devices at no cost.
You can notify a client app that new message has been arrived.



Question: How does FCM works?
App server interacts with FCM (HTTP or XMPP protocol) and a client app. You can compose and send messages.
FCM built on Firebase Cloud Messaging.


Question: What is FCM Server?
FCM servers take messages from an app server and send to cient app.
FCM connection servers provided by Google.


Question: What is App Server?
App Server sends data to a client app (via the chosen FCM connection server) using XMPP or HTTP protocol.



Question: What are role of App Server?

• Communicate with your client
• Send properly formatted requests to the FCM connection server
• Securely store the Server key and client registration tokens

Question:How to send notification to android/IOS device with FCM server?

$jsonData='{
  "to": "dhkC5_jTnck:APA91bF7L_KN7GFOPMiVsykjMGqydlftItfapC4Va63hRBuhFCrRKMdUonqhO1qjKT5_OYPMRAZFMA2UDVA1spAw9SpCsLE7B05vGtNttvuykIdxL7jKWWvJkA51T98O8ZZkubhXwQyRx",
  "notification": {
    "body": "New Gr sent you a message",
    "title": "domain.com ",
    "icon": "main_ve_logo",
    "click_action": "com.domain.fcm"
  },
  "data": {
    "type": "message",    
    "avatar": "http://img.domain.com/upload/default.jpg",
    "message_id": 1
  }
}';
$curl = curl_init();
curl_setopt_array($curl, array(
    CURLOPT_URL => "https://fcm.googleapis.com/fcm/send",
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_ENCODING => "",
    CURLOPT_MAXREDIRS => 10,
    CURLOPT_TIMEOUT => 30,
    CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
    CURLOPT_CUSTOMREQUEST => "POST",
    CURLOPT_POSTFIELDS => json_encode($fields),
    CURLOPT_HTTPHEADER => array(
      "authorization: key=FCM_SERVER_KEY",
      "cache-control: no-cache",
      "content-type: application/json"
    ),
));

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

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Node JS tutorial for beginner

Question: What is NodeJS
Node.js is a platform built for fast and scalable network applications. It uses an event-driven, non-blocking I/O model that makes it lightweight and efficient, perfect for data-intensive real-time applications that run across distributed devices. It can be used in Websites application, Android applicationa and IOS application etc.


Question: What type of framework is Nodejs?
NodeJS is JavaScript-based framework/platform



Question: Is Nodejs Server OR Cient Side?
Both, Node work for both.



Question: What is REPL?
REPL stands for Read Eval Print Loop
Node.js comes with virtual environment called REPL (also Node shell).


Question: What are most common REPL Commands?

ctrl + c

Terminate the current command.

ctrl + c twice 

terminate the Node REPL.

Up/Down Keys

see command history.

tab Keys

list of current commands.

.help

list of all commands.

.break

exit from multiline expression.

.save filename 

save the current Node REPL session to a file.

.load filename

load file content in current Node REPL session.



Question: How to exist from REPL?

ctrl + c twice 

Question: How to install module in NodeJS?

npm install express

for install express.


Question: How to uninstall module in NodeJS?

npm uninstall express

for uninstall express.

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