pam-diff
Version:
Measure differences between pixel arrays extracted from pam images
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Markdown
Measure differences between pixel arrays extracted from pam images. Works well with node module [pipe2pam](https://www.npmjs.com/package/pipe2pam) to extract pam images from an ffmpeg pipe. Supported ***tupltypes*** are ***rgb***, ***rgb_alpha***, ***grayscale***, and ***blackandwhite***. It is currently being used for a video motion detection project.
```
npm install pam-diff --save
```
**To run the example below, also install pipe2pam:**
```
npm install pipe2pam --save
```
The following [example](https://github.com/kevinGodell/pam-diff/tree/master/examples/example.js) uses ffmpeg to connect to a rtsp ip camera video feed and generates 1000 downscaled rgb24 pam images at a rate of 1 per second. The pam images are piped from ffmpeg's stdout into pipe2pam to parse them into into pam objects. The pam objects are then piped into pam-diff to measure pixel differences. For each compared pixel that has a **difference** that exceeds the setting, it will be calculated to determine the percent of difference. If the **percent** of changed pixels exceeds the setting, a **diff** event will be emitted which contains a data object containing details. This example also shows how to take the pam image that triggered the diff event and convert it to a jpeg using ffmpeg.
```
const P2P = require('pipe2pam');
const PamDiff = require('pam-diff');
const ChildProcess = require('child_process');
const spawn = ChildProcess.spawn;
const execFile = ChildProcess.execFile;
const params = [
'-loglevel',
'quiet',
/* use hardware acceleration */
'-hwaccel',
'auto', //vda, videotoolbox, none, auto
/* use an artificial video input */
/*'-re',
'-f',
'lavfi',
'-i',
'testsrc=size=1920x1080:rate=15',*/
/* use an rtsp ip cam video input */
'-rtsp_transport',
'tcp',
'-i',
'rtsp://192.168.1.4:554/user=admin_password=pass_channel=1_stream=0.sdp',
/* set output flags */
'-an',
'-c:v',
'pam',
'-pix_fmt',
'rgb24',//rgba, rgb24, gray
'-f',
'image2pipe',
'-vf',
'fps=1,scale=320:180',//1920:1080 scaled down: 400:225, 384:216, 368:207, 352:198, 336:189, 320:180
//'fps=1,scale=iw*1/6:ih*1/6',
'-frames',
'1000',
'pipe:1'
];
const ffmpeg = spawn('ffmpeg', params);
console.log(ffmpeg.spawnargs.join(' '));
ffmpeg.on('error', (error) => {
console.log(error);
});
ffmpeg.on('exit', (code, signal) => {
console.log('exit', code, signal);
});
const p2p = new P2P();
let counter = 0;
p2p.on('pam', (data) => {
//you do not have to listen to this event if you are just piping this data to pam-diff
console.log(`received pam ${++counter}`);
});
const pamDiff = new PamDiff({difference: 5, percent: 5});
pamDiff.on('diff', (data) => {
console.log(data);
//comment out the following line if you want to use ffmpeg to create a jpeg from the pam image that triggered an image difference event
if(true){return;}
const date = new Date();
let name = `${date.getUTCFullYear()}-${date.getUTCMonth() + 1}-${date.getUTCDate()}_${date.getHours()}-${date.getUTCMinutes()}-${date.getUTCSeconds()}-${date.getUTCMilliseconds()}`;
for (const region of data.trigger) {
name += `(${region.name}=${region.percent})`;
}
const jpeg = `${name}.jpeg`;
const ff = execFile('ffmpeg', ['-f', 'pam_pipe', '-c:v', 'pam', '-i', 'pipe:0', '-c:v', 'mjpeg', '-pix_fmt', 'yuvj422p', '-q:v', '1', '-huffman', 'optimal', jpeg]);
ff.stdin.end(data.pam);
ff.on('exit', (data) => {
if (data === 0) {
console.log(`FFMPEG clean exit after creating ${jpeg}`);
} else {
throw new Error('FFMPEG is not working with current parameters');
}
});
});
ffmpeg.stdout.pipe(p2p).pipe(pamDiff);
```