Adding very basic library to emit image events from ffmpeg rtsp stream

src/index.ts

@@ -0,0 +1,94 @@
+import { ChildProcess, spawn } from "child_process"
+import { EventEmitter } from "events";
+import { Writable } from "stream";
+import { IOptions } from "./options";
+
+const ef1 = "ff";
+const ef2 = "d9";
+
+export class Rtsp extends EventEmitter {
+    private _connecteionString: string;
+    private _childProcess: ChildProcess | undefined;
+    private _started: boolean;
+    private _buffer: Buffer;
+    private _options: IOptions;
+
+    constructor(connectionString: string, options: IOptions) {
+        super();
+        this._started = false;
+        this._connecteionString = connectionString;
+        this._childProcess = undefined;
+        this._buffer = Buffer.from('');
+        this._options = options;
+    }
+
+    public get isStarted(): boolean {
+        return this._started;
+    }
+
+    public start(): void {
+        const argStrings = [
+            `-i ${this._connecteionString}`,
+            `-r ${this._options.rate ?? 10}`,
+            `-f image2`,
+            `-codec:v ${this._options.codec ?? 'libx264'}`,
+            `-update 1 -`
+        ];
+        const args = argStrings.join(" ");
+        this._childProcess = spawn("ffmpeg", args.split(/\s+/));
+
+        if(!this._childProcess){
+            return;
+        }
+        
+        this._childProcess.stdout?.on('data', this.onData)
+        this._childProcess.on('exit', this.onExit);
+        this._childProcess.on('error', this.onError);
+
+        if (this._childProcess.stderr) {
+            this._childProcess.stderr.on('data', this.onStdErrorData);
+          }  
+    }
+
+    public close(): void {
+        this._childProcess && this._childProcess.kill('SIGKILL');
+        this.emit('closed');
+    }
+
+    public getStdin(): Writable | null {
+        return this._childProcess ? this._childProcess.stdin : null;
+      }
+
+    private onError = (err: Error): void => {
+        this.emit('error', new Error('Failed to start stream: ' + err.message));
+    }
+
+    private onStdErrorData = (data: any): void => {
+        if (!this._started) {
+            this._started = true;
+            
+          }
+        let msg = "";
+        data.toString().split(/\n/).forEach((line: string) => {
+            msg += `line\n`;
+        });
+
+        this.emit("error", msg);
+    }
+
+    private onExit = (code: number, signal: NodeJS.Signals): void => {
+        const message = 'FFmpeg exited with code: ' + code + ' and signal: ' + signal;
+        this.emit('closed', message);
+    }
+
+    private onData = (data: Buffer): void  => {
+        if (data.length > 1) {
+            this._buffer = this._buffer ? Buffer.concat([this._buffer, data]) : this._buffer = Buffer.from(data);
+            //End of image
+            if(data[data.length - 2].toString(16) == ef1 && data[data.length -1].toString(16) == ef2){
+                this.emit('data', this._buffer)
+                this._buffer = Buffer.from('');
+            }
+	    }
+    }
+}

src/options.ts

@@ -0,0 +1,6 @@
+export interface IOptions {
+    rate?: number,
+    quality?: number,
+    resolution?: string,
+    codec?: string,
+}