feat(streams): allow changing the RTSP URI

Adds a URI option to the describe method in the RTSP session.
If provided, it's used for that session instead of the URI that
was provided to the constructor. The latter now only serves as
default URI when none is provided to describe.
On teardown, the session control URL is restored to the default.

Fixes #1077

src/streams/components/rtsp/session.ts

@@ -55,14 +55,14 @@ type RtspState = 'idle' | 'playing' | 'paused'
  * and sending request on the outgoing stream.
  */
 export class RtspSession {
+  public auth?: Auth
+  public readonly commands: ReadableStream<Uint8Array>
   public readonly demuxer: TransformStream<
     Uint8Array,
     RtpMessage | RtcpMessage | SdpMessage
   >
-  public readonly commands: ReadableStream<Uint8Array>
   public onRtcp?: (rtcp: Rtcp) => void
   public retry = { max: 20, codes: [503] }
-  public auth?: Auth
 
   private clockrates?: { [key: number]: number }
   private cseq: number = 0
@@ -76,7 +76,7 @@ export class RtspSession {
   private sessionId?: string
   private state?: RtspState
   private t0?: { [key: number]: number }
-  private uri: string
+  private defaultUri: string
 
   /** Create a new RTSP session controller component. */
   public constructor({
@@ -90,7 +90,7 @@ export class RtspSession {
     }
     this.sessionControlUrl = uri
     this.state = 'idle'
-    this.uri = uri
+    this.defaultUri = uri
 
     const parser = new RtspParser()
     this.demuxer = new TransformStream({
@@ -151,11 +151,11 @@ export class RtspSession {
   }
 
   /** Send a DESCRIBE request to get a presentation description of available media . */
-  public async describe(): Promise<Sdp> {
+  public async describe(uri: string = this.defaultUri): Promise<Sdp> {
     const rsp = await this.fetch(
       new RtspRequestMessage({
         method: 'DESCRIBE',
-        uri: this.sessionControlUrl,
+        uri,
         headers: { ...this.headers.DESCRIBE },
       })
     )
@@ -167,7 +167,7 @@ export class RtspSession {
     this.sessionControlUrl =
       rsp.headers.get('Content-Base') ??
       rsp.headers.get('Content-Location') ??
-      this.uri
+      uri
 
     if (
       rsp.headers.get('Content-Type') !== 'application/sdp' ||
@@ -317,8 +317,8 @@ export class RtspSession {
       throw new Error(`response not OK: ${rsp.statusCode}`)
     }
 
+    this.sessionControlUrl = this.defaultUri
     this.sessionId = undefined
-
     this.state = 'idle'
   }