Add RTCP SLI feedback packet

src/packets/RTCP/SliPacket.ts

@@ -0,0 +1,221 @@
+import { RtcpPacketType } from './RtcpPacket';
+import {
+	FeedbackPacket,
+	PsFeedbackMessageType,
+	FeedbackPacketDump,
+	FIXED_HEADER_LENGTH
+} from './FeedbackPacket';
+
+/**
+ * RTCP SLI packet info dump.
+ *
+ * @category RTCP
+ */
+export type SliPacketDump = FeedbackPacketDump &
+{
+	items: { first: number; number: number; pictureId: number }[];
+};
+
+/**
+ * RTCP SLI packet (RTCP Payload Specific Feedback).
+ *
+ * ```text
+ *  0                   1                   2                   3
+ *  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |V=2|P|  FMT=2  |  PT=PSFB=206  |          length               |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |                  SSRC of packet sender                        |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |                  SSRC of media source                         |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |            First        |        Number           | PictureID |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * :                              ...                              :
+ * +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+ * ```
+ *
+ * @category RTCP
+ *
+ * @see
+ * - [RFC 4585 section 6.3.2](https://datatracker.ietf.org/doc/html/rfc4585#section-6.3.2)
+ */
+export class SliPacket extends FeedbackPacket
+{
+	#items: { first: number; number: number; pictureId: number }[] = [];
+
+	/**
+	 * @param view - If given it will be parsed. Otherwise an empty RTCP SLI
+	 *   packet will be created.
+	 *
+	 * @throws
+	 * - If given `view` does not contain a valid RTCP SLI packet.
+	 */
+	constructor(view?: DataView)
+	{
+		super(RtcpPacketType.PSFB, PsFeedbackMessageType.SLI, view);
+
+		if (!this.view)
+		{
+			this.view = new DataView(new ArrayBuffer(FIXED_HEADER_LENGTH));
+
+			// Write version, packet type and feedback message type.
+			this.writeFixedHeader();
+
+			return;
+		}
+
+		// Position relative to the DataView byte offset.
+		let pos = 0;
+
+		// Move to items.
+		pos += FIXED_HEADER_LENGTH;
+
+		while (pos < this.view.byteLength - this.padding)
+		{
+			const first = this.view.getUint16(pos) >> 3;
+
+			const number =
+				(this.view.getUint32(pos) & 0b00000000000001111111111111000000) >> 6;
+
+			const pictureId = this.view.getUint8(pos + 3) & 0b00111111;
+
+			pos += 4;
+
+			this.#items.push({ first, number, pictureId });
+		}
+
+		pos += this.padding;
+
+		// Ensure that view length and parsed length match.
+		if (pos !== this.view.byteLength)
+		{
+			throw new RangeError(
+				`parsed length (${pos} bytes) does not match view length (${this.view.byteLength} bytes)`
+			);
+		}
+	}
+
+	/**
+	 * Dump RTCP SLI packet info.
+	 */
+	dump(): SliPacketDump
+	{
+		return {
+			...super.dump(),
+			items : this.getItems()
+		};
+	}
+
+	/**
+	 * @inheritDoc
+	 */
+	getByteLength(): number
+	{
+		if (!this.needsSerialization())
+		{
+			return this.view.byteLength;
+		}
+
+		const packetLength =
+			FIXED_HEADER_LENGTH +
+			(this.#items.length * 4) +
+			this.padding;
+
+		return packetLength;
+	}
+
+	/**
+	 * @inheritDoc
+	 */
+	serialize(buffer?: ArrayBuffer, byteOffset?: number): void
+	{
+		const view = this.serializeBase(buffer, byteOffset);
+
+		// Position relative to the DataView byte offset.
+		let pos = 0;
+
+		// Move to items.
+		pos += FIXED_HEADER_LENGTH;
+
+		// Write items.
+		for (const { first, number, pictureId } of this.#items)
+		{
+			view.setUint32(
+				pos,
+				(first << 19) + (number << 6) + pictureId
+			);
+
+			pos += 4;
+		}
+
+		pos += this.padding;
+
+		// Assert that current position is equal than new buffer length.
+		if (pos !== view.byteLength)
+		{
+			throw new RangeError(
+				`filled length (${pos} bytes) is different than the available buffer size (${view.byteLength} bytes)`
+			);
+		}
+
+		// Update DataView.
+		this.view = view;
+
+		this.setSerializationNeeded(false);
+	}
+
+	/**
+	 * @inheritDoc
+	 */
+	clone(
+		buffer?: ArrayBuffer,
+		byteOffset?: number,
+		serializationBuffer?: ArrayBuffer,
+		serializationByteOffset?: number
+	): SliPacket
+	{
+		const view = this.cloneInternal(
+			buffer,
+			byteOffset,
+			serializationBuffer,
+			serializationByteOffset
+		);
+
+		return new SliPacket(view);
+	}
+
+	/**
+	 * Get SLI items.
+	 */
+	getItems(): { first: number; number: number; pictureId: number }[]
+	{
+		return Array.from(this.#items);
+	}
+
+	/**
+	 * Set SLI items.
+	 *
+	 * @remarks
+	 * - Serialization is needed after calling this method.
+	 */
+	setItems(items: { first: number; number: number; pictureId: number }[]): void
+	{
+		this.#items = Array.from(items);
+
+		this.setSerializationNeeded(true);
+	}
+
+	/**
+	 * Add SLI item value.
+	 *
+	 * @remarks
+	 * - Serialization is needed after calling this method.
+	 */
+	addItem(first: number, number: number, pictureId: number): void
+	{
+		this.#items.push({ first, number, pictureId });
+
+		this.setSerializationNeeded(true);
+	}
+}

src/packets/public.ts

@@ -76,6 +76,11 @@ export {
 	PliPacketDump
 } from './RTCP/PliPacket';
 
+export {
+	SliPacket,
+	SliPacketDump
+} from './RTCP/SliPacket';
+
 export {
 	GenericFeedbackPacket,
 	GenericFeedbackPacketDump

src/tests/packets/RTCP/SliPacket.test.ts

@@ -0,0 +1,87 @@
+import {
+	SliPacket,
+	SliPacketDump
+} from '../../../packets/RTCP/SliPacket';
+import { PsFeedbackMessageType } from '../../../packets/RTCP/FeedbackPacket';
+import { isRtcp, RtcpPacketType } from '../../../packets/RTCP/RtcpPacket';
+import { areDataViewsEqual } from '../../../utils/helpers';
+
+const sliPacketDump: SliPacketDump =
+{
+	byteLength  : 20,
+	padding     : 0,
+	packetType  : RtcpPacketType.PSFB,
+	count       : 2, // Used to indicate FMT, so 2 for SLI.
+	messageType : PsFeedbackMessageType.SLI,
+	senderSsrc  : 0x11223344,
+	mediaSsrc   : 0x55667788,
+	items       :
+	[
+		{ first: 0b1100000000011, number: 0b1111000001111, pictureId: 0b101010 },
+		{ first: 0b0100000000011, number: 0b0111000001111, pictureId: 0b001010 }
+	]
+};
+
+describe('parse RTCP SLI packet', () =>
+{
+	const array = new Uint8Array(
+		[
+			0x82, 0xce, 0x00, 0x04, // FMT: 2 (SLI), Type: 206 (PSFB), Count: 0, length: 4
+			0x11, 0x22, 0x33, 0x44, // Sender SSRC: 0x11223344
+			0x55, 0x66, 0x77, 0x88, // Media SSRC: 0x55667788
+			0b11000000, 0b00011111, 0b10000011, 0b11101010, // Item
+			0b01000000, 0b00011011, 0b10000011, 0b11001010 // Item
+		]
+	);
+
+	const view = new DataView(
+		array.buffer,
+		array.byteOffset,
+		array.byteLength
+	);
+
+	test('buffer view is RTCP', () =>
+	{
+		expect(isRtcp(view)).toBe(true);
+	});
+
+	test('packet processing succeeds', () =>
+	{
+		const packet = new SliPacket(view);
+
+		expect(packet.needsSerialization()).toBe(false);
+		expect(packet.dump()).toEqual(sliPacketDump);
+		expect(packet.needsSerialization()).toBe(false);
+		expect(areDataViewsEqual(packet.getView(), view)).toBe(true);
+
+		packet.serialize();
+		expect(packet.dump()).toEqual(sliPacketDump);
+		expect(areDataViewsEqual(packet.getView(), view)).toBe(true);
+
+		const clonedPacket = packet.clone();
+
+		expect(clonedPacket.dump()).toEqual(sliPacketDump);
+		expect(areDataViewsEqual(clonedPacket.getView(), view)).toBe(true);
+	});
+});
+
+describe('create RTCP SLI packet', () =>
+{
+	test('creating a SLI packet with padding succeeds', () =>
+	{
+		const packet = new SliPacket();
+
+		packet.setSenderSsrc(sliPacketDump.senderSsrc);
+		packet.setMediaSsrc(sliPacketDump.mediaSsrc);
+		packet.setItems(sliPacketDump.items);
+
+		expect(packet.dump()).toEqual(sliPacketDump);
+
+		packet.serialize();
+		expect(packet.dump()).toEqual(sliPacketDump);
+
+		const clonedPacket = packet.clone();
+
+		expect(clonedPacket.dump()).toEqual(sliPacketDump);
+	});
+});