diff --git a/media/generate b/media/generate
index 922d2bc..5105c06 100755
--- a/media/generate
+++ b/media/generate
@@ -6,8 +6,7 @@ cd "$(dirname "$0")"
 # separate_moof:    Splits audio and video into separate moof flags.
 # omit_tfhd_offset: Removes absolute byte offsets so we can fragment.
 
-ffmpeg -i source.mp4 \
+ffmpeg -i source.mp4 -y \
+	-c copy \
 	-movflags empty_moov+frag_every_frame+separate_moof+omit_tfhd_offset \
-	-c:v copy \
-	-an \
-	fragmented.mp4
+	fragmented.mp4 2>&1
diff --git a/player/src/index.ts b/player/src/index.ts
index 89e2e22..5882480 100644
--- a/player/src/index.ts
+++ b/player/src/index.ts
@@ -1,4 +1,5 @@
 import Player from "./player"
+import Transport from "./transport"
 
 // @ts-ignore embed the certificate fingerprint using bundler
 import fingerprintHex from 'bundle-text:../fingerprint.hex';
@@ -14,19 +15,23 @@ const params = new URLSearchParams(window.location.search)
 const url = params.get("url") || "https://127.0.0.1:4443/watch"
 const canvas = document.querySelector<HTMLCanvasElement>("canvas#video")!
 
-const player = new Player({
+const transport = new Transport({
     url: url,
     fingerprint: { // TODO remove when Chrome accepts the system CA
         "algorithm": "sha-256",
         "value": new Uint8Array(fingerprint),
     },
-    canvas: canvas,
+})
+
+const player = new Player({
+    transport,
+    canvas: canvas.transferControlToOffscreen(),
 })
 
 const play = document.querySelector<HTMLElement>("#screen #play")!
 
 let playFunc = (e: Event) => {
-    player.play()
+    player.play({})
     e.preventDefault()
 
     play.removeEventListener('click', playFunc)
diff --git a/player/src/media/index.ts b/player/src/media/index.ts
deleted file mode 100644
index 376052a..0000000
--- a/player/src/media/index.ts
+++ /dev/null
@@ -1,81 +0,0 @@
-import * as Message from "./message"
-import { RingInit } from "./ring"
-
-// Abstracts the Worker and Worklet into a simpler API
-// This class must be created on the main thread due to AudioContext.
-export default class Media {
-    context: AudioContext;
-    worker: Worker;
-    worklet: Promise<AudioWorkletNode>;
-
-    constructor(videoConfig: Message.VideoConfig) {
-        // Assume 44.1kHz and two audio channels
-        const audioConfig = {
-            sampleRate: 44100,
-            ring: new RingInit(2, 4410), // 100ms at 44.1khz
-        }
-
-        const config = {
-            audio: audioConfig,
-            video: videoConfig,
-        }
-
-        this.context = new AudioContext({
-            latencyHint: "interactive",
-            sampleRate: config.audio.sampleRate,
-        })
-
-
-        this.worker = this.setupWorker(config)
-        this.worklet = this.setupWorklet(config)
-    }
-
-    private setupWorker(config: Message.Config): Worker {
-        const url = new URL('worker.ts', import.meta.url)
-
-        const worker = new Worker(url, {
-            type: "module",
-            name: "media",
-        })
-
-        worker.postMessage({ config }, [ config.video.canvas ])
-
-        return worker
-    }
-
-    private async setupWorklet(config: Message.Config): Promise<AudioWorkletNode> {
-        // Load the worklet source code.
-        const url = new URL('worklet.ts', import.meta.url)
-        await this.context.audioWorklet.addModule(url)
-
-        const volume = this.context.createGain()
-        volume.gain.value = 2.0;
-
-        // Create a worklet
-        const worklet = new AudioWorkletNode(this.context, 'renderer');
-        worklet.onprocessorerror = (e: Event) => {
-            console.error("Audio worklet error:", e)
-        };
-
-        worklet.port.postMessage({ config })
-
-        // Connect the worklet to the volume node and then to the speakers
-        worklet.connect(volume)
-        volume.connect(this.context.destination)
-
-        return worklet
-    }
-
-    init(init: Message.Init) {
-        this.worker.postMessage({ init }, [ init.buffer.buffer, init.reader ])
-    }
-
-    segment(segment: Message.Segment) {
-        this.worker.postMessage({ segment }, [ segment.buffer.buffer, segment.reader ])
-    }
-
-    play(play: Message.Play) {
-        this.context.resume()
-        //this.worker.postMessage({ play })
-    }
-}
\ No newline at end of file
diff --git a/player/src/mp4/index.ts b/player/src/mp4/index.ts
index ca1a0bd..b375434 100644
--- a/player/src/mp4/index.ts
+++ b/player/src/mp4/index.ts
@@ -1,12 +1,16 @@
-import * as MP4 from "./rename"
-export * from "./rename"
+// Rename some stuff so it's on brand.
+export {
+	createFile as New,
+	MP4File as File,
+	MP4ArrayBuffer as ArrayBuffer,
+	MP4Info as Info,
+	MP4Track as Track,
+	MP4AudioTrack as AudioTrack,
+	MP4VideoTrack as VideoTrack,
+	DataStream as Stream,
+	Box,
+	ISOFile,
+	Sample,
+} from "mp4box"
 
-export { Init, InitParser } from "./init"
-
-export function isAudioTrack(track: MP4.Track): track is MP4.AudioTrack {
-	return (track as MP4.AudioTrack).audio !== undefined;
-}
-
-export function isVideoTrack(track: MP4.Track): track is MP4.VideoTrack {
-	return (track as MP4.VideoTrack).video !== undefined;
-}
\ No newline at end of file
+export { Init, InitParser } from "./init"
\ No newline at end of file
diff --git a/player/src/mp4/mp4box.d.ts b/player/src/mp4/mp4box.d.ts
index 018f185..2f95f94 100644
--- a/player/src/mp4/mp4box.d.ts
+++ b/player/src/mp4/mp4box.d.ts
@@ -82,7 +82,7 @@ declare module "mp4box" {
         description: any;
         data: ArrayBuffer;
         size: number;
-        alreadyRead: number;
+        alreadyRead?: number;
         duration: number;
         cts: number;
         dts: number;
@@ -104,7 +104,7 @@ declare module "mp4box" {
     const LITTLE_ENDIAN: boolean;
 
     export class DataStream {
-        constructor(buffer: ArrayBuffer, byteOffset?: number, littleEndian?: boolean);
+        constructor(buffer?: ArrayBuffer, byteOffset?: number, littleEndian?: boolean);
         getPosition(): number;
 
         get byteLength(): number;
@@ -144,5 +144,82 @@ declare module "mp4box" {
         // TODO I got bored porting the remaining functions
     }
 
+    export class Box {
+        write(stream: DataStream): void;
+    }
+
+    export interface TrackOptions {
+        id?: number;
+        type?: string;
+        width?: number;
+        height?: number;
+        duration?: number;
+        layer?: number;
+        timescale?: number;
+        media_duration?: number;
+        language?: string;
+        hdlr?: string;
+
+        // video
+        avcDecoderConfigRecord?: any;
+
+        // audio
+        balance?: number;
+        channel_count?: number;
+        samplesize?: number;
+        samplerate?: number;
+
+        //captions
+        namespace?: string;
+        schema_location?: string;
+        auxiliary_mime_types?: string;
+
+        description?: any;
+        description_boxes?: Box[];
+
+        default_sample_description_index_id?: number;
+        default_sample_duration?: number;
+        default_sample_size?: number;
+        default_sample_flags?: number;
+    }
+
+    export interface FileOptions {
+        brands?: string[];
+        timescale?: number;
+        rate?: number;
+        duration?: number;
+        width?: number;
+    }
+
+    export interface SampleOptions {
+        sample_description_index?: number;
+        duration?: number;
+        cts?: number;
+        dts?: number;
+        is_sync?: boolean;
+        is_leading?: number;
+        depends_on?: number;
+        is_depended_on?: number;
+        has_redundancy?: number;
+        degradation_priority?: number;
+        subsamples?: any;
+    }
+
+    // TODO add the remaining functions
+    // TODO move to another module
+    export class ISOFile {
+        constructor(stream?: DataStream);
+
+        init(options?: FileOptions): ISOFile;
+        addTrack(options?: TrackOptions): number;
+        addSample(track: number, data: ArrayBuffer, options?: SampleOptions): Sample;
+
+        createSingleSampleMoof(sample: Sample): Box;
+
+        // helpers
+        getTrackById(id: number): Box | undefined;
+        getTrexById(id: number): Box | undefined;
+    }
+
     export { };
 }
\ No newline at end of file
diff --git a/player/src/mp4/rename.ts b/player/src/mp4/rename.ts
deleted file mode 100644
index d45682b..0000000
--- a/player/src/mp4/rename.ts
+++ /dev/null
@@ -1,12 +0,0 @@
-// Rename some stuff so it's on brand.
-export {
-	createFile as New,
-	MP4File as File,
-	MP4ArrayBuffer as ArrayBuffer,
-	MP4Info as Info,
-	MP4Track as Track,
-	MP4AudioTrack as AudioTrack,
-	MP4VideoTrack as VideoTrack,
-	DataStream as Stream,
-	Sample,
-} from "mp4box"
\ No newline at end of file
diff --git a/player/src/media/decoder.ts b/player/src/player/decoder.ts
similarity index 94%
rename from player/src/media/decoder.ts
rename to player/src/player/decoder.ts
index ca2f639..64c5683 100644
--- a/player/src/media/decoder.ts
+++ b/player/src/player/decoder.ts
@@ -1,7 +1,6 @@
 import * as Message from "./message";
 import * as MP4 from "../mp4"
 import * as Stream from "../stream"
-import * as Util from "../util"
 
 import Renderer from "./renderer"
 
@@ -82,7 +81,7 @@ export default class Decoder {
             // We need a sample to initalize the video decoder, because of mp4box limitations.
             let sample = samples[0];
 
-            if (MP4.isVideoTrack(track)) {
+            if (isVideoTrack(track)) {
                 // Configure the decoder using the AVC box for H.264
                 // TODO it should be easy to support other codecs, just need to know the right boxes.
                 const avcc = sample.description.avcC;
@@ -105,7 +104,7 @@ export default class Decoder {
                 })
 
                 decoder = videoDecoder
-            } else if (MP4.isAudioTrack(track)) {
+            } else if (isAudioTrack(track)) {
                 const audioDecoder = new AudioDecoder({
                     output: this.renderer.push.bind(this.renderer),
                     error: console.warn,
@@ -157,4 +156,12 @@ function isAudioDecoder(decoder: AudioDecoder | VideoDecoder): decoder is AudioD
 
 function isVideoDecoder(decoder: AudioDecoder | VideoDecoder): decoder is VideoDecoder {
     return decoder instanceof VideoDecoder
+}
+
+function isAudioTrack(track: MP4.Track): track is MP4.AudioTrack {
+	return (track as MP4.AudioTrack).audio !== undefined;
+}
+
+function isVideoTrack(track: MP4.Track): track is MP4.VideoTrack {
+	return (track as MP4.VideoTrack).video !== undefined;
 }
\ No newline at end of file
diff --git a/player/src/player/index.ts b/player/src/player/index.ts
index 9e9c2a6..1ef73b2 100644
--- a/player/src/player/index.ts
+++ b/player/src/player/index.ts
@@ -1,33 +1,89 @@
+import * as Message from "./message"
+import * as Ring from "./ring"
 import Transport from "../transport"
-import Media from "../media"
 
-export interface PlayerInit {
-	url: string;
-	fingerprint?: WebTransportHash; // the certificate fingerprint, temporarily needed for local development
-	canvas: HTMLCanvasElement;
+export interface Config {
+    transport: Transport
+    canvas: OffscreenCanvas;
 }
 
+// This class must be created on the main thread due to AudioContext.
 export default class Player {
-	media: Media;
-    transport: Transport;
+    context: AudioContext;
+    worker: Worker;
+    worklet: Promise<AudioWorkletNode>;
 
-	constructor(props: PlayerInit) {
-		this.media = new Media({
-			canvas: props.canvas.transferControlToOffscreen(),
-		})
+    transport: Transport
 
-        this.transport = new Transport({
-            url: props.url,
-			fingerprint: props.fingerprint,
-            media: this.media,
+    constructor(config: Config) {
+        this.transport = config.transport
+        this.transport.callback = this;
+
+        const video = {
+            canvas: config.canvas,
+        };
+
+        // Assume 44.1kHz and two audio channels
+        const audio = {
+            sampleRate: 44100,
+            ring: new Ring.Buffer(2, 4410), // 100ms at 44.1khz
+        }
+
+        this.context = new AudioContext({
+            latencyHint: "interactive",
+            sampleRate: audio.sampleRate,
         })
-	}
 
-	async close() {
-        this.transport.close()
-	}
+        this.worker = this.setupWorker({ audio, video })
+        this.worklet = this.setupWorklet(audio)
+    }
 
-	play() {
-		this.media.play({})
-	}
+    private setupWorker(config: Message.Config): Worker {
+        const url = new URL('worker.ts', import.meta.url)
+
+        const worker = new Worker(url, {
+            type: "module",
+            name: "media",
+        })
+
+        worker.postMessage({ config }, [ config.video.canvas ])
+
+        return worker
+    }
+
+    private async setupWorklet(config: Message.AudioConfig): Promise<AudioWorkletNode> {
+        // Load the worklet source code.
+        const url = new URL('worklet.ts', import.meta.url)
+        await this.context.audioWorklet.addModule(url)
+
+        const volume = this.context.createGain()
+        volume.gain.value = 2.0;
+
+        // Create a worklet
+        const worklet = new AudioWorkletNode(this.context, 'renderer');
+        worklet.onprocessorerror = (e: Event) => {
+            console.error("Audio worklet error:", e)
+        };
+
+        worklet.port.postMessage({ config })
+
+        // Connect the worklet to the volume node and then to the speakers
+        worklet.connect(volume)
+        volume.connect(this.context.destination)
+
+        return worklet
+    }
+
+    onInit(init: Message.Init) {
+        this.worker.postMessage({ init }, [ init.buffer.buffer, init.reader ])
+    }
+
+    onSegment(segment: Message.Segment) {
+        this.worker.postMessage({ segment }, [ segment.buffer.buffer, segment.reader ])
+    }
+
+    play(play: Message.Play) {
+        this.context.resume()
+        //this.worker.postMessage({ play })
+    }
 }
\ No newline at end of file
diff --git a/player/src/media/message.ts b/player/src/player/message.ts
similarity index 85%
rename from player/src/media/message.ts
rename to player/src/player/message.ts
index a457200..dcad2e0 100644
--- a/player/src/media/message.ts
+++ b/player/src/player/message.ts
@@ -1,5 +1,4 @@
-import * as MP4 from "../mp4"
-import { RingInit } from "../media/ring"
+import * as Ring from "./ring"
 
 export interface Config {
     audio: AudioConfig;
@@ -13,7 +12,7 @@ export interface VideoConfig {
 export interface AudioConfig {
     // audio stuff
     sampleRate: number;
-    ring: RingInit;
+    ring: Ring.Buffer;
 }
 
 export interface Init {
diff --git a/player/src/media/renderer.ts b/player/src/player/renderer.ts
similarity index 94%
rename from player/src/media/renderer.ts
rename to player/src/player/renderer.ts
index af56e2a..d2d6c86 100644
--- a/player/src/media/renderer.ts
+++ b/player/src/player/renderer.ts
@@ -68,8 +68,11 @@ export default class Renderer {
     }
 
     draw(now: DOMHighResTimeStamp) {
+        // Convert to microseconds
+        now *= 1000;
+
         // Determine the target timestamp.
-        const target = 1000 * now - this.sync!
+        const target = now - this.sync!
 
         this.drawAudio(now, target)
         this.drawVideo(now, target)
@@ -85,9 +88,11 @@ export default class Renderer {
         // Check if we should skip some frames
         while (this.audioQueue.length) {
             const next = this.audioQueue[0]
-            if (next.timestamp >= target) {
+
+            if (next.timestamp > target) {
                 let ok = this.audioRing.write(next)
                 if (!ok) {
+                    console.warn("ring buffer is full")
                     // No more space in the ring
                     break
                 }
@@ -101,7 +106,7 @@ export default class Renderer {
     }
 
     drawVideo(now: DOMHighResTimeStamp, target: DOMHighResTimeStamp) {
-        if (this.videoQueue.length == 0) return;
+        if (!this.videoQueue.length) return;
 
         let frame = this.videoQueue[0];
         if (frame.timestamp >= target) {
diff --git a/player/src/media/ring.ts b/player/src/player/ring.ts
similarity index 95%
rename from player/src/media/ring.ts
rename to player/src/player/ring.ts
index cd796ee..ffc1c6b 100644
--- a/player/src/media/ring.ts
+++ b/player/src/player/ring.ts
@@ -11,15 +11,15 @@ export class Ring {
     channels: Float32Array[];
     capacity: number;
 
-    constructor(init: RingInit) {
-        this.state = new Int32Array(init.state)
+    constructor(buf: Buffer) {
+        this.state = new Int32Array(buf.state)
 
         this.channels = []
-        for (let channel of init.channels) {
+        for (let channel of buf.channels) {
             this.channels.push(new Float32Array(channel))
         }
 
-        this.capacity = init.capacity
+        this.capacity = buf.capacity
     }
 
     // Add the samples for single audio frame
@@ -121,7 +121,7 @@ export class Ring {
 }
 
 // No prototype to make this easier to send via postMessage
-export class RingInit {
+export class Buffer {
     state: SharedArrayBuffer;
 
     channels: SharedArrayBuffer[];
diff --git a/player/src/media/worker.ts b/player/src/player/worker.ts
similarity index 100%
rename from player/src/media/worker.ts
rename to player/src/player/worker.ts
diff --git a/player/src/media/worklet.ts b/player/src/player/worklet.ts
similarity index 87%
rename from player/src/media/worklet.ts
rename to player/src/player/worklet.ts
index 5961c32..4946bd8 100644
--- a/player/src/media/worklet.ts
+++ b/player/src/player/worklet.ts
@@ -20,12 +20,12 @@ class Renderer extends AudioWorkletProcessor {
 
     onMessage(e: MessageEvent) {
         if (e.data.config) {
-            this.config(e.data.config)
+            this.onConfig(e.data.config)
         }
     }
 
-    config(config: Message.Config) {
-        this.ring = new Ring(config.audio.ring)
+    onConfig(config: Message.AudioConfig) {
+        this.ring = new Ring(config.ring)
     }
 
     // Inputs and outputs in groups of 128 samples.
diff --git a/player/src/transport/index.ts b/player/src/transport/index.ts
index e588a8f..72eb4fd 100644
--- a/player/src/transport/index.ts
+++ b/player/src/transport/index.ts
@@ -1,25 +1,18 @@
-import * as Message from "./message"
 import * as Stream from "../stream"
-import * as MP4 from "../mp4"
+import * as Interface from "./interface"
 
-import Media from "../media"
-
-export interface TransportInit {
+export interface Config {
 	url: string;
 	fingerprint?: WebTransportHash; // the certificate fingerprint, temporarily needed for local development
-	media: Media;
 }
 
 export default class Transport {
 	quic: Promise<WebTransport>;
 	api: Promise<WritableStream>;
+	callback?: Interface.Callback;
 
-	media: Media;
-
-	constructor(props: TransportInit) {
-		this.media = props.media;
-
-		this.quic = this.connect(props)
+	constructor(config: Config) {
+		this.quic = this.connect(config)
 
 		// Create a unidirectional stream for all of our messages
 		this.api = this.quic.then((q) => {
@@ -35,13 +28,13 @@ export default class Transport {
 	}
 
 	// Helper function to make creating a promise easier
-	private async connect(props: TransportInit): Promise<WebTransport> {
+	private async connect(config: Config): Promise<WebTransport> {
 		let options: WebTransportOptions = {};
-		if (props.fingerprint) {
-			options.serverCertificateHashes = [ props.fingerprint ]
+		if (config.fingerprint) {
+			options.serverCertificateHashes = [ config.fingerprint ]
 		}
 
-		const quic = new WebTransport(props.url, options)
+		const quic = new WebTransport(config.url, options)
 		await quic.ready
 		return quic
 	}
@@ -86,12 +79,12 @@ export default class Transport {
 			const msg = JSON.parse(payload)
 
 			if (msg.init) {
-				return this.media.init({
+				return this.callback?.onInit({
 					buffer: r.buffer,
 					reader: r.reader,
 				})
 			} else if (msg.segment) {
-				return this.media.segment({
+				return this.callback?.onSegment({
 					buffer: r.buffer,
 					reader: r.reader,
 				})
diff --git a/player/src/transport/interface.ts b/player/src/transport/interface.ts
new file mode 100644
index 0000000..cc5e3aa
--- /dev/null
+++ b/player/src/transport/interface.ts
@@ -0,0 +1,14 @@
+export interface Callback {
+	onInit(init: Init): any
+	onSegment(segment: Segment): any
+}
+
+export interface Init {
+    buffer: Uint8Array;     // unread buffered data
+    reader: ReadableStream; // unread unbuffered data
+}
+
+export interface Segment {
+    buffer: Uint8Array;     // unread buffered data
+    reader: ReadableStream; // unread unbuffered data
+}
\ No newline at end of file
diff --git a/player/src/transport/message.ts b/player/src/transport/message.ts
index d151538..7cb511f 100644
--- a/player/src/transport/message.ts
+++ b/player/src/transport/message.ts
@@ -1,12 +1,5 @@
-export interface Init {
-	id: string
-}
-
-export interface Segment {
-	init: string // id of the init segment
-	timestamp: number // presentation timestamp in milliseconds of the first sample
-	// TODO track would be nice
-}
+export interface Init {}
+export interface Segment {}
 
 export interface Debug {
 	max_bitrate: number