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Live Streaming from Unity - Multi-Camera Streams (Part 6)

Live Streaming from Unity - Multi-Camera Streams (Part 6)

Let's see how to stream more than one camera to the same Amazon IVS stage.

Todd Sharp
Amazon Employee
Published Feb 27, 2024
So far in this series, we've looked at broadcasting from a game built in Unity to an Amazon Interactive Video Service (Amazon IVS) real-time stage, integrated chat, and enhanced the experience with viewer-controlled cameras, and dynamic objectives and environments. In this post, we'll talk about another possible use-case: multi-camera streams.
In addition to viewer-controlled camera views, wouldn't it be super cool to see the action from multiple POVs as a stream viewer? Building on the same concepts that we've established in this series, this is totally possible.

Create a Reusable Class

Because we have some functionality that will be shared across several scripts, we'll encapsulate some of the logic that we've been using in this series into a reusable WebRTCUtils class. This will allow us to establish multiple streams from our game.
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namespace WebRTCUtil
{
using UnityEngine;
using System.Threading.Tasks;
using UnityEngine.Networking;

[System.Serializable]
public class ParticipantToken
{
public string token;
public string participantId;
public System.DateTime expirationTime;
public static ParticipantToken CreateFromJSON(string jsonString)
{
return JsonUtility.FromJson<ParticipantToken>(jsonString);
}
}

[System.Serializable]
public class StageToken
{
public ParticipantToken participantToken;
public static StageToken CreateFromJSON(string jsonString)
{
return JsonUtility.FromJson<StageToken>(jsonString);
}
}

[System.Serializable]
public class StageTokenRequestAttributes
{
public string username;
public StageTokenRequestAttributes(string username)
{
this.username = username;
}
}

[System.Serializable]
public class StageTokenRequest
{
public string stageArn;
public string userId;
public int duration;
public StageTokenRequestAttributes attributes;
public string[] capabilities;
public StageTokenRequest(string stageArn, string userId, int duration, string[] capabilities, StageTokenRequestAttributes attributes)
{
this.stageArn = stageArn;
this.userId = userId;
this.duration = duration;
this.capabilities = capabilities;
this.attributes = attributes;
}
}

[System.Serializable]
public class ChatTokenRequest
{
public string chatArn;
public string username;
public string userId;
public ChatTokenRequest(string chatArn, string username, string userId)
{
this.chatArn = chatArn;
this.username = username;
this.userId = userId;
}
}

public class WebRTCUtils
{
public async Task<StageToken> GetStageToken(string username)
{
using UnityWebRequest www = new UnityWebRequest("http://localhost:3000/token");
StageTokenRequest tokenRequest = new StageTokenRequest(
"[YOUR STAGE ARN]",
System.Guid.NewGuid().ToString(),
1440,
new string[] { "PUBLISH", "SUBSCRIBE" },
new StageTokenRequestAttributes(username)
);
www.uploadHandler = new UploadHandlerRaw(System.Text.Encoding.ASCII.GetBytes(JsonUtility.ToJson(tokenRequest)));
www.downloadHandler = new DownloadHandlerBuffer();
www.method = UnityWebRequest.kHttpVerbPOST;
www.SetRequestHeader("Content-Type", "application/json");
var request = www.SendWebRequest();
while (!request.isDone)
{
await Task.Yield();
};
var response = www.downloadHandler.text;
Debug.Log(response);
if (www.result != UnityWebRequest.Result.Success)
{
Debug.Log(www.error);
return default;
}
else
{
StageToken stageToken = StageToken.CreateFromJSON(www.downloadHandler.text);
Debug.Log(stageToken);
return stageToken;
}
}

}
}

Player Stream

We'll use the 'FPS' demo game for this demo, and create a player camera to broadcast the player's POV just as we did before.
Player cam
Next, create and associate a WebRTCPlayerPublish script.
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using System.Collections;
using System.Collections.Generic;
using System.Threading.Tasks;
using UnityEngine;
using Unity.WebRTC;
using UnityEngine.Networking;
using WebRTCUtil;

[RequireComponent(typeof(AudioListener))]
public class WebRTCPlayerPublish : MonoBehaviour
{
WebRTCUtils util = new WebRTCUtils();
RTCPeerConnection peerConnection;
MediaStreamTrack videoTrack;
public AudioStreamTrack audioTrack;
Camera cam;
ParticipantToken participantToken;
async void Start()
{
StartCoroutine(WebRTC.Update());
peerConnection = new RTCPeerConnection
{
OnIceConnectionChange = state => { Debug.Log("Peer Connection: " + state); }
};
cam = GetComponent<Camera>();
videoTrack = cam.CaptureStreamTrack(1280, 720);
peerConnection.AddTrack(videoTrack);
AudioListener audioListener = cam.GetComponent<AudioListener>();
audioTrack = new AudioStreamTrack(audioListener) { Loopback = true };
peerConnection.AddTrack(audioTrack);
StartCoroutine(DoWHIP());
}

IEnumerator DoWHIP()
{
Task<StageToken> stageTokenRequest = util.GetStageToken("ivs-rtx-broadcast-multicam-player");
yield return new WaitUntil(() => stageTokenRequest.IsCompleted);
StageToken stageToken = stageTokenRequest.Result;
participantToken = stageToken.participantToken;
Debug.Log(participantToken.token);
Debug.Log(participantToken.participantId);

var offer = peerConnection.CreateOffer();
yield return offer;

var offerDesc = offer.Desc;
var opLocal = peerConnection.SetLocalDescription(ref offerDesc);
yield return opLocal;

var filteredSdp = "";
foreach (string sdpLine in offer.Desc.sdp.Split("\r\n"))
{
if (!sdpLine.StartsWith("a=extmap"))
{
filteredSdp += sdpLine + "\r\n";
}
}
using (UnityWebRequest www = new UnityWebRequest("https://global.whip.live-video.net/"))
{
www.uploadHandler = new UploadHandlerRaw(System.Text.Encoding.ASCII.GetBytes(filteredSdp));
www.downloadHandler = new DownloadHandlerBuffer();
www.method = UnityWebRequest.kHttpVerbPOST;
www.SetRequestHeader("Content-Type", "application/sdp");
www.SetRequestHeader("Authorization", "Bearer " + participantToken.token);
yield return www.SendWebRequest();
if (www.result != UnityWebRequest.Result.Success)
{
Debug.Log(www.error);
}
else
{
var answer = new RTCSessionDescription { type = RTCSdpType.Answer, sdp = www.downloadHandler.text };
var opRemote = peerConnection.SetRemoteDescription(ref answer);
yield return opRemote;
if (opRemote.IsError)
{
Debug.Log(opRemote.Error);
}
}
}
}

async void OnDestroy()
{
Debug.Log("OnDestroy");
peerConnection.Close();
peerConnection.Dispose();
if (videoTrack != null) videoTrack.Dispose();
if (audioTrack != null) audioTrack.Dispose();
}
}

Boss Stream

To add another camera for the main turret's POV, create an empty game object on the turret called TurretCameraThing.
Turret camera thing
Because we want this camera to always look at whatever the turret is looking at, we'll need to create a TurretCameraThing script that is bound to the turret's health bar and update the turret camera's transform in Update().
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using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class TurretCameraThing : MonoBehaviour
{
[SerializeField]
private Transform turretTransform;

void Update()
{
this.transform.rotation = turretTransform.rotation;
}
}
Now we can add a camera as a child of TurretCameraThing and attach a new WebRTCBossPublish script that will broadcast this camera's view as a separate stream to the same Amazon IVS stage.
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using System.Collections;
using System.Collections.Generic;
using System.Threading.Tasks;
using UnityEngine;
using Unity.WebRTC;
using UnityEngine.Networking;
using WebRTCUtil;

[RequireComponent(typeof(AudioListener))]
public class WebRTCBossPublish : MonoBehaviour
{
WebRTCUtils util = new WebRTCUtils();
RTCPeerConnection peerConnection;
MediaStreamTrack videoTrack;
public AudioStreamTrack audioTrack;
Camera cam;
ParticipantToken participantToken;
async void Start()
{
StartCoroutine(WebRTC.Update());
peerConnection = new RTCPeerConnection
{
OnIceConnectionChange = state => { Debug.Log("Peer Connection: " + state); }
};
cam = GetComponent<Camera>();
videoTrack = cam.CaptureStreamTrack(1280, 720);
peerConnection.AddTrack(videoTrack);
AudioListener audioListener = cam.GetComponent<AudioListener>();
audioTrack = new AudioStreamTrack(audioListener) { Loopback = true };
peerConnection.AddTrack(audioTrack);
StartCoroutine(DoWHIP());
}

IEnumerator DoWHIP()
{
Task<StageToken> stageTokenRequest = util.GetStageToken("ivs-rtx-broadcast-multicam-boss");
yield return new WaitUntil(() => stageTokenRequest.IsCompleted);
StageToken stageToken = stageTokenRequest.Result;
participantToken = stageToken.participantToken;
Debug.Log(participantToken.token);
Debug.Log(participantToken.participantId);

var offer = peerConnection.CreateOffer();
yield return offer;

var offerDesc = offer.Desc;
var opLocal = peerConnection.SetLocalDescription(ref offerDesc);
yield return opLocal;

var filteredSdp = "";
foreach (string sdpLine in offer.Desc.sdp.Split("\r\n"))
{
if (!sdpLine.StartsWith("a=extmap"))
{
filteredSdp += sdpLine + "\r\n";
}
}
using (UnityWebRequest www = new UnityWebRequest("https://global.whip.live-video.net/"))
{
www.uploadHandler = new UploadHandlerRaw(System.Text.Encoding.ASCII.GetBytes(filteredSdp));
www.downloadHandler = new DownloadHandlerBuffer();
www.method = UnityWebRequest.kHttpVerbPOST;
www.SetRequestHeader("Content-Type", "application/sdp");
www.SetRequestHeader("Authorization", "Bearer " + participantToken.token);
yield return www.SendWebRequest();
if (www.result != UnityWebRequest.Result.Success)
{
Debug.Log(www.error);
}
else
{
var answer = new RTCSessionDescription { type = RTCSdpType.Answer, sdp = www.downloadHandler.text };
var opRemote = peerConnection.SetRemoteDescription(ref answer);
yield return opRemote;
if (opRemote.IsError)
{
Debug.Log(opRemote.Error);
}
}
}
}

async void OnDestroy()
{
Debug.Log("OnDestroy");
peerConnection.Close();
peerConnection.Dispose();
if (videoTrack != null) videoTrack.Dispose();
if (audioTrack != null) audioTrack.Dispose();
}
}

Testing Multi-Cam Streams

Once we launch the game, we can see that both cameras are broadcasting their own view to the Amazon IVS stage!

Summary

In this post, we learned how to broadcast multiple cameras from a game built in Unity to an Amazon IVS real-time stage. In the next post, we'll switch gears and look at real-time stream playback in a Unity game.
 

Any opinions in this post are those of the individual author and may not reflect the opinions of AWS.