Overview

WCS provides a way to take a snapshot of the published stream using REST-queries as well as using JavaScript API.

Supported protocols

• WebRTC
• RTMP
• RTSP

Supported snapshot formats

• PNG

Operation flowchart

1: Using the REST query

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2: Using JavaScript API

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1. The browser connects to the server via the Websocket protocol and sends the publish command.
2. The browser captures the microphone and the camera and sends the WebRTC stream to the server.
3. The second browser establishes a connection also via Websocket and sends the play command.
4. The second browser receives the WebRTC stream and plays this stream on the page.
5. The second browser invokes stream.snapshot() to take a snapshot.
6. The second browser receives a response with the base64-encoded snapshot of the stream.

REST queries

WCS-server supports the /stream/snapshot REST method to take a snapshot:

A REST-query must be an HTTP/HTTPS POST request as follows:

• HTTP: http://streaming.flashphoner.com:8081/rest-api/stream/snapshot
• HTTPS: https://streaming.flashphoner.com:8444/rest-api/stream/snapshot

Here:

• streaming.flashphoner.com - is the address WCS server
• 8081 - is the standard REST / HTTP port of the WCS server
• 8444 - is the standard HTTPS port
• rest-api - is the required part of the URL
• /stream/snapshot - is the REST method used

REST-methods and response statuses

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REST-method

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Example of the REST query

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Example of the REST response body

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Response statuses

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/stream/snapshot

...

{
  "streamName" : "64966f33"
}

...

{
"data": "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"
}

...

200 - Snapshot is taken

404 - Stream not found

Parameters

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Parameter name

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Description

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Example

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streamName

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Unique stream name

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64966f33

...

data

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Snapshot file encoded to base64

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iVBORw0KGgoAAAANSUhEUgAAAUAAAADwCAYAAABxLb1rAAAACXBIWXMAAAAAAAAAAQCEeRdzAAAQA

Sending the REST query to the WCS server

To send the REST query to the WCS server you need to use a REST-client.

JavaScript API

The snapshot method of the Stream object in WebSDK is intended to take stream snapshots. Example of use of this method can be found in the Stream Snapshot web applications that publishes a stream and take a snapshot.

stream-snapshot.html

stream-snapshot.js

1. Creating a new stream from the published stream

code:

function snapshot(name) {
    setSnapshotStatus();
    var session = Flashphoner.getSessions()[0];
    session.createStream({name: name}).on(STREAM_STATUS.SNAPSHOT_COMPLETE, function(stream){
    ...
}

2. Invoking the snapshot() method

code:

function snapshot(name) {
    setSnapshotStatus();
    var session = Flashphoner.getSessions()[0];
    session.createStream({name: name}).on(STREAM_STATUS.SNAPSHOT_COMPLETE, function(stream){
        ...
    }).snapshot();
}

3. Upon receiving the SNAPSHOT_COMPLETE event, the stream.getInfo() function returns the base64 encoded snapshot

code:

function snapshot(name) {
    setSnapshotStatus();
    var session = Flashphoner.getSessions()[0];
    session.createStream({name: name}).on(STREAM_STATUS.SNAPSHOT_COMPLETE, function(stream){
        console.log("Snapshot complete");
        setSnapshotStatus(STREAM_STATUS.SNAPSHOT_COMPLETE);
        snapshotImg.src = "data:image/png;base64,"+stream.getInfo();
        ...
}

4. The stream stops

code:

function snapshot(name) {
    setSnapshotStatus();
    var session = Flashphoner.getSessions()[0];
    session.createStream({name: name}).on(STREAM_STATUS.SNAPSHOT_COMPLETE, function(stream){
        ...
        stream.stop();
    }).on(STREAM_STATUS.FAILED, function(stream){
        setSnapshotStatus(STREAM_STATUS.FAILED);
        console.log("Snapshot failed, info: " + stream.getInfo());
    }).snapshot();
}

Quick manual on testing

1. For the test we use:

• the demo server at demo.flashphoner.com;
• the Chrome browser and the REST-client to send queries to the server;
• the Two Way Streaming web application to publish the stream;
• the https://www.motobit.com/util/base64-decoder-encoder.asp service to decode the snapshot.

2. Open the page of the Two Way Streaming application. Click "Connect", then click "Publish" to publish the stream:

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3. Open the REST-client. Send the /stream/snapshot query and pass the name of the published stream in parameters:

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5. Open the online decoder and copy the response content to the form, then click "Convert the source data":

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6. Here is the snapshot we have received:

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Call flow

Below is the call flow when using the Stream Snapshot example to publish the stream and take a snapshot

stream-snapshot.html

stream-snapshot.js

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1. Establishing a connection to the server.

Flashphoner.createSession(); code

        Flashphoner.createSession({urlServer: url}).on(SESSION_STATUS.ESTABLISHED, function(session){
            ...
        });

...

ConnectionStatusEvent ESTABLISHED code

        Flashphoner.createSession({urlServer: url}).on(SESSION_STATUS.ESTABLISHED, function(session){
            //session connected, start streaming
            startStreaming(session);
        }).on(SESSION_STATUS.DISCONNECTED, function(){
            ...
        }).on(SESSION_STATUS.FAILED, function(){
            ...
        });

...

stream.publish(); code

    session.createStream({
        name: streamName,
        display: localVideo,
        cacheLocalResources: true,
        receiveVideo: false,
        receiveAudio: false
        ...
    }).publish();

...

StreamStatusEvent, status PUBLISHING code

     session.createStream({
        name: streamName,
        display: localVideo,
        cacheLocalResources: true,
        receiveVideo: false,
        receiveAudio: false
    }).on(STREAM_STATUS.PUBLISHING, function(publishStream){
        setStatus(STREAM_STATUS.PUBLISHING);
        onPublishing(publishStream);
    }).on(STREAM_STATUS.UNPUBLISHED, function(){
        ...
    }).on(STREAM_STATUS.FAILED, function(stream){
        ...
    }).publish();

...

6. Taking a snapshot of the broadcast. A new stream is created from the published one specially to take a snapshot.

stream.snapshot(); code

function snapshot(name) {
    setSnapshotStatus();
    var session = Flashphoner.getSessions()[0];
    session.createStream({name: name}).on(STREAM_STATUS.SNAPSHOT_COMPLETE, function(stream){
        console.log("Snapshot complete");
        setSnapshotStatus(STREAM_STATUS.SNAPSHOT_COMPLETE);
        snapshotImg.src = "data:image/png;base64,"+stream.getInfo();
        //remove failed callback
        stream.on(STREAM_STATUS.FAILED, function(){});
        //release stream object
        stream.stop();
    }).on(STREAM_STATUS.FAILED, function(stream){
        setSnapshotStatus(STREAM_STATUS.FAILED);
        console.log("Snapshot failed, info: " + stream.getInfo());
    }).snapshot();
}

7. Stopping publishing the stream.

stream.stop(); code

function onPublishing(stream) {
    $("#publishBtn").text("Stop").off('click').click(function(){
        $(this).prop('disabled', true);
        stream.stop();
    }).prop('disabled', false);
    ...
}

8. Receiving from the server an event confirming unpublishing the stream.

StreamStatusEvent, status UNPUBLISHED code

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