Overview

A video stream is captured from an RTSP source that provides audio and video in the supported codecs. Then, the server transforms this video stream for playing in browsers and mobile devices.

RTSP sources:

• IP cameras
• Media servers
• Surveillance systems
• Conference servers

Supported codecs:

• H.264
• VP8
• AAC
• G.711
• Speex

Supported platforms and browsers

Operation flowchart

1. The browser establishes a connection to the server via the Websocket protocol and sends the play command.

2. The server connects to the RTSP source and send the play command.

3. The RTSP source sends the RTSP stream to the server.

4. The server transforms the stream to WebRTC and gives the stream to the browser.

Configuration

Sometimes, when IP camera should be connected through VPN, RTSP client should be bound to certain IP address. The option rtsp_client_address in settings file flashphoner.properties defines this address, for example:

rtsp_client_address=172.16.0.3

Quick manual on testing

Capturing of a video stream from the IP camera and playing it in a browser

1. For this test we use:

• the demo server at demo.flashphoner.com;
• the Player web application to play the captured stream in the browser.

2. Open the Player web app and specify the URL of the camera in the "Stream" field:

3. Click the "Start" button. Broadcasting of the captured stream begins.

4. WebRTC internals diagrams:

Stream capture from the IP camera management by REST API

Usually, it is enough to set the camera URL as stream name to capture stream from IP camera. However, it is possible to manage RTSP stream capture by REST API if necessary.

Testing

1. For this test we use:

• the demo server at demo.flashphoner.com;
• the Chrome browser and the REST-client to send queries to the server;
• the Player web application to play the captured stream in the browser.

2. Open the REST client. Send the /rtsp/startup query specifying the URL of the web camera in parameters:

3. Make sure the stream is captured by the server. To do this, send the /rtsp/find_all query:

4. Open the Player web app and in the "Stream" field specify the URL of the web camera and click Start. Browser starts to play the stream:

5. Send the /rtsp/terminate query specifying the URL of the web camera in parameters:

6. Stream playback will terminate displaying an error:

REST-queries

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

• HTTP: http://test.flashphoner.com:9091/rest-api/rtsp/startup
• HTTPS: https://test.flashphoner.com:8888/rest-api/rtsp/startup

Where:

• test.flashphoner.com - is the address of the WCS server
• 9091 - is the standard REST / HTTP port of the WCS server
• 8888 - is the standard HTTPS port
• rest-api - is the required part of the URL
• /rtsp/startup - REST-method to use

REST-methods and response statuses

{
 "uri":"rtsp://myserver.com/live/myStream"
}

{
"uri": "rtsp://myserver.com/live/myStream",
"status": "PLAYING"
}

{
"uri":"rtsp://myserver.com/live/myStream"
}

Parameters

Call flow

Below is the call flow when using the Player example

player.html

player.js

1. Establishing a connection to the server.

Flashphoner.createSession(); code

    Flashphoner.createSession({urlServer: url}).on(SESSION_STATUS.ESTABLISHED, function(session){
        setStatus(session.status());
        //session connected, start playback
        playStream(session);
    }).on(SESSION_STATUS.DISCONNECTED, function(){
        setStatus(SESSION_STATUS.DISCONNECTED);
        onStopped();
    }).on(SESSION_STATUS.FAILED, function(){
        setStatus(SESSION_STATUS.FAILED);
        onStopped();
    });

2. Receiving from the server an event confirming successful connection.

ConnectionStatusEvent ESTABLISHED code

    Flashphoner.createSession({urlServer: url}).on(SESSION_STATUS.ESTABLISHED, function(session){
        setStatus(session.status());
        //session connected, start playback
        playStream(session);
    }).on(SESSION_STATUS.DISCONNECTED, function(){
        ...
    }).on(SESSION_STATUS.FAILED, function(){
        ...
    });

3. Request to play the stream.

session.createStream(), stream.play(); code

IP camera URL is passed to createStream() method as stream name

function playStream(session) {
    var streamName = $('#streamName').val();
    var options = {
        name: streamName,
        display: remoteVideo,
        flashShowFullScreenButton: true
    };
    ...    
    stream = session.createStream(options).on(STREAM_STATUS.PENDING, function(stream) {
        var video = document.getElementById(stream.id());
        if (!video.hasListeners) {
            video.hasListeners = true;
            video.addEventListener('playing', function () {
                $("#preloader").hide();
            });
            video.addEventListener('resize', function (event) {
                var streamResolution = stream.videoResolution();
                if (Object.keys(streamResolution).length === 0) {
                    resizeVideo(event.target);
                } else {
                    // Change aspect ratio to prevent video stretching
                    var ratio = streamResolution.width / streamResolution.height;
                    var newHeight = Math.floor(options.playWidth / ratio);
                    resizeVideo(event.target, options.playWidth, newHeight);
                }
            });
        }
        ...
    });
    stream.play();
}

4. Request from WCS to the RTSP source to broadcast the stream.

5. Broadcasting the RTSP stream

6. Receiving from the server an event confirming successful capturing and playing of the stream.

StreamStatusEvent, статус PLAYING code

    stream = session.createStream(options).on(STREAM_STATUS.PENDING, function(stream) {
        ...
    }).on(STREAM_STATUS.PLAYING, function(stream) {
        $("#preloader").show();
        setStatus(stream.status());
        onStarted(stream);
        ...
    });
    stream.play();

7. Sending audio- and video stream via WebRTC

8. Stopping playing the stream.

stream.stop(); code

function onStarted(stream) {
    $("#playBtn").text("Stop").off('click').click(function(){
        $(this).prop('disabled', true);
        stream.stop();
    }).prop('disabled', false);
    $("#fullScreenBtn").off('click').click(function(){
       stream.fullScreen();
    }).prop('disabled', false);
    $("#volumeControl").slider("enable");
    stream.setVolume(currentVolumeValue);
}

9. Receiving from the server an event confirming successful stop of the stream playback.

StreamStatusEvent, статус STOPPED code

    stream = session.createStream(options).on(STREAM_STATUS.PENDING, function(stream) {
        ...
    }).on(STREAM_STATUS.PLAYING, function(stream) {
        ...
    }).on(STREAM_STATUS.STOPPED, function() {
        setStatus(STREAM_STATUS.STOPPED);
        onStopped();
    }).on(STREAM_STATUS.FAILED, function(stream) {
        ...
    }).on(STREAM_STATUS.NOT_ENOUGH_BANDWIDTH, function(stream){
        ...
    });
    stream.play();

Known issues

1. A stream containing B-frames does not play or plays with artifacts (latencies, lags)

Symptoms:

• a stream sent by the IP camera via RTSP does not play or plays with latencies or lags
• warnings in the client log:

09:32:31,238 WARN 4BitstreamNormalizer - RTMP-pool-10-thread-5 It is B-frame!

Solution: request lower resolution video from the camera to avoid using B-frames or transcode that stream.

2. Connection to the IP camera is lost on error in any track (audio or video)

Symptoms: connection to the IP camera is lost if one of tracks returns error 4**.
Solution: this behavior is enabled by default. However if one-time errors are not critical and should not terminate broadcasting, in the flashphoner.properties files set

rtsp_fail_on_error_track=false
rtp_force_synchronization=true

3. AAC frames of type 0 are not supported by decoder and will be ignored while stream pulled playback

In this case, warnings will be displayed in the client log:

10:13:06,815 WARN AAC - AudioProcessor-c6c22de8-a129-43b2-bf67-1f433a814ba9 Dropping AAC frame that starts with 0, 119056e500

function playStream(session) {
    var streamName = $('#streamName').val();
    var options = {
        name: streamName,
        display: remoteVideo,
        flashShowFullScreenButton: true
    };
    ...    
    stream = session.createStream(options).on(STREAM_STATUS.PENDING, function(stream) {
        var video = document.getElementById(stream.id());
        if (!video.hasListeners) {
            video.hasListeners = true;
            video.addEventListener('playing', function () {
                $("#preloader").hide();
            });
            video.addEventListener('resize', function (event) {
                var streamResolution = stream.videoResolution();
                if (Object.keys(streamResolution).length === 0) {
                    resizeVideo(event.target);
                } else {
                    // Change aspect ratio to prevent video stretching
                    var ratio = streamResolution.width / streamResolution.height;
                    var newHeight = Math.floor(options.playWidth / ratio);
                    resizeVideo(event.target, options.playWidth, newHeight);
                }
            });
        }
        ...
    });
    stream.play();
}