Section 6.4. Building a Surveillance Application

6.4. Building a Surveillance Application

In the previous example, you had the chance to build an application that uses the Camera and Microphone classes. Next , we'll build a simple surveillance application that records to a stream only when the activity levels are high enough to warrant it.

To build the application, complete the following steps:

1. Create a new FlashCom application on the server. Within the FlashCom applications directory, create a new subdirectory named surveillance .

2. Create a new Flash document, and save it as Surveillance.fla .

3. Within the Flash document, create a new Video symbol in the Library.

4. Create an instance of the Video symbol on the main timeline, and give it the instance name content_vid . Place the instance approximately in the center of the Stage.

5. Create a TextArea component instance on the Stage just below the Video object. Use the Properties panel to give it an instance name of ctaLog and change its dimensions to 160 x 200.

6. Rename the default layer to Contents , and create a new layer above it named Actions .

7. Select the first keyframe of the Actions layer, and open the Actions panel.

8. Add the following code to the Actions panel:

    // Create the Camera and Microphone objects. var user_mic = Microphone.get( ); var user_cam = Camera.get( ); // Create the NetConnection object to connect to the server. var fcs_nc = new NetConnection( ); // Create a NetStream variable. var record_ns; // Initialize two Boolean variables to false. They indicate whether the // activity level is high enough and whether the stream is currently recording. var activity = false; var recording = false; // Set the minimum activity level for the microphone and camera. user_mic.setSilenceLevel(10, 2000); user_cam.setMotionLevel(50, 2000); // Set the camera mode and quality. user_cam.setMode(320, 240, 30); user_cam.setQuality(0, 100); // Attach the video to the Video object. content_vid.attachVideo(user_cam); // Connect to the FlashCom application, and open a stream. fcs_nc.connect("rtmp:/ surveillance"); record_ns = new NetStream(fcs_nc); // Determine when the microphone and camera are activated and deactivated. // In all cases, call the   calculate( )   function. user_mic.onActivity = function (activated) {   calculate(activated); }; user_cam.onActivity = function (activated) {   calculate(activated); }; //   calculate( )   determines what action should take place when // the microphone and/or camera is activated or deactivated. function calculate (activated) {   activity = activated;   if (activity && !recording) {     startRecording( );   }   else if (!activity && recording) {     pauseRecording( );   } }; // Start recording the stream. function startRecording ( ) {   recording = true;   record_ns.attachAudio(user_mic);   record_ns.attachVideo(user_cam);   record_ns.publish("security", "append");   // Display date/time recording begins, such as "Thu Dec 9 22:32:32 GMT-0500 2004"   ctaLog.text += "Started recording" + new Date( ) + newline; } // Stop recording the stream. function pauseRecording ( ) {   recording = false;   record_ns.publish(false);   ctaLog.text += "Paused recording" + new Date( ) + newline; } // Initialize application by starting to record. startRecording( ); 

   
   

9. Test the movie. You should see the TextArea report when the video is recording and pausing.

10. Create a new Flash document, and save it as SurveillanceView.fla .

11. Create a new Video symbol in the Library of SurveillanceView.fla .

12. Create an instance of the Video object on the Stage, and give it an instance name of content_vid .

13. Rename the default layer to Content , and create a new layer named Actions .

14. Select the first keyframe of the Actions layer, and open the Actions panel.

15. Add the following code to the Actions panel:

     // Create the NetConnection object, and connect to the FlashComm // application on the server. var fcs_nc = new NetConnection(  ); fcs_nc.connect("rtmp:/surveillance"); // Create the NetStream object, and play back the stream. var playback_ns = new NetStream(fcs_nc); playback_ns.play("security"); content_vid.attachVideo(playback_ns); 

    
    

16. Test the movie. You should see the surveillance stream play. Only the portions in which the activity level was high enough were recorded.

The code from SurveillanceView.fla is fairly straightforward. However, the code from Surveillance.fla is complex enough that it could benefit from some further explanation.

As with any application that uses audio and video input, the first step is to create Camera and Microphone objects:

 var user_mic = Microphone.get(  ); var user_cam = Camera.get(  ); 

After creating the NetConnection object and a variable to store the NetStream object, you next want to declare and initialize two Boolean variables. The activity variable indicates whether the activity level of the microphone and/or camera is currently high enough. The recording variable simply indicates whether the stream is currently recording.

 var activity = false; var recording = false; 

The application records audio and video only when the activity levels exceed the thresholds set via Microphone.setSilenceLevel( ) and Camera.setMotionLevel( ) . In the example code, the minimum activity levels are set to 10 and 50, with a 2-second timeout. You may want to adjust those levels in your own application if you find that they are not optimal.

 user_mic.setSilenceLevel(10, 2000); user_cam.setMotionLevel(50, 2000); 

Even when the stream is not recording, the code still displays the video. Cameras usually take a short while to initialize, and so the delay could cause difficulties if you had to reinitialize the camera connection each time you resumed recording. By continuously displaying the camera input in the Video object, we initialize the camera only once:

 content_vid.attachVideo(user_cam); 

The onActivity( ) event handlers are called automatically when the microphone or camera is activated or deactivated. This surveillance application handles both in the same way, so each of the event handler methods simply proxies the call to a custom function called calculate( ) .

The calculate( ) function determines what action should take place when a camera and/or microphone is activated and/or deactivated. It's not as simple as starting to publish the stream when one of the devices is activated and stopping it when one of the devices is deactivated. Remember that, since either device can cause the stream to start publishing, you need to check to see whether the stream is already being published. The calculate( ) function does that. It starts to publish the stream (by calling startRecording( ) ) only if the activity level is high enough and if the recording variable is false . Otherwise, it stops publishing the stream only if the activity level is not high enough and the stream is currently publishing.

Publishing the stream is fairly basic. Of course, you'll want to set the recording variable to true so that Flash will be able to make the appropriate calculations subsequently. Then, as usual, attach the audio and video to the NetStream object and publish it. Additionally, add a line of text to the text area to indicate when the stream started recording:

 function startRecording (  ) {   recording = true;   record_ns.attachAudio(user_mic);   record_ns.attachVideo(user_cam);   record_ns.publish("security", "append");   // Display date/time recording begins, such as "Thu Dec 9 22:32:32 GMT-0500 2004"   ctaLog.text += "Started recording" + new Date( ) + newline; } 

Pausing the stream is also very basic. Of course, you'll want to set recording to false so adjustments can be made correctly when a microphone or camera is activated or deactivated. Then, as usual, call publish( ) with a value of false to stop publishing the stream. And add a line of text to the text area to indicate when the stream paused:

 function pauseRecording (  ) {   recording = false;   record_ns.publish(false);   ctaLog.text += "Paused recording" + new Date( ) + newline; }