RTMP(3) - Flash Media Live Encoder的使用

Every now and then an amazing piece of software hits the street. Inevitably,the company puts it out in public beta and you can't help but think,at some point in the process,"Dang,this is sweet. I sure hope I can afford it." I had that reaction when I first tried out Flash Media Live Encoder (FME). If the truth be known,I still have a hard time grasping the fact that this powerful piece of software is a freebie.

Its purpose is quite focused: to grab a video or audio feed,on the fly,and either encode it or stream it out—live. In this part of the exercise,I'll take you through the FME interface and use it to create an FLV. Keep in mind this will be a "drive-by" exercise; I won't get into the nuts and bolts of using FME. My colleague,Greg Hamer,has already done a really good overview of this process in his article, Webcasting live video with Flash Media Live Encoder.

Follow these steps to make the initial configuration in Flash Media Live Encoder:

1. Make sure you have a webcam (microphone is optional) attached to your computer,and then launch Flash Media Live Encoder. When it opens (see Figure 1),you will see that the interface is essentially divided into two distinct areas: Input on the left and Output on the right. If you don't want the split Input and Output view,deselect the Output Video option. All this does is remove the preview on the right. It has no effect on the final file.

Figure 1. Flash Media Live Encoder interface (click to enlarge)

The input area is further subdivided into separate Video and Audio areas where you can tweak the settings prior to capture or broadcast. If you are unsure of the settings to use,select one of the three presets in the Preset pop-up menu. Still,it doesn't hurt to try this application out,so let's create a simple capture.

2. Select your webcam from the Device pop-up menu. I am using a MacBook Pro with a built-in iSight camera,which explains why I can select only USB Video Device. Were I to have more than one camera connected to my computer,I would be able to choose either my iSight or the Logitech webcam plugged into my USB hub (see Figure 2).

Note: You can use a variety of webcams and even digital video recorders to capture the video. As it says in the FME support documents: Flash Media Live Encoder is designed to work with any Microsoft DirectShow–compliant device or driver. For a list of devices that Adobe has specifically tested,visit the Flash Media Live Encoder Device Compatibility Matrix (PDF,13K). This list is in no way definitive; it simply lists devices tested by Adobe so far. Your first clue as to its (in)completeness should be the missing iSight camera.

3. In the format pop-up menu,select VP6. This will be the codec used to compress the resulting FLV file. The other choice is H.264. If you have a DV camera that can do HD,select this one. Just be aware that the resulting file won't be the expected QuickTime file. It will be an F4V file,which is the FLV equivalent of an MP4 file.
4. Select a bit rate of 350 Kbps from the pop-up menu. You will be running this out locally,so 350 Kbps will pose no issues.
5. Select 640 × 480 as the physical size for the FLV file and set the frame rate to 24 fps by selecting it from the Frame Rate pop-up menu.
6. If you use an external microphone,such as the R?de Podcaster I use,select it from the Audio Device pop-up menu.
7. Set the audio format to MP3 Mono.
8. Finally,select 22050 kHz from the Sample rate pop-up menu and set the bit rate to 48 Kbps.
9. Use the volume slider to adjust the volume levels of the microphone.

At the bottom of the window,you will see the total bit rate,which is the sum of the audio and video bit rates. This is an important number because it has a direct effect on user experience. If you are unsure as to what numbers to use,head over to Robert Reinhardt's Flash Video Bitrate Calculator.

Having dealt with FLV settings,you can turn your attention to actually creating the FLV file:

1. In the Output area,deselect Stream to Flash Media Server. You don't need this because this capture won't be live.
2. Click the Browse button to open the Save As dialog box. Navigate to your vod folder (C:Program FilesAdobeFlash Media Server 3.5applicationsvodmedia),name the file,and click the Save button.
3. To start recording and creating the FLV file,click the green Start button. When you click this button,the interface switches to show you the log,which informs you that the video recording process has started (see Figure 3). When you see your video preview,start moving and talking.
4. To finish recording,click the red Stop button. You will be returned to the FME interface.
5. If you wish,feel free to quit FME.

Now that you have created an FLV file,it's time to play it:

1. Launch Flash CS4 Professional (or CS3) and create a new ActionScript 3.0 document.
2. Set the Stage size to 640 × 520 to match the dimensions of the FLV just created and to leave room for the FLVPlayback skin.
3. Drag a copy of the FLVPlayback component to the Stage and set its dimensions to 640 × 480. With the component selected,select Window > Component inspector if you are using Flash CS4 (or click the Parameters tab in the Property inspector if you are using Flash CS3).
4. Double-click the skin parameter and select SkinUnderAllNoFullNoCaption.swf. Click OK.
5. Click the source parameter and enter rtmp://localhost/vod/YourFLVName. Keep in mind that you only need to enter the name of the FLV; you don't need the extension.
6. Save and test the file. As shown in Figure 4,your webcam or other device has moved from an interesting,fun tool to something really practical and important.