Capture Activities on Screen in a Movie

• Download source and demo files - 82.4 Kb

Introduction

bkniazi asked me a question on experts-exchange.com, about how to capture the activities going on on a machine as a movie. I found the question interesting, so looked for it, but could not find any good solution for it. Though, I found some software which do this kind of work. I found Windows Media Encoder 9 very interesting. While looking into it, I found its SDK and I started looking into it. It is quite interesting. So I made this small sample after looking into the API and seeing some samples.

Prerequisites

You will be needing Windows Media Encoder 9 Series and SDK.

Using the code

Best thing about this API is that it is totally interface based. WMEncoder is the main class. Set its parameters and start the encoder to start encoding. Stop it to save in file.

Encoder = New WMEncoder

Create a Source Group named SG_1 in Encoder's Collection.

Dim SrcGrp As IWMEncSourceGroup2
Dim SrcGrpColl As IWMEncSourceGroupCollection
SrcGrpColl = Encoder.SourceGroupCollection
SrcGrp = SrcGrpColl.Add("SG_1")

Specify the input types for Video and Audio. Specify the screen capture plug-in to set up the video source.

SrcVid.SetInput("ScreenCap://ScreenCapture1")
SrcAud.SetInput("Device://Default_Audio_Device")

Find the profile and set Encoder's group profile from all the profiles available.

ProColl = Encoder.ProfileCollection
lLength = ProColl.Count
For i = 0 To lLength - 1
    Pro = ProColl.Item(i)
    If Pro.Name = "Windows Media Video 8 for Local Area Network (384 Kbps)" Then
        SrcGrp.Profile = Pro
        Exit For
    End If
Next

Specify header information of the Encoder. I.e., description or attributes.

Dim Descr As IWMEncDisplayInfo
Descr = Encoder.DisplayInfo
Descr.Author = "Armoghan Asif"
Descr.Copyright = "Copyright information"
Descr.Description = "Text description of encoded content"
Descr.Rating = "Rating information"
Descr.Title = "Title of encoded content"

' Add an attribute to the collection.
Dim Attr As IWMEncAttributes
Attr = Encoder.Attributes
Attr.Add("URL", "IP address")

You may do some cropping of the Encoder if required.

' Crop 2 pixels from each edge of the video image.
SrcVid.CroppingBottomMargin = 2
SrcVid.CroppingTopMargin = 2
SrcVid.CroppingLeftMargin = 2
SrcVid.CroppingRightMargin = 2

Specify the Local File as output. You may also set additional fields of the file, like size of file, seconds of file etc.

Dim File As IWMEncFile
File = Encoder.File
File.LocalFileName = "C:\OutputFile.avi"

Start the encoding process:

' Start the encoding process.
Encoder.Start()

Stop the encoding process:

' Stop the encoding process.
Encoder.Stop()

Points of Interest

No fancy things are placed in the demo. It just illustrates the screen capture. It can be easily added in any existing application. Nothing else :)