# Windows Media Audio encoder

Video Capture SDK .Net Video Edit SDK .Net Media Blocks SDK .Net

Windows Media Audio (WMA) is a popular audio codec developed by Microsoft for efficient audio compression. This documentation covers the WMA encoder implementations available in the VisioForge .Net SDKs.

# Overview

The VisioForge SDK provides two distinct approaches for WMA encoding: the platform-specific WMAOutput for Windows environments and the cross-platform WMAEncoderSettings. Let's explore both implementations in detail to understand their capabilities and use cases.

# Cross-platform WMA output

VideoCaptureCoreX VideoEditCoreX MediaBlocksPipeline

The WMAEncoderSettings provides a cross-platform solution for WMA encoding. This implementation is built on SDK and offers consistent behavior across different operating systems.

# Key Features

The encoder supports the following audio configurations:

  • Sample rates: 44.1 kHz and 48 kHz
  • Bitrates: 128, 192, 256, and 320 Kbps
  • Channel configurations: Mono (1) and Stereo (2)

# Rate Control

The WMA encoder implements constant bitrate (CBR) encoding, allowing you to specify a fixed bitrate from the supported values. This ensures consistent audio quality and predictable file sizes throughout the encoded content.

# Usage Example

Add the WMA output to the Video Capture SDK core instance:

// Create a Video Capture SDK core instance
var core = new VideoCaptureCoreX();

// Create a WMA output
var wmaOutput = new WMAOutput("output.wma");
wmaOutput.Audio.SampleRate = 48000;
wmaOutput.Audio.Channels = 2;
wmaOutput.Audio.Bitrate = 320;

// Add the WMA output
core.Outputs_Add(wmaOutput, true);

Set the output format for the Video Edit SDK core instance:

// Create a Video Edit SDK core instance
var core = new VideoEditCoreX();

// Create a WMA output
var wmaOutput = new WMAOutput("output.wma");
wmaOutput.Audio.SampleRate = 48000;
wmaOutput.Audio.Channels = 2;
wmaOutput.Audio.Bitrate = 320;

// Add the WMA output
core.Output_Format = wmaOutput;

Create a Media Blocks WMA output instance:

// Create a WMA encoder settings instance
var wmaSettings = new WMAEncoderSettings();

// Create a WMA output instance
var wmaOutput = new WMAEncoderBlock(wmaSettings);

// Create a ASF output instance
var asfOutput = new ASFSinkBlock(new ASFSinkSettings("output.wma"));

// Connect the WMA encoder to the ASF output
pipeline.Connect(wmaOutput.Output, asfOutput.Input); // pipeline is MediaBlocksPipeline

Check if MP3 encoding is available.

if (!MP3EncoderSettings.IsAvailable())
{
   // Handle error
}

# Windows-only WMA output

VideoCaptureCore VideoEditCore

The WMAOutput class provides a comprehensive Windows-specific implementation with advanced features and configuration options. This implementation leverages the Windows Media Format SDK for optimal performance on Windows systems.

# Key Features

The Windows-specific implementation offers:

  • Multiple profile support (internal, external, and custom)
  • Language and localization settings
  • Quality-based encoding
  • Advanced bitrate control with peak bitrate settings
  • Buffer size configuration

# Rate Control

The Windows implementation supports three stream modes through the WMVStreamMode enumeration:

  • CBR (Constant Bitrate)
  • VBR (Variable Bitrate)
  • Quality-based VBR

# Usage Example

Here's how to set up the Windows-specific WMA encoder:

Use an internal profile for simple configuration

var wmaOutput = new WMAOutput
{
    // Use an internal profile for simple configuration
    Mode = WMVMode.InternalProfile,
    Internal_Profile_Name = "Windows Media Audio 9 High (192K)"
};

core.Output_Format = wmaOutput; // Core is VideoCaptureCore or VideoEditCore

Or configure custom settings

var wmaOutput = new WMAOutput
{
    Mode = WMVMode.CustomSettings,
    Custom_Audio_StreamPresent = true,
    Custom_Audio_Quality = 98,        // High quality setting
    Custom_Audio_PeakBitrate = 320,   // Maximum bitrate in Kbps
    Custom_Audio_PeakBufferSize = 3   // Buffer size for streaming
};

core.Output_Format = wmaOutput; // Core is VideoCaptureCore or VideoEditCore

# Profile Management

The Windows implementation supports three profile modes:

  1. Internal Profiles:

    • Pre-configured profiles for common use cases
    • Access through Internal_Profile_Name

  2. External Profiles:

    • Load profiles from external files
    • Configure using External_Profile_FileName or External_Profile_Text

  3. Custom Profiles:

    • Fine-grained control over encoding parameters
    • Configure through Custom_* properties

# Best Practices

When implementing WMA encoding in your application:

  1. For Windows applications requiring advanced features:

    • Use WMAOutput for access to Windows-specific optimizations
    • Consider saving configurations to JSON for reuse
    • Implement proper error handling for profile loading

  2. For cross-platform applications:

    • Stick to WMAEncoderSettings for consistent behavior
    • Verify supported rates before setting configuration
    • Use the highest supported sample rate and bitrate for best quality

This documentation provides a foundation for implementing WMA encoding in your applications. The choice between cross-platform and Windows-specific implementations should be based on your application's requirements for platform support, encoding features, and quality control.