MP3 encoder

SDK contains MP3 audio encoder that can be used to encode audio streams to MP3 format using the LAME library. MP3 is a lossy audio compression format that is widely used in audio streaming and storage.

You can use MP3 encode to encode audio in MP4, AVI, MKV, and other containers.

Cross-platform MP3 output (X-engines: VideoCaptureCoreX, VideoEditCoreX, Media Blocks)

The MP3EncoderSettings class provides a straightforward way to configure MP3 encoding with support for different rate controls and quality settings.

Supported Formats and Specifications

• Input Format: S16LE (Signed 16-bit Little Endian)
• Sample Rates: 8000, 11025, 12000, 16000, 22050, 24000, 32000, 44100, 48000 Hz
• Channels: Mono (1) or Stereo (2)

Rate Control Modes

The encoder supports three rate control modes:

1. CBR (Constant Bit Rate)

   • Fixed bitrate throughout the entire encoding process
   • Supported bitrates: 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320 Kbit/s
   • Best for streaming and when consistent file size is important

2. ABR (Average Bit Rate)

   • Maintains an average bitrate while allowing some variation
   • More efficient than CBR while still maintaining predictable file sizes
   • Useful for streaming services that need approximate file size estimates

3. Quality-based VBR

   • Variable Bit Rate based on sound complexity
   • Quality setting ranges from 0 (best) to 10
   • Most efficient for storage and best quality-to-size ratio

Sample Usage

Create basic MP3 encoder settings with CBR.

var mp3Settings = new MP3EncoderSettings
{
    RateControl = MP3EncoderRateControl.CBR,
    Bitrate = 192,
    EncodingEngineQuality = MP3EncodingQuality.Standard,
    ForceMono = false
};

Quality-based VBR configuration.

var vbrSettings = new MP3EncoderSettings
{
    RateControl = MP3EncoderRateControl.Quality,
    Quality = 2.0f,  // High quality VBR
    EncodingEngineQuality = MP3EncodingQuality.High
};

Add the MP3 output to the Video Capture SDK core instance:

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

// Create a MP3 output instance
var mp3Output = new MP3Output("output.mp3");

// Set the bitrate
mp3Output.Audio.RateControl = MP3EncoderRateControl.CBR;
mp3Output.Audio.Bitrate = 128;

// Add the MP3 output
core.Outputs_Add(mp3Output, 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 MP3 output instance
var mp3Output = new MP3Output("output.mp3");

// Set the quality 
mp3Output.Audio.RateControl = MP3EncoderRateControl.Quality;
mp3Output.Audio.Quality = 5.0f;

// Set the output format
core.Output_Format = mp3Output;

Create a Media Blocks MP3 output instance:

// Create a MP3 encoder settings instance
var mp3Settings = new MP3EncoderSettings();

// Create a MP3 output instance
var mp3Output = new MP3OutputBlock("output.mp3", mp3Settings);

Check if MP3 encoding is available.

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

Encoding Quality Levels

The encoder supports three quality presets that affect the encoding speed and CPU usage:

• Fast: Quickest encoding, lower CPU usage
• Standard: Balanced speed and quality (default)
• High: Best quality, higher CPU usage

Common Scenarios

High-Quality Music Encoding

var highQualitySettings = new MP3EncoderSettings
{
    RateControl = MP3EncoderRateControl.Quality,
    Quality = 0.0f,
    EncodingEngineQuality = MP3EncodingQuality.High
};

Streaming Audio

var streamingSettings = new MP3EncoderSettings
{
    RateControl = MP3EncoderRateControl.CBR,
    Bitrate = 128,
    EncodingEngineQuality = MP3EncodingQuality.Fast
};

Windows-only MP3 output (VideoCaptureCore and VideoEditCore engines)

The MP3 file output class provides advanced configuration options for MP3 encoding in video capture and editing scenarios.

Key Features

• Flexible channel mode selection
• VBR and CBR encoding support
• Advanced encoding parameters
• Quality control settings

Channel Modes

The MP3Output supports four channel modes:

1. Standard Stereo

   • Independent channel encoding
   • Best for tracks with significant stereo separation

2. Joint Stereo

   • Uses mid/side stereo coding
   • Efficient for most stereo content
   • Default for VBR below quality level 4 or CBR below 160kbps

3. Dual Stereo

   • Independent encoding with equal bitrate allocation
   • Useful for dual-language content

4. Mono

   • Single channel output
   • 6dB attenuated downmix for stereo inputs

Sample Usage

Basic settings.

var mp3Output = new MP3Output
{
    CBR_Bitrate = 192,
    SampleRate = 44100,
    ChannelsMode = MP3ChannelsMode.JointStereo,
};

core.Output_Format = mp3Output; // Core is VideoCaptureCore or VideoEditCore

VBR configuration.

var mp3Output = new MP3Output
{    
    VBR_Mode = true,
    VBR_MinBitrate = 96,
    VBR_MaxBitrate = 192,
    VBR_Quality = 6,
};

core.Output_Format = mp3Output; // Core is VideoCaptureCore or VideoEditCore

Advanced options.

var mp3Output = new MP3Output
{
    EncodingQuality = 6,
    EnableXingVBRTag = true,
    Copyright = false,
    Original = true
};

core.Output_Format = mp3Output; // Core is VideoCaptureCore or VideoEditCore

Advanced Settings

• CRC Protection: Adds error detection capability at the cost of 16 bits per frame
• Short Blocks: Can be disabled to potentially increase quality at very low bitrates
• Frequency Range: Option to keep all frequencies (disables automatic lowpass filtering)
• Voice Mode: Experimental mode optimized for voice content

Best Practices

1. Choosing Rate Control

   • Use CBR for streaming and real-time applications
   • Use Quality-based VBR for archival and highest quality
   • Use ABR when you need a balance between consistent size and quality

2. Quality Settings

   • For archival: Use VBR with quality 0-2
   • For general use: VBR with quality 3-5 or CBR 192-256kbps
   • For voice: Consider using voice encoding mode with lower bitrates

3. Channel Mode Selection

   • Use Joint Stereo for most music content
   • Use Standard Stereo for critical listening and complex stereo mixes
   • Use Mono for voice recordings or when bandwidth is critical

4. Performance Optimization

   • Use Fast encoding quality for real-time applications
   • Use Standard quality for general purpose encoding
   • Use High quality only for archival purposes where encoding time is not critical