Encoders

Fraunhofer FDK AAC (Advanced Audio Coding)

• Type/Purpose: Modern, high-performance audio encoder achieving great results even at low bitrates. It is a data compression method that can sound similar to a non-compressed file at high bitrates.

• Encoders Available:

  • Fraunhofer FDK-AAC (all platforms): Industry-standard reference encoder, considered one of the best AAC encoders (with Apple's being arguably superior).

  • Apple AudioToolbox AAC (macOS only): Native, hardware-accelerated encoder optimized for Apple Silicon.

• Bitrate Details:

  • Simple Mode: Set to 256 kbit/s, which gives very good results.

  • Maximum Bitrate: 512 kbit/s.

  • Quality Note: At 320 kbit/s, the encoder tends to lose almost all of its encoding artifacts.

• Filesize Example: Thirty seconds of audio encoded with 256 kbit/s results in approximately 1 MB filesize.

Opus Interactive Audio Format

• Type/Purpose: One of the newest audio encoders available. It's a modern data compression method that achieves very good results even with lower bitrates. It's an open-source format.

• Best Suited For: Live applications due to its low algorithmic delay. It is also exceptionally great for human voice (radio, etc.) as it can be optimized for speech (utilized by TNT by a click of a button).

• Bitrate Details:

  • Minimum Bitrate: 6 kbit/s (UI limits the minimum to 12 kbit/s).

  • Maximum Bitrate: 510 kbit/s.

FLAC (Free Lossless Audio Codec)

• Type/Purpose: A lossless compression format that compresses audio without any quality loss, preserving the original audio data perfectly.

• Ideal For: A wide range of applications such as archiving or digital delivery/fidelity when perfect audio fidelity is required.

• Compression/Filesize: Reduces file size significantly (typically 40-60% of uncompressed PCM, depending on the compression level selected) while keeping the decompressed audio perfect. It is widely supported.

LAME / MPEG-II Layer 3 (MP3)

• Type/Purpose: An older format, but one of the most compatible encoding formats available. Use this if the end-user may not be able to decode AAC or Opus.

• Quality/Bitrate: It's not as capable at lower bitrates compared to AAC or Opus, but is usable at high bitrates (>320 kbit/s).

• Filesize Example: Filesize for MP3 at 160 kbit/s for 30 second audio file is 0.6 MB.

PCM (Pulse Code Modulation) / WAV

• Type/Purpose: Raw, uncompressed audio data (WAV is the container) used to digitally represent analog signals. It's the highest quality, but comes with the largest size cost.

• Bitrate/Settings: This format does not have a single bitrate setting but is determined by two other settings:

  • Sample Rate: (e.g., 44.1, 48, 88.2, 96, 192 kHz) - Dictates how often the original data is converted into audio in a second (e.g., 48 kHz samples 48,000 times per second).

  • Bit Depth: (16, 24, 32, or 64) - Controls how precisely each sample is captured (32 and 64 are floating-point, used in specific scenarios).

• Filesize Example: A thirty-second audio file with 48 kHz, 24-bit audio is 8.64 MB.