Sample Rates

Sample Rates in Rivendell

This page documents how audio sample rates are handled in the Rivendell Radio Automation System, including supported rates, configuration considerations, and best practices for production and ingestion.

Overview

Rivendell supports a fixed system‑wide sample rate. All audio stored in the Rivendell audio store must match the system's configured rate to ensure correct playback, timing accuracy, and log integrity.

Unlike some modern media systems, Rivendell does not transparently mix or resample audio files with differing sample rates at runtime.

Supported Sample Rates

Rivendell supports the following PCM audio sample rates:

• 44,100 Hz (44.1 kHz)
• 48,000 Hz (48 kHz)

Only **one sample rate may be used per Rivendell system at a time**, and all audio files must match the configured rate.

Important: The chosen sample rate is a system‑level configuration decision. Mixing 44.1 kHz and 48 kHz audio in the same Rivendell system is not supported.

Choosing a Sample Rate

44.1 kHz

44.1 kHz has historically been the most common Rivendell configuration.

Advantages:

• Compatible with legacy CD‑based and broadcast workflows
• Widely used in existing Rivendell installations
• Proven stability

48 kHz

48 kHz is commonly used in modern broadcast and video‑adjacent workflows.

Advantages:

• Industry standard for video and many modern broadcast chains
• Reduces the need for external sample‑rate conversion when interfacing with video systems
• Supported by Rivendell when configured consistently

Note: Switching an existing system from 44.1 kHz to 48 kHz requires re‑importing or converting all stored audio.

Bit Depth

While this page focuses on sample rates, bit depth is also relevant.

• 16‑bit linear PCM is the standard and recommended format.
• Some workflows may allow import of higher bit‑depth material, but audio is typically stored and processed as 16‑bit PCM.

Channel Configuration

Rivendell supports both mono and stereo audio at either supported sample rate.

• Mono: Single channel PCM
• Stereo: Left / Right PCM

The configured system sample rate (44.1 kHz or 48 kHz) applies equally to mono and stereo files.

Importing Audio

When importing audio into Rivendell using:

• rdimport
• Rivendell GUI import tools
• Automated ingest workflows

Ensure that all source files meet the system requirements:

• Sample Rate: Matches the system configuration (44.1 kHz or 48 kHz)
• Encoding: Linear PCM (WAV)
• Bit Depth: 16‑bit recommended
• Channels: Mono or Stereo

Files with mismatched sample rates must be converted before import.

Sample Rate Conversion

Common source sample rates that may require conversion include:

• 44.1 kHz (if the system is configured for 48 kHz)
• 48 kHz (if the system is configured for 44.1 kHz)
• 96 kHz or higher (high‑resolution recording)

Best practices:

• Perform high‑quality offline resampling
• Avoid repeated conversion of the same audio
• Use dithering when reducing bit depth

Clocking and Audio Hardware

System‑level sample rate configuration must align with audio hardware settings.

• Audio interfaces should run at the same sample rate as Rivendell
• External word clock sources should be stable and correctly distributed
• Hardware sample‑rate conversion should be avoided where possible

Improper clocking or mismatched rates may cause:

• Clicks or pops
• Timing drift
• Unstable playback

Timing and Logs

Rivendell log timing and audio length calculations depend on a consistent sample rate.

• Segue calculations
• Event timing
• Length metadata