Latest revision as of 10:32, 29 January 2026

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

@@ Line 1: / Line 1: @@
 = Sample Rates in Rivendell =
-This page documents how audio sample rates are handled in the '''Rivendell Radio Automation System''', including supported rates, system limitations, and best practices for production and ingestion.
+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 is designed primarily for broadcast radio environments and assumes a fixed digital audio sample rate throughout the system. Correct configuration and consistent audio formatting are critical to ensure reliable playback, accurate timing, and predictable audio quality.
+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 '''44,100 Hz (44.1 kHz)''' PCM audio.
+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 is the **native and required sample rate** for all audio stored in the Rivendell audio store.
+.1 kHz has historically been the most common Rivendell configuration.
-* Audio at other sample rates must be converted before being imported into Rivendell.
-{{Note|
+Advantages:
-Rivendell does not dynamically resample audio during playback. Files not at the correct sample rate may fail to import or play incorrectly.
+* Compatible with legacy CD‑based and broadcast workflows
-}}
+* Widely used in existing Rivendell installations
+* Proven stability
+=== 48 kHz ===
+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 closely related and must also be considered.
+While this page focuses on sample rates, bit depth is also relevant.
-* '''16-bit''' linear PCM is the standard and most commonly used format.
+* '''16‑bit''' linear PCM is the standard and recommended format.
-* Some workflows may support '''24-bit''' audio during import, but files are typically stored and processed as 16-bit audio internally.
+* 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 the supported sample rate.
+Rivendell supports both mono and stereo audio at either supported sample rate.
 * Mono: Single channel PCM
-* Stereo: Two-channel PCM (Left / Right)
+* Stereo: Left / Right PCM
-The sample rate requirement (44.1 kHz) applies equally to mono and stereo files.
+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 tools such as:
+When importing audio into Rivendell using:
 * '''rdimport'''
-* '''Rivendell Import GUI'''
+* Rivendell GUI import tools
-* External production workflows
+* Automated ingest workflows
-ensure that all source files meet the following criteria:
+Ensure that all source files meet the system requirements:
-* Sample Rate: '''44,100 Hz'''
+* Sample Rate: '''Matches the system configuration (44.1 kHz or 48 kHz)'''
 * Encoding: Linear PCM (WAV)
-* Bit Depth: 16-bit (recommended)
+* Bit Depth: 16‑bit recommended
-* Channel Count: Mono or Stereo
+* Channels: Mono or Stereo
-If a file does not meet these requirements, it should be converted prior to import using an external audio editor or batch processing tool.
+Files with mismatched sample rates must be converted before import.
 == Sample Rate Conversion ==
-Audio files created at common production or distribution sample rates such as:
+Common source sample rates that may require conversion include:
-* 48,000 Hz (video production)
-* 96,000 Hz (high‑resolution recording)
-must be resampled to 44.1 kHz before use in Rivendell.
+* 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)
-Recommended practices:
+Best practices:
-* Use high‑quality offline resampling
+* Perform high‑quality offline resampling
-* Avoid repeated resampling of the same audio
+* Avoid repeated conversion of the same audio
-* Apply dithering when reducing bit depth
+* Use dithering when reducing bit depth
 == Clocking and Audio Hardware ==
-Although Rivendell software assumes a 44.1 kHz internal rate, audio hardware configuration is also important.
+System‑level sample rate configuration must align with audio hardware settings.
-* Audio interfaces should be locked to a stable clock source
+* Audio interfaces should run at the same sample rate as Rivendell
-* Hardware may run at 44.1 kHz or perform real‑time sample rate conversion internally
+* External word clock sources should be stable and correctly distributed
-* Mixing differing hardware clock rates without proper synchronization can cause clicks, pops, or drift
+* 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 ==
-Precise timing in Rivendell logs depends on all audio sharing the same sample rate.
+Rivendell log timing and audio length calculations depend on a consistent sample rate.
 * Segue calculations
 * Event timing
 * Length metadata
-are all based on the assumption of 44.1 kHz source audio.
-Using non‑conforming files may result in:
-* Incorrect length reporting
-* Timing drift
-* Playback errors
-== Best Practices ==
-* Standardize production workflows at 44.1 kHz
-* Validate audio files before import
-* Avoid on‑the‑fly sample rate conversion
-* Document any exceptions clearly for engineering staff
-== See Also ==
-* [[Audio Formats in Rivendell]]
-* [[rdimport]]
-* [[Audio Hardware Configuration]]
-* [[Digital Audio Basics]]