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Audio filters let you modify the audio stream before it reaches the audio output. The filter chain syntax is identical to video filters. 
mpv --af=<filter1[=param1:param2],filter2,...> audio.flac
Run mpv --af=help to list all available audio filters. Most filters are available via the lavfi wrapper, which exposes all of libavfilter’s audio filters.

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Filter chain syntax

The syntax for --af is the same as --vf. See video filters for full details on labels, the ! prefix for disabled-by-default filters, and runtime toggling. 
# Single filter
mpv --af=scaletempo2 audio.flac

# Filter chain
mpv --af=scaletempo2,lavfi=loudnorm audio.flac

# Add to an existing filter list
mpv --af-add=rubberband audio.flac
Filter list management options: --af-add, --af-pre, --af-clr. See --vf group of options for their behavior.

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Available filters

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lavcac3enc — AC-3 encoding

Encodes multi-channel audio to AC-3 at runtime using libavcodec. Supports up to 6 channels. Output is big-endian for raw AC-3, or native-endian for S/PDIF. Input is resampled to 48 kHz, 44.1 kHz, or 32 kHz if needed. 
# Encode to AC-3 and output via S/PDIF (default)
mpv --af=lavcac3enc audio.flac

# Raw AC-3 stream output
mpv --af=lavcac3enc=tospdif=no audio.flac

# Set bitrate to 384 kbps
mpv --af=lavcac3enc=bitrate=384 audio.flac
ParameterDescription
tospdif=<yes|no>Output via S/PDIF passthrough (yes, default) or raw AC-3 stream (no)
bitrate=<rate>Bitrate in kbps (default: 640). Valid values: 32, 40, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320, 384, 448, 512, 576, 640. Use auto to select based on channel count.
minch=<n>Detach filter if input has fewer than n channels (default: 3)
encoder=<name>libavcodec encoder to use (must be an AC-3 encoder)
Auto bitrate by channel count:
ChannelsBitrate
196 kbps
2192 kbps
3224 kbps
4384 kbps
5–6448 kbps

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format — audio format control

Forces a specific audio format, sample rate, or channel layout. Does not perform conversion itself; it instructs the filter system to insert necessary conversion filters. 
# Force 48000 Hz sample rate
mpv --af=format=srate=48000 audio.flac

# Force stereo output
mpv --af=format=channels=stereo audio.flac

# List available formats
mpv --af=format=format=help
ParameterDescription
formatForce a specific sample format (e.g. s16, float)
srateForce a specific sample rate (e.g. 48000)
channelsForce a specific channel layout
To control audio output format (as opposed to mid-chain format), use --audio-format, --audio-samplerate, and --audio-channels instead.

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scaletempo — tempo scaling (legacy)

Scales audio tempo without altering pitch, optionally synced to playback speed. Uses a time-domain WSOLA-like algorithm. 
# Play at 1.2x speed with normal pitch
mpv --af=scaletempo --speed=1.2 audio.flac

# Sync tempo to speed, but don't respond to speed changes
mpv --af=scaletempo=scale=1.2:speed=none --speed=1.2 audio.flac
ParameterDefaultDescription
scale=<amount>1.0Additional tempo scale factor
stride=<ms>60Output stride length in milliseconds
overlap=<factor>0.20Overlap fraction of stride
search=<ms>14Search length for best overlap position
speed=<tempo|pitch|both|none>tempoHow to respond to speed changes: tempo (scale tempo), pitch (scale pitch instead, loses video sync), both, or none
Scales audio tempo without altering pitch using the WSOLA (Waveform Similarity Overlap-and-Add) algorithm, ported from Chromium. Higher audio quality than scaletempo and rubberband R2 engine. This filter is inserted automatically when --audio-pitch-correction is enabled (the default) and playback speed changes. 
mpv --af=scaletempo2 --speed=1.5 audio.flac
ParameterDefaultDescription
min-speed=<speed>0.25Mute audio below this playback speed
max-speed=<speed>8.0Mute audio above this playback speed (0 = disabled)
search-interval=<ms>40Length in ms to search for best overlap position
window-size=<ms>12Length in ms of the overlap-and-add window

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rubberband — high-quality pitch correction

High-quality pitch correction using librubberband. Can replace scaletempo and scaletempo2, and supports pitch adjustment independent of speed. 
mpv --af=rubberband --speed=1.5 audio.flac

# Adjust pitch upward by a musical semitone
mpv --af=rubberband=pitch-scale=1.059463 audio.flac
ParameterDescription
pitch-scale=<amount>Pitch scaling factor; frequencies are multiplied by this value (default: 1.0)
engine=<faster|finer>Rubberband engine: faster (R2, less CPU) or finer (R3, higher quality — default if librubberband ≥ 3)
List all available rubberband sub-options: 
mpv --af=rubberband=help
Runtime commands (via af-command):
  • set-pitch <value> — Change pitch-scale dynamically at runtime
  • multiply-pitch <factor> — Multiply the current pitch-scale dynamically
Example input.conf for semitone pitch stepping: 
[ multiply speed 0.9438743126816935
] multiply speed 1.059463094352953

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lavfi — libavfilter wrapper

Filters audio using FFmpeg’s libavfilter. Provides access to all of libavfilter’s audio filters. 
mpv --af='lavfi=loudnorm' audio.flac

# EQ: boost bass by 5 dB below 200 Hz
mpv --af='lavfi=equalizer=f=200:width_type=h:width=200:g=5' audio.flac

# Normalize loudness
mpv --af='lavfi=loudnorm=I=-16:TP=-1.5:LRA=11' audio.flac
Quote libavfilter graphs to avoid conflicts with mpv’s own syntax. Use the same quoting strategies as described in the video filters lavfi section.
Additional options:
ParameterDescription
o=<string>AVOptions passed to the filter graph
fix-pts=<yes|no>Compute PTS from sample count instead of relying on libavfilter (default: no). Use for filters that reset or recompute PTS.

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drop — frame dropping for SPDIF

Drops or repeats audio frames to adapt to playback speed. Operates on full audio frames, designed for S/PDIF (compressed audio passthrough). Used automatically with --video-sync=display-adrop.
This filter is extremely low quality. Do not use it unless you have a specific need for S/PDIF with display-adrop.

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Common use cases

# scaletempo2 is used automatically, but you can be explicit:
mpv --speed=1.5 audio.flac

# Or force rubberband for higher quality:
mpv --af=rubberband --speed=1.5 audio.flac

mpv --af=lavcac3enc audio.mkv
This is useful when your audio output device requires AC-3 but the source file is in a different multichannel format.
mpv --af='lavfi=loudnorm=I=-16:TP=-1.5:LRA=11' audio.flac

# 5 dB boost at 100 Hz with 50 Hz bandwidth
mpv --af='lavfi=equalizer=f=100:width_type=h:width=50:g=5' audio.flac

# Shift pitch up by one semitone
mpv --af=rubberband=pitch-scale=1.059463 audio.flac

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Filter help

# List all available audio filters
mpv --af=help

# Show parameters for a specific filter
mpv --af=scaletempo=help
For libavfilter audio filters, refer to the FFmpeg filter documentation.

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