mpv-skipsilence

Increase playback speed during silence - a revolution in attention-deficit
induction technology.

Main repository: https://codeberg.org/ferreum/mpv-skipsilence/

Based on the script https://gist.github.com/bitingsock/e8a56446ad9c1ed92d872aeb38edf124

This is inspired by the NewPipe app's built-in "Fast-forward during silence"
feature.

Note: In mpv version 0.36 and below, the scaletempo2 filter (default since
mpv version 0.34) caused audio-video de-synchronization when changing speed
a lot. This has been fixed in mpv 0.37. See mpv issue
#12028. Small, frequent
speed changes instead of large steps may help to reduce this problem. The
scaletempo and rubberband filters didn't have this problem, but have
different audio quality characteristics.

Features:

• Parameterized speedup ramp, allowing profiles for different kinds of
  media (ramp_*, speed_*, startdelay options).
• Noise reduction of the detected signal. This allows to speed up
  pauses in speech despite background noise. The output audio is
  unaffected by default (arnndn_* options).
• Saved time estimation.
• Integration with osd-msg, auto profiles, etc. (with user-data, mpv 0.36 and
  above only).
• Experimental: Lookahead for dynamic slowdown and faster reaction time
  (lookahead, slowdown_ramp_*, margin_* options).
• Workaround for scaletempo2 audio-video desynchronization in mpv 0.36 and
  below (resync_threshold_droppedframes option).
• Workaround for clicks during speed changes with scaletempo2 in mpv 0.36 and
  below (alt_normal_speed option).

Silence detection visualized

The following graph shows an example silence detection and resulting playback
speed, annotated with options that impact speed changes.

If the experimental lookahead option is set to a positive value, the effect
of some options changes:

¹⁾ Without lookahead, Silence Start is delayed by
threshold_duration. If lookahead is active, it reduces this delay by up to
that configured lookahead duration.

²⁾ minduration is only supported with lookahead.

³⁾ startdelay is ignored if lookahead is enabled and
margin_start is used instead.

⁴⁾ The box marked if lookahead only applies if lookahead is
active. Otherwise, the speed is reverted in a single step exactly at the time
of Silence End detection.

Default bindings

• F2 - toggle
• F3 - threshold-down
• F4 - threshold-up

Documentation

For detailed usage check the comments at the top of the script.

Recommendations

Temporarily disable display sync

When using video-sync=display-*, speed changes tend to cause increased video
lag. Because display sync is less useful while speed keeps changing, it's
recommended to use video-sync=audio (the default) while this script is
active. This results in smoother video playback during speed transitions.

The following profile can be used to automatically switch to video-sync=audio
when skipsilence is enabled and restore it when disabled (requires mpv 0.36 or
above for user-data):

[auto-skipsilence-videosync]
profile-cond=get("user-data/skipsilence/enabled")
profile-restore=copy-equal
video-sync=audio

Fix clicking sounds/gaps when switching to and from 1x speed

In the default configuration, mpv automatically inserts scaletempo2 filter when
changing speed and removes it when returning to 1x playback speed. This often
causes clicks in audio playback. To prevent this, add scaletempo2 to the af
filter list explicitly:

af-add=scaletempo2

In mpv 0.36 and below, the scaletempo2 filter itself additionally caused
similar artifacts when switching to and from 1x speed. This has been fixed in
mpv 0.37. The alt_normal_speed option of this script is a workaround for
older versions.

Fix silence at high playback speed

By default, scaletempo2 produces silence above 8x playback speed (4x in mpv
0.36 and below). To lift this limit, set the max-speed parameter in the
filter definition (see above) like this:

af-add=scaletempo2=max-speed=32.0

Maximize skipping speed

Because of the asynchronous nature of scripts, there is latency between silence
detection and speed changes. The higher the playback speed, the more noticeably
playback will overshoot before normal speed is restored. What speeds are
acceptable depends on the performance/latency of the system.

To maximize skipping speed, start with the extreme profile (see
Profiles below). Then adjust ramp_constant, ramp_factor,
max_speed options as needed.

• If overshooting happens all the time, even for very short pauses, reduce
  ramp_constant.
• If it happens after the speed ramped up more, focus on ramp_factor.
• For the occasional long stretch of silence this may be less of a problem, but
  can be improved by reducing max_speed at a cost of slower skipping.
• Notice that extreme values of ramp_exponent tend to be less useful. It's
  recommended to keep the ramp_exponent around 0.9 for aggressive profiles.

Lookahead

The experimental lookahead option makes much higher maximum speed practical by
gradually slowing down before the end of silence is reached. See the
lookahead, slowdown_ramp_* and margin_* options. To maximize skipping
speed, use a slowdown ramp that is as steep as possible without overshooting on
slowdown. margin_end can help, but is usually not required.

Profiles

Mpv's profiles can be used to switch between different presets. Create profiles
in mpv.conf and apply them with the apply-profile command.

[skipsilence-default]
script-opts-append=skipsilence-ramp_constant=1.25
script-opts-append=skipsilence-ramp_factor=2.5
script-opts-append=skipsilence-ramp_exponent=1
script-opts-append=skipsilence-speed_max=4
script-opts-append=skipsilence-speed_updateinterval=0.05
script-opts-append=skipsilence-startdelay=0.05

Bind it to a key in input.conf:

F5 script-message-to skipsilence enable no-osd; apply-profile skipsilence-default; show-text "skipsilence profile: default"

Examples

# very smooth speed increase, up to 3x
[skipsilence-smooth]
script-opts-append=skipsilence-ramp_constant=1
script-opts-append=skipsilence-ramp_factor=0.4
script-opts-append=skipsilence-ramp_exponent=1.45
script-opts-append=skipsilence-speed_max=3
script-opts-append=skipsilence-speed_updateinterval=0.05
script-opts-append=skipsilence-startdelay=0
script-opts-append=skipsilence-threshold_duration=0.25

# very aggressive skipping, can make it hard to listen
[skipsilence-extreme]
script-opts-append=skipsilence-ramp_constant=2.5
script-opts-append=skipsilence-ramp_factor=10
script-opts-append=skipsilence-ramp_exponent=0.9
script-opts-append=skipsilence-speed_max=6
script-opts-append=skipsilence-speed_updateinterval=0.05
script-opts-append=skipsilence-startdelay=0
script-opts-append=skipsilence-threshold_duration=0.05

# long wait (1s) before speeding up quickly
[skipsilence-patient]
script-opts-append=skipsilence-ramp_constant=1.25
script-opts-append=skipsilence-ramp_factor=3
script-opts-append=skipsilence-ramp_exponent=0.9
script-opts-append=skipsilence-speed_max=4
script-opts-append=skipsilence-speed_updateinterval=0.05
script-opts-append=skipsilence-startdelay=0
script-opts-append=skipsilence-threshold_duration=1

Examples with lookahead

These use the advanced lookahead feature. It works better with much higher
skipping speeds.

These use the same lookahead duration (1s) and threshold_duration, so
switching between them does not cause a playback interruption.

# Good default profile with smooth speed-up and slow-down.
[skipsilence-normal]
script-opts-append=skipsilence-lookahead=1
script-opts-append=skipsilence-ramp_constant=1.25
script-opts-append=skipsilence-ramp_factor=2.5
script-opts-append=skipsilence-ramp_exponent=1
script-opts-append=skipsilence-speed_max=6
script-opts-append=skipsilence-minduration=0.05
script-opts-append=skipsilence-margin_start=0.03
script-opts-append=skipsilence-margin_end=0.02
script-opts-append=skipsilence-speed_updateinterval=0.02
script-opts-append=skipsilence-threshold_duration=0.025
script-opts-append=skipsilence-slowdown_ramp_constant=1
script-opts-append=skipsilence-slowdown_ramp_factor=3
script-opts-append=skipsilence-slowdown_ramp_exponent=.5

# Very extreme speed-up and slow-down. You can increase max_speed even
# higher to skip longer pauses even faster. Make sure you have an updated
# mpv and unlocked scaletempo2 max-speed parameter (see above).
[skipsilence-extreme]
script-opts-append=skipsilence-lookahead=1
script-opts-append=skipsilence-ramp_constant=5
script-opts-append=skipsilence-ramp_factor=32
script-opts-append=skipsilence-ramp_exponent=.9
script-opts-append=skipsilence-speed_max=16
script-opts-append=skipsilence-minduration=0.05
script-opts-append=skipsilence-margin_start=0.05
script-opts-append=skipsilence-margin_end=0
script-opts-append=skipsilence-speed_updateinterval=0.02
script-opts-append=skipsilence-threshold_duration=0.025
script-opts-append=skipsilence-slowdown_ramp_constant=1.25
script-opts-append=skipsilence-slowdown_ramp_factor=20
script-opts-append=skipsilence-slowdown_ramp_exponent=.5

# Very smooth speed-up and slow-down, max_speed 2.5
[skipsilence-smooth]
script-opts-append=skipsilence-lookahead=1
script-opts-append=skipsilence-ramp_constant=1
script-opts-append=skipsilence-ramp_factor=1.5
script-opts-append=skipsilence-ramp_exponent=1.2
script-opts-append=skipsilence-speed_max=2.5
script-opts-append=skipsilence-minduration=0.25
script-opts-append=skipsilence-margin_start=0.05
script-opts-append=skipsilence-margin_end=0.05
script-opts-append=skipsilence-speed_updateinterval=0.02
script-opts-append=skipsilence-threshold_duration=0.025
script-opts-append=skipsilence-slowdown_ramp_constant=1
script-opts-append=skipsilence-slowdown_ramp_factor=1.5
script-opts-append=skipsilence-slowdown_ramp_exponent=.8