fun

--[[

  * skipsilence.lua versie 2

  *

  * AUTHOR: Maarten Vangeneugden

  * License: GNU GPLv3+

  * link: https://maartenv.be/gitar/fun/master/

  * 

  * This script can be used to skip all silent parts while watching

  * a video. I made this during the COVID-19 pandemic because all

  * my courses were being taught online. I noticed that up to a third

  * of what I "watched" was actually silence, which I could skip,

  * saving me a lot of time. However, doing this manually is error-

  * prone and not very convenient.

  *

  * The way this works is actually kind of a hack: It uses ffmpeg's

  * detectsilence filter, but that doesn't give reliable results as to

  * how much I can skip. So when you activate this script, it rapidly

  * goes over the entire video, storing all silent parts in a Lua table.

  * (Which, should you be somebody that thinks Lua tables are incredibly

  * weird, they're definitely not). After that, it returns to the point

  * where it was called, and resumes playback. When a silent part pops up,

  * the data is retrieved from the table, and the silence is skipped

  * immediately. I had to do it this way, because there was literally no

  * other way to do this, except for writing a custom ffmpeg filter, but

  * let's not resort to radicalism.

  * The default keybind is F3, but change that to your liking below. 

  * You can change this by adding

  * the following line to your input.conf:

  *     KEY script-binding skip-to-silence

  * 

  * In order to tweak the script parameters, you can place the

  * text below, between the template markers, in a new file at

  * script-opts/skiptosilence.conf in mpv's user folder. The

  * parameters will be automatically loaded on start.

  *

*** FUCKING USEFUL INFORMATION FOR WORKING WITH THE SILENCEDETECT FILTER

This filter fires a string at TWO moments:

1. When the silence starts

2. The frame after the silence ends

The first time, it sends a message like this:

{"lavfi.silence_start":"1095.34"}

The second time, it sends like this:

{"lavfi.silence_start":"1095.34","lavfi.silence_end":"1101.16","lavfi.silence_duration":"5.81419"}

Notice how the start tag has remained the same, but there are two tags that have been added:

The duration and the end tag.

WHY IS THIS IMPORTANT? Because the next time a silence is detected, it sends this shit out:

{"lavfi.silence_start":"1102.37","lavfi.silence_end":"1101.16","lavfi.silence_duration":"5.81419"}

Notice how suddenly, even though this is step 1, it does have an end and duration!

BUT THESE ARE JUST THE NOT-UPDATED VALUES OF THE PREVIOUS SILENCE! So you ought to ignore these,

since IT IS NOT INFO ABOUT THIS SILENCE!

I'm pretty pissed off about this because apparently nobody at ffmpeg thought

it was important to document this, and I've been spending quite some time 

trying to find out why my own script wouldn't fucking work. But it's because

some twat didn't document per shit properly, got it now.

This is version two, a version with less than half the amount of code from

the previous version, and one that works a thousand times better.

****************** TEMPLATE FOR skiptosilence.conf ******************

# Maximum amount of noise to trigger, in terms of dB.

# The default is -30 (yes, negative). -60 is very sensitive,

# -10 is more tolerant to noise.

quietness = -30

# Minimum duration of silence to trigger.

duration = 0.1

# The fast-forwarded audio can sound jarring. Set to 'yes'

# to mute it while skipping.

mutewhileskipping = no

************************** END OF TEMPLATE **************************

--]]

local opts = {

    quietness = -40,

    duration = 1.5,

    mutewhileskipping = true

}

local mp = require 'mp'

local msg = require 'mp.msg'

local options = require 'mp.options'

local enabled = false

-- I added resetSkip because the skipper sometimes goes haywire and skips over

-- parts that are clearly not silent. Don't know why, but if this happens,

-- resetSkip takes you back 10 seconds and resets everything.

function resetSkip()

    setAudioFilter(false)

    enabled=false

    mp.unobserve_property(silenceDetected)

    if old_speed ~= 10 then

        mp.set_property("speed", old_speed)

    else

        mp.set_property("speed", 1)

    end

    mp.set_property_bool("mute", false)

    in_silence = false

    last_silence_start = 0

    last_silence_end = 0

    last_silence_duration = 0

    -- Go back 10 seconds because there's probably a part that was skipped over

    current_time = mp.get_property_native("time-pos")

    mp.set_property_number("time-pos", current_time - 10)

    print("RESET")

end

function toggleSkip()

    if enabled then

        mp.unobserve_property(silenceDetected)

        print("TOGGLE OFF")

    else

        print("TOGGLE ON")

        mp.observe_property("af-metadata/skipsilence", "string", silenceDetected) -- Start listening

    end

    setAudioFilter(not enabled)

    --setVideoFilter(not enabled, mp.get_property_native("width"), mp.get_property_native("height"))

    enabled = not enabled

end

in_silence = false

-- Normally I'd use a simple in_silence state variable, but because this ffmpeg

-- filter was written by people who can't even log shit correctly, I have to

-- manually check every log entry for the values to see if they changed.

last_silence_start = 0

last_silence_end = 0

last_silence_duration = 0

old_speed = 1

-- This function is triggered whenever the skip feature is enabled and a silent

-- part occurs in the stream.

function silenceDetected(name, value)

    --print("SPEED UP")

    --mp.set_property("speed", 10)

    if value == "{}" or value == nil then

        return -- For some reason these are sometimes emitted. Ignore.

    end

    i = 1

    for silence in string.gmatch(value, "%d+%.?%d+") do

        if i==1 then

            silence_start = silence

        elseif i==2 then

            silence_end = silence

        elseif i==3 then

            silence_duration = silence

        end

    end

    -- If we're in a silence, then we need to reduce the speed again

    --if silence_start==last_silence_start then

    if in_silence then

        mp.set_property("speed", old_speed)

        print("SPEED DOWN")

        --mp.unobserve_property(silenceDetected)

        --now = mp.get_property_native("time-pos")  -- get current time

        --mp.set_property_number("time-pos", now) -- A little bit before the end of the silence

        --mp.add_timeout(2.0, function() mp.observe_property("af-metadata/skipsilence", "string", silenceDetected) end) -- Wait half a second before observing silences again

        mp.set_property_bool("mute", false)

        in_silence = false -- And finally, disable the in-silence state

    else

        in_silence = true

        mp.set_property_bool("mute", true)

        old_speed = mp.get_property_native("speed")  -- get current speed

        mp.set_property("speed", 10)

        print("SPEED UP")

    end

    print(value) --DEBUG

    last_silence_start = silence_start

    last_silence_end= silence_end

    last_silence_duration = silence_duration

end

-- Adds the filters to the filtergraph on mpv init

-- in a disabled state.

-- Filter documentation: https://ffmpeg.org/ffmpeg-filters.html

function init()

    -- `silencedetect` is an audio filter that listens for silence

    -- and emits text output with details whenever silence is detected.

    local af_table = mp.get_property_native("af")

    af_table[#af_table + 1] = {

        enabled=false,

        label="skipsilence",

        name="lavfi",

        params= {

            graph = "silencedetect=noise="..opts.quietness.."dB:d="..opts.duration

        }

    }

    mp.set_property_native("af", af_table)

    -- `nullsink` interrupts the video stream requests to the decoder,

    -- which stops it from bogging down the fast-forward.

    -- `color` generates a blank image, which renders very quickly and

    -- is good for fast-forwarding.

    -- The graph is not actually filled in now, but when toggled on,

    -- as it needs the resolution information.

    local vf_table = mp.get_property_native("vf")

    vf_table[#vf_table + 1] = {

        enabled=false,

        label="skipsilence-blackout",

        name="lavfi",

        params= {

            graph = "" --"nullsink,color=c=black:s=1920x1080"

        }

    }

    mp.set_property_native("vf", vf_table)

end

function setAudioFilter(state)

    local af_table = mp.get_property_native("af")

    if #af_table > 0 then

        for i = #af_table, 1, -1 do

            if af_table[i].label == "skipsilence" then

                af_table[i].enabled = state

                mp.set_property_native("af", af_table)

                return

            end

        end

    end

end

function setVideoFilter(state, width, height)

    local vf_table = mp.get_property_native("vf")

    if #vf_table > 0 then

        for i = #vf_table, 1, -1 do

            if vf_table[i].label == "skipsilence-blackout" then

                vf_table[i].enabled = state

                vf_table[i].params = {

                    graph = "nullsink,color=c=black:s="..width.."x"..height

                }

                mp.set_property_native("vf", vf_table)

                return

            end

        end

    end

end

options.read_options(opts)

init()

mp.add_key_binding("F3", "toggle-skip-silence", toggleSkip)

mp.add_key_binding("F4", "reset-skip-silence", resetSkip)