skip_silence_ffmpeg.lua

local utils = require 'mp.utils'
local enabled = false

local silence_threshold = -20
local edge_delta = 0.06

local file = nil
local silenceData = {}
local currentIndex = 1
local result = ""
local block_refresh = false
local next_skip_start = -1
local next_skip_end = -1
local next_duration = -1
local silence_list = {}

function refresh_ffmpeg_silent_parts()
	if not block_refresh then
		block_refresh = true

	    -- Find silent parts with ffmpeg
	    file = mp.get_property("path")
	    print("file: " .. file)
	    local command = { "ffmpeg", "-i", file, "-af", string.format("silencedetect=noise=%ddB:d=0.5", silence_threshold), "-f", "null", "-" }
	    result = utils.subprocess({ args = command, cancellable = false, capture_stdout = true, capture_stderr = true })
	    if result.error then
	        print("Error running ffmpeg command")
	        return
	    end
	    print(result.stderr)

	    -- Parse detected silent parts into a list
	    silence_list = {}
	    for start, endtime, duration in result.stderr:gmatch("silence_start: (%S+)\n.-silence_end: (%S+) | silence_duration: (%S+)") do
		table.insert(silence_list, { tonumber(start), tonumber(endtime), tonumber(duration) })
	    end

	    print("Silence List:")
	    for i, data in ipairs(silence_list) do
		print(i, "Start:", data[1], "End:", data[2], "Dur:", data[3])
	    end

	    print("done finding silence")
            mp.osd_message("done finding silence")
	    block_refresh = false
	else
		print("refresh already running")
	end
end


function recalc_next_skip()
	--print("recalc now")
	local current_time = mp.get_property_number("time-pos", 0)

	--print("current_time: " .. current_time)
	next_skip_start = mp.get_property_number("duration")
	for _, silence in ipairs(silence_list) do
	    local start_time, end_time, duration = silence[1], silence[2], silence[3]
	    if current_time <= (start_time+edge_delta) and start_time < next_skip_start then
	        next_skip_start = start_time
	        next_skip_end = end_time
	        next_duration = duration
	    end
	end
	--print("   next skip: " .. next_skip_start .. " for " .. next_duration .. " in " .. (next_skip_start-current_time))
end

function toggle_skip_silent()
	enabled = not enabled

	if enabled then
		print("Skip Silence enabled, finding silence...")
		mp.osd_message("Silence skipping enabled, finding silence...")
		refresh_ffmpeg_silent_parts()

		function skip_silent_parts()
			if enabled then
				local current_time = mp.get_property_number("time-pos", 0)
				if current_time >= (next_skip_start + edge_delta) and current_time <= (next_skip_end - edge_delta) then
					print("skipping to " .. next_skip_end-edge_delta)
			    	mp.commandv("seek", next_skip_end-edge_delta, "absolute+exact")
			    end

			    --todo: this recalc should only be calculated when it is necessary
			    --      but it is currently still no performance bottleneck
				recalc_next_skip()
			end
		end
		mp.observe_property("time-pos", "native", skip_silent_parts)
	else
		mp.osd_message("Skip Silence disabled")
		mp.osd_message("Skip Silence disabled")
	end
end


mp.add_key_binding("F2", "toggle_skip_silent", toggle_skip_silent)


function change_threshold(delta)
	silence_threshold = silence_threshold + delta
	mp.osd_message("silence_threshold: "..silence_threshold.."dB , finding silence...")
	refresh_ffmpeg_silent_parts()
end
mp.add_key_binding("F3", "threshold-down", function() change_threshold(-1) end, "repeatable")
mp.add_key_binding("F4", "threshold-up", function() change_threshold(1) end, "repeatable")