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• ffmpeg encoding leaves me with blank space at the end where the video pauses and there is nothing ahead

  6 novembre 2022, par Nisarg Desai

  I was trying to slice some of the video being played and clip it in mpv.net using a .lua script which uses ffmpeg to encode the webm output. ffmpeg sometimes leaves some seconds blank and without any video/audio ahead while clipping from source. Is there any solution to this ?

  


  The code for the script is given below (was taken from here https://github.com/occivink/mpv-scripts) :

  


  local utils = require "mp.utils"
local msg = require "mp.msg"
local options = require "mp.options"

local ON_WINDOWS = (package.config:sub(1,1) ~= "/")

local start_timestamp = nil
local profile_start = ""

-- implementation detail of the osd message
local timer = nil
local timer_duration = 2

-- folder creation if it doesnt exist
function exists(file)
   local ok, err, code = os.rename(file, file)
   if not ok then
      if code == 13 then
         return true
      end
   end
   return ok, err
end

--- Check if a directory exists in this path
function create_dir(path)
    local dir = "\"" .. path .. "\""
    if not exists(path .."/") then
        os.execute("mkdir " .. dir)
    end
end

function append_table(lhs, rhs)
    for i = 1,#rhs do
        lhs[#lhs+1] = rhs[i]
    end
    return lhs
end

function file_exists(name)
    local f = io.open(name, "r")
    if f ~= nil then
        io.close(f)
        return true
    else
        return false
    end
end

function get_extension(path)
    local candidate = string.match(path, "%.([^.]+)$")
    if candidate then
        for _, ext in ipairs({ "mkv", "webm", "mp4", "avi" }) do
            if candidate == ext then
                return candidate
            end
        end
    end
    return "mkv"
end

function get_output_string(dir, format, input, extension, title, from, to, profile)
    local res = utils.readdir(dir)
    if not res then
        return nil
    end
    local files = {}
    for _, f in ipairs(res) do
        files[f] = true
    end
    local output = format
    output = string.gsub(output, "$f", function() return input end)
    output = string.gsub(output, "$t", function() return title end)
    output = string.gsub(output, "$s", function() return seconds_to_time_string(from, true) end)
    output = string.gsub(output, "$e", function() return seconds_to_time_string(to, true) end)
    output = string.gsub(output, "$d", function() return seconds_to_time_string(to-from, true) end)
    output = string.gsub(output, "$x", function() return extension end)
    output = string.gsub(output, "$p", function() return profile end)
    if ON_WINDOWS then
        output = string.gsub(output, "[/\\|<>?:\"*]", "_")
    end
    if not string.find(output, "$n") then
        return files[output] and nil or output
    end
    local i = 1
    while true do
        local potential_name = string.gsub(output, "$n", tostring(i))
        if not files[potential_name] then
            return potential_name
        end
        i = i + 1
    end
end

function get_video_filters()
    local filters = {}
    for _, vf in ipairs(mp.get_property_native("vf")) do
        local name = vf["name"]
        name = string.gsub(name, '^lavfi%-', '')
        local filter
        if name == "crop" then
            local p = vf["params"]
            filter = string.format("crop=%d:%d:%d:%d", p.w, p.h, p.x, p.y)
        elseif name == "mirror" then
            filter = "hflip"
        elseif name == "flip" then
            filter = "vflip"
        elseif name == "rotate" then
            local rotation = vf["params"]["angle"]
            -- rotate is NOT the filter we want here
            if rotation == "90" then
                filter = "transpose=clock"
            elseif rotation == "180" then
                filter = "transpose=clock,transpose=clock"
            elseif rotation == "270" then
                filter = "transpose=cclock"
            end
        end
        filters[#filters + 1] = filter
    end
    return filters
end

function get_input_info(default_path, only_active)
    local accepted = {
        video = true,
        audio = not mp.get_property_bool("mute"),
        sub = mp.get_property_bool("sub-visibility")
    }
    local ret = {}
    for _, track in ipairs(mp.get_property_native("track-list")) do
        local track_path = track["external-filename"] or default_path
        if not only_active or (track["selected"] and accepted[track["type"]]) then
            local tracks = ret[track_path]
            if not tracks then
                ret[track_path] = { track["ff-index"] }
            else
                tracks[#tracks + 1] = track["ff-index"]
            end
        end
    end
    return ret
end

function seconds_to_time_string(seconds, full)
    local ret = string.format("%02d:%02d.%03d"
        , math.floor(seconds / 60) % 60
        , math.floor(seconds) % 60
        , seconds * 1000 % 1000
    )
    if full or seconds > 3600 then
        ret = string.format("%d:%s", math.floor(seconds / 3600), ret)
    end
    return ret
end

function start_encoding(from, to, settings)
    local args = {
        settings.ffmpeg_command,
        "-loglevel", "panic", "-hide_banner",
    }
    local append_args = function(table) args = append_table(args, table) end

    local path = mp.get_property("path")
    local is_stream = not file_exists(path)
    if is_stream then
        path = mp.get_property("stream-path")
    end

    local track_args = {}
    local start = seconds_to_time_string(from, false)
    local input_index = 0
    for input_path, tracks in pairs(get_input_info(path, settings.only_active_tracks)) do
       append_args({
            "-ss", start,
            "-i", input_path,
        })
        if settings.only_active_tracks then
            for _, track_index in ipairs(tracks) do
                track_args = append_table(track_args, { "-map", string.format("%d:%d", input_index, track_index)})
            end
        else
            track_args = append_table(track_args, { "-map", tostring(input_index)})
        end
        input_index = input_index + 1
    end

    append_args({"-to", tostring(to-from)})
    append_args(track_args)

    -- apply some of the video filters currently in the chain
    local filters = {}
    if settings.preserve_filters then
        filters = get_video_filters()
    end
    if settings.append_filter ~= "" then
        filters[#filters + 1] = settings.append_filter
    end
    if #filters > 0 then
        append_args({ "-filter:v", table.concat(filters, ",") })
    end

    -- split the user-passed settings on whitespace
    for token in string.gmatch(settings.codec, "[^%s]+") do
        args[#args + 1] = token
    end

    -- path of the output
    local output_directory = mp.get_property("options/screenshot-directory")
    -- local checkbool = exists(output_directory.."/")
    -- mp.osd_message("" .. type(checkbool), timer_duration)
    -- if not checkbool then    
    --     os.execute("mkdir" .. output_directory)
    -- end
    if output_directory == "" then
        if is_stream then
            output_directory = "."
        else
            output_directory, _ = utils.split_path(path)
        end
    else
        output_directory = string.gsub(output_directory, "^~", os.getenv("HOME") or "~")
    end
    local input_name = mp.get_property("filename/no-ext") or "encode"
    local title = mp.get_property("media-title")
    local extension = get_extension(path)
    local output_name = get_output_string(output_directory, settings.output_format, input_name, extension, title, from, to, settings.profile)
    if not output_name then
        mp.osd_message("Invalid path " .. output_directory)
        return
    end
    args[#args + 1] = utils.join_path(output_directory, output_name)

    if settings.print then
        local o = ""
        -- fuck this is ugly
        for i = 1, #args do
            local fmt = ""
            if i == 1 then
                fmt = "%s%s"
            elseif i >= 2 and i <= 4 then
                fmt = "%s"
            elseif args[i-1] == "-i" or i == #args or args[i-1] == "-filter:v" then
                fmt = "%s '%s'"
            else
                fmt = "%s %s"
            end
            o = string.format(fmt, o, args[i])
        end
        print(o)
    end
    if settings.detached then
        utils.subprocess_detached({ args = args })
    else
        local res = utils.subprocess({ args = args, max_size = 0, cancellable = false })
        if res.status == 0 then
            mp.osd_message("Finished encoding succesfully")
        else
            mp.osd_message("Failed to encode, check the log")
        end
    end
end

function clear_timestamp()
    timer:kill()
    start_timestamp = nil
    profile_start = ""
    mp.remove_key_binding("encode-ESC")
    mp.remove_key_binding("encode-ENTER")
    mp.osd_message("", 0)
end

function set_timestamp(profile)
    if not mp.get_property("path") then
        mp.osd_message("No file currently playing")
        return
    end
    if not mp.get_property_bool("seekable") then
        mp.osd_message("Cannot encode non-seekable media")
        return
    end
    create_dir(mp.get_property("options/screenshot-directory"))
    if not start_timestamp or profile ~= profile_start then
        profile_start = profile
        start_timestamp = mp.get_property_number("time-pos")
        local msg = function()
            mp.osd_message(
                string.format("encode [%s]: waiting for end timestamp", profile or "default"),
                timer_duration
            )
        end
        msg()
        timer = mp.add_periodic_timer(timer_duration, msg)
        mp.add_forced_key_binding("ESC", "encode-ESC", clear_timestamp)
        mp.add_forced_key_binding("ENTER", "encode-ENTER", function() set_timestamp(profile) end)
    else
        local from = start_timestamp
        local to = mp.get_property_number("time-pos")
        if to <= from then
            mp.osd_message("Second timestamp cannot be before the first", timer_duration)
            timer:kill()
            timer:resume()
            return
        end
        clear_timestamp()
        mp.osd_message(string.format("Encoding from %s to %s"
            , seconds_to_time_string(from, false)
            , seconds_to_time_string(to, false)
        ), timer_duration)
        -- include the current frame into the extract
        local fps = mp.get_property_number("container-fps") or 30
        to = to + 1 / fps / 2
        local settings = {
            detached = false,
            container = "",
            only_active_tracks = false,
            preserve_filters = true,
            append_filter = "",
            codec = "-c:v libvpx-vp9 -lossless 1 -b:v 1000k -deadline good",
            output_format = "$f_$n.webm",
            output_directory = "",
            ffmpeg_command = "ffmpeg",
            print = true,
        }
        if profile then
            options.read_options(settings, profile)
            if settings.container ~= "" then
                msg.warn("The 'container' setting is deprecated, use 'output_format' now")
                settings.output_format = settings.output_format .. "." .. settings.container
            end
            settings.profile = profile
        else
            settings.profile = "default"
        end        
        start_encoding(from, to, settings)
    end
end

mp.add_key_binding(nil, "set-timestamp", set_timestamp)


  


• ffplay : decrease max audio callbacks per second

  14 juin 2014, par Marton Balint

  ffplay : decrease max audio callbacks per second
  Too many audio callbacks per second can cause buffer underruns especially under
  
  load. As now we take into accound the elapsed time after an audio callback when
  
  determining current audio clock, it is not that important to use small buffer
  
  sizes and frequent audio callbacks, so lets remove the comment.
  Signed-off-by : Marton Balint <cus@passwd.hu>
  

  • [DH] ffplay.c

• openCV VideoCapture doesn't work with gstreamer x264

  18 juin 2014, par nschoe

  I’d like to display a rtp / vp8 video stream that comes from gstreamer, in openCV.

  I have already a working solution which is implemented like this :

  gst-launch-0.10 udpsrc port=6666 ! "application/x-rtp,media=(string)video,clock-rate=(int)90000,encoding-name=(string)VP8-DRAFT-IETF-01,payload=(int)120" ! rtpvp8depay ! vp8dec ! ffmpegcolorspace ! ffenc_mpeg4 ! filesink location=videoStream

  Basically it grabs incoming data from a UDP socket, depacketize rtp, decode vp8, pass to ffmpegcolorspace (I still don’t understand what this is for, I see it everywhere in gstreamer).

  The videoStream is a pipe I created with mkfifo. On the side, I have my openCV code that does :

  VideoCapture cap("videoStream");

  and uses cap.read() to push into a Mat.

  My main concern is that I use ffenc_mpeg4 here and I believe this alters my video quality. I tried using x264enc in place of ffenc_mpeg4 but I have no output : openCV doesn’t react, neither does gstreamer, and after a couple of seconds, gst-launch just stops.

  Any idea what I could use instead of ffenc_mpeg4 ? I looked for "lossless codec" on the net, but it seems I am confusing things such as codec, contains, format, compression and encoding ; so any help would be (greatly) appreciated !

  Thanks in advance !