Rewrite MP4/MOV binaries to be faststart
In some cases, MP4/MOV files can have the data _before_ the meta-data. Thus, ffmpeg (and all similar tools) cannot really process the input if it's given over stdin/streaming/pipes. BUT I REALLY DON'T WANT TO MAKE TEMPORARY FILES so here we go, an implementation of qtfaststart in elixir.
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@ -14,8 +14,7 @@ defmodule Pleroma.Helpers.MediaHelper do
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{:ok, args} <- prepare_image_resize_args(options),
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url = Pleroma.Web.MediaProxy.url(url),
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{:ok, env} <- Pleroma.HTTP.get(url),
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{:ok, fifo_path} <- mkfifo()
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do
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{:ok, fifo_path} <- mkfifo() do
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args = List.flatten([fifo_path, args])
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run_fifo(fifo_path, env, executable, args)
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else
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@ -27,12 +26,17 @@ defmodule Pleroma.Helpers.MediaHelper do
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defp prepare_image_resize_args(%{max_width: max_width, max_height: max_height} = options) do
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quality = options[:quality] || 85
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resize = Enum.join([max_width, "x", max_height, ">"])
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args = [
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"-interlace", "Plane",
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"-resize", resize,
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"-quality", to_string(quality),
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"-interlace",
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"Plane",
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"-resize",
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resize,
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"-quality",
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to_string(quality),
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"jpg:-"
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]
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{:ok, args}
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end
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@ -45,11 +49,15 @@ defmodule Pleroma.Helpers.MediaHelper do
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{:ok, fifo_path} <- mkfifo(),
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args = [
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"-y",
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"-i", fifo_path,
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"-vframes", "1",
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"-f", "mjpeg",
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"-loglevel", "error",
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"pipe:"
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"-i",
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fifo_path,
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"-vframes",
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"1",
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"-f",
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"mjpeg",
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"-loglevel",
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"error",
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"-"
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] do
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run_fifo(fifo_path, env, executable, args)
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else
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@ -59,9 +67,18 @@ defmodule Pleroma.Helpers.MediaHelper do
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end
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defp run_fifo(fifo_path, env, executable, args) do
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pid = Port.open({:spawn_executable, executable}, [:use_stdio, :stream, :exit_status, :binary, args: args])
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pid =
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Port.open({:spawn_executable, executable}, [
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:use_stdio,
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:stream,
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:exit_status,
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:binary,
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args: args
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])
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fifo = Port.open(to_charlist(fifo_path), [:eof, :binary, :stream, :out])
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true = Port.command(fifo, env.body)
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fix = Pleroma.Helpers.QtFastStart.fix(env.body)
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true = Port.command(fifo, fix)
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:erlang.port_close(fifo)
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loop_recv(pid)
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after
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@ -70,10 +87,12 @@ defmodule Pleroma.Helpers.MediaHelper do
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defp mkfifo() do
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path = "#{@tmp_base}#{to_charlist(:erlang.phash2(self()))}"
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case System.cmd("mkfifo", [path]) do
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{_, 0} ->
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spawn(fifo_guard(path))
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{:ok, path}
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{_, err} ->
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{:error, {:fifo_failed, err}}
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end
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@ -81,8 +100,10 @@ defmodule Pleroma.Helpers.MediaHelper do
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defp fifo_guard(path) do
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pid = self()
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fn() ->
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fn ->
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ref = Process.monitor(pid)
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receive do
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{:DOWN, ^ref, :process, ^pid, _} ->
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File.rm(path)
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@ -98,8 +119,10 @@ defmodule Pleroma.Helpers.MediaHelper do
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receive do
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{^pid, {:data, data}} ->
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loop_recv(pid, acc <> data)
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{^pid, {:exit_status, 0}} ->
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{:ok, acc}
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{^pid, {:exit_status, status}} ->
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{:error, status}
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after
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131
lib/pleroma/helpers/qt_fast_start.ex
Normal file
131
lib/pleroma/helpers/qt_fast_start.ex
Normal file
@ -0,0 +1,131 @@
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# Pleroma: A lightweight social networking server
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# Copyright © 2017-2020 Pleroma Authors <https://pleroma.social/>
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# SPDX-License-Identifier: AGPL-3.0-only
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defmodule Pleroma.Helpers.QtFastStart do
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@moduledoc """
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(WIP) Converts a "slow start" (data before metadatas) mov/mp4 file to a "fast start" one (metadatas before data).
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"""
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# TODO: Cleanup and optimizations
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# Inspirations: https://www.ffmpeg.org/doxygen/3.4/qt-faststart_8c_source.html
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# https://github.com/danielgtaylor/qtfaststart/blob/master/qtfaststart/processor.py
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# ISO/IEC 14496-12:2015, ISO/IEC 15444-12:2015
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# Paracetamol
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def fix(binary = <<0x00, 0x00, 0x00, _, 0x66, 0x74, 0x79, 0x70, _::binary>>) do
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index = fix(binary, binary, 0, [])
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case index do
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[{"ftyp", _, _, _, _}, {"mdat", _, _, _, _} | _] -> faststart(index)
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[{"ftyp", _, _, _, _}, {"free", _, _, _, _}, {"mdat", _, _, _, _} | _] -> faststart(index)
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_ -> binary
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end
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end
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def fix(binary) do
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binary
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end
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defp fix(<<>>, _bin, _pos, acc) do
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:lists.reverse(acc)
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end
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defp fix(
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<<size::integer-big-size(4)-unit(8), fourcc::binary-size(4), rest::binary>>,
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bin,
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pos,
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acc
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) do
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if fourcc == "mdat" && size == 0 do
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# mdat with 0 size means "seek to the end" -- also, in that case the file is probably OK.
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acc = [
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{fourcc, pos, byte_size(bin) - pos, byte_size(bin) - pos,
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<<size::integer-big-size(4)-unit(8), fourcc::binary-size(4), rest::binary>>}
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]
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fix(<<>>, bin, byte_size(bin), acc)
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else
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full_size = size - 8
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<<data::binary-size(full_size), rest::binary>> = rest
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acc = [
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{fourcc, pos, pos + size, size,
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<<size::integer-big-size(4)-unit(8), fourcc::binary-size(4), data::binary>>}
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]
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fix(rest, bin, pos + size, acc)
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end
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end
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defp faststart(index) do
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{{_ftyp, _, _, _, ftyp}, index} = List.keytake(index, "ftyp", 0)
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# Skip re-writing the free fourcc as it's kind of useless. Why stream useless bytes when you can do without?
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{free_size, index} =
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case List.keytake(index, "free", 0) do
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{{_, _, _, size, _}, index} -> {size, index}
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_ -> {0, index}
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end
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{{_moov, _, _, moov_size, moov}, index} = List.keytake(index, "moov", 0)
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offset = -free_size + moov_size
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rest = for {_, _, _, _, data} <- index, do: data, into: <<>>
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<<moov_head::binary-size(8), moov_data::binary>> = moov
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new_moov = fix_moov(moov_data, offset)
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<<ftyp::binary, moov_head::binary, new_moov::binary, rest::binary>>
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end
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defp fix_moov(moov, offset) do
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fix_moov(moov, offset, <<>>)
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end
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defp fix_moov(<<>>, _, acc), do: acc
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defp fix_moov(
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<<size::integer-big-size(4)-unit(8), fourcc::binary-size(4), rest::binary>>,
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offset,
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acc
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) do
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full_size = size - 8
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<<data::binary-size(full_size), rest::binary>> = rest
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data =
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cond do
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fourcc in ["trak", "mdia", "minf", "stbl"] ->
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# Theses contains sto or co64 part
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<<size::integer-big-size(4)-unit(8), fourcc::binary-size(4),
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fix_moov(data, offset, <<>>)::binary>>
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fourcc in ["stco", "co64"] ->
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# fix the damn thing
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<<version::integer-big-size(4)-unit(8), count::integer-big-size(4)-unit(8),
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rest::binary>> = data
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entry_size =
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case fourcc do
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"stco" -> 4
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"co64" -> 8
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end
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{_, result} =
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Enum.reduce(1..count, {rest, <<>>}, fn _,
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{<<pos::integer-big-size(entry_size)-unit(8),
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rest::binary>>, acc} ->
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{rest, <<acc::binary, pos + offset::integer-big-size(entry_size)-unit(8)>>}
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end)
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<<size::integer-big-size(4)-unit(8), fourcc::binary-size(4),
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version::integer-big-size(4)-unit(8), count::integer-big-size(4)-unit(8),
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result::binary>>
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true ->
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<<size::integer-big-size(4)-unit(8), fourcc::binary-size(4), data::binary>>
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end
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acc = <<acc::binary, data::binary>>
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fix_moov(rest, offset, acc)
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end
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end
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