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Rewrite MP4/MOV binaries to be faststart

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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.
This commit is contained in:
href 2020-08-28 21:14:28 +02:00
parent 5b4d483f52
commit dfceb03cf4
2 changed files with 172 additions and 18 deletions
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59
lib/pleroma/helpers/media_helper.ex
View file

@ -14,8 +14,7 @@ def image_resize(url, options) do
{:ok, args} <- prepare_image_resize_args(options),
url = Pleroma.Web.MediaProxy.url(url),
{:ok, env} <- Pleroma.HTTP.get(url),
{:ok, fifo_path} <- mkfifo()
do
{:ok, fifo_path} <- mkfifo() do
args = List.flatten([fifo_path, args])
run_fifo(fifo_path, env, executable, args)
else
@ -27,12 +26,17 @@ def image_resize(url, options) do
defp prepare_image_resize_args(%{max_width: max_width, max_height: max_height} = options) do
quality = options[:quality] || 85
resize = Enum.join([max_width, "x", max_height, ">"])
args = [
"-interlace", "Plane",
"-resize", resize,
"-quality", to_string(quality),
"jpg:-"
"-interlace",
"Plane",
"-resize",
resize,
"-quality",
to_string(quality),
"jpg:-"
]
{:ok, args}
end
@ -45,11 +49,15 @@ def video_framegrab(url) do
{:ok, fifo_path} <- mkfifo(),
args = [
"-y",
"-i", fifo_path,
"-vframes", "1",
"-f", "mjpeg",
"-loglevel", "error",
"pipe:"
"-i",
fifo_path,
"-vframes",
"1",
"-f",
"mjpeg",
"-loglevel",
"error",
"-"
] do
run_fifo(fifo_path, env, executable, args)
else
@ -59,9 +67,18 @@ def video_framegrab(url) do
end
defp run_fifo(fifo_path, env, executable, args) do
pid = Port.open({:spawn_executable, executable}, [:use_stdio, :stream, :exit_status, :binary, args: args])
pid =
Port.open({:spawn_executable, executable}, [
:use_stdio,
:stream,
:exit_status,
:binary,
args: args
])
fifo = Port.open(to_charlist(fifo_path), [:eof, :binary, :stream, :out])
true = Port.command(fifo, env.body)
fix = Pleroma.Helpers.QtFastStart.fix(env.body)
true = Port.command(fifo, fix)
:erlang.port_close(fifo)
loop_recv(pid)
after
@ -70,10 +87,12 @@ defp run_fifo(fifo_path, env, executable, args) do
defp mkfifo() do
path = "#{@tmp_base}#{to_charlist(:erlang.phash2(self()))}"
case System.cmd("mkfifo", [path]) do
{_, 0} ->
spawn(fifo_guard(path))
{:ok, path}
{_, err} ->
{:error, {:fifo_failed, err}}
end
@ -81,8 +100,10 @@ defp mkfifo() do
defp fifo_guard(path) do
pid = self()
fn() ->
fn ->
ref = Process.monitor(pid)
receive do
{:DOWN, ^ref, :process, ^pid, _} ->
File.rm(path)
@ -98,14 +119,16 @@ defp loop_recv(pid, acc) do
receive do
{^pid, {:data, data}} ->
loop_recv(pid, acc <> data)
{^pid, {:exit_status, 0}} ->
{:ok, acc}
{^pid, {:exit_status, status}} ->
{:error, status}
after
5000 ->
:erlang.port_close(pid)
{:error, :timeout}
after
5000 ->
:erlang.port_close(pid)
{:error, :timeout}
end
end
end

131
lib/pleroma/helpers/qt_fast_start.ex Normal file
View file

@ -0,0 +1,131 @@
# Pleroma: A lightweight social networking server
# Copyright © 2017-2020 Pleroma Authors <https://pleroma.social/>
# SPDX-License-Identifier: AGPL-3.0-only
defmodule Pleroma.Helpers.QtFastStart do
@moduledoc """
(WIP) Converts a "slow start" (data before metadatas) mov/mp4 file to a "fast start" one (metadatas before data).
"""
# TODO: Cleanup and optimizations
# Inspirations: https://www.ffmpeg.org/doxygen/3.4/qt-faststart_8c_source.html
# https://github.com/danielgtaylor/qtfaststart/blob/master/qtfaststart/processor.py
# ISO/IEC 14496-12:2015, ISO/IEC 15444-12:2015
# Paracetamol
def fix(binary = <<0x00, 0x00, 0x00, _, 0x66, 0x74, 0x79, 0x70, _::binary>>) do
index = fix(binary, binary, 0, [])
case index do
[{"ftyp", _, _, _, _}, {"mdat", _, _, _, _} | _] -> faststart(index)
[{"ftyp", _, _, _, _}, {"free", _, _, _, _}, {"mdat", _, _, _, _} | _] -> faststart(index)
_ -> binary
end
end
def fix(binary) do
binary
end
defp fix(<<>>, _bin, _pos, acc) do
:lists.reverse(acc)
end
defp fix(
<<size::integer-big-size(4)-unit(8), fourcc::binary-size(4), rest::binary>>,
bin,
pos,
acc
) do
if fourcc == "mdat" && size == 0 do
# mdat with 0 size means "seek to the end" -- also, in that case the file is probably OK.
acc = [
{fourcc, pos, byte_size(bin) - pos, byte_size(bin) - pos,
<<size::integer-big-size(4)-unit(8), fourcc::binary-size(4), rest::binary>>}
| acc
]
fix(<<>>, bin, byte_size(bin), acc)
else
full_size = size - 8
<<data::binary-size(full_size), rest::binary>> = rest
acc = [
{fourcc, pos, pos + size, size,
<<size::integer-big-size(4)-unit(8), fourcc::binary-size(4), data::binary>>}
| acc
]
fix(rest, bin, pos + size, acc)
end
end
defp faststart(index) do
{{_ftyp, _, _, _, ftyp}, index} = List.keytake(index, "ftyp", 0)
# Skip re-writing the free fourcc as it's kind of useless. Why stream useless bytes when you can do without?
{free_size, index} =
case List.keytake(index, "free", 0) do
{{_, _, _, size, _}, index} -> {size, index}
_ -> {0, index}
end
{{_moov, _, _, moov_size, moov}, index} = List.keytake(index, "moov", 0)
offset = -free_size + moov_size
rest = for {_, _, _, _, data} <- index, do: data, into: <<>>
<<moov_head::binary-size(8), moov_data::binary>> = moov
new_moov = fix_moov(moov_data, offset)
<<ftyp::binary, moov_head::binary, new_moov::binary, rest::binary>>
end
defp fix_moov(moov, offset) do
fix_moov(moov, offset, <<>>)
end
defp fix_moov(<<>>, _, acc), do: acc
defp fix_moov(
<<size::integer-big-size(4)-unit(8), fourcc::binary-size(4), rest::binary>>,
offset,
acc
) do
full_size = size - 8
<<data::binary-size(full_size), rest::binary>> = rest
data =
cond do
fourcc in ["trak", "mdia", "minf", "stbl"] ->
# Theses contains sto or co64 part
<<size::integer-big-size(4)-unit(8), fourcc::binary-size(4),
fix_moov(data, offset, <<>>)::binary>>
fourcc in ["stco", "co64"] ->
# fix the damn thing
<<version::integer-big-size(4)-unit(8), count::integer-big-size(4)-unit(8),
rest::binary>> = data
entry_size =
case fourcc do
"stco" -> 4
"co64" -> 8
end
{_, result} =
Enum.reduce(1..count, {rest, <<>>}, fn _,
{<<pos::integer-big-size(entry_size)-unit(8),
rest::binary>>, acc} ->
{rest, <<acc::binary, pos + offset::integer-big-size(entry_size)-unit(8)>>}
end)
<<size::integer-big-size(4)-unit(8), fourcc::binary-size(4),
version::integer-big-size(4)-unit(8), count::integer-big-size(4)-unit(8),
result::binary>>
true ->
<<size::integer-big-size(4)-unit(8), fourcc::binary-size(4), data::binary>>
end
acc = <<acc::binary, data::binary>>
fix_moov(rest, offset, acc)
end
end