NodeJS spawning FFMPEG process does not understand arguments right - node.js

Question

I am writing code to speed up video using FFMPEG with multiplier. 5X for five times faster video, 0.5X for twice slower video etc.
This code has worked previously in other use case, but it looks like there is something wrong with args array.
var spawn = require('child_process').spawn;
var cmd = 'node_modules\\ffmpeg-binaries\\bin\\ffmpeg.exe';
speedupFilename = tmpdir + vts + 'speedup.mp4';
var args = ['-i', filename, '-filter:v ', '"setpts=PTS/' + multiplier + '"', speedupFilename];
console.log(cmd + ' ' + args.join(' '));
var proc = spawn(cmd, args);
/* code that reads stdout and print it out to console */
This prints out in console:
node_modules\ffmpeg-binaries\bin\ffmpeg.exe -i C:\Users\User\AppData\Local\Temp\1533658543video.mp4 -filter:v "setpts=PTS/0.10" C:\Users\User\AppData\Local\Temp\1533658543speedup.mp4
ffmpeg version 3.2 Copyright (c) 2000-2016 the FFmpeg developers
built with gcc 5.4.0 (GCC)
configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-dxva2 --enable-libmfx --enable-nvenc --enable-avisynth --enable-bzlib --enable-libebur128 --enable-fontconfig --enable-frei0r --enable-gnutls --enable-iconv --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libfreetype --enable-libgme --enable-libgsm --enable-libilbc --enable-libmodplug --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenh264 --enable-libopenjpeg --enable-libopus --enable-librtmp --enable-libschroedinger --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxavs --enable-libxvid --enable-libzimg --enable-lzma --enable-decklink --enable-zlib
libavutil 55. 34.100 / 55. 34.100
libavcodec 57. 64.100 / 57. 64.100
libavformat 57. 56.100 / 57. 56.100
libavdevice 57. 1.100 / 57. 1.100
libavfilter 6. 65.100 / 6. 65.100
libswscale 4. 2.100 / 4. 2.100
libswresample 2. 3.100 / 2. 3.100
libpostproc 54. 1.100 / 54. 1.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'C:\Users\User\AppData\Local\Temp\1533658543video.mp4':
Metadata:
major_brand : isom
minor_version : 512
compatible_brands:
script.js:337 isomiso2avc1mp41
encoder : Lavf57.56.100
Duration: 00:00:00.12, start: 0.000000, bitrate: 9398 kb/s
Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1280x720, 9340 kb/s, 25 fps, 25 tbr, 12800 tbn, 50 tbc (default)
Metadata:
handler_name : VideoHandler
[AVFilterGraph # 05c67dc0] No such filter: '"setpts'
Error opening filters!
I have setpts filter in my FFMPEG, I have looked into ffmpeg -filters.
If I run command (first line in output) in console, it works fine.
If I change -filter:v ', '"setpts=PTS/' + multiplier + '"' to -filter:v "setpts=PTS/' + multiplier + '"' in args array (remove ', ' to connect those two array items), then it just says At least one output file must be specified:
ffmpeg version 3.2 Copyright (c) 2000-2016 the FFmpeg developers
built with gcc 5.4.0 (GCC)
configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-dxva2 --enable-libmfx --enable-nvenc --enable-avisynth --enable-bzlib --enable-libebur128 --enable-fontconfig --enable-frei0r --enable-gnutls --enable-iconv --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libfreetype --enable-libgme --enable-libgsm --enable-libilbc --enable-libmodplug --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenh264 --enable-libopenjpeg --enable-libopus --enable-librtmp --enable-libschroedinger --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxavs --enable-libxvid --enable-libzimg --enable-lzma --enable-decklink --enable-zlib
libavutil 55. 34.100 / 55. 34.100
libavcodec 57. 64.100 / 57. 64.100
libavformat 57. 56.100 / 57. 56.100
libavdevice 57. 1.100 / 57. 1.100
libavfilter 6. 65.100 / 6. 65.100
libswscale 4. 2.100 / 4. 2.100
libswresample 2. 3.100 / 2. 3.100
libpostproc 54. 1.100 / 54. 1.100
Trailing options were found on the commandline.
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'C:\Users\User\AppData\Local\Temp\1533659280video.mp4':
Metadata:
major_brand : isom
minor_version : 512
compatible_brands:
isomiso2avc1mp41
encoder : Lavf57.56.100
Duration: 00:00:00.12, start: 0.000000, bitrate: 9398 kb/s
Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1280x720, 9340 kb/s, 25 fps, 25 tbr, 12800 tbn, 50 tbc (default)
Metadata:
handler_name : VideoHandler
At least one output file must be specified

Answer 1

I finally figured out the solution.
In the array item '"pts=PTS/' + multiplier + '"' I had to remove quotation marks. They are useless, because argument is anyways isolated unlike in command line space is not enough.