Calling python script through a php script accessed by the browser

I have a php script that will get uploaded videos and I would like to convert these videos using ffmpeg.

I created a python script that receives php parameters and calls ffmpeg to do the conversion.

index.php

<?php

$data = array('filePath' => 'video.mov');

$result = shell_exec('/usr/bin/python /home/fernando/Workspace/lab1/public_html/converter.py ' . escapeshellarg(json_encode($data)));

converter.py

#!/usr/bin/env python

import os, sys, json, subprocess, string, random

class Converter():

WORK_DIR = '/home/fernando/Workspace/lab1/public_html'
DESTINATION_DIR = '/home/fernando/Workspace/lab1/public_html/videos/'
NEW_AUDIO = 'audio.mp3'

def __init__(self, data):
    try:
        os.chdir(self.WORK_DIR)
        self.arg = data
    except:
        print "ERROR"
        sys.exit(1)     


def generateId():
    return ''.join(random.choice(string.ascii_uppercase + string.digits + string.ascii_lowercase ) for _ in range(12))      


def convertVideo(self, type):

    convertedFileName = self.DESTINATION_DIR + self.generateId() + '.' + type

    typesDic = {
                'mp4': ['/usr/bin/ffmpeg', '-loglevel', 'quiet', '-i', self.arg['filePath'], '-i', self.NEW_AUDIO, '-map', '0:0', '-map', '1', '-shortest', '-codec', 'copy', convertedFileName, '-y'], 
                'ogv': ['/usr/bin/ffmpeg', '-loglevel', 'quiet', '-i', self.arg['filePath'], '-i', self.NEW_AUDIO, '-map', '0:0', '-map', '1', '-shortest', '-vcodec', 'libtheora', '-acodec', 'libvorbis',  convertedFileName, '-y'] 
               }

    sp = subprocess.Popen(typesDic[type], shell=True)

    out, err = sp.communicate()

    if err:
        return {'status': 'error'}

    return {'status': 'success', 'filename': convertedFileName}




data = json.loads(sys.argv[1])

c = Converter(data)
print c.convertVideo('mp4')
print c.convertVideo('ogv')

These codes are working the way I need them, but only if I call them   via command line . Home Ex: $ php index.php
or: $ ./converter.py '{"fileName": "video.avi"}'

If I access via browser, which was my main intention, it does not work.

What is wrong? Home Is it possible to do this via browser?
Would you have a better approach?

Edited:

Exit the apache log:

Use -h to get full help or even better, run 'man ffmpeg' ffmpeg version 1.2.6-7: 1.2.6-1 ~ trusty1 Copyright (c) 2000-2014 the FFmpeg developers built on Apr 26 2014 18:52:58 with gcc 4.8 (Ubuntu 4.8.2-19ubuntu1) configuration: --arch = amd64 --disable-stripping --enable-avresample --enable-pthreads --enable-runtime-cpudetect --extra-version = '7: 1.2.6-1 ~ trusty1' -libdir = / usr / lib / x86_64-linux-gnu --prefix = / usr --enable -bzlib --enable -libdc1394 --enable-libfreetype --enable -frei0r --enable-gnutls --enable-libgsm --enable-libmp3lame --enable-librtmp --enable-libopencv --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-libschroedinger --enable -libspeex --enable-libtheora --enable-vaapi --enable -vdpau --enable-libvorbis --enable -libvpx --enable -libile --enable -gpl --enable -postproc --enable -libcdio --enable -x11grab --enable-libx264 --shlibdir = / usr / lib / x86_64-linux-gnu --enable-shared --disable-static libavutil 52. 18.100 / 52. 18.100 libavcodec 54. 92,100 / 54. 92,100 libavformat 54. 63.104 / 54. 63.104 libavdevice 53. 5.103 / 53. 5.103 libavfilter 3. 42.103 / 3. 42.103 libswscale 2. 2.100 / 2. 2.100 libswresample 0. 17.102 / 0. 17.102 libpostproc 52. 2.100 / 52. 2.100 Hyper fast Audio and Video encoder usage: ffmpeg [options] [[infile options] -i infile] ... {[outfile options] outfile}