ffmpeg video conversion

[eluser]montassis[/eluser]
Hey All,

I am writing a CI application where users can upload video files. I have read quite a lot about doing video conversion using ffmpeg and understand the basics. My problem is that I cannot seem to work out how to run this process in the background so the website doesn't just hang on a blank page while the video is being converted. Currently, I am attempting to run ffmpeg as a background process, but the view is not loaded until the conversion is complete.

Here is a portion of code from my Upload controller

Code:

function uploadVideo() {
        $config['upload_path'] = getcwd() . '/uservids/' . $this->session->userdata('accountid');
        $config['allowed_types'] = 'mov|wmv|ogv';
        $filename = md5(date(DATE_RFC822));
        $config['file_name'] = $filename;

        $this->load->library('upload', $config);

        if (!$this->upload->do_upload('videoFile')) {
            [removed code]
        } else {

            $videoDetails = $this->upload->data();
            $videoDetails['accountid'] = $this->session->userdata('accountid');
            $videoid = $this->_createVideo($videoDetails);

            // page data
            $mainData['success'] = $this->upload->data();
            $mainData['firstName'] = $this->session->userdata('firstName');
            $mainData['lastName'] = $this->session->userdata('lastName');

            // form data
            $mainData['title'] = array('name' => 'title', 'id' => 'title');
            $mainData['comment'] = array('name' => 'title', 'id' => 'title', 'rows' => '8', 'cols' => '37');
            $mainData['videoid'] = array('name' => 'videoid', 'value' => $videoid);

            // load the view
            $data['mainView'] = 'upload/upload_success';
            $data['mainData'] = $mainData;
            $this->load->view('template', $data);

            // conversion
            $command = 'ffmpeg -i ' . $videoDetails['full_path'] . ' ' . $videoDetails['file_path'] . $filename . '.ogv';

            echo("Running file conversion");
            $ps = $this->_runInBackground($command);
            // while process is running, print a nice little dot
            while ($this->_isProcessRunning($ps)) {
                echo(" . ");
                ob_flush();
                flush();
                // sleep for .25 seconds
                usleep(250000);
            }
                
        }
    }

    // inserts into database, returns new videoid
    function _createVideo($details) {
        return $this->Video->createVideo($details);
    }

    // executes function to run in the background (not working)
    function _runInBackground($command, $priority = 0) {
        if ($priority)
            $PID = shell_exec("nohup nice -n $priority $command 2> /dev/null & echo $! &");

        else
            $PID = shell_exec("nohup $command > /dev/null 2> /dev/null & echo $! &");
        return($PID);
    }

    // this works
    function _isProcessRunning($PID) {
        exec("ps $PID", $ProcessState);
        return(count($ProcessState) >= 2);
    }
}

I know the conversion is working, because I get the output file and a line up the top that says "Running file conversion................................" with a bunch of dots.

So does anyone know how to run this type of thing in the background? Also, if possible, rather than sending the output to /dev/null I wouldnt mind sending it to a text file that I could read and then get info like the duration and number of frames so i could come up with a progress bar.

Any help or info much appreciated.