ffmpeg格式转换

//要执行的cmd命令
        //$cmd = "ffmpeg -i $base" . "$filepath " . "$base$outfile";
        $directory = "D:\ipwebV2\htdocs\ipweb2.0\public\uploads\medias\downloads";
        $path = str_replace('\\', '/', mb_convert_encoding($directory, 'UTF-8','UTF-8'));
        $path = str_replace('//', '/', $path);
        $cmd = "D:/ffmpeg/bin/ffmpeg.exe -i {$path}/pre_4.wav -f mp3 -acodec libmp3lame -y {$path}/pre_4.mp3";
        echo $cmd;
        system($cmd, $output);
        //echo "成功";exit;
        print_r($output);exit;