Video heavily out of sync after using Ripbot

[Okys]

Hello guys.
Please help me solve this problem. I'm a complete noob in these things and not English, but will try my best to explain it.

I have a video file, created using Galaxy S4 smartphone.
Details here:

Format                                   : MPEG-4
Format profile                           : Base Media
Codec ID                                 : isom
File size                                : 113 MiB
Duration                                 : 55s 701ms
Overall bit rate                         : 17.1 Mbps
Encoded date                             : UTC 2014-08-15 10:23:32
Tagged date                              : UTC 2014-08-15 10:23:32

Video
ID                                       : 1
Format                                   : AVC
Format/Info                              : Advanced Video Codec
Format profile                           : High@L4.0
Format settings, CABAC                   : Yes
Format settings, ReFrames                : 1 frame
Format settings, GOP                     : M=1, N=30
Codec ID                                 : avc1
Codec ID/Info                            : Advanced Video Coding
Duration                                 : 55s 396ms
Source duration                          : 55s 409ms
Bit rate                                 : 17.0 Mbps
Width                                    : 1 920 pixels
Height                                   : 1 080 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Variable
Frame rate                               : 30.000 fps
Minimum frame rate                       : 21.786 fps
Maximum frame rate                       : 31.326 fps
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Progressive
Bits/(Pixel*Frame)                       : 0.273
Stream size                              : 112 MiB (99%)
Source stream size                       : 112 MiB (99%)
Title                                    : VideoHandle
Language                                 : English
Encoded date                             : UTC 2014-08-15 10:23:32
Tagged date                              : UTC 2014-08-15 10:23:32
mdhd_Duration                            : 55396

Audio
ID                                       : 2
Format                                   : AAC
Format/Info                              : Advanced Audio Codec
Format profile                           : LC
Codec ID                                 : 40
Duration                                 : 55s 701ms
Bit rate mode                            : Constant
Bit rate                                 : 128 Kbps
Channel(s)                               : 2 channels
Channel positions                        : Front: L R
Sampling rate                            : 48.0 KHz
Compression mode                         : Lossy
Stream size                              : 859 KiB (1%)
Title                                    : SoundHandle
Language                                 : English
Encoded date                             : UTC 2014-08-15 10:23:32
Tagged date                              : UTC 2014-08-15 10:23:32

Using Ripbot (tried 2 different versions) i am trying to decrease the file size a little. I meet all the requirements, Ripbot needed. Everything works, but problem comes when i playback the newly created file. Duration of file is 55 seconds, there is an audible hand clap at 40 seconds (in both files), but in picture i only see it at 48 seconds in the new file. So, audio is always where it should be but video plays back slower and loses several frames at the end.
The only thing i can think of, is the variable frame rate of original file, and constant 25 fps for my new file.
If that's the problem, how can i tell RipBot not to touch the frame rate?

I have these default commands for encoder settings:
--level 4.0 --aud --nal-hrd vbr --vbv-bufsize 25000 --vbv-maxrate 25000 --b-pyramid none

Thanks in advance!

[smrpix]

These kinds of problems are typical when interpreting variable frame rate video.

Try a different encoder. Avanti or Winff are good front ends for ffmpeg. Handbrake may work for you as well.

[Okys]

Thanks, smrpix. I tried Avanti first and it worked. Now audio and video is sync, as far as i can notice. But anyway, the frame rate came out constant (30 fps) for my new file after setting Frame Rate and Frame Size to Source (i understand as "keep it unchanged"). I can't notice any differences in quality in both files, but i'm worried, there will still be some problems for larger files, where picture quality is better and less hand shaking.