user12500: I have the following VOB file:
→ ffmpeg -i input.vob output:
ffmpeg version N-77455-g4707497 Copyright (c) 2000-2015 the FFmpeg developers
  built with gcc 4.8 (Ubuntu 4.8.4-2ubuntu1~14.04)
  configuration: --extra-libs=-ldl --prefix=/opt/ffmpeg --mandir=/usr/share/man --enable-avresample --disable-debug --enable-nonfree --enable-gpl --enable-version3 --enable-libopencore-amrnb --enable-libopencore-amrwb --disable-decoder=amrnb --disable-decoder=amrwb --enable-libpulse --enable-libdcadec --enable-libfreetype --enable-libx264 --enable-libx265 --enable-libfdk-aac --enable-libvorbis --enable-libmp3lame --enable-libopus --enable-libvpx --enable-libspeex --enable-libass --enable-avisynth --enable-libsoxr --enable-libxvid --enable-libvo-aacenc --enable-libvidstab
  libavutil      55. 11.100 / 55. 11.100
  libavcodec     57. 20.100 / 57. 20.100
  libavformat    57. 20.100 / 57. 20.100
  libavdevice    57.  0.100 / 57.  0.100
  libavfilter     6. 21.101 /  6. 21.101
  libavresample   3.  0.  0 /  3.  0.  0
  libswscale      4.  0.100 /  4.  0.100
  libswresample   2.  0.101 /  2.  0.101
  libpostproc    54.  0.100 / 54.  0.100
Input #0, mpeg, from 'input.vob':
  Duration: 00:31:36.96, start: 0.335967, bitrate: 6517 kb/s
    Stream #0:0[0x1e0]: Video: mpeg2video (Main), yuv420p(tv, bt470bg), 720x576 [SAR 64:45 DAR 16:9], max. 9800 kb/s, 25 fps, 25 tbr, 90k tbn, 50 tbc
    Stream #0:1[0x80]: Audio: ac3, 48000 Hz, stereo, fltp, 256 kb/s

→ mediainfo input.vob output:
General
Complete name                            : input.vob
Format                                   : MPEG-PS
File size                                : 1.44 GiB
Duration                                 : 31mn 36s
Overall bit rate mode                    : Variable
Overall bit rate                         : 6 518 Kbps

Video
ID                                       : 224 (0xE0)
Format                                   : MPEG Video
Format version                           : Version 2
Format profile                           : Main@Main
Format settings, BVOP                    : Yes
Format settings, Matrix                  : Default
Format settings, GOP                     : M=3, N=12
Format settings, picture structure       : Frame
Duration                                 : 31mn 36s
Bit rate mode                            : Variable
Bit rate                                 : 6 132 Kbps
Maximum bit rate                         : 9 800 Kbps
Width                                    : 720 pixels
Height                                   : 576 pixels
Display aspect ratio                     : 16:9
Frame rate                               : 25.000 fps
Standard                                 : PAL
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Interlaced
Scan order                               : Top Field First
Compression mode                         : Lossy
Bits/(Pixel*Frame)                       : 0.591
Time code of first frame                 : 00:00:00:00
Time code source                         : Group of pictures header
Stream size                              : 1.35 GiB (94%)
Color primaries                          : BT.601 PAL
Transfer characteristics                 : BT.470 System B, BT.470 System G
Matrix coefficients                      : BT.601

Audio
ID                                       : 189 (0xBD)-128 (0x80)
Format                                   : AC-3
Format/Info                              : Audio Coding 3
Mode extension                           : CM (complete main)
Format settings, Endianness              : Big
Muxing mode                              : DVD-Video
Duration                                 : 31mn 36s
Bit rate mode                            : Constant
Bit rate                                 : 256 Kbps
Channel(s)                               : 2 channels
Channel positions                        : Front: L R
Sampling rate                            : 48.0 KHz
Compression mode                         : Lossy
Stream size                              : 57.9 MiB (4%)

I have converted it to mp4 with the following command:
ffmpeg -i input.vob -c:v libx264 -preset slow -crf 19 -c:a aac -b:a 256k -threads 0 output.mp4

In the resulting video I see this effect:
  
How can I solve?

user1871: Add the yadif filter i.e.
ffmpeg -i input.vob -vf yadif -c:v libx264 -preset slow -crf 19 -c:a aac -b:a 256k output.mp4

See yadif docs for more info.

12500: <p>I have the following VOB file:</p>

<p>→ <code>ffmpeg -i input.vob</code> output:</p>

<pre><code>ffmpeg version N-77455-g4707497 Copyright (c) 2000-2015 the FFmpeg developers
  built with gcc 4.8 (Ubuntu 4.8.4-2ubuntu1~14.04)
  configuration: --extra-libs=-ldl --prefix=/opt/ffmpeg --mandir=/usr/share/man --enable-avresample --disable-debug --enable-nonfree --enable-gpl --enable-version3 --enable-libopencore-amrnb --enable-libopencore-amrwb --disable-decoder=amrnb --disable-decoder=amrwb --enable-libpulse --enable-libdcadec --enable-libfreetype --enable-libx264 --enable-libx265 --enable-libfdk-aac --enable-libvorbis --enable-libmp3lame --enable-libopus --enable-libvpx --enable-libspeex --enable-libass --enable-avisynth --enable-libsoxr --enable-libxvid --enable-libvo-aacenc --enable-libvidstab
  libavutil      55. 11.100 / 55. 11.100
  libavcodec     57. 20.100 / 57. 20.100
  libavformat    57. 20.100 / 57. 20.100
  libavdevice    57.  0.100 / 57.  0.100
  libavfilter     6. 21.101 /  6. 21.101
  libavresample   3.  0.  0 /  3.  0.  0
  libswscale      4.  0.100 /  4.  0.100
  libswresample   2.  0.101 /  2.  0.101
  libpostproc    54.  0.100 / 54.  0.100
Input #0, mpeg, from 'input.vob':
  Duration: 00:31:36.96, start: 0.335967, bitrate: 6517 kb/s
    Stream #0:0[0x1e0]: Video: mpeg2video (Main), yuv420p(tv, bt470bg), 720x576 [SAR 64:45 DAR 16:9], max. 9800 kb/s, 25 fps, 25 tbr, 90k tbn, 50 tbc
    Stream #0:1[0x80]: Audio: ac3, 48000 Hz, stereo, fltp, 256 kb/s
</code></pre>

<p>→ <code>mediainfo input.vob</code> output:</p>

<pre><code>General
Complete name                            : input.vob
Format                                   : MPEG-PS
File size                                : 1.44 GiB
Duration                                 : 31mn 36s
Overall bit rate mode                    : Variable
Overall bit rate                         : 6 518 Kbps

Video
ID                                       : 224 (0xE0)
Format                                   : MPEG Video
Format version                           : Version 2
Format profile                           : Main@Main
Format settings, BVOP                    : Yes
Format settings, Matrix                  : Default
Format settings, GOP                     : M=3, N=12
Format settings, picture structure       : Frame
Duration                                 : 31mn 36s
Bit rate mode                            : Variable
Bit rate                                 : 6 132 Kbps
Maximum bit rate                         : 9 800 Kbps
Width                                    : 720 pixels
Height                                   : 576 pixels
Display aspect ratio                     : 16:9
Frame rate                               : 25.000 fps
Standard                                 : PAL
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Interlaced
Scan order                               : Top Field First
Compression mode                         : Lossy
Bits/(Pixel*Frame)                       : 0.591
Time code of first frame                 : 00:00:00:00
Time code source                         : Group of pictures header
Stream size                              : 1.35 GiB (94%)
Color primaries                          : BT.601 PAL
Transfer characteristics                 : BT.470 System B, BT.470 System G
Matrix coefficients                      : BT.601

Audio
ID                                       : 189 (0xBD)-128 (0x80)
Format                                   : AC-3
Format/Info                              : Audio Coding 3
Mode extension                           : CM (complete main)
Format settings, Endianness              : Big
Muxing mode                              : DVD-Video
Duration                                 : 31mn 36s
Bit rate mode                            : Constant
Bit rate                                 : 256 Kbps
Channel(s)                               : 2 channels
Channel positions                        : Front: L R
Sampling rate                            : 48.0 KHz
Compression mode                         : Lossy
Stream size                              : 57.9 MiB (4%)
</code></pre>

<p>I have converted it to mp4 with the following command:</p>

<pre><code>ffmpeg -i input.vob -c:v libx264 -preset slow -crf 19 -c:a aac -b:a 256k -threads 0 output.mp4
</code></pre>

<p>In the resulting video I see this effect:</p>

<p><a href="https://i.stack.imgur.com/mh7yr.png" rel="noreferrer"><img src="https://i.stack.imgur.com/mh7yr.png" alt="img1"></a> <a href="https://i.stack.imgur.com/WdyOG.png" rel="noreferrer"><img src="https://i.stack.imgur.com/WdyOG.png" alt="img2"></a> <a href="https://i.stack.imgur.com/4vOt3.png" rel="noreferrer"><img src="https://i.stack.imgur.com/4vOt3.png" alt="img3"></a></p>

<p>How can I solve?</p>
 1871: <p>Add the yadif filter i.e.</p>
<pre><code>ffmpeg -i input.vob -vf yadif -c:v libx264 -preset slow -crf 19 -c:a aac -b:a 256k output.mp4
</code></pre>
<p>See <a href="https://ffmpeg.org/ffmpeg-filters.html#yadif-1" rel="noreferrer">yadif docs</a> for more info.</p>
