[FFmpeg-user] Changing aspect ratios

[Yan Seiner]

I have a bunch of movies with the aspect ratio messed up.  The container 
correctly identifies the aspect ratio, but the pixel ratio is wrong.  
These are for playback on a Roku.

Width                                    : 640 pixels
Height                                   : 480 pixels
Display aspect ratio                     : 16:9

I tried MP4Box, but even then my Roku doesn't show them correctly.

These are encoded as h264 files in an mp4 container.  What's the best 
way to re-encode them with the correct aspect ratio?

Full info on the files (from mediainfo):

General
Format                                   : MPEG-4
Format profile                           : Base Media
Codec ID                                 : isom
File size                                : 1.04 GiB
Duration                                 : 1h 48mn
Overall bit rate mode                    : Variable
Overall bit rate                         : 1 371 Kbps
Writing application                      : Lavf52.103.0

Video
ID                                       : 1
Format                                   : AVC
Format/Info                              : Advanced Video Codec
Format profile                           : Baseline at L3.0
Format settings, CABAC                   : No
Format settings, ReFrames                : 5 frames
Format settings, GOP                     : N=1
Codec ID                                 : avc1
Codec ID/Info                            : Advanced Video Coding
Duration                                 : 1h 48mn
Bit rate                                 : 1 200 Kbps
Width                                    : 640 pixels
Height                                   : 480 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Constant
Frame rate                               : 23.976 fps
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Progressive
Bits/(Pixel*Frame)                       : 0.163
Stream size                              : 937 MiB (88%)
Writing library                          : x264 core 114
Encoding settings                        : cabac=0 / ref=5 / 
deblock=1:0:0 / analyse=0x1:0x111 / me=umh / subme=8 / psy=1 / 
psy_rd=1.00:0.00 / mixed_ref=1 / me_range=16 / chroma_me=1 / trellis=1 / 
8x8dct=0 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=-2 / 
threads=3 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / 
constrained_intra=0 / bframes=0 / weightp=0 / keyint=250 / keyint_min=25 
/ scenecut=40 / intra_refresh=0 / rc_lookahead=50 / rc=abr / mbtree=1 / 
bitrate=1200 / ratetol=1.0 / qcomp=0.60 / qpmin=0 / qpmax=69 / qpstep=4 
/ ip_ratio=1.41 / aq=1:1.00

Audio
ID                                       : 2
Format                                   : AAC
Format/Info                              : Advanced Audio Codec
Format profile                           : LC
Codec ID                                 : 40
Duration                                 : 1h 48mn
Bit rate mode                            : Variable
Bit rate                                 : 160 Kbps
Channel(s)                               : 2 channels
Channel positions                        : Front: L R
Sampling rate                            : 48.0 KHz
Compression mode                         : Lossy
Delay relative to video                  : 83ms
Stream size                              : 124 MiB (12%)