16:9 to 4:3 confusion

[zabolots]

I've got the following video (MediaInfo output):

General #0
Complete name        : J:\Temp\test.mpg
Format               : MPEG-2 Program
Format/Family        : MPEG-2
File size            : 167 MiB
PlayTime             : 4mn 32s
Bit rate             : 5149 Kbps
Writing library      :
Apr 29 2003

Video #0
Codec                : MPEG-2 Video
Codec profile        : Main@Main
Codec settings/Matri : Custom
PlayTime             : 4mn 32s
Bit rate             : 9800 Kbps
Bit rate mode        : CBR
Width                : 720 pixels
Height               : 480 pixels
Aspect ratio         : 16/9
Frame rate           : 29.970 fps
Standard             : Composite
Chroma               : 4:2:0
Interlacement        : Top Field First
Bits/(Pixel*Frame)   : 0.946
Writing library      :
Apr 29 2003

Audio #0
Codec                : AC3
Codec profile        : Dolby Digital
PlayTime             : 4mn 32s
Bit rate             : 192 Kbps
Bit rate mode        : CBR
Channel(s)           : 2 channels
Sampling rate        : 48 KHz
Video0 delay         : 31ms
ChannelPositions     : L R

How can it be 720x480 AND 16:9? 720x480 is 4:3 so why is the aspect ratio being reported as 16:9? It IS a letterbox video pulled from an episodic television series DVD so I believe the 16:9 part but how can it be 720x480?

I'm trying to convert it to 4:3 720x480 with ffmpeg so I can view the video on my ReplayTV DVR but everything I try ends up with the aspect ratio all screwed up. I've tried various attempts at padding and/or cropping but still haven't found the correct combination to result in a properly formatted 4:3 video.

[jagabo]

Display aspect ratio can be independent of frame size. DVD/MPEG has a flag that specifies whether the 720x480 frame should be displayed as 4:3 or 16:9.

There are two ways you can convert 16:9 to 4:3:

1) Cut a total of 180 pixels off the right and left (eg 90 off the left, 90 off the right), stretch what's left to 720x480 and encode as 4:3.

2) Resize the 720x480 frame to 720x360, add a total of 120 lines of black to the top and bottom (eg, 60 top, 60 bottom), then encode as 4:3.

[guns1inger]

DVD uses non-square pixels. The pixel aspect ratio helps display the image correctly based o the AR flag. If you changed the AR flag (ReStream can do this for you, if you want to play around with it) then you will find the image appears to be tall and thin.

To truely convert it to 4:3 you will have to resize the video, then re-encode it. If you are trying to convert it to full screen 4:3 then you will also have to crop, then resize the video. Given the source is interlaced, you risk doing quite some damage to it.

What do you really want to do with it ?

[manono]

How can it be 720x480 AND 16:9? 720x480 is 4:3 so why is the aspect ratio being reported as 16:9?

No, 720x480 is 3:2. It gets resized by the player based on the DAR, in this case 16:9.

[edDV]

Quick overview.

720x480 is displayed as 640x480 (4:3) or ~854x480 (16x9) on square pixel displays or is upscaled from there to the TV resolution.

For analog TV sets the TV will horizontally squeeze it if the flag indicates 4:3. If the video is flagged 16:9 or "wide", the set top box, DVD player or TV will default rescale the image vertically for letterbox display.

If the set top box or DVD player are set to wide display the video is passed as is to the wide TV which then stretches the picture horizontally to 16:9.

[theewizard]

like THEY say, ALL mpeg files for DVD & TV are 720*480 resolution, std is display as 4:3

widescreen is displayed as 16:9

to keep circles round and people in perspective ( correctly proportioned )

you have to crop the video frame if you want the picture to fill the 4:3 TV screen

too top it off, movies are not 4:3 or 16:9 they are 2:21 2:35 18:1 or something else

it is fitted/encoded to 16:9 DAR or 4:3 DAR with a 720*480 real data/pixel resolution when the DVD is made