Video output not at the resolution it says it is

[tiny-e]

Hi-

I'm converting a 2.35:1 DiVX movie to (hopefully) be playable on a standard DVD player, I think I have all my values right as far as padding goes -- and ffmpegX says it's outputting the video size that I'm looking for (720 x 480) -- but the resultant MPG (which I can preview before ffmpegX converts it to DVD format) file is only coming out at 640 x 480.

Source video is 640 x 230, I'm converting it to 720 x 304 and padding 88 pixels top and bottom. I've tried selecting various aspect ratios, DVD, 16:9, 2.35:1, Unconstrained, etc... all seem to yield the same result

Why is that? Thanks in advance for any help you can offer.

FFmpeg version CVS, Copyright (c) 2000-2004 Fabrice Bellard
Mac OSX universal build for ffmpegX
  libavutil version: 49.0.0
  libavcodec version: 51.9.0
  libavformat version: 50.4.0
Fri Sep 21 06:37:22 CDT 2007
Seems that stream 0 comes from film source: 2997.00 (2997/1) -> 23.98 (24000/1001)
Input #0, avi, from '/Users/ME/Music/iTunes/iTunes Music/Movies/MY_MOVIE.avi':
  Duration: 01:51:55.3, start: 0.000000, bitrate: 930 kb/s
  Stream #0.0, 23.98 fps(r): Video: mpeg4, yuv420p, 640x230
  Stream #0.1: Audio: mp3, 48000 Hz, stereo, 128 kb/s
Output #0, dvd, to '/Users/ME/Desktop/MY_MOVIE-DVD.mpg':
  Stream #0.0, 29.97 fps(c): Video: mpeg2video, yuv420p, 720x480, q=2-20, 4000 kb/s
  Stream #0.1: Audio: ac3, 48000 Hz, 5:1, 448 kb/s
Stream mapping:
  Stream #0.0 -> #0.0
  Stream #0.1 -> #0.1

[mats.hogberg]

Output #0, dvd, to '/Users/ME/Desktop/MY_MOVIE-DVD.mpg':
Stream #0.0, 29.97 fps(c): Video: mpeg2video, yuv420p, 720x480, q=2-20, 4000 kb/s
Stream #0.1: Audio: ac3, 48000 Hz, 5:1, 448 kb/s

What says the ouput is 640x480? The log says it's creating a 720x480 (what it should be) video.

/Mats

[tiny-e]

When I open the resultant MPG file in Quicktime or (or VLC) the video properties show as 640 x 480.

That's what's weird... it's telling me it's doing one thing... but I'm getting output to the contrary.

[mats.hogberg]

You sure you're looking at the source video resolution, not the display resolution?

/Mats

[tiny-e]

Yep-

Please see attached screenshot from Quicktime Player:

[Case]

Welcome to the wonderful world of MPEG-1/-2,
where pixels don't have to be square
where rectangular pixels are the norm
where pixel aspect ratios vary: 0.9 - 1.066 - 1.2 - 1.422
where DVD (and DV) don't allow for square pixels

So how do you display rectangular pixel video on a square pixel monitor?
- You fake it. It's better than distorted (stretched) video.
But how does an application tell this to the end user?
- The QuickTime team decided to NOT tell 'em. Just give a number that matches what you see on screen. Even if it isn't true.
If you want to know the frame size in pixels of a MPEG-1/MPEG-2 file, you can't trust QuickTime to give you the numbers. Instead, look what other applications say. Drop you converted file back on ffmpegX. Not for a second conversion, but just to see what the Summary window says about its dimensions.

[tiny-e]

Thanks Case-

When I drop the resultant MPG on ffmpegX it does indeed show me that its 720 x 480... but things look "squished" when I play it back (in Quicktime Player, mplayer, DiVX player, VLC, Apple's DVD Player.app etc).... quicktime player still says it's 640 x 480

I wonder now if my padding isn't working correctly...

Welcome to the wonderful world of MPEG-1/-2,
where pixels don't have to be square
where rectangular pixels are the norm
where pixel aspect ratios vary: 0.9 - 1.066 - 1.2 - 1.422
where DVD (and DV) don't allow for square pixels

So how do you display rectangular pixel video on a square pixel monitor?
- You fake it. It's better than distorted (stretched) video.
But how does an application tell this to the end user?
- The QuickTime team decided to NOT tell 'em. Just give a number that matches what you see on screen. Even if it isn't true.
If you want to know the frame size in pixels of a MPEG-1/MPEG-2 file, you can't trust QuickTime to give you the numbers. Instead, look what other applications say. Drop you converted file back on ffmpegX. Not for a second conversion, but just to see what the Summary window says about its dimensions.

[Case]

I wonder now if my padding isn't working correctly...

Your padding is fine. Something else is going on:
DVD compliant MPEG-2 video at 720x480 can have a setting for 16:9 or 4:3 display. This is just a setting, so you won't have to encode all over to change it. Next time, set the autosize selector at "DVD 16:9" to get it right in one go; this embeds the "16:9" setting.
For some reason right now it is set for 4:3 display (640/480=1.33), but when adjusted for 16:9 it will be okay.
Make your authored VIDEO_TS folder as usual. Then use myDVDEdit to change the frame aspect ratio of this video title set (VTS) from '4:3' to '16:9 auto letterbox' (so that it plays full frame on 16:9 screens, but automatically letterboxes on 4:3 screens).

[tiny-e]

Thanks for the help -- I got it to work by figuring out what resolution I wanted (minus padding), set the autosize to "DVD 16:9' and then manually put in the un-padded height of the new video (after scaling it up to 720 W at 2.35:1), entered my padding values, and then encoded. Resultant output was 720 x 480 with propper padding and aspect ratio.