Correcting video ratio in avi file

[skaleton]

Hi,
I have a whole series of tv episodes that were encoded with the wrong format i.e. 16:9 instead of 4:3, so people look fatter than they should.

GSpot[/url]]--- Video Information ---
Video Codec: XVID [XviD ISO MPEG-4]
Frame Count: 72756
Resolution: 576 x 336 (AR: 1.714)
Frames Per Second: 23.976
Video Bitrate: 865 kbps
--- Audio Information ---
Audio Codec: 0x0055 MPEG-1 Layer 3
Audio Sample Rate: 48000 Hz
Audio Bitrate: 87 kbps
Audio Bitrate Type: VBR
Audio Channel Count: 2
Number of Audio Streams: 1

Of course I can easily change the aspect ratio in VLC to 4:3 but If I wanted to make a permanent correction, what would be the method with the least loss of quality?

[jagabo]

Use MPEG4Modifier to change the display aspect ratio. Some players will igore the AR flag though. Otherwise you'll have to resize to 448x336 and renencode.

[Baldrick]

You can change the aspect ratio to 4:3 using MPEG4 Modifier but some players will ignore it. So if you would like all players to play it then you must reconvert with for example avi recomp.

[jagabo]

Or you could resize to 576x432 and reencode. Or any 4:3 ratio frame size you want.

[skaleton]

Thank you Jagabo and Baldrick for your replies.
Will MPEG4Modifier generate a loss in quality?
If I had to re-encode, would converting to DVD give me better results?

[skaleton]

When I tried to open MPEG4Modifier.exe, I received the following message.

[jagabo]

Do you have Microsoft's .Net Framework 2.0 installed?

[skaleton]

yes, I have .Net Framework 2.0 but apparently there is a problem with it.
I thought that maybe it was corrupted and tried to repair according to the instructions from Microsoft
But it failed with this messsage

I left a message in the Microsoft forum to see what the problem is

[poisondeathray]

Your computer details say xp, but that looks very "vista-ish"? or is that just a "skin"?

Might that be the problem?

[skaleton]

No I have XP Pro SP2
What do you mean "skin"?

[jagabo]

Did MPEG4Modifier crash on startup or after you started working with the file?

[skaleton]

MPEG4Modifier crashed on start up as soon as I tried to open the MPEG4Modifier.exe

[jagabo]

That sounds like a .net framework problem then. I don't know where you go from here...

[BiggerJim]

Just a thought, I haven't tried it myself: Use VirtualDub (if you like, in connection with Cut Assistant) to cut off the first frame of your video. In VirtualDub, use SmartRendering. As Codec for SmartRendering, use FFDShow. Config FFDShow Encoder to the same FourCC as in your original Movie and use the settings for AspectRatio in FFDSHow to Correct your A/R in the avi.

This could have the following effect: YirtualDub will re-encode the first couple of frames up to the next keyframe, using the settings of FFDShow. So you could set a new A/R for the AVI. Again, this is just a thought...

[jagabo]

Just a thought, I haven't tried it myself: Use VirtualDub (if you like, in connection with Cut Assistant) to cut off the first frame of your video. In VirtualDub, use SmartRendering. As Codec for SmartRendering, use FFDShow. Config FFDShow Encoder to the same FourCC as in your original Movie and use the settings for AspectRatio in FFDSHow to Correct your A/R in the avi.

This could have the following effect: YirtualDub will re-encode the first couple of frames up to the next keyframe, using the settings of FFDShow. So you could set a new A/R for the AVI. Again, this is just a thought...

Cool idea! I just tried it with Xvid and it didn't seem to work right. The file started playing back with the new aspect ratio but it switched back to the original at the second keyframe.

[poisondeathray]

I have a suggestion if this is just for PC playback:

Wrap your .avi file in an .mkv container with mkvmergegui. There is no need to extract raw streams, it should work fine already in an .avi container.

Select the video stream, and under the "format specific options" tab, there is a drop down menu for aspect ratio. In your case, select 4/3

This was successful for me: both in MPC played the file correctly, and mediainfo displayed DAR 4/3

There is no re-encoding, just "repackaging" of the video file and it takes only a few seconds. In fact, you can just "undo" the process with mkvmergegui. So this is "permanent" as long as you leave it in the .mkv, but has the option of transforming the video at a later date, without destroying the original quality.

Cheers