Changing A/R of an MP4 video

[pooksahib]

Hi. I have this mp4 video which plays 16:9 when it really should be 4:3. I was just about to use MPEG4Modifier (sounded logical...) but that's only for avi files. I read somewhere that YAMB or My MP4Box GUI was what I wanted but in neither can I find an option to change the A/R.

If there is such an option in YAMB or My MP4Box, can someone point me to it please?

Or is there a tool such as MPEG4Modifier for use on mp4 files?

Many thanks for all suggestions/advice given.

[Baldrick]

It's not as simple as with mpeg4modifier, see https://forum.videohelp.com/threads/301849-Change-Aspect-Ratio-of-mp4-without-re-encodi...=1#post1847272

[pooksahib]

Thanks, that's the thread I alluded to in my orginal post. So now I have YAMB and My MP4Box, both in GUI style. But I'm damned if I can see any way of tinkering with A/R. Does that option exist in any of them? Or do I need to use the 'command line interface' version of MP4Box (I'd like to stick with a GUI if poss)?

Thanks again.

[Baldrick]

It's in the gui, in yamb 2 after you selected create an mp4 and on the video track and then properties,

[pooksahib]

Aha. I had YAMB 1.6, not 2. I'll report back...

Hmm, not good. After inputting Pixel Aspect Ratio as 4:3 PAL, I checked the old and new files with MedioInfo - the Display Aspect Ratio of the original is 16:9 but for the YAMB conversion MedioInfo says 1.939. And on my TV, the new file still gives a 'wrong' picture plus there are white lines along the top that aren't in the original.

I've used xmediarecode to convert to avi then used mpeg4modifier to change the A/R. The result is fine but I'd still welcome details of a simpler way to change an mp4's A/R.

Thanks, Baldrick, for taking the time to assist.

[shaema]

It may be easier if you convert the container from mp4 into mkv. there will be no loss of quality.

Try this:

1 - Download and install mktoolnix and run mmg.exe

2 - Add your mp4 file e.g myvideo.mp4

3 - In the [Tracks, chapters and tags] panel highlight your mp4 video

4 - Click on (Format specific options) tab and click on Aspect ratio. Change it to 4/3 and click on (Start muxing) button

5 - A new myvideo.mkv file is produced with 4/3 aspect ratio

6 - Download and install Avidemux 2.5.4. Open myvideo.mkv

7 - Select video=copy, audio=copy and format=mp4. Click file>Save>Save video and give it a new name: myvideo_new.mp4

These steps worked for me without a hitch.

[pooksahib]

Hi shaema and thanks for that, it's a great solution. I only needed the first half though as the media player I have can handle mkv's. In fact, I think it prefers them. Thanks again.

[shaema]

Glad it worked for you.

[jagabo]

Hmm, not good. After inputting Pixel Aspect Ratio as 4:3 PAL, I checked the old and new files with MedioInfo - the Display Aspect Ratio of the original is 16:9 but for the YAMB conversion MedioInfo says 1.939.

That suggests your video has a 16:9 frame size even though the video it encodes has a 4:3 DAR. The "4:3 PAL" setting in yamb is for a 720x576 frame size encoding a 16:9 video -- not what you want. You need to input a custom pixel aspect ratio of 3:4.

And on my TV, the new file still gives a 'wrong' picture plus there are white lines along the top that aren't in the original.

The lines are probably in your original (they're closed caption text), just hidden by the TV's overscan.

[pooksahib]

Thanks jagabo. I've already got a 'proper' copy of the video thanks to shaema but the info you've given is welcome. As for the white lines, I discovered later that they weren't caused by Yamb as they were also present on another conversion I tried using xmediarecode. Good to know what it is so thanks again.