How to change aspect ratio and how to crop a video without reencoding?

[DigitalJockey]

Hello,

This is my first post! Yay!

I have two questions and I was hoping someone could help me.

I have an VCR with HDMI out and when playing a VHS tape, it will play on 16:9. My capture box won't allow me to correct to 4:3. Is there any way I can correct the aspect ratio without reecoding. I've tried MKVToolnix and the ony player that was able to play the file on the 4:3 aspect ratio was WMP from the K-lite package.

I also have the opposite problem as well. When recording from TV a 4:3 video, I'll get a 16:9 video with black borders on the side. Is there any way to crop the black bars without reencoding?

Thanks!

[smrpix]

Be sure your VCR can output, and your capture box can capture 4:3 modes.
With no model numbers it's hard to be more specific.

[hello_hello]

What video codec are you using when capturing?
The aspect ratio can generally be stored in two places, The video stream and the container (ie MKV). When they're different, a player has to pick one to use, and some players will only ever use one or the other. I'm fairly sure my Bluray player only reads the container aspect ratio.

Anyway, if the video is h264, you can use this to change the stream aspect ratio.
https://forum.doom9.org/showthread.php?t=152419
It sets the SAR though (storage/pixel aspect ratio) not the display aspect ratio. For PAL it'd be 12/11 and for NTSC 16/11 (or alternatively for PAL 16/15 and NTSC 65/45).

It doesn't set the container aspect ratio though, which means you then need to open the output file with MKVToolNix and remux while specifying the display aspect ratio. I'd only use it to copy the video anyway. I can't find a way to get it to copy more than one audio stream and it makes a mess of subtitles.

I've used AnotherGUI for doing it a little more automatically in the past. Create a preset for the ffmpeg I linked to above, with the following command line:

-i "<FullSourceFileName>" -y -vcodec copy -an -sn -vbsf h264_changesps=sar=16:11/fps=24000:1001 "<OutputPath><OutputFileName>.mkv"

It pays to set both the SAR and the frame rate, otherwise it changes the default duration. In the real world I don't think it matters but.....
Click on any files you've added to AnotherGUI, select an output location (not the same as the source files) and click "Go".

Then open the output with MKVToolNix and set the appropriate display aspect ratio when remuxing.

The reason I mentioned two different SARs, is older analogue video technically isn't exactly 4:3. It's a little wider. A display aspect ratio of 15:11 is probably more technically correct, but if you want exactly 4:3 use that instead.

SAR for PAL 12/11 or NTSC 16/11 = Display Aspect Ratio 1.363634 (15:11)
SAR for PAL 16/15 or NTSC 64/45 = Display Aspect Ratio 1.333333 (4:3)

[DigitalJockey]

What video codec are you using when capturing?
The aspect ratio can generally be stored in two places, The video stream and the container (ie MKV). When they're different, a player has to pick one to use, and some players will only ever use one or the other. I'm fairly sure my Bluray player only reads the container aspect ratio.

Anyway, if the video is h264, you can use this to change the stream aspect ratio.
https://forum.doom9.org/showthread.php?t=152419
It sets the SAR though (storage/pixel aspect ratio) not the display aspect ratio. For PAL it'd be 12/11 and for NTSC 16/11 (or alternatively for PAL 16/15 and NTSC 65/45).

It doesn't set the container aspect ratio though, which means you then need to open the output file with MKVToolNix and remux while specifying the display aspect ratio. I'd only use it to copy the video anyway. I can't find a way to get it to copy more than one audio stream and it makes a mess of subtitles.

I've used AnotherGUI for doing it a little more automatically in the past. Create a preset for the ffmpeg I linked to above, with the following command line:

-i "<FullSourceFileName>" -y -vcodec copy -an -sn -vbsf h264_changesps=sar=16:11/fps=24000:1001 "<OutputPath><OutputFileName>.mkv"

It pays to set both the SAR and the frame rate, otherwise it changes the default duration. In the real world I don't think it matters but.....
Click on any files you've added to AnotherGUI, select an output location (not the same as the source files) and click "Go".

Then open the output with MKVToolNix and set the appropriate display aspect ratio when remuxing.

The reason I mentioned two different SARs, is older analogue video technically isn't exactly 4:3. It's a little wider. A display aspect ratio of 15:11 is probably more technically correct, but if you want exactly 4:3 use that instead.

SAR for PAL 12/11 or NTSC 16/11 = Display Aspect Ratio 1.363634 (15:11)
SAR for PAL 16/15 or NTSC 64/45 = Display Aspect Ratio 1.333333 (4:3)

Thank you so much! I'll try that and let you know the results!