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Aspect Ratio Correction

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Wed, 02/10/2010 - 14:57
#1
pchristy
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Aspect Ratio Correction

I occasionally have to handle clips that have been incorrectly saved in the wrong aspect ratio, and are consequently stretched either horizontally of vertically.

The pan and zoom feature only seems to allow re-sizing of the whole picture.

Is there any method of stretching pictures vertically or horizontally to restore the correct aspect ratio? Or indeed any plans to incorporate any other DVE features that are almost standard on most editing packages these days?

(Please don't regard this as a criticism! I appreciate that kdenlive is a work-in-progress - and very promising so far!)

--
Pete
"Duct tape is like the Force. It has a light side and a dark side, and it binds the universe together!"

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Wed, 02/10/2010 - 15:37
#2
r_mano
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Re: Aspect Ratio Correction

I normally use ffmpeg to adjust the aspect ratio before further use. I know itś not exactly an answer, but a command like:

ffmpeg -i from.mpg -aspect 16:9 resized.mpg

will force the aspect ratio on the output stream.

Hope this helps,
Romano

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Wed, 02/10/2010 - 19:25
#3
j-b-m
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Re: Aspect Ratio Correction

In the project tree, right click on the clip you want to adjust, select "Clip properties", in the "advanced" tab, you can force the aspect ratio of the clip

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Fri, 02/19/2010 - 06:07
#4
ddennedy
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Re: Aspect Ratio Correction

It is important to note that advanced setting is the pixel aspect ratio, not the display aspect! Yes, I agree setting the display aspect would be more friendly.

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Tue, 09/21/2010 - 01:35
#5
Mad_Sunday
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Re: Aspect Ratio Correction

This is also a situation I'm struggling with. I have captured composite video from my Sky+ box which is 16:9 and the mpeg2 encoder on my capture device (Hauppauge PVR150) is 720x526 (PAL 4:3). When I play these files using VLC they look "squashed" and square (4:3) if I force 16:9 it looks fine (it looks like a true 16:9 picture). I would however like to re-render (don't know what other options I have) to native 16:9 mpeg4. Whenever I render the file (using rescale) I end up with a 16:9 file that has the "squashed" picture between 2 black sides which is obviously not what I want to achieve. Is this because of the pixel resolution? If so, how do I get the desired format?

Pete

Edit..... I have had some success by forcing the pixel aspect ratio to 1.5, now I get 16:9 with a tiny black border all around the picture (looks fine) so I just need to learn how to trim this out, but I can't figure out why it's not simply displayed as 16:9 from the outset?

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Wed, 09/22/2010 - 06:19
#6
ddennedy
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Re: Aspect Ratio Correction

The reason your aspect ratio is incorrect is because the capture device is either configured incorrectly (you wrote 'PAL 4:3') or it lacks a setting. As much as I recall, unlike component, composite video does not carry a signal to indicate widescreen. So, you are forced to override it. Instead of sample aspect ratio 1.5, please try 1.42.

Then, there should be no need to rescale when rendering if you use a project setting such as "1024x576 16:9 PAL" if that suits what you are trying to achieve for the project output (except DVD).

Your project setting does not have to match your clips even though that is a convenient guideline. That is only a guideline and not a rule because you are not limited to only putting a certain class of clips in the project; rather, you can mix and match. So, another guideline for project setting is to use one based on your intended output. If you intend a wide variety and want a little future-proofing, then you would choose the setting based on the largest resolution, highest framerate clip you plan to add. Then use render rescale for any smaller outputs.

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Sat, 09/25/2010 - 16:49
#7
Mad_Sunday
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Re: Aspect Ratio Correction

Thank you for that informative post ddennedy. Do you know if using Svideo will improve the situation? I will also try your suggestion of using a ratio of 1.42.

Thanks, Pete.

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Wed, 12/22/2010 - 18:26
#8
thulu
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Re: Aspect Ratio Correction

I recently started using Kdenlive to edit video, and so far I am very happy with it. There is only one problem: I would like to be able to create a video in 4:3 aspect ratio, but it must show correctly on a wide-screen (16:9 aspect ratio) TV set. In other words, I want pillarboxes on the side to prevent the picture from being stretched horizontally. I know this must be possible, because commercial DVD videos that are marked 4:3 show correctly on a wide-screen TV.

Does anyone know how I can do this?

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Tue, 12/28/2010 - 15:27
#9
jjfro
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Re: Aspect Ratio Correction

Nobody has replied to this yet so I'll chime in with my experience. I'm new to Kdenlive too and don't understand the intricacies of all the different video formats but I'll just relate what worked for me. I've been converting old VHS tapes to DVD. They are obviously in 4:3 format. I've been using a Windows program (One Touch Video Capture) to get them into MPEG format. I just open those clips in Kdenlive with project settings of DV/DVD NTSC (which is fixed at 4:3) and then render them using Destination DVD with a format of NTSC 4:3 VOB. Then I use DVD Styler to create the menus and chapters. Since the clips are already in VOB format, DVD Styler doesn't have to transcode them again.

When I play the DVDs on my widescreen TV from my Panasonic DVR, they are automatically displayed correctly in 4:3 format. I thought I might have to manually adjust the settings on the TV to get them to display that way, but I didn't. I don't know if that's a function of my TV and that others may behave differently or not. Like I said, I don't really understand all this stuff. I was just pleasantly surprised that it worked for me without having to do anything special.

I'm using Kdenlive 0.7.8 and DVD Styler 1.8.0.2. This version of DVD Styler does actually have a problem displaying the menus in the correct aspect ratio. Even if you tell it you want 4:3, it creates them as 16:9 so they get scrunched when displayed on the TV. But it apparently handles the actual video okay.

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Sun, 02/20/2011 - 11:27
#10
eriksl
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Re: Aspect Ratio Correction

(regarding the ffmpeg command line post)

This is wrong as it recodes the clip, which is not necessary. Also when encoding using ffmpeg you really should supply some basic parameters like codec, quality/bit rate or be prepared for total lack of quality.

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Sun, 02/20/2011 - 11:31
#11
eriksl
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Re: Aspect Ratio Correction

(Regarding "automatic" showing correct aspect ratio by TV or STB)

The video stream does contain the aspect ratio. If the complete signal path is digital and the video stream remains untouched, the final component (either TV or STB) is able to retrieve the actual aspect ratio and display it correctly. That is different from analogue video where the receiver more or less has to guess the aspect ratio (if it missed the WSS pulse, IF that is used anyway).

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Sun, 02/20/2011 - 17:25
#12
Thailandian
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Re: Aspect Ratio Correction

I suspect the problem thulu reports may be to do with the DVD authoring application. I have come across this problem myself, but I cannot remember exactly which application I was using to author the DVDs at the time.

There are actually two fields that contain the aspect ratio - one in the VOB header and one in the main DVD header. And there is at least one DVD authoring application out there that sets the incorrect aspect ratio in the DVD header.

Unfortunately, most commercial DVD players ignore the aspect in the VOB header, and take it from the DVD header. So, DVDs will play back with correct 4:3 aspect on your computer, but stretch to 16:9 when played on a stand-alone DVD player.

There are probably better ways to solve this problem, but I saved the DVD as an .iso image on my hard drive, edited the aspect fields manually with a program called ISOEdit, and re-burnt the image.

Hope this helps.

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Mon, 02/21/2011 - 23:24
#13
eriksl
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Re: Aspect Ratio Correction

Yes, you could do either that, or recode and then do it properly, that means, using an up to date video codec (like h264) in high quality mode, so then at least you'll have the advantage of (a lot!) extra compression at the same quality. Of course only do that at the final step, if you're doing multiple steps.

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