Author Topic: Converting to MKV and screen fit  (Read 498 times)

bitboy

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Converting to MKV and screen fit
« on: May 17, 2018, 10:50:50 AM »
I am using avidemux 2.7.0 on a LinuxMint 18.3 Cinnamon machine.

I have a TV recording with 720x576 pixels. I cut out the advertisements and tried to create a .mkv file.
If i open the file its playing fine but the size seems to be fixed to 720x576, it is not scaled up to fit the screen size. So the video has large black bars around it.

is there anoption to fix it?
« Last Edit: May 17, 2018, 10:57:00 AM by bitboy »

eumagga0x2a

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Re: Converting to MKV and screen fit
« Reply #1 on: May 17, 2018, 11:11:18 AM »
Use the "force display width" option of the MKV muxer to set the display aspect ratio of anamorphic video correctly (768 for 4:3 or 1024 for 16:9). If the video is still not upscaled by the video player you are using, it is a problem with your player and/or display driver, not with Avidemux.

In any case, please use an Avidemux build generated from the current git master, not the outdated 2.7.0 release.

AQUAR

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Re: Converting to MKV and screen fit
« Reply #2 on: May 17, 2018, 11:24:25 AM »
I would think the Player/Monitor/TV combination is just displaying 720 by 576 square pixels, hence the black borders.
You need to pass on information (metadata) for pixel aspect ratio or display aspect for scaling to take place along the processing chain.
This info also needs to match the "type" of video that was recorded (might be anamorphic or 4:3 material!).

There is a configuration option in the MKV muxer to set the display width in pixels.
This might be all you need to set to get the video to scale to full screen.   

bitboy

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Re: Converting to MKV and screen fit
« Reply #3 on: May 17, 2018, 11:50:50 AM »
I tried the pixel width in the mkv muxer settings (set to 720) with "force" enabled and disabled, but there is no difference.
I will try with video codec setting -> IDC / SAR -> Custom setting.
Why is "Same as input" greyed out?

AQUAR

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Re: Converting to MKV and screen fit
« Reply #4 on: May 17, 2018, 12:53:11 PM »
Probably your media player isn't taking any notice of the MKV metadata.

You could recode with the resize filter (that is doing the rescaling in Avidemux!).

bitboy

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Re: Converting to MKV and screen fit
« Reply #5 on: May 17, 2018, 01:59:02 PM »
i entered the ratio manually. Its a bit better now but there a still black bars around the video.
Im using vlc and the included player from cinnamon and both showing the same.

eumagga0x2a

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Re: Converting to MKV and screen fit
« Reply #6 on: May 17, 2018, 02:13:04 PM »
I tried the pixel width in the mkv muxer settings (set to 720) with "force" enabled and disabled, but there is no difference.

720 is wrong. Either 768 for standard 4:3 display aspect ratio or 1024 for widescreen.

i entered the ratio manually. Its a bit better now but there a still black bars around the video.
Im using vlc and the included player from cinnamon and both showing the same.

Probably a graphics card driver issue resulting in 2D acceleration completely missing e.g. like in an VM installation.

bitboy

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Re: Converting to MKV and screen fit
« Reply #7 on: May 17, 2018, 02:31:24 PM »
Use the "force display width" option of the MKV muxer to set the display aspect ratio of anamorphic video correctly (768 for 4:3 or 1024 for 16:9).

Got this wrong...
you are right. If i set the muxer setting to 1024 it works.
But im interested why i need a higher value than the video width is.


eumagga0x2a

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Re: Converting to MKV and screen fit
« Reply #8 on: May 17, 2018, 07:38:33 PM »

AQUAR

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Re: Converting to MKV and screen fit
« Reply #9 on: May 21, 2018, 01:52:49 AM »
Put simply:
Anamorphic means that the horizontal dimension of the scan line needs to be stretched by a factor of 1.33 to get a proper display.
On projectors this is done with lenses, on analogue TV's this might be done with stretched pixels (scan line frequency really!).
For digital panels which have square pixels, that means scaling each horizontal row by resampling its video content to increase the number of pixels by that same factor. Hence 768 x 1.33 = 1024.

You can also rescale both horizontal and vertical to generate that 16:9 display aspect - best done at the native resolution of you TV/Monitor
(eg 1920 : 1080).  Avidemux can do that with the resize filter during a recode.  This is also what happens on the fly if your media player and TV/montor and video metadata are communicated properly (apparently not in your case!). 
« Last Edit: May 21, 2018, 01:54:32 AM by AQUAR »