Cropping or downsizing from 720x576 to 720x540?

[EmielBoss]

I want to go from 720x576 to 720x540. Because the horizontal resolution is already there, I won't touch that (apart from masking and recentering, but no resizing). However, because there are 554 "meaningful pixels" vertically, I need to either resize or crop some of the usable image away. What would the DigitalFaq overlords advice in this case? In case resizing is better, how exactly should I go about that?

[latreche34]

I'm not sure if that's a legal resolution, You can crop down to 704x576 and mask the remaining junk, That's the lowest legal resolution you can go down too, From there set the aspect ratio flag to 12/11 non square pixel to get a perfect 4:3 frame.

Check this thread: http://www.digitalfaq.com/forum/vide...mp4-frame.html

[lordsmurf]

It's "legal" for non-standards like streaming. ("legal" because there are no legalities/standards to a non-format)

Streaming is often a non-format, and 720x540 is a 1:1 pixel 4x3.

But we all know that, mostly replying for the sake of other/future readers of this thread.

[EmielBoss]

Quote:

Originally Posted by latreche34

From there set the aspect ratio flag to 12/11 non square pixel to get a perfect 4:3 frame.

I think I prefer to store my end files with 1:1 square pixels. That way I'm certain that every player will always play in the correct 4:3 DAR (because I read that there may be players that ignore PAR information), and that resizing is done correctly (because some players may resize in a shitty way):

Quote:

Originally Posted by keaton

Resizing is only involved if you find the players you are using are not using the aspect ratio settings you specify for your encoded video. Outside of physical formats such as DVD or Blu-Ray, which would honor aspect ratio data, it is much harder to guarantee that all software players out there are going to use this data to render the video in correct 4:3 aspect ratio. So, that's why I tend to favor resizing the file and setting aspect ratio data to 1:1. Even if I don't have issues now, I cannot guarantee I won't encounter it some day with another player. It's the fault of a lack of standardization compliance for all the media player apps out there. Another thought is that some players may not be the best at resizing the video. Were as, I know that Spline36Resize does a good job of resizing things without creating distracting video issues. I'd rather have it "baked in" as good than to hope another player will do as good of a job with it. I don't know if a resize is available in Hybrid. If not, and you want to do so, you could use a simple Avisynth script to call Spline36Resize. Example scripts are out there on the forum. Load that .avs script file into say Virtualdub and save it back to a lossless AVI file. Then, you could use Hybrid to do the rest.

But this is just my understanding at the moment.

[lollo2]

If you wish a PAR=1 I would not touch the heigth (that is the base for all PAR, DAR, SAR, etc.. calculation) but the width.

In addition, you experimented yourself that if you touch the height is not easy to understand when you have to crop, to resize or whatever.

If (wished) PAR=1, DAR=4/3 and height=576 then width=768 (SAR=4/3). Hence resize to 768x576.

Some useful information:

http://www.arachnotron.nl/videocap/d..._cap_v1_en.pdf

https://web.archive.org/web/20140816...eo/conversion/

[EmielBoss]

Quote:

Originally Posted by lollo2

Hence resize to 768x576

Lordsmurf advices against upsizing, because upsize artifacts are worse than downsize artifacts.

[lollo2]

https://forum.videohelp.com/threads/...on#post2067841

https://forum.videohelp.com/threads/...on#post2068007

[latreche34]

Quote:

Originally Posted by EmielBoss

I think I prefer to store my end files with 1:1 square pixels. That way I'm certain that every player will always play in the correct 4:3 DAR (because I read that there may be players that ignore PAR information), and that resizing is done correctly (because some players may resize in a shitty way):.

I haven't come across one, Tried multiple TV's from the 2000's to 2020's, smart phones (iOS and Android), tablets, media players, Blu-ray players, Youtube upload, Computer players. If anyone has a device that ignore the aspect ratio flag please let me know please.

[latreche34]

Quote:

Originally Posted by lollo2

https://forum.videohelp.com/threads/...on#post2067841

https://forum.videohelp.com/threads/...on#post2068007

Indeed, a lot of people don't know the fact that the aspect ratio is based on 704x576(480) and not on 720x576(480) for analog capturing, Even when resizing horizontally always resize from 704.

In the subject of square and non square, Here is a nice read for one of VH members from 2011:

Quote:

Originally Posted by edDV

Sorry for the mocking tone toward computer nerds but the worlds of Rec-601 non-square pixels and computer oriented square pixels evolved separately. Other video parameters differ as well

Rec-601 SD video uses Y,Cb,Cr color space, is mostly interlace and is optimized for analog to digital conversion plus efficient use of transmission bandwidth. A key issue is support of both 704x480i 29.97 fps ("NTSC") and 704x576i 25 fps ("PAL") using the same 13.5 MHz sample rate. Rec-601 supports 4:3 or 16:9 aspect ratios by altering pixel aspect ratio. This means all world standards can be handled in a single transmission channel at the same bit rate. Formats derived from Rec-601 include DV, DVD, DVB, ATSC, AVC and VC-1.

Computer square pixel video is generally RGB, progressive, has a more linear gamma and is based on a 4:3 aspect ratio, 640x480 frame at nominal 60Hz display rate. Computer display cards include "full screen" scaling.

The two worlds are bridged by capture hardware, display cards with video overlay buffers and specialized software players. Essentially, analog or digital video must be converted to square pixel, RGB for computer display.

Divx and Xvid commonly use square pixels and have limited support for Rec-601 resolution. In the PAL case, 704x576 is usually deinterlaced, then converted to 704x528 or other multiple of 16 on both axies. Other aspect ratios are accommodated with square pixels such as 2.35 to 1 movies to 720x306 again sized to 16x16 pixel blocks. Often slight side crops or aspect ratio distortions are needed to fit the 16 rule.

These aspect ratios are not strictly legal for DVD without conversion back to 704x576 or 720x576. Divx the company scored a major coup by convincing some DVD player manufacturers to include square pixel divx/xvid codec support with auto scaling into a 720x576 frame. This feature has also been included in many digital TV sets.

So, one can stay in strict Rec-601 resolution and MPeg2 for DVD authoring, or can go rouge with square pixel divx/xvid codecs. All DVD players must play a formal DVD. Results using divx/xvid codecs may vary since this is outside the DVD standard. Screen scaling, levels and gamma may be off when divx/xvid is used. The main quality killers can be artifacts from deinterlace or from over-compression.

And then he goes on to say:

Quote:

Originally Posted by lordsmurf

Quote:

Nice.

[lollo2]

Quote:

If anyone has a device that ignore the aspect ratio flag please let me know please

I don't

Maybe EmielBoss refers to files where AR is not set (i.e. HuffYUV avi), and you do not tell the DAR to the player (i.e. leaving "Video" ~> "Aspect Ratio" ~> "Default" in VLC)

[lollo2]

Quote:

In the subject of square and non square, Here is a nice read for one of VH members

You linked the same post I did

On the references I mentioned the difference between 704x and 720x is clearly explained

[EmielBoss]

Quote:

Originally Posted by latreche34

I haven't come across one, Tried multiple TV's from the 2000's to 2020's, smart phones (iOS and Android), tablets, media players, Blu-ray players, Youtube upload, Computer players. If anyone has a device that ignore the aspect ratio flag please let me know please.

That's good to know!

Quote:

Originally Posted by lollo2

Maybe EmielBoss refers to files where AR is not set (i.e. HuffYUV avi), and you do not tell the DAR to the player (i.e. leaving "Video" ~> "Aspect Ratio" ~> "Default" in VLC)

I honestly don't have much experience with many players, but my impression was based on keaton's post that I linked.

But you got me convinced to just use a 12/11 PAR!

[lollo2]

Don't blindly follow any suggestion, but experiment yourself. If you have a doubt, try a resize and compare to a 720x540, moving frame by frame, zoom 400% in small details area, compare high motion transitions and judge yourself.
Watch your (important archive) files with different players changing their settings, and different media and verify you are satisfied.

On the other hand, is always better to stick to the standards