Question / Help Regarding Cropping

[Rajesh Singh]

The cropping and scaling facility is available at two places:(1) On right clicking a scene ,in General filters as Transform and Scale Filtering heading

(2) In the same menu under Filters function as crop/pad and Scaling/ Aspect ratio
Both (1) and (2) which act independently of each other.

Is there any difference between the two? Do they act at different stages of processing i.e. maybe before rendering or after rendering. Which option is better ?
Also does stretching a cropped video to fill the screen also automatically involve using scale filters such as Lancoz when the filters are chosen in the scale filtering option? What is best in terms of quality when i want to expand a cropped video(to remove black borders ) to fill the 1920x1080 screen. Stretching or something else ?

IF MY QUERY IS NOT CLEAR , I WILL POST SNAPSHOTS TO ILLUSTRATE THE DIFFERENT OPTIONS ASKED IN THE QUESTION.

 

[Rektroth]

To answer the part of your question about scale filtering, when you right click on a source and set its scale filter, yes, that is the scale filter it will use when you expand it to fill a larger space.
Personally, I prefer lanczos, but you should experiment yourself to figure out which scale filter you prefer. Also note that each one will also affect file size and stream latency differently.

Now, your question about the cropping.
I don't think there is any difference in how the two are processed (can a dev confirm?). However, using both in different ways is helpful depending on what you're doing.
Let's say you want a certain video source to be cropped a certain way in every scene no matter what. You'll set that in the filters menu.
But now, let's say there's another scene where you want to crop it a little more. You'll use the transform menu to do that for just that specific scene.

 

[Rajesh Singh]

Hi Rektroth, thanks for reply I also use/prefer The Transform menu for the purpose of its run-time adjustments feature as you have mentioned but i had doubts about the stage when the two options come into play ..

 

[Suslik V]

...Is there any difference between the two? Do they act at different stages of processing i.e. maybe before rendering or after rendering. Which option is better ?...

Crop/Pad filter was developed before cropping options were added to Transform. And later, the developer (@Jim ) decided to leave it for compatibility purposes (or so). Cropping under Transform window - more flexible in use but it lacks absolute/relative coordinates switch like Crop/Pad filter do.
No differences in filtering. Same shaders used. Equal usage. Avoid double filtering (Scaling/Aspect Ratio filter over the Scale Filtering and vise versa). In current version of OBS Studio (v19.0.3) there is bug in Studio Mode - https://obsproject.com/mantis/view.php?id=909 - in this case use filters instead of Scale Filtering.
Scale Filtering easier to use and you don't need to specify new scale manually (without new scale or new aspect ratio filter didn't work). Also, you need to place Scaling/Aspect Ratio filter last in the list to make it work (otherwise it will be overridden by any following filter). The top filter in the list applies first in filters queue, the bottom - applies last from all filters.

...Also does stretching a cropped video to fill the screen also automatically involve using scale filters such as Lancoz when the filters are chosen in the scale filtering option? What is best in terms of quality when i want to expand a cropped video(to remove black borders ) to fill the 1920x1080 screen. Stretching or something else ?...

From the naming - it is designed for this. Scale Filtering overrides default filtering used for any resizing operations (up/downscale). Lanczos uses 32 samples (more samples - better quality). bicubic vs lanczos downscale filter - Performance

 

[Rajesh Singh]

Thanks Suslik for the info. That cleared my doubt . My query regarding quality was a bit wrongly stated/put forth: I wanted to ask the difference in quality between a cropped video which is stretched VS cropped video which is scaled. ( From my query it appears as if i am asking quality diff between Lancoz, Bicubic, Jinc etc which i already know. Sorry for that)

 

[Rajesh Singh]

One more query to this : Since i have set Scale filtering by right clicking on the scene, do i need to also select Rescale Output (1920) option in the output settings for recording( I do local high quality recordings ONLY. No Streaming) . My base canvas(1920x1080) and output canvas(1920x1080) are same. I have selected Rescale output on the assumption that since i am cropping my 1920x1080 videos to 1920x816 to remove black borders and then stretching it back to 1920x1080. For this i expect it to be upscaled using high quality algorithms like lancoz . Will simply stretching them in Transform filter also bring the upscaling filters in play or do i need to rescale ouput in output recording section of the setttings.

 

[Suslik V]

Rescale is second scaling. So, you do not need this - leave it unchecked. Also, it has another bug ^_^ (x264 Rescale Output, Over Saturating Colors).

You only need to keep aspect ratio of your source. As far as I understand, you cannot scale 21:9 video (1920x816) to 16:9 video (1920x1080) without distortion or information loss. If distortion acceptable, you can use Undistort center of image when scaling from ultrawide option of the Scaling/Aspect Ratio filter (available for Bicubic and Lanczos). Otherwise you'll get stretched picture. Or you need second crop - to cut off parts from left/right sides of your footage.

If I have to capture 1920x1080 that is letterboxed.
To keep image undistorted, I can:

• set Base (Canvas) Resolution = Output (Scaled) Resolution = WidthxHeight (but 21:9), cut off pixels from top and bottom and record 21:9 video;
• set Base (Canvas) Resolution = Output (Scaled) Resolution = WidthxHeight (but 21:9), then center input source and record 21:9 video;
• set Base (Canvas) Resolution = Output (Scaled) Resolution = 1920x1080, then center input source (right and left sides cuts off, yeah), and record at 1920x1080.

If distortion acceptable for me, I can:

• set Base (Canvas) Resolution = Output (Scaled) Resolution = 1920x1080, apply Scaling/Aspect Ratio filter size 1920x1080 to the source and check Undistort center of image when scaling from ultrawide.

Anyway, it is better to run your source (game) at 1920x1080 and then record it at 1920x1080 too.

 

[Rajesh Singh]

Hi Suslik, i record HDTV set-top box signals via Avermedia 710 for local high quality recording. I will illustrate the steps in snapshots below: (1) Snapshot 1 is Final after stretching cropped video to fill 1920x1080
(2)Snapshot 2 is original 1080i signal with deinterlaced filter
(3) Snapshot 3 is after cropping black borders

I need final processed and recorded video of 1980x1080p/30 FPS 16:9 as per my laptop screen resolution(1920/60 Hz).

Am i doing things right or is there a better way ?