Strange letterboxing of 720x480 videos

C2 /w 8.90.5
Kodi Resolution set 1920x1080
Whitelisted 720x480
Adjust Refresh start / stop
Default video settings / view mode set stretch 16:9 for all videos.

All 720x480 resolution videos initially have strange vertical letterboxing where none should be present. About half of them will self correct after about 2 seconds into the video taking up the full screen as expected. The other half the letterboxing remains throughout the video. I have no idea why the behavior would be different.

This can be reliably reproduced using the following video:

In this image stars should fill the screen and white flash should take up all the vertical space of the display.

This seems to have something to do with resolution switching as video is being started.

Here are some ways the problem does not occur or can be corrected.

Once the video starts manually change view mode from stretch 16:9 to normal or any other mode and then back to 16:9… the lines will go away.

Don’t have resolution change. Either set Kodi resolution to 720x480 or remove 720x480 from the whitelist.

Whitelist also has frame rate - 720x480/24 /25 /30 /50… Hz.
To work correctly video must match both - picture format and video frame rate.

Btw, the sample video plays OK (905W box) on my (LG) tv at 720x480/30Hz with Kodi interface set at 1920x1080/60Hz

720x480 video resulution is only for legacy SD TV with 4:3 screen. If you whitelist it for HD TV you demaged aspect ratio.

Not sure what frame rate matching has to do with letterboxing.

When you say the video plays ok does it take up entire vertical area of your display?

Unfortunately I can’t control format of content. We have quite a lot that will only ever be available at DVD resolution.

My TV supports 4:3 aspect and will add horizontal letterboxing as appropriate to maintain aspect ratio.

My choice is pass-thru native resolution and let the TV deal with/upscale with excellent results or leave amlogic do it with noticeably reduced quality.

All works great for the most part :sunglasses: except for this bug :frowning_face:

Frame rate has to do with proper TV/display aspect ratio switching.

Video is not letterboxed, it takes entire vertical area.

Different box and different tv gives different result…

Did you set stretch 16:9 as the default view mode in video settings before testing?

No, I always set 4:3 display as Normal, and sample video is 4:3…

This problem does not show up when set normal.

Perfect, that’s how it should work. I’m not interested in distorting original material…

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Sorry for any confusion. I was aware of this in my testing prior to starting this thread and mentioned the setting multiple times to avoid this.

The concern you raise is not something I wish to debate in this forum. I personally tend to agree yet everyone has their own personal preferences. It’s why these options exist. In this specific case the outcome you raise is not possible as there is nothing to “stretch” into. Video matches output resolution therefore any distortion would depend entirely on configuration of display.

It should essentially be a null operation WRT to Kodi stretching under this condition yet something is causing output of some videos to be distorted anyway. I suspect somewhere there is some data gathered prior to resolution switch that is no longer valid after it occurs causing this. While different videos with the same exact resolutions and frame rate start out with the distortion some self correct after a couple of seconds yet others do not which is something I don’t understand.

The interesting thing is I’m wrong about the problem not showing up. A setting of Normal is worse. Stretch 16:9 is the only mode that outputs a proper undistorted image when viewing 720x480 content with an output resolution of 720x480. ALL other modes “Normal”, “Original size”…etc. incorrectly CAUSE distortion of output image.

This is easy to reproduce.

When playing any 720x480 content at 720x480 the image should entirely fill the appropriate display area subject to the aspect mode (Normal,Full…etc) of the TV/display. When you pause a video the video framing/controls should extend horizontally to the same extent as the video itself since 720 display width = 720 content width. This NEVER happens using Normal, Original size or Custom with 1.0 pixel ratio no matter what 720x480 content I try there is always significant horizontal letterboxing present where none should exist. The only way to get a proper output is to select view mode of Stretch 16:9.

It’s like something always assumes output is 16:9 even when it isn’t.

I see that you are a bit mixed up with “frame sizes” and “frame formats”

On 720x480 frame size you can have 2 frame formats/aspect ratio:

Anamorphic Frame Size Display Aspect Ratio Square Pixel Frame Size
720 x 480 4:3 640 x 480
720 x 480 16:9 853 x 480 or 864 x 480

Using “Normal” setting will properly display 720x480 4:3 and 16:9 material on all my TVs (LGs and Panasonics)

Aspect only looks right /w 720x480 output when TV (not Kodi) is set “Full” which is 16:9 instead of TV’s Normal 4:3. When the TV (Sony Bravia) and Kodi are both set “Normal” image is way too tall/skinny. When video is “stretched” in Kodi then TV’s “Full” looks like stretch 16:9 and TV’s “Normal” looks like 4:3 which is what I expect/want.

What I was looking for in my test is for 480 4:3 content to display as 480 4:3 simply without anything messing with it. Looks like Kodi assumes 16:9 and so it messes with video to look right on 480 assuming 16:9 display.

Ended up finding a different workaround to my original problem. Keep Kodi view mode set “Normal” instead of stretch yet max out minimize black bars in player video settings. This seems to work for everything without strange intermittent letterboxing problems when switching down to 480.

To put things in different terms. If Kodi adds letterbox framing to make 4:3 720x480 appear properly while always assuming TV is in 16:9 mode rather then 4:3 at 720x480 resolution then detail is being lost since Kodi is now downscaling video content to account for differences in pixel shape.

If instead everything was simply passed-thru as 4:3 not only is proper aspect maintained but letterboxing added by TV/display would not eat into resolution of content.