Resolution Differences

Harrison

Hey there,

some time ago I observed an additional strange eyestrain behavior. With my Raspberry Pi and OSMC (built version 1.1.2018), which is totally Ok for me, I was watching a movie on my trusted Samsung LED TV 2013.

Something weird happend there. I downloaded the movie twice. Once with 1080p and once with 720p.

I started the movie watching with Full HD 1080p and the eyestrain and tearing eyes were there after some minutes. At the point where there were too much "impression", I'll tryed something out and switched to the same movie with 720p. The eyestrain was immediately gone and I could go on watching the movie with ease.

JTL

Harrison Maybe it's switching the screen resolution of the Pi's output when it plays the 720p movie?

Just a thought?

KM

I think the Pi always outputs in monitor's native resolution. The Pi GPU does the upscaling, bypassing the monitor. At least that's what I observed on my Pis.

hpst

I've seen people mentioned resolution changves helping before, but what does that mean? Is it meaning only a panel's native resolution is strain free? Or that the input's default only is? Or it's just size difference?

For me a 1080 native laptop display has things too tiny so I can't use it for any length to test, but changing to to lower res doesn't help my eye strain. I don't know if that means anything because I don't know if there is a difference between a 1080 and 768 panel natively for this issue. Simply scaling or adjusting resolution could be adding or canceling out something else. It's impossible to say "this resolution is good" because of all this.

Harrison

Hey,

well I don't think that the Pi is changing the output resolution when it plays a 720p movie. It's always Full HD output.

Maybe it's meaning the the visual center is on its limit with signal processing. I just don't know. However I don't think that here pwm, dithering and all other picture "conditioner" are the cause of the strain.

@hpst
I'm with you. FullHD and a 15" notebook is much too small. However also changing the display resolution usually don't make a difference for me.
In this case. The two different movies are both played on a display with its natural Full HD resoltion. However the 1080p file leads to eyestrain and the 720p file not.

KM

Harrison Under Linux, ffprobe which is part of ffmpeg might reveal differences between the video files. Or avprobe which AFAIK is part of libav/avconv.

Seagull

Could be a human thing, I have noticed something similar when using plasma tv to watch non-hd tv channels and hd channels. The HD channels caused more strain than the non-HD.

I think I was focusing differently when watching HD content, as my eyes were trying to pick out specific details, whereas they were more relaxed with the lower detail content. I think my issue with this plasma tv was ultimately caused by it flickering, but focusing more acutely may have aggravated it.

Of course all conjecture, I don't really know.

Harrison

Cool. I'll try ffprobe. Is there also a windows app which you can recommend me?

Here I can exclude flickering as the root cause. Why should there any flickering difference between two different video files? To my knowledge files do not have any influence on the hardware.

JTL

Harrison

Is there also a windows app which you can recommend me?

MediaInfo

Seagull

I wasn't suggesting that your problem was caused by flickering, just that HD content may aggravate a strain problem specific to you.

andc

I think 720p may be easier to render for Pi, which could result in better refresh rate. I changed my cable TV decoder to output 720p instead of 1080 as it resulted in more fluid image and less flickering observed through camera (usual black PWM lines).

JTL

andc

andc as it resulted in more fluid image and less flickering observed through camera (usual black PWM lines).

Huh, how does that work?

Blank Frame Insertion done by the TV?

Sunspark

andc That's not really surprising.. A lot of 720 broadcast is 720p60, progressive, while 1080 broadcast is almost always 1080i interlaced.

In addition to that, on downloads often the 720 image can show more detail despite lower resolution due to the BITRATE used. When I have a download choice between 720 and 1080 of the same thing I always compare the bitrate. If the bitrate of the 1080 file is not more than 2x that of the 720 one, then I won't get it as it'll have less detail and smoothness. If it's more than 2x then I usually get the 1080 one.