Difference between 720 and 1080 encodes at respective bitrates

[tufffta]

Let's assume I encode a 1080p video to 720 at 6000 kbps and to 1080 at 10000 kbps. The difference between the bitrates is less than 2 times (only 1.66). Theoretically 720@6000 would be better than 1080@10000 - would it?
But would it make sense choosing 1080@10000 if I am watching in on 1366x768 screen (meaning 720 video is upscaled and 1080 is downscaled during viewing)?
I understad that depends on a particular video, but how's theoretically (or statistically)?

I know I should just encode samples and see for myself, but the thing is that usually when I see the difference, I don't know which one is better (one may look better to me one time, but the other time the other version may seem better to me).

[Blue_MiSfit]

It depends on the content.

In your specific case of a 1366x768 screen, you will probably be best off encoding at 720p, but it really depends.

Both examples are fairly high bitrates.

[nibus]

Find a CRF value that is transparent to your eyes and stick with that.

As far as resolution, if you plan on upgrading your monitor to 1080p at some point then I would encode to 1080p. However, some movies don't have much more than 720p's worth of detail, so it really depends. The newer bluray's that are shot in 5k definitely need 1080p to keep all that detail.

[sneaker_ger]

Though in the case of 720p@6000 and 1080p@10000 I'd be surprised if the 720p encode came out better looking. x264 does not scale perfectly with resolution, but it shouldn't be that bad.

[Groucho2004]

However, some movies don't have much more than 720p's worth of detail
My experience is rather that it applies to most movies.

I usually check the level of detail before encoding with this script:

#Test resolution loss for 1080 -> 720
a = last
Spline36Resize(1280, 720).Spline36Resize(1920, 1080)
Interleave(a, last)


So far, only 2 movies from my BR collection (which is not that large, I admit) showed enough detail to justify keeping the full resolution - Wall-E (Pixar) and Avatar.

[pandy]

As i said previously on different site - going for 1080 can provide slightly higher quality thanks to reduced quantization errors.

[tufffta]

My experience is rather that it applies to most movies.

I usually check the level of detail before encoding with this script:

#Test resolution loss for 1080 -> 720
a = last
Spline36Resize(1280, 720).Spline36Resize(1920, 1080)
Interleave(a, last)


How could I use this script? What software do I need and how to interpret the results?

[pandy]

How could I use this script? What software do I need and how to interpret the results?

Avisynth and Your vision system (eyes + brain)

[turab]

As i said previously on different site - going for 1080 can provide slightly higher quality thanks to reduced quantization errors.
The bitrate for 1080p is lower, though, when you consider how much higher the resolution is compared to 720p. I doubt it's proportional, but still, it's difficult to claim something like that. How do you know it's not the opposite? The 1080p video may look better, but that could just be because of a greater amount of detail.

[pandy]

For 720 almost all display's ENLARGE video data, for 1080 almost all displays downscale video, up-scaling emphasize all errors present in decoded video, down-scaling act in opposite direction, reducing errors. For example ringing artifacts should be reduced when video is downscaled.

[benwaggoner]

The classic rule of thumb for varying bitrate to achieve consistant quality at different frame sizes is to take the ratio of areas to the power of 0.75.

So, if 10 Mbps is "good enough" for 1080p, "good enough" for 720p with the same content should be 10*(((1280x720)/(1920x1080))^0.75), or 5.4 Mbps. So 6 Mbps @ 720p is in the ballpark in terms of seeing a similar amount of artifacts and such. 1366x768 is only 14% more pixels than 720p, versus the 125% more pixels of a full 1920x1080.

If you're bitrate constrained and not planning on playing these encodes on a 1080p display someday, I'd stick with 720p and get higher bits per pixel, or fewer bits per minute.