1080p vs 720p MKV Files

[esabet]

I have just strated learning about MKV files and how to play them back on my Plasma TV. But now I have a question about the different resolutions of the the MKV files.

The MAX resolution that my Plasam TV can support is 1080i. It also supports 720p.

My question is what would give me a better picture quality: an MKV file that is 1080p or one that is 720p?

[fritzi93]

You need to tell us the *native* resolution of the HDTV. Of course it will accept 1080i and 720p signals.

[guns1inger]

A 720pMKV at 4.3GB in size will most likely look better than a 1080p at 4.3 GB file size, simply because it gets more bits per pixel when encoding, and will suffer less from compression artifacts.

There is no absolute answer to your question. The answer is - it depends, and will vary from file to file.

There are no legitimate MKV files. That is to say, no studio encodes and delivers content using the MKV container. Unless the file is 25 - 50GB in size, the content has been re-encoded by some amateur on the net, and the quality could be anything from quite good to absolute crap. It may have been badly de-interlaced, poorly cropped, stupidly resized. It may have been crushed in a single pass, or had a multi-pass VBR done on it. Or it may have been quantizer encoded. All of these factors influence the quality far more than the difference in resolution.

[esabet]

You need to tell us the *native* resolution of the HDTV. Of course it will accept 1080i and 720p signals.

The "native" resolution of my Plasma is 1,366x768!

I am new so can you kindly explain how the native resolution matters?

[guns1inger]

1080p/i has a resolution of 1920 x 1080. 720p has a resolution of 1280 x 720. Yours is closest to 720, so you get far less from 1080p.

That said, see my previous post on all the issues with MKV files (or indeed, anything you download) and why your first question can't be answered with a simple yes or no.

[esabet]

A 720pMKV at 4.3GB in size will most likely look better than a 1080p at 4.3 GB file size, simply because it gets more bits per pixel when encoding, and will suffer less from compression artifacts.

There is no absolute answer to your question. The answer is - it depends, and will vary from file to file.

There are no legitimate MKV files. That is to say, no studio encodes and delivers content using the MKV container. Unless the file is 25 - 50GB in size, the content has been re-encoded by some amateur on the net, and the quality could be anything from quite good to absolute crap. It may have been badly de-interlaced, poorly cropped, stupidly resized. It may have been crushed in a single pass, or had a multi-pass VBR done on it. Or it may have been quantizer encoded. All of these factors influence the quality far more than the difference in resolution.

So if I understand it correctly, an MKV file is simply a compression method to reduce the size of the file, in this case, the video/audio tracks of a movie!! So a "true" Blu-Ray movie is in fact 25 - 50GB in size and they use MKV to compress it to a much smaller file!! I always wondered if the file is only 4.8GB why you need a Blu-Ray!!!

Thanks for the explanation!!! That was great!

So am I correct to assume that the picture quality of an MKV file will never get close to a real Blu-Ray movie? If that is the case, then would you also say that a true DVD quality will be better than a Blu-Ray movie compressed to an MKV file?

Now, somewhat back to my original question, assuming we are talking about two MKV files of "equal" quality, but one is 720p and the other 1080p (in which case I would assume is bigger in size), then would I get better results if I played back the 1080p file even though my Plasma does not support it?

[jagabo]

MKV is a "box" that contains audio and video (and other stuff). The compression codecs and the settings used determine the size of the file.

The native resolution indicates the actual resolution of the TV's screen and the max resolution you'll ever see on it. With a 1366x768 screen an incoming 1280x720 frame will be upscaled to 1366x768, an incoming 1920x1080 frame will be downscaled to 1366x768. Actually it's slightly worse than that. Most 1366x768 HDTVs overscan the image. That means they size the incoming signal to something slightly larger than 1366x768 then show only the inner 1366x768, cutting off a little at all four edges. So most likely your HDTV is upscaling a 1280x720 frame to about 1434x806, or downscaling a 1920x1080 frame to 1434x806, and displaying the inner 1366x768 portion.

With a 1920x1080i frame the video also has to be deinterlaced before display. You will get some artifacts from doing that. Exactly how much depends on the quality of the deinterlacer in your TV.

So sending a 1080p video to the HDTV as 1080i has the potential to show more detail than sending it to the TV as 720p. But it also has the potential to display more artifacts. You have to try both with a variety of material to see which actually looks better to you.

[poisondeathray]

So if I understand it correctly, an MKV file is simply a compression method to reduce the size of the file, in this case, the video/audio tracks of a movie!!

No. MKV is a container format that holds audio, video, subtitles and metadata. Think of it as a box that holds audio & video. The types of audio & video can be different.

So am I correct to assume that the picture quality of an MKV file will never get close to a real Blu-Ray movie?

It depends on many factors, how it was prepared, encoded etc... gunslinger touched on this above; go reread it.

If that is the case, then would you also say that a true DVD quality will be better than a Blu-Ray movie compressed to an MKV file?

It depends how it was done. A properly made blu-ray rip will look much better than a retail DVD.

Now, somewhat back to my original question, assuming we are talking about two MKV files of "equal" quality, but one is 720p and the other 1080p (in which case I would assume is bigger in size), then would I get better results if I played back the 1080p file even though my Plasma does not support it?

You're not going to like this answer , but the truth is the can't be equal in quality because resolution is part of quality.

You're going to have to see for yourself. There are too many variables going on here - that's the honest truth - not trying to be evasive here.

Theoretically you would get better results from the 1080p file, but then there are all the other gazillion factors which might give you a worse playback experience

Native resolution matters - because anything looks worse when scaled to display. Having said that, upscaling is always worse then downscaling

[esabet]

Wow, there is so much to know I see.

Thanks everyone for all the info.

[guns1inger]

Having said that, upscaling is always worse then downscaling

Assuming equal quality sources. I would rather upscale slightly a good quality 720p source than downscale a poor quality 1080 source.

[jagabo]

Having said that, upscaling is always worse then downscaling

Assuming equal quality sources. I would rather upscale slightly a good quality 720p source than downscale a poor quality 1080 source.

Then they're not equal quality. Maybe you meant equal size?

[guns1inger]

Re-read my post - I am saying that only if they are equal quality would downscaling be better than upscaling in this case. In most cases the 1080 aren't as good as the 720 because they have been squeezed much more.

[jagabo]

Sorry, I thought there was a comma after "equal quality sources". I see now it's a period.

[esabet]

Having said that, upscaling is always worse then downscaling

Assuming equal quality sources. I would rather upscale slightly a good quality 720p source than downscale a poor quality 1080 source.

Ok, if the sources are equal quality, and we use the same method (same compression method, same encoder, and all other possible variables) to produce both the 720p and the 1080p, hence equal quality, then obviously the 1080p file will be bigger, no?

In that case would you still rather to upscale a 720p over downscaling a 1080p?

[jagabo]

Ok, if the sources are equal quality, and we use the same method (same compression method, same encoder, and all other possible variables) to produce both the 720p and the 1080p, hence equal quality, then obviously the 1080p file will be bigger, no?

Yes, the 1080p file will be bigger.

In that case would you still rather to upscale a 720p over downscaling a 1080p?

Downscaling the 1080p video has the potential to show a little more detail on your 1366x768 TV. But as I mentioned earlier, if you send the 1080p video to the TV as 1080i, the video will be interlaced for transmission to the TV, then the TV will have to deinterlace it for display. That could result in a worse picture with the 1080p source, depending on the quality of the TV's deinterlacer.

[edDV]

Not to complicate matters (but maybe to complete), you need to take into consideration source frame rate.

Most movies and TV dramatic series are native 23.976p. You didn't provide your location but PAL regions differ somewhat.

Most Americas 1366x768 plasma displays will not handle 23.976p directly (some do). Most expect broadcast telecine 1080i/29.97 or 720p/59.94 with frame repeats (3 then 2 do the math).

For this type of source, the TV must inverse telecine 1080i to 23.976p or frame decimate 720p/59.94 to 720p/23.976 before internally frame repeating to the display frame rate (typically 59.94 or 119.88). Some current Panasonic plasmas frame repeat or interpolate 10x to 599.4p (advertised as 600Hz refresh).

So the "MKV" needs further definition. Is it telecine 1080i/29.97 or 720p/59.94 (as broadcast) or a 23.976 fps file ripped from a DVD or Blu-Ray?

Separating simple resolution, proper frame rate handling is as or more important for picture quality.

If you don't believe me watch action scenes or the credit role on Dr Who (BBC America or Netflix). What a scrambled egg that is.