Bitrate and resolution

[carlmart]

A lot of files available lately have a 1080p resolution and bitrates lower than 5000Kbps.

Isn't that too low? It looks more like DVD bitrate instead of supposed HD.

Where will it show in the image? Fast movements and all that will, of course, but I'm afraid it might lurk in general image quality, dark scenes and so on.

It looks as videos that might look fine in small portable screen, but not in 42" plasmas or more.

[Selur]

Where will it show in the image?

details get blurry, blocking in low detail areas, more blocking if the bit rate is to low.

Also 5MBit does not have to be too low, since:
a. the codec used might be really effective compared to MPEG-2 (which is used for DVDs)
b. the movie might be really compressible
c. if it's a reencode you always lose some info on re-compression to a lossy format and if you don't aim for in example blu-ray compatibility you can get better compression rations by using more demanding features. (e.g. 10bit precision, more references and b-frames,...)

[carlmart]

Yes, I guess movies with little or no action might not suffer.

The rest looks a big interrogation mark...

[Selur]

Even movies with normal action can look quite good at 5MBit and below,... a lot of HD content is not compressed really efficient, most peope that to production work are more concerned about speed and quality not bit rate so. (otherwise hardware encoders wouldn't sell so good )

[carlmart]

"Look quite good" is a bit vague to me.

In general, being a filmmaker and cameraman trained in the "old school", I tend to be a bit demanding.

Even if those demands also try to be practical. HD arrival has been a great things for movies, particularly to old classics, which were many times remastered from the original negatives. That had started with DVD but got better with Bluray and even from HDTV screenings, captured in excellent quality. Sometimes even the BD release is the same quality, with very little more to offer in image quality. E.g.: The original Star Wars movies, or Indiana Jones movies, very recently released in BD.

One thing that did associate with detail and contrast resolution seemed to be bitrate, though as you said that would much depend on codec, compression and re-encoding.

Even if my plasma is still 720p, I have been preferring 1080p releases in the last year. As I then burn some videos to DVD as mkv files, 8Gb limits my size. Even so sometimes I prefer to re-encode an 1080p file to a lower bitrate than use a 720p version.

[Selur]

"Look quite good" is a bit vague to me.

if you show me a reliable measurement for quality, I can try to give more precise statements about quality.
(all quality measure methods I know of only provide rough estimates)

[carlmart]

Indeed. That's why I tried to say that for me it's a question of "quality" and practical terms. Quality is really an ethereal thing, and what you think as quality may not be so for me or for him.

My original question tried to ask how much was compromised by the bitrate figure. And I do know that is also a relative term. Upscaling DVD on a good player can deliver very good results, good enough that let you forget where it came from. And the bitrate was low.

When I started viewing mkv files I was pleasantly surprised. Surprised at the image quality considering it's a compressed file, but a great advance over avi compression when compared to the original DVD. I did compare the HDV images, converted to 1080p, with the final file in mkv 720p and you could not "see" anything that made it look different from the original. Remarkable.

The camera was a Sony Z1, which has some limitations and compromises, and a better camera might show differences when its images are converted to mkv on a very large screen.

But is here when I go back to the practical things.

I view TV series daily that were converted to 720p, and weeks later many times I have the chance to view them when broadcasted in HD satellite, and there doesn't seem to be any difference. So in practical terms, those first 720p I viewed, even if lower in bitrate, are a great option too.