HDTV in DVD-9 thanks to MPEG4 codec?

[pirata]

Just a brief question. I have read that MPEG4 is 7 to 10 times more efficient than MPEG2. This has automatically brought 2 questions to my mind:

1)Could it be possible to have HDTV recorded on DVD-9 or DVD-R media? Could content providers start up a new product line, publishing their DVD titles in HD/AAC by using HD-enhanced MPEG4 format?

2) The second question has to do with picture quality at DVD bitrates using MPEG4. MPEG4 is better than MPEG2 when bitrates are small, but I wonder if that superiority is still true when the bitrate climbs up to the usual DVD values. I am fearing that once a given, DVD-typical bitrate is reached, MPEG2 provides higher quality than MPEG4, because MPEG4 is more high-compression-oriented than MPEG2. MPEG2, while being older/simpler, and unable to harshly compress movies for Internet streaming, maybe is the best for high bitrates, since its older algorithms are less agresive to image ans more scalable towarsd high quality.

Thanks to the ones answering!

[trbarry]

Just a brief question. I have read that MPEG4 is 7 to 10 times more efficient than MPEG2. This has automatically brought 2 questions to my mind:

pirata -

I don't have any hard data but maybe can give you a general feel for it given my experiences reencoding HDTV to Xvid.

I think the 7 to 10 figure is way overstated. OTOH, even at HDTV resolutions there is maybe a 30 to 40% improvement in size with Xvid over MPEG2.

Also maybe the transitted MPEG2 HDTV is not being done as efficiently as possible due to the use of single pass real time stat muxing encoders that often don't even bother to use the repeat flags. So there might be some additional savings there.

What all this adds up to in my own mind is that 1280x720p @ 24 HD-DVD would be very easy to do on a DVD-9.

But 1920x1080 might be pushing it a bit.

- Tom

[pirata]

I think the 7 to 10 figure is way overstated. OTOH, even at HDTV resolutions there is maybe a 30 to 40% improvement in size with Xvid over MPEG2.

I guess you mean that when transcoding, when you have reached a quality level of the MPEG4 output that is almost equal to the original MPEG2, you have saved 30-40% space.
That's quite right...

Of course it is overstated: the statement said that MPEG4 would generate files from 7 up to 10 times smaller for same quality. If you take a DVD movie (more or less 7GB) and compress it with DivX to fit onto one CD (700MB, 10 times smaller), you get shity quality. Period. Even your statement of 30-40% sounds a bit too much.

Anyway, I'd really like to see a new cast of DVD-9s, using MPEG4 to increase resolution.

About MPEG2 quality: I have always thought that people in the industry always do know what they do. Now I don't know what to think. I have recently had a look at the innards of a DVD, and I was quite disappointed. I thought the DVD releases are done taking care of every detail. Is it professional to encode a movie (plus featurettes) to take just 6GB and then print it onto a DVD-9 disc? Is that the work of a craftman, committed to provide the best quality possible to the people buying his work? No. It seems like they don't care about what they release.

I can't also understand why they encode at 720x576, in 16:9 movies. The sampling frequency is higher in the vertical direction instead of being equal in both directions!

Anyway, I can easily imagine the same degree of "perfection" in digital TV. One pass, real-time is the only way when you are broadcasting live contents, but not with movies!

Where are you based? Japan? I say it because while you already enjoy HD, digital TV, down here we are still crying out for some digital TV that never seems to come around.

Just one question: what are the repeat flags?

Thank you for answering.
Bye

[trbarry]

Where are you based? Japan? I say it because while you already enjoy HD, digital TV, down here we are still crying out for some digital TV that never seems to come around.

I'm in Southfield MI USA. We've had HDTV broadcasts for a 2-3 years now. Currently there are 7 stations here I can receive in digital, though most of it is not HDTV yet except in maybe prime time (if that). Starting a couple months ago I can even get a few HDTV stations on my cable TV.

I can capture the over the air broadcasts with a HiDTV card. No way to do a digital capture on cable yet though.

edit: oops, missed your last question. By repeat flags I mean the MPEG2 RFF flags that say repeat the last field or frame when it's a duplicate and you would otherwise have to waste bits and send it twice.

- Tom

[pirata]

Yeah, sorry. It was my mistake. Your location is on the left column. I just rushed through the thread because I was in a hurry.

Well, what can I say. Be thankful for what you have, man...

[eXistenZ]

Originally posted by pirata
Of course it is overstated: the statement said that MPEG4 would generate files from 7 up to 10 times smaller for same quality. If you take a DVD movie (more or less 7GB) and compress it with DivX to fit onto one CD (700MB, 10 times smaller), you get shity quality. Period.


Yeah, 7 up to 10 times is overstated (my 1CD backups aren't the same as DVD, neither shity although :p !)
Maybe it's possible to go up to 5 times...
Remember that if you take a DVD movie, you have an already compressed source, so this is not the right way to think about it...
You should take the original master, then compress it in both MPEG4 and MPEG2, and compare these...


I can't also understand why they encode at 720x576, in 16:9 movies. The sampling frequency is higher in the vertical direction instead of being equal in both directions!


Take a look at http://www.iki.fi/znark/video/conversion/ for an insightful explanation on it.
Basically every digital resolution is derived by sampling an analogic signal...

Bye, eXistenZ

[trbarry]

eXistenZ -

Link was a nifty site I hadn't seen before. Thanks.

- Tom