Apple TV Take 2: an in-depth review (part 1): what's new - Page 3

Yes, the error-free compression algorithms that make this possible are a triumph of modern mathematics. Digital broadcasting (or DVDs or Photo CDs) would be impossible without them. I know most people think they can't be error-free since they compress the signal so much more than audio compression can, but that's because pictures are two-dimensional and one line is usually much like the ones above and below it. Motion pictures could be compressed a lot more than they are if DVD players could be counted on to have a lot more memory and computational power than they do, because then they could compare a lot more frames at a time, but we work with what we have.

The lossy compression formats that have been added on are fairly robust ("robust" meaning small errors result in small differences,) but they still cause visible artifacts even at just another 2x. Try watching a broadcast HDTV program--you'll be amazed.

(If you think DVD-video at ~50x is lossy, that means you think JPEG photo CDs at ~33x are lossy as well, and I think we can both agree they're not.)

We can't agree. I don't care how high the profile or bitrate is a lossy compression is by definition data compression in which unnecessary information is discarded. JPEG, GIF, MP3, AAC, MPEG-2 and MPEG-4 are all common lossy algorithms in which the decoded data will mostly likely not be the same as the original.

Can you expand on that? What do you mean by 'import your radio station into iTunes as a music track? That's not an obvious action.

tks

Assuming you already have the Internet Radio streams in iTunes v7.6 under Radio.

Step 1: Create Playlist(s)
Step 2: Drag and drop internet radio streams from Radio onto new playlist(s)
Step 3: Sync new playlist(s) to AppleTV

Cool! Tks
(It was 'import' that threw me...)

This depends on what you mean by "the original." I agree that on a DVD for example, "unnecessary information" has been discarded between the master tape and your TV screen. The original 24 (32?) bits per pixel has, in particular, been reduced by making the chroma resolution half what the luminance resolution is. (This is so much better than the broad swathes of misplaced colors painted in on the retrace in the NTSC system that we don't care.) So yes, the information content of the picture has been reduced. But after that point the compression algorithm used on DVDs or digital broadcasting, is error-free: meaning, when re-expanded, it's exactly the same as before. The further, lossy compression used by cable companies, or worse yet, internet downloads, introduces discrepancies that are anything from noticeable to atrocious.

Download a 640x480 .jpg picture from a web page sometime: you'll find it's been compressed from its original 640x480x24=7,372,800 bits (900 KB) to about 28 KB, ~3% of its original size--losslessly.

Actually what I was thinking of was taking the URL of a web based radio station and inputting it to iTunes like you do podcasts. But I haven't found such a radio station.

But if you go to a web based radio station like live365 it opens up a track in iTunes for playback. You can drag that track into your playlist and play it from the AppleTV.

That's what lossy means, and the same is done at the DVD encoding stage too. Lossless and lossy are about information theory. Sometimes too much information is thrown away and you get obvious mosquito noise, blockiness and other problems, all on DVD because MPEG-2 is lossy and throws too much away.

Codecs that don't throw information away are called lossless, meaning the decoded information is exactly bit-for-bit what it was before it was encoded. Just because you can't see the information loss doesn't mean it's not lost. You are not using the compression industry's definition of lossless. What you're really saying is that DVD is good enough. But to say it's lossless is false.

That is completely wrong.

DVDs are pretty heavily compressed. Bluray and HDDVD are compressed. Broadcast hdtv is compressed.

I'm not sure what gave you the idea that any of those formats are uncompressed, but none of them are, I don't think there has ever been an uncompressed consumer digital video format.

Uncompressed HDTV takes up hundreds of gigs per hour.

720p HDTV uncompressed;
8 bit @ 1280 x 720 @ 59.94field = 105 MB per/sec, or 370 GB per/hr.
10 bit @ 1280 x 720 @ 59.94field = 140 MB per/sec, or 494 GB per/hr.
http://www.colorlab.com/telecine/colorlab_HD_guide.pdf

And based on the rest of your post, I assume you're wrong about 50 to 1 lossless video compresson? Or do you have a source on that?


It can be compressed that much, but it's definitely not lossless. If DVDs had lossless video, why do we see compression artifacts (you can see them on HD discs as well).




That's exactly how lossy is defined. You just said that DVDs are lossy.


Nobody is arguing that it's not way smaller than the uncompressed version. You just have the flawed notion that it's lossless, not sure what gave you that mistaken idea. WHY do you think that is lossless and not lossy?

Lossless means that the image is exactly the same as the original, meaning you can see zero difference from the original (not the case with any consumer video format) and that you can convert the compressed file back into an uncompressed form and it will be bit for bit identical to the original.

Find an uncompressed picture file and convert it to 3% of its original size with JPG. If you compare the two, you will see differences, especially if you zoom in. And if you convert that JPG into the original file format, if it were uncompressed you'd end up with the exact file you started with, identical to the last bit. That won't happen.

JPEG is defined as a lossy format:
http://en.wikipedia.org/wiki/Jpeg

mpeg2 used on DVD is defined as a lossy format:
http://en.wikipedia.org/wiki/MPEG-2

My girlfriend and I are very interested in purchasing an Apple TV. The main reason is to store all of our movies digitally rather than having a dvd upconvertor or a blue ray player.

So my first question is. If Apple ever decided to release movies in 1080p, would the Apple TV be able to play those?

My second question is, I have around 200 non-hd dvd's I want to burn into iTunes and then stream to my tv. What will ATV do with the resolution? Will it looks as good as what a dvd upconvertor can do, or does it just play whatever format the dvd is in? I'm conserned because I don't want to spend months converting all my movies if what I am trying to do is not going to end up looking good on a tv.

Finally, at the apple store they had an apple tv setup on a HDTV and I must say the resolution of the menus/text was unimpressive. My xbox 360 menues looked more crisp on a standard definition tv. I expected the letters and lines to be very sharp like when you are looking at OS X for example on a computer. Were perhaps the settings incorrect?

Any information you guys have about ATV and how you use it would be much apprecitated. I love the idea of having all my movies stored digitally and at my finger tips but if ATV isn't at that point yet with non-HD movies and HD movies I don't want to waste and time or money, and i'd rather wait.

Thanks so much!


martin

tv does not support 1080p playback. Your ripped DVDs will look just as good as the original discs.