PDA

View Full Version : Why do iTunes Store Movies look so good compared to DVD rips?




skunkworker
Sep 21, 2009, 10:19 AM
I have been noticing recently that the iTunes Store Movies have been looking unusually good for their size. Is it they take the HD source and oversample it down to 720x400? or are they using better h.264 b-frames?



markfc
Sep 21, 2009, 10:32 AM
I would imagine that If Apple encode them themselves, they do it direct from the master tapes rather than ripping from DVDs.

janstett
Sep 21, 2009, 12:04 PM
Yeah I would surmise that Apple has access to better sources than DVD from which to do their master encodings, plus the fact that they wouldn't be going through multiple encodings... I.E. going from some high quality source to H.264 instead of high quality source to MPEG-2 to raw to H.264 (two levels of compression artifacting).

theBB
Sep 21, 2009, 12:25 PM
Their encoding algorithms may be more sophisticated than what is available for free to the public. They may also have the ability to manually increase bit rates or change compression algorithms for certain sections of the movie to get better image quality. I've heard that even for DVDs they don't just feed it into a program to do it, they actually spend quite a bit of time to make the movie look as good as they can.

paduck
Sep 21, 2009, 01:18 PM
I don't think it is Apple that is doing the encoding. I think that they get it that way from the distributor/studio. Other than that, all the points above would apply to the distributor.

pacmania1982
Sep 21, 2009, 01:40 PM
I was thinking about this the other day as I watched a movie I had ripped on my Apple TV. I sure would love to know how Apple do it - as in what their process is.

pac

spice weasel
Sep 21, 2009, 01:57 PM
I was thinking about this the other day as I watched a movie I had ripped on my Apple TV. I sure would love to know how Apple do it - as in what their process is.

pac

I heard that Steve spends his evenings encoding content for the iTMS, using the latest HandBrake snapshot :D

Aldaris
Sep 21, 2009, 02:28 PM
"I heard that Steve spends his evenings encoding content for the iTMS, using the latest HandBrake snapshot"

Made my day, him and a tin of ben an' jerry's!

Well, I have had some good rips and some bad rips, if you look at "sleepy hollow'" on iTunes it looks like crap, same with the original pirates, before they upped it to HD.

As for us using handbrake, we have limited systems compared to duplication/encoding houses, but I think if we tweak a bit and put more time in it we can get some nicer stuff too.

zedsdead
Sep 21, 2009, 02:34 PM
The recent update to HD also brought Anamorphic Encoding w/ 5.1 Dolby Surround Sound to SD content as well. As stated by Apple at NAB 2007 (or '06, don't remember), they use Compressor to encode all video content on the store.

To answer your question, any of the recently encoded content from within the past year looks just as good as a DVD Handbrake rip (HD obviously better) due to the anamorphic encoding.

dynaflash
Sep 21, 2009, 02:38 PM
No mystery. Sources much higher res than even blu ray. Bring a macpro octo to its knees running that source through hb. Nothing more and nothing less. To think you can duplicate it from a 480p dvd source (or even come close) is craziness.

Realize that transcoders like hb can only calculate compression based upon what they are given for sources. each transcode drops the visual quality. Thats why blu ray rips transcoded down to 480p look so much better than the sd dvd 480p source transcoded to a 480p hb encode and on and on.

I would say that *if* you had access to the sources the studios had, you could get close if not comparable output (maybe even better?). Of course you might need a server farm to do it in any meaningful amount of time.

SAIRUS
Sep 21, 2009, 10:09 PM
actually Steve's macbook pro has a blu-ray drive...:eek:

GermanSuplex
Sep 22, 2009, 12:51 AM
Yeah, with iTunes, its consistent file size but inconsistent quality.

Most of the movies look very good. Some, even at 640x480, I can't distinguish from an upscaled DVD (not that I go out of my way to try to compare. If it looks good, it looks good and I leave it at that).

However, as someone mentioned, there are a few times when something looks crap. It's not often, and the filesize and consistency of filesize overrides any issues I have with that.

Meanwhile, movies I encode with Handbrake at the universal setting, look good but are wildly inconsistent in filesize. When I go the iPod legacy route, I end up with similar filesize to that of the iTunes store. I find most films (dramas, non-animated) are perfectly fine with the iPod legacy preset in Handbrake. However, I go with Universal anyways.

With TV shows, that's an entirely different story, especially with animated and older comedies. They look like crap from the iTunes store. I encode those myself.

Like I said, file size is significantly larger (some episodes of The Simpsons ring it at a whopping half a gig per episode), but that also includes two or three audio tracks.

Michael CM1
Sep 22, 2009, 03:45 AM
I would imagine that If Apple encode them themselves, they do it direct from the master tapes rather than ripping from DVDs.

Although I doubt it's literally "tapes," Apple likely has access to the master video copies, or at least uncompressed. Don't forget that DVDs are compressed video, which means some data was already lost going from master to DVD. Apple's software for encoding is probably written better since it's not some open-source "we're trying our best" effort like HandBrake.

What's hilarious is I bet there's a room somewhere that uses Blu-ray Discs since those are lossless media. I know zip about the movie industry, but that sounds like an easy way to give Apple an uncompressed copy.

Diveflo
Sep 22, 2009, 05:16 AM
BluRays are not uncompressed.

mooblie
Sep 22, 2009, 06:03 AM
....I bet there's a room somewhere that uses Blu-ray Discs since those are lossless media. I know zip about the movie industry, but that sounds like an easy way to give Apple an uncompressed copy.

The video content on Blu-ray video discs is compressed.

Blu-ray discs are only "lossless" in the sense that ANY digital storage medium is lossless - you read from them exactly whatever you write to them, but what gets written to them is a compressed version of the original images.

You admit you know "zip" about the movie industry, but please don't inadvertently start an apocryphal tale that "Blu-Ray is lossless" - like the tale that everybody latched onto about ten years ago that "DVD was a good medium for archiving movies". Both completely untrue.

Wotan31
Sep 22, 2009, 09:13 AM
I have been noticing recently that the iTunes Store Movies have been looking unusually good for their size. Is it they take the HD source and oversample it down to 720x400? or are they using better h.264 b-frames?
LOL what does "oversample it down" mean? :confused: DVD native resolution is 720x480 in the US and 720x576 in europe.

They will look exactly the same as a DVD ISO image. If you're using something like Handbrake to rip a DVD and make it into a smaller file size, you are compressing the crap out of your DVD and killing the quality.

jaw04005
Sep 22, 2009, 09:40 AM
Blu-ray sound on certain titles is lossless, but video is compressed.

GermanSuplex
Sep 22, 2009, 09:47 AM
Blu-ray sound on certain titles is lossless, but video is compressed.

Audio on many DVD's is lossless too.

dynaflash
Sep 22, 2009, 10:04 AM
Audio on many DVD's is lossless too.
Er, lossless vs. what ? The original master the film was shot in ? Even DTS is compressed from the original. AC3 (which the dvd spec requires) is also compressed. Not sure what you mean by "Lossless".

Rich1963
Sep 22, 2009, 12:34 PM
Spice Weasel - Thank you. That has made my day. I've got this great image of Steve Jobs in a turtle neck, boxers, and rabbit slippers, eating a bologna sandwich, a coke can with a straw sticking out of it next to him, staring at an apple cinema display, shaking his head because Handbrake isn't supporting Blu-ray subs. Maybe even throw in the Woz walking into the room in a bathrobe and black socks eating a slice of pizza asking if Jobs wants to go outside and play Segway polo... (by the way, in my cartoon bubble, Jobs and Woz aren't gay, just roomies in the same apartment.)

GermanSuplex
Sep 22, 2009, 12:44 PM
Er, lossless vs. what ? The original master the film was shot in ? Even DTS is compressed from the original. AC3 (which the dvd spec requires) is also compressed. Not sure what you mean by "Lossless".

PCM audio.

dynaflash
Sep 22, 2009, 12:58 PM
PCM audio.

mea culpa. compressed though lossless. I stand corrected. sorry.

mchalebk
Sep 22, 2009, 01:25 PM
mea culpa. compressed though lossless. I stand corrected. sorry.

Not actually. PCM is not compressed. However, I believe that DVDs are limited to 2.0 sound if using PCM.

dynaflash
Sep 22, 2009, 01:37 PM
Not actually. PCM is not compressed. However, I believe that DVDs are limited to 2.0 sound if using PCM.

I guess I was referring to MLP (lossless encoding) for pcm which is quite common. Though afaik pcm tracks generally lend themselves to music dvd's etc. especially when they were originally recorded in stereo.

To the OP: apologies for derailing the thread. But to the point of the title.

in terms of video, the extremely high quality of the *video* source lends itself to the relatively excellent quality. Yes, even blu ray is compressed (video) though with better codecs (like h.264, etc.) than the mpeg-2 used on standard dvd's.

roidy
Sep 22, 2009, 01:42 PM
But surely the very act of taking any analogue signal, be it audio or video, and converting it to digital results in some form of loss, unless you can sample it with an infinate resolution. Or am I just talking rubbish ;)

mchalebk
Sep 22, 2009, 04:01 PM
But surely the very act of taking any analogue signal, be it audio or video, and converting it to digital results in some form of loss, unless you can sample it with an infinate resolution. Or am I just talking rubbish ;)

Technically, that's true. When you digitally sample an analog signal, some information is lost (whatever is happening between samples). However, if you sample at a high enough rate, the lost information will be a much higher frequency that you're interested in and the end result is a signal that is indistinguishable from the original.

Of course, that's not what people mean when they use the term "lossless", though.

janstett
Sep 23, 2009, 12:41 PM
The video content on Blu-ray video discs is compressed.

Blu-ray discs are only "lossless" in the sense that ANY digital storage medium is lossless - you read from them exactly whatever you write to them, but what gets written to them is a compressed version of the original images.
.

Well, the AUDIO is lossless that's probably what he's thinking about.

But I want people to understand just how much space lossless video would take.

Each frame of video is 1920x1080. Stored in YUV format, that's 1.5 bytes per pixel = 3 megabytes per frame. * 24 fps * a 2 hour movie = 540 Terabytes. Blu-Ray currently maxes out at 50 Gigabytes.

Currently the best lossless compression such as FLAC or LZ(Zip) could shave off 1/3 to 1/2. But that's still 260 Terabytes.

janstett
Sep 23, 2009, 12:46 PM
Audio on many DVD's is lossless too.

Hardly. Only PCM tracks are lossless. DTS and Dolby Digital are lossy.

And PCM tracks on DVD can only be 48/16 stereo.

There's DVD-Audio (which is not the same as DVD) which offers MLP lossless and I think mulitchannel PCM.

cube
Sep 23, 2009, 12:46 PM
540 Terabytes

Gigabytes

KevinC867
Sep 23, 2009, 01:06 PM
Well, the AUDIO is lossless that's probably what he's thinking about.

But I want people to understand just how much space lossless video would take.

Each frame of video is 1920x1080. Stored in YUV format, that's 1.5 bytes per pixel = 3 megabytes per frame. * 24 fps * a 2 hour movie = 540 Terabytes. Blu-Ray currently maxes out at 50 Gigabytes.

Currently the best lossless compression such as FLAC or LZ(Zip) could shave off 1/3 to 1/2. But that's still 260 Terabytes.

I think the math for the uncompressed movie actually comes out to 540 *Gigabytes* (537,477,120,000). But that's still a hell of a lot of space for one movie.

GermanSuplex
Sep 23, 2009, 01:56 PM
Hardly. Only PCM tracks are lossless. DTS and Dolby Digital are lossy.

And PCM tracks on DVD can only be 48/16 stereo.

There's DVD-Audio (which is not the same as DVD) which offers MLP lossless and I think mulitchannel PCM.

I never said DTS or Dolby Digital were lossless. I simply stated many DVD's have lossless audio, and then clarified that I meant PCM. And many DVDs, particularly concert DVDs, do have lossless audio.

Maybe it's just because I own several live concert/performance DVDs that I said that, but I've got a few dozen DVDs packed in with CDs as well as concert DVDs that have PCM audio.

skunkworker
Sep 23, 2009, 04:15 PM
I know that on the Ratatouille Bluray it has the uncompressed 9 mbit soundtrack. Not PCM or Dolby TrueHD.

RedTomato
Sep 23, 2009, 06:11 PM
Back to the topic of compression. Don't forget they also have guys who are *experts* on movie compression and probably *wrote* the h.264 codecs.

Do you have an intimate knowledge of what every single parameter of a professional movie compression encoder does? Are you the person who coded it in the first place or do you work with the guys who wrote/maintain it?

If the answer is no, then you probably won't get the same results in the same amount of time as the Apple guys.

GermanSuplex
Sep 23, 2009, 06:29 PM
Yeah, most likely they simply have better tools for the job, better coding and a better source.

Has anyone compared a 720x480 anamorphic encode from a regular DVD and a 720x480 anamorphic encode from a Blu-Ray rip with the same settings? I'd love to see a comparison.

dynaflash
Sep 23, 2009, 11:14 PM
Has anyone compared a 720x480 anamorphic encode from a regular DVD and a 720x480 anamorphic encode from a Blu-Ray rip with the same settings? I'd love to see a comparison.

Been done to death. same settings between the two sources produce very different results .... both in encode time and final visual quality.

The encoder runs its algorithms on the available info in the source video frame. Less info in, worse results.

As far as who wrote the encoder .... depends on the encoder. Suffice it to say you can google encoder comparisons and you will find that the x264 encoder used in hb is held in *very* high regard. Both in terms of speed and quality.

janstett
Sep 24, 2009, 09:08 AM
I think the math for the uncompressed movie actually comes out to 540 *Gigabytes* (537,477,120,000). But that's still a hell of a lot of space for one movie.

Oops my bad

janstett
Sep 24, 2009, 09:09 AM
I never said DTS or Dolby Digital were lossless. I simply stated many DVD's have lossless audio, and then clarified that I meant PCM. And many DVDs, particularly concert DVDs, do have lossless audio.

Maybe it's just because I own several live concert/performance DVDs that I said that, but I've got a few dozen DVDs packed in with CDs as well as concert DVDs that have PCM audio.

Well when you said "many DVDs have lossless audio" they don't, but within the small niche of music DVDs yes you will often find PCM. In fact I would challenge you to find a movie DVD that has a PCM soundtrack. I can think of a few launch releases but that's about it. On Blu-Ray however I've come across a small handfull with PCM.

GermanSuplex
Sep 24, 2009, 01:33 PM
Well when you said "many DVDs have lossless audio" they don't, but within the small niche of music DVDs yes you will often find PCM. In fact I would challenge you to find a movie DVD that has a PCM soundtrack. I can think of a few launch releases but that's about it. On Blu-Ray however I've come across a small handfull with PCM.

Semantics. There are many concert DVDs with lossless audio. There, clarified fully I hope.