Why do iTunes Store Movies look so good compared to DVD rips?

[mchalebk]

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]

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]

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]

540 Terabytes

Gigabytes

 

[KevinC867]

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]

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]

I know that on the Ratatouille Bluray it has the uncompressed 9 mbit soundtrack. Not PCM or Dolby TrueHD.

 

[RedTomato]

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]

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]

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]

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]

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]

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.