AAC quality

[bop]

Hi!
I was wondering what the results will be (are) on standalone DVD/MP4 players. If I understand the process correctly:
x->AC3->AAC->AC3 meaning x->lossy->lossy->lossy
In adition - why is AC3 not part of MP4 standard - what is the logic behind it?
Thanks
bop

[Sharktooth]

ac3 is not a MPEG audio standard.
it is from ATSC:

ATSC Standard A/52A:
Digital Audio Compression (AC-3) Standard, Rev. A

20 August 2001, Download PDF File (http://www.atsc.org/standards/a_52a.pdf)

This document specifies coded representation of audio information and the decoding process, as well as information on the encoding process. The coded representation specified is suitable for use in digital audio transmission and storage applications, and may convey from 1 to 5 full bandwidth audio channels, along with a low-frequency enhancement channel. A wide range of encoded bit-rates is supported by this specification. Typical applications of digital audio compression are in satellite or terrestrial audio broadcasting, delivery of audio over metallic or optical cables, or storage of audio on magnetic, optical, semiconductor, or other storage media.

[bop]

Yes I know but why? Legal reasons?
Why was this moved from "New A/V Formats"? I am trying to figure out what new standard is all about. So far I see only trouble (time, $, quality).

[Teegedeck]

I would think 'legal reasons' it is. And why bother with AC3 if there is a technically far superior format like (HE) AAC defined? I also don't see that the process would be 'uncompressed' master -> AC3 -> AAC but rather master -> AAC for next-gen DVDs and master -> 'whatever bloated format seen fit to impress cinema-goers' for the big screen.

Also, why: 'AAC->AC3'?

[bop]

to AC3 (or DTS) for DD/DTS home entertainment systems.

[bond]

Originally posted by bop
Why was this moved from "New A/V Formats"?because audio topics belong to audio coding :)

[Teegedeck]

Originally posted by bop
to AC3 (or DTS) for DD/DTS home entertainment systems.
Nah, you won't have to convert to AC3, you'll just have to buy a new entertainment-system with inbuilt AAC-decoder chip! I bet they'll get available in time... ;)

Seriously, the tendency seems to go in the direction of heavily integrated players that decode the audio to analogue, discrete 5.1-outputs (in pre-amp fashion) themselves. Or am I under a wrong impression here?

[Andrey]

Seriously, the tendency seems to go in the direction of heavily integrated players that decode the audio to analogue, discrete 5.1-outputs (in pre-amp fashion) themselves. Or am I under a wrong impression here?
Yep.
The dark side of it is that if you buy a new amplifier today, it will not support aac... :(
Still have to wait.

To bop:
Why no AC3 ?
AC3 is old crappy codec not situated not for high quality, nor for anything else. Why to bother with it ? And it not belongs to the memebrs of DVD and other video groups...

EDIT: quote have no boundaries...

[bop]

Yep.
The dark side of it is that if you buy a new amplifier today, it will not support aac...
Still have to wait.


Are you thinking of buying 100$ player and amplifying each channel? Or even out of sound card analog?
Sorry but OH MY GOD!!!

Lets throw away AAC for the moment. Blu-ray: there are ideas of uncompressed audio. I claim that for an average earthling even this advance will barely be an experience. Why?
Equation consists of listening conditions and equipment. Throw in a scent of hearing "resolution" of an average human and ask yourself what the POINT of watching a movie or listening to the music really is. At least for non-extremists. Calculate yourself.
I expect Blu-ray (and HD-DVD) to include uncompressed + AC3/DTS. Everything else would just be ******* you dry. At least for those with K's of $ worth receivers. Those with 10's of K's $ worth probably wont mind because they usually can afford to buy anything they see.

Back to AAC. Give me pass-trough, a decent receiver and listening conditions and.... No, stop. 8 million DD receivers and 2 million DTS receivers sold so far (I dont know what the cross-section of the 2 is and not counting crapy kits which will have to go due to Blue-ray and HD-DVD anyway) make you wonder what kind of FREAKY REVOLUTION AAC must be to even start thinking of throwing all that in the can.

What is the point of AAC again?

[bond]

aac (aac-lc and aac-he) will be part of the dvd-audio rom zone

[Teegedeck]

I expect Blu-ray (and HD-DVD) to include uncompressed + AC3/DTS. Everything else would just be ******* you dry. At least for those with K's of $ worth receivers. Those with 10's of K's $ worth probably wont mind because they usually can afford to buy anything they see.


Well, I think you just realized that the most important rationale of all those companies is making money! :) Of course you don't need SACD - because you cannot tell it from a regular CD, unless you are a bat - or 6, 7 or 67-channel audio; or HDTV (well, I need it...).

But as it still is illegal to build players that autodestruct after a year or so, new, better stuff has to be invented regularly to motivate us to buy it. :)

One nice consequence of next-gen DVDs will certainly be that commercially sold, pressed DVDs will again be too big to be backed-up on a consumer BluRay(or whatever the correct spelling)-burner.

[bop]

Just realized :confused:

I am just sad people buy anything you serve them even if it is utter crap. I am not stimulated by it.

If you think this fidgety something is great, so be it. I personally expect them to make steps and wish they would make LEAPS as I dont like the idea of dying before something interesting and useful is discovered (long way I hope knock knock).
If there is nothing left - you are in the wrong busines man.
If there is but you cant figure it out - you are incompetent.

But because there are ****** people that buy anything you serve them even if it is utter crap, Im just sad. Only thing I can do is SAY IT.

bop

PS: Blu-ray and HD-DVD are fine (space wise and even more so if DD & DTS stay), many other things are not.

[Teegedeck]

These days you can't even buy any AAC-capable standalone, yet. It is a little early to get worked up about things that haven't happened yet (and who knows, maybe never will if the battle between HD-DVD and BluRay doesn't reach a settlement?).

[SeeMoreDigital]

Originally posted by Teegedeck
These days you can't even buy any AAC-capable standalone, yet. Not entirely old chap!

The new Siemssen (http://forum.doom9.org/showthread.php?s=&threadid=88568) and I-O DATA (http://forum.doom9.org/showthread.php?s=&threadid=84003) stand-alone players can spin AAC-LC streams in .MP4


Cheers

[Teegedeck]

Whoa! :D

[bop]

From New A/V Formats - Containers > MP4 FAQ:


3) hardware/standalone players: As the most popular MPEG-4 ASP implementations (DivX5/XviD) were often placed in AVI, thats the most widely supported format on hardware players atm. Still the guys from Nero, together with increasing consumer demand, try to push support for the MP4 container on hardware players, with increasing success:
The first MP4 (only ASP video support, not AVC) enabled hardware players are:
- KiSS's DP-558 supports AAC, ASP (no QPel/GMC), VobSubs and Chapters in MP4 (Sigma Designs EM8560 chipset)
- Siemssen's SCO 5000ND supports AAC (no MP3/MP2), ASP (QPel/1WP GMC), VobSubs, Chapters in MP4 (Zoran Vaddis 776 chipset)
- Xoro's HSD 415/310 players supports AAC, ASP (QPel/GMC?), VobSubs, Chapters in MP4 (ESS Vibratto-II chipset)
- Tevion DR 2004, supports AAC, ASP (QPel/GMC?) and VobSubs in MP4
- Tevion DVD-4000, with the latest firmware supports ASP and MP3 audio (no AAC) in MP4 (ESS Vibratto-II chipset)
- Philips's DVP630/632/642 players support ASP and MP3 audio (no AAC) in MP4 (ESS Vibratto-II chipset)
- M$'s Xbox with the Xbox Media Center is supposed to support MP2, MP3, AAC and AVC in MP4
- Sony's Playstation Portable (PSP) is supposed to support AAC and AVC in MP4
- Apple's iPod supports AAC in MP4 (no video)
- Sigma Designs' Xcard handles hardware MPEG-4 decoding on PC including the MP4 container

[KpeX]

Originally posted by Teegedeck
Seriously, the tendency seems to go in the direction of heavily integrated players that decode the audio to analogue, discrete 5.1-outputs (in pre-amp fashion) themselves. Or am I under a wrong impression here? That's the impression I get as well, and I think it's a good direction to go because it will slightly decrease the cost of receiver/amplifier units by having one less decoding chip (and any associated licensing fees).

That being said, the influence of all the existing AC3 capable devices with S/PDIF interfaces may be holding back future audio players. If you look around on the dolby site on the dolby digital plus pages they have several diagrams of a DD+ decoder that appears to downmix DD+ to 5.1 DD and spit it out via S/PDIF.

At this point for me it doesn't make sense to buy one of these 'mpeg-4' players when one can use an HTPC and play any combination of video, audio, and container formats that someone has written a software decoder for. Not to mention not having to worry about whether you encoded your mpeg-4 with GMC (that these players actually sell as much as they do amazes me).

[Doom9]

when talking about audio formats not supported by hardware, do not forget that the first two generations of DVD players had no idea what DTS is, and lots of people had to upgrade their receivers to make use of DTS as well.

AC3 and DTS are part of the HD DVD and BluRay specs, so you won't be left out to dry with your current receiver, but you won't be able to take advantage of the improved AC3 and DTS versions that'll be used on pre-recorded BD and HD DVD content either. It's not much different from cars: A 10 year old Toyota will work just fine on the road, but if you want to have all the nifty gadgets, you'll have to buy the most recent S class Mercedes. Just as you'll have to buy a new TV to take full advantage of the increased video resolution of the new HD formats, and a new player of course. Such is life..

[SeeMoreDigital]

Originally posted by Teegedeck
Seriously, the tendency seems to go in the direction of heavily integrated players that decode the audio to analogue, discrete 5.1-outputs (in pre-amp fashion) themselves. Or am I under a wrong impression here? You'll get no argument here from me either!

The only way most of us can hear 2Ch and 6Ch AAC audio is via analogue output. Sure there was an Sony amp that had an AAC decoder chip on-board... but as far as I could work out it could only decode 2Ch AAC.

Sadly, the latest AAC capable stand-alone players have not got off to a very good start either. Because neither of the I-O DATA players offer 6No analogue outputs (just 2No pairs of stereo outputs). And although the Siemssen has 6No analogue outputs, it can't correctly pass/map 6Ch AAC audio out of them!

There's more bad news too. A couple of days ago I asked Valex if he would support AAC transcoding to his AC3Filter. And he replied:

"AAC decoder will be in far-far future..."

...Which is a great shame because it can already correctly decode WMA9pro to DolbyDigital... Bummer!


Cheers