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Topic: MP2 and aac (Read 8032 times) previous topic - next topic
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MP2 and aac

Can aac be contained in .MP2 ?  My player plays mp2 files created with TooLame and I thought aac was a layer of mpeg2.  I want to create aac files that are playable on my Archos Jukebox V2.  The chip documentation shows it supports MP1/2 layers 1/2/3.

MP2 and aac

Reply #1 –
AAC used to be known as MPEG-2 NBC (non backwards compatible).  It is an entirely different beast than MPEG layers I-III.  .mp2 is usually layer II just like .mp3 is usually layer III.
Nero AAC 1.5.1.0: -q0.45

MP2 and aac

Reply #2 –
I thought the 1st rendition of AAC was based on MPEG-2, but all current versions are based on MPEG-4.

MP3 is MPEG-1 Layer 3. I don't know what "layering" AAC has or uses.
<==== Hydrogen Audio Bomb

MP2 and aac

Reply #3 –
MP2 does not means only MPEG-2. MP2 is MPEG1 or MPEG2 layer II. The difference between MPEG1 and MPEG2 in case of Layer II is that MPEG2 Layer II allows myultichannel.

AAC is a completely different thing from MP2. AAC is MPEG2 or MPEG4 AAC.
In its infancy AAC has been know for a very short time as Layer IV, but doesn't share any backward compatibility with other layers.

note: the "backward compatibility" between Layer I, II and III is a bit odd...

MP2 and aac

Reply #4 –
>>MP3 is MPEG-1 Layer 3.
Or MPEG2 Layer 3. The difference between this two is in sample rates/bitrates defined by standart. Unsure about multichannel...

MP2 and aac

Reply #5 –
Quote
>>MP3 is MPEG-1 Layer 3.
Or MPEG2 Layer 3. The difference between this two is in sample rates/bitrates defined by standart. Unsure about multichannel...
[a href="index.php?act=findpost&pid=250602"][{POST_SNAPBACK}][/a]


Yeah that was always confusing me...

While the MPEG site says MP3 is MPEG1, the Fraunhofer site says its MPEG2 !?!


Bye
The unbeaten master of crappy linebreak layout...

MP2 and aac

Reply #6 –
It's simply in both standards, just as AAC is in MPEG2 and MPEG4.

MP2 and aac

Reply #7 –
Quote
Quote
>>MP3 is MPEG-1 Layer 3.
Or MPEG2 Layer 3. The difference between this two is in sample rates/bitrates defined by standart. Unsure about multichannel...
[a href="index.php?act=findpost&pid=250602"][{POST_SNAPBACK}][/a]


Yeah that was always confusing me...

While the MPEG site says MP3 is MPEG1, the Fraunhofer site says its MPEG2 !?!


Bye
[a href="index.php?act=findpost&pid=251128"][{POST_SNAPBACK}][/a]

It depends on sample rate / bitrate

MP2 and aac

Reply #8 –
>>While the MPEG site says MP3 is MPEG1, the Fraunhofer site says its MPEG2 !?!
As Garf already mentioned, it is in both standarts.
Really confusing is that DVD is mpeg2 compartible standart(by idea), but it does not support layer 3. Why ?
Offtopic:
are you Soulhunter from doom9 ?
Then greetings from Andrey ) Have a nice day !

MP2 and aac

Reply #9 –
Quote
Offtopic:
are you Soulhunter from doom9 ?
Then greetings from Andrey ) Have a nice day !
[a href="index.php?act=findpost&pid=251162"][{POST_SNAPBACK}][/a]

Yap, I am the Soulhunter from Doom9's !!!

The master of crappy linebreak layout explores new territory...

Quote
Really confusing is that DVD is mpeg2 compartible standart(by idea), but it does not support layer 3. Why ?
[a href="index.php?act=findpost&pid=251162"][{POST_SNAPBACK}][/a]

IIRC (not quit sure) its not possible to mux mp3 into the mpg container !?!

Dunno, maybe it has to to with the characteristics of the bitstream...


Bye
The unbeaten master of crappy linebreak layout...

MP2 and aac

Reply #10 –
Quote
Quote
Really confusing is that DVD is mpeg2 compartible standart(by idea), but it does not support layer 3. Why ?
[a href="index.php?act=findpost&pid=251162"][{POST_SNAPBACK}][/a]

IIRC (not quit sure) its not possible to mux mp3 into the mpg container !?!

Dunno, maybe it has to to with the characteristics of the bitstream...
[a href="index.php?act=findpost&pid=251168"][{POST_SNAPBACK}][/a]

It is possible to mux mp3 files into .mpg files. Mp3 audio just isn't supported by DVD because it is completely different codec than layer 2 which is supporte. All in all, MPEG-2 is like a bunch of codecs + a container and DVD only supports some of them (+ dolby digital and dts - container).

MP2 and aac

Reply #11 –
Quote
It is possible to mux mp3 files into .mpg files. Mp3 audio just isn't supported by DVD because it is completely different codec than layer 2 which is supported. All in all, MPEG-2 is like a bunch of codecs + a container and DVD only supports some of them (+ dolby digital and dts - container).
[a href="index.php?act=findpost&pid=251191"][{POST_SNAPBACK}][/a]

Interesting...

But then I cant understand why all the mpeg net-clips use mp2 streams !?!

Guess coz most mpeg encoding tools dont have support for mp3 streams...


Bye
The unbeaten master of crappy linebreak layout...

MP2 and aac

Reply #12 –
Most decoders don't support layer 2 and aac either eventhough they are part of mpeg-2. It is worth remembering that aac (imho layer 3 also) was added to mpeg-2 after the video codec and layer 2.

MP2 and aac

Reply #13 –
>>was added to mpeg-2 after the video codec and layer 2.
Yep. This could be a reason for this mess with mpeg2...

MP2 and aac

Reply #14 –
Crap, that makes everything seem a lot more confusing.

I don't completely understand the technicalities of how a video format can be used solely for audio.

But theoretically, would MPEG-2 be the best format then? Because it is the highest quality MPEG format and is used in DVD's. MPEG-1 and MPEG-4 are overall lower video qualities used for other purposes (MPEG-4 is for streaming video, teleconferencing etc. I think)
<==== Hydrogen Audio Bomb

MP2 and aac

Reply #15 –
>>I don't completely understand the technicalities of how a video format can be used solely for audio.
You mean not video, but container format, I think.
As example, the stream usually consist of 3 "data types" - video stream, audio stream, container. Container can do a lot of things such synchronize audio and video, help for seeking, contain special marks and so on.
MPEG2 defines a lot of things, the most imortant are video codecs, audio codecs and container. That what we meant.
Quote
But theoretically, would MPEG-2 be the best format then? Because it is the highest quality MPEG format and is used in DVD's. MPEG-1 and MPEG-4 are overall lower video qualities used for other purposes (MPEG-4 is for streaming video, teleconferencing etc. I think)

MPEG-4 should give a better quality than MPEG-2 while using same bitrates...
EDIT: MPEG-4 AVC simply must (because it is designed for it) give a better quality at same bitrate

MP2 and aac

Reply #16 –
MPEG-2 is not a format or a compression scheme, but rather a framework.

Inside this framework, some compression schemes have been defined: 1 video one (extension of the MPEG-1 one), a backward compatible audio compression scheme made of 3 different layers (extension  from the MPEG-1 one), and a non-backward compatible audio compression scheme (AAC).

MP2 and aac

Reply #17 –
MPEG was designed in the first place to be a video compression format (using pixel averaging).

From what I've read, MPEG-1 had limits up to VCR quality (certain no of pixels x certain no of pixels at certain frame rate) [approx 320x280x20 or something like that]

MPEG-2 is used in DVD's (DVD's aren't lossless movies) [i.e. every frame isn't a bitmap, otherwise they'd need 500 Terabyte DVD's]. Up to 1120x800pixels x30fps [or something very close to that, this is off the top of my head]

I understand the concept of different "streams". Like audio+video in MPEG. The concept of a container is a little rougher though, but I think I get it.

Are these streams the same as layers? I wouldn't think so, because theres MPEG-1 layer 1,2 and 3

AAC has no relation to MPEG-1. I think initial versions used MPEG-2, but all now use MPEG-4 (which is apparently lower quality/higher compression than MPEG-2 in terms of video formats)

By backward compatible, do you mean an MP3 decoder/player supports MPEG-1 layer 1,2 and 3, while an MP2 decoder/player supports only layer 1 and 2??

More confusing than it seems this stuff, not all headphones and sound waves
<==== Hydrogen Audio Bomb

MP2 and aac

Reply #18 –
>>Are these streams the same as layers? I wouldn't think so, because theres
>>MPEG-1 layer 1,2 and 3
The three audio codecs defined for mpeg1-2 are called layers (I think, because they were meant to be backward compartible).

>>By backward compatible, do you mean an MP3 decoder/player supports MPEG-
>>1 layer 1,2 and 3, while an MP2 decoder/player supports only layer 1 and 2??
Idea for backward compartibility is that when old player plays newer layer, it can play at least part of it. As for layer 1,2,3 this not true, as I understand

MP2 and aac

Reply #19 –
Layer III decoder can playback layers I-III
Layer II decoder can playback layers I and II
Layer I decoder can only playback layer I
Nero AAC 1.5.1.0: -q0.45

MP2 and aac

Reply #20 –
Quote
...but all now use MPEG-4 (which is apparently lower quality/higher compression than MPEG-2 in terms of video formats)
[a href="index.php?act=findpost&pid=251509"][{POST_SNAPBACK}][/a]


Only coz most ppl squeeze their movies @ 1xCD that doesnt mean that MPEG4 is only good for LQ encodes...

Imo good implementations (like XviD) are able to reach same (visually) quality as MPEG2, but @ 25% lower bitrates !!!


Bye
The unbeaten master of crappy linebreak layout...