PDA

View Full Version : AAC Encoding




sourcemonkey
Mar 18, 2005, 04:30 AM
From what i had gathered the 'convert to AAC' option in iTunes would simply convert an Mp3 encoded file into mpeg4 so that, for example, a 5 meg file would be reduced to 4, that is, the converted file couldn't be greater in size to the mp3 file it was converting. not so. i just AAC'd an mp3 encoded at 64kbps and ended up with a file almost twice the size of the mp3. therefore: AAC must be decoding the mp3 i guess to aiff THEN encoding again. since [i'm guessing] the loss of quality of the 64kbps encoding will always be present, encoding a poorly encoded mp3 to 128 kbps AAC will only result in #1: larger file size; and #2: even less audio quality. Can someone please tell me i'm wrong.



Blue Velvet
Mar 18, 2005, 04:39 AM
You're right.
Converting an mp3 to AAC brings no advantages.

Going from one lossy format to another results in decreased audio quality.

Even if it was converted to Apple Lossless, the audible result would be the same as the mp3 -- you can't improve on the original and the Mac can't put back what isn't there in the first place

WinterMute
Mar 18, 2005, 05:50 AM
You're right.
Converting an mp3 to AAC brings no advantages.

Going from one lossy format to another results in decreased audio quality.

Even if it was converted to Apple Lossless, the audible result would be the same as the mp3 -- you can't improve on the original and the Mac can't put back what isn't there in the first place

Very true, but you can take advantage of reducing the bit rate of the AAC file as AAC sound subjectively better than MP3, so a 320Kbps MP3 can comfortably be reduced to 240 or even 160Kbps AAC with no adverse effect on the subjective quality of the audio, thus saving half the disc space.

Transcoding from a lower bit rate to a higher one will always result in a bigger file and no increase in quality, but transcoding does not use the aiff file structure in any way.

Rocky3478
Mar 18, 2005, 11:33 AM
You're right.
Converting an mp3 to AAC brings no advantages.

Going from one lossy format to another results in decreased audio quality.

Even if it was converted to Apple Lossless, the audible result would be the same as the mp3 -- you can't improve on the original and the Mac can't put back what isn't there in the first place

Is AAC a bad file format? I just ripped a half-dozen CDs in 320kbps AAC and they sound really good...

WinterMute
Mar 18, 2005, 11:41 AM
Is AAC a bad file format? I just ripped a half-dozen CDs in 320kbps AAC and they sound really good...

AAC sounds better that MP3 at any comparable bitrate, and is a lot more musical than MP3.

320Kbps should sound very nice.

Mitthrawnuruodo
Mar 18, 2005, 12:08 PM
Is AAC a bad file format? I just ripped a half-dozen CDs in 320kbps AAC and they sound really good...Lossy does not, necessarily mean bad, just that the algorithm that compresses the audio takes out bits (and pieces) to make the filesize smaller.

The point is that they should just take out those things that are redundant and cannot be heard, and leave the rest. Different codecs (algorithms) does this in different ways, and some, like aac are better at what they are doing than others, like mp3 and atrac.

The lower bitrate you choose, the more bits (and pieces again) the algorithm must remove, so high bitrate will mean higher quality.

If you have ripped your CDs in aac@320 you probably have some of the best quality you can without going lossless...

Edit: Maybe it's better to read what wikipedia has to say about Lossy data compression (http://en.wikipedia.org/wiki/Lossy_data_compression) and Advanced Audio Coding (http://en.wikipedia.org/wiki/Advanced_Audio_Coding)... they're often more accurate then me...

Norouzi
Mar 18, 2005, 12:31 PM
I think encoding really comes down to personal prefrence. Now granted anything encoded at a bitrate lower than 128 sound bad to me, but I think 128 AAC sounds fine. My friend on the other hand refuses to encode anything lower then 320 and says that anything encoded lower sound bad. I think all my songs sound fine, but I'm not the music buff he is. So if you think it sounds good then go with it.

dsharits
Mar 18, 2005, 12:33 PM
You won't save space going from 64 kbps MP3 to 128 kbps AAC. You will only save space going from a higher bitrate MP3 to a lower bitrate AAC. For example, If you want to go from 128 kbps MP3 to 128 kbps AAC, the resulting file will be larger. If you want to go from 160 kbps MP3 to 128 kbps AAC, the resulting file will be smaller than the original.

sourcemonkey
Mar 18, 2005, 03:55 PM
thanks for your responses. i had read in another forum that AAC would encode the mp3 file from its mp3 form without without decoding it to another format first; meaning if you encoded a 64kbps mp3 to m4a you would end up with a smaller file with moderately less quality audio. -i mean, what would all the extra data represent?- that, initially, didn't seem logical to me. anyway, to be frank --in terms of audio quality-- i had no problems enjoying my music listening to it on old analogue casettes so the quality debate is maybe a bit overblown when all is said and done--necessary and of value, but overblown... [or maybe i'm trying to convince myself that i didn't make a mistake AACing my rare radiohead tracks and discarding the mp3s] ;)

smurfsgonewild
Mar 21, 2005, 09:45 PM
Is there away to convert wma to aac? I found a few programs for pc but none for mac. I figured this would be the best way to ask instead of starting a new thread. Thanks in advance.

Lacero
Mar 21, 2005, 09:47 PM
Anything above 160Kbps AAC is overkill.

dotdotdot
Mar 21, 2005, 10:01 PM
I convert everything to 128 AAC unless:

-The originating file is a lower bitrate, in which I do not convert the file
-The originating file is a 128 MP3, see above
-The originating file is an amazing quality file (DVD-Audio, FLAC...) in which I encode at 320 AAC

sourcemonkey
Mar 21, 2005, 10:42 PM
Is there away to convert wma to aac? I found a few programs for pc but none for mac. I figured this would be the best way to ask instead of starting a new thread. Thanks in advance.

remember, obviously if you convert wma to aac you'll suffer the same kind of losses we've been talking about. but apparently it seems you can do it if you're running i-tunes on a pc...see: http://www.apple.com/itunes/import.html.
or try versiontracker.com for an os x solution...just type 'wma' in an os x search and theres somthing there to convert to mp3, if the files are drm protected i guess burn a cd and re-import. sorry i can't be any more help.

dotdotdot
Mar 21, 2005, 11:01 PM
Is there away to convert wma to aac? I found a few programs for pc but none for mac. I figured this would be the best way to ask instead of starting a new thread. Thanks in advance.

Import into iTunes and it will convert automatically...

Create WMA:

Taken from internet-nexus.com:

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Do you want to produce Windows Media 9 content faster, easier and cheaper on your Mac?

Popwire's WMV-9 QuickTime Export Component is the answer for you.

Combining industry-leading coding technologies from Popwire with the ease-of-use of QuickTime, you enable new possibilities to your workflow.

It's so easy just open any media format supported by QuickTime and Popwire's WMV-9 Export Component will do the rest. With full support for QuickTime based applications like: Final Cut Pro, iMovie and Discreet Cleaner, creating Windows Media content on your Mac has never been easier!

Best of all, with its professionally designed presets, Popwire's WMV-9 Export Component lets you produce windows media content of unsurpassed quality at any given bitrate or connection in no time on your Mac.

$29.95

mad jew
Mar 21, 2005, 11:05 PM
Is there away to convert wma to aac? I found a few programs for pc but none for mac. I figured this would be the best way to ask instead of starting a new thread. Thanks in advance.

Don't know about aac, but this will change them to mp3:
http://www.versiontracker.com/dyn/moreinfo/macosx/23003

BTW, only the Windows version of iTunes changes the wmas automatically. :(

spacepower7
Mar 22, 2005, 02:30 AM
I tried EasyWMA mentioned in the versiontracker link. It converts WMA to MP3, and supports ID Tags. It worked great for me awhile back.

I keep all my stuff in MP3 192 format. It keeps things simple if i want to make an MP3 CD for a CD player (portable or in a car.) Or for MP3 CD or MP3 DVD to play in a DVD player connected to the home stereo.

On my Mac, MP3's at 192 sound close enough to the original CD's when going from Mac to my Mackie 1604 mixer to my Mackie 824 Studio monitors. The roadblock/limitation here is probably the Mac's Analog to Digital converters.
So if you are going out your Mac or iPod, MP3 192 is fine, which is usually deemed equal to AAC 128, or AAC 160.

WinterMute
Mar 22, 2005, 04:49 AM
Anything above 160Kbps AAC is overkill.

Depends how good your ears are and what you're listening to the music on, I can hear the encoding in 44.1Khz CD's on the right system, but am perfectly happy to listen to 160Kbps on my iPod on a train, however, once my 60gig iPod turns up, I'll re-rip all my tunes to 320, which does sound much better through the Sennhiesser MX500 phones I've got.

I'd run Apple Lossless, but it canes the battery time.

Horses for courses I think.