Which Compression Format Is Best?

Question

Level 2

177 points

Which Compression Format Is Best?

There are various recording formats available for iTunes and playback on iPod. iTunes Store bought music is in AAC, and ripping CD's are defaulted to WAV. But there are various others to choose from including MP3, AIFF and Apple Lossless.

I presume some compress more and produce smaller files but have poorer quality sound. I also assume that WAV has the highest quality of those offered, but also the largest files and an inability to support album art.

Does the Apple Store use AAC because of quality, or because of file size?

I need to know what the relative merits of the various formats are so I can decide the trade off of file size with quality that would suit me best Which is the worst? Do any of them have particular advantages? Any particular disadvantages?

Or is there an article that discusses the relative merits of these formats that I can read?

eMac G4 + iBook 12 inch G3 (10.3.9 on both) + iPod 5th Generation 60 GB, Mac OS X (10.3.9), PowerPC G4 1 GHz 1 GB SDRAM + (iBook) PowerPC G3 500 MHz 384 MHz SDRAM

Posted on Sep 20, 2006 8:25 AM

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Answer 1

JereH

Level 1

10 points

Sep 20, 2006 9:30 AM in response to artistjoh

AAC is MPEG4, MP3 is MPEG1. There is about a 10 year difference between releasing these formats, and audio processing algorithms have come a long way in ten years.

The Apple store likely uses AAC because of quality and file size: compared to MP3, you can get the same audio quality with a lower bitrate and therefore a lower file size using AAC.

Apple Lossless will have the same audio quality as WAV or AIFF, but it will be compressed. The compression is more like a ZIP file, though, where no bits of audio are removed. Audio frequencies are removed using MP3 and AAC, but depending on the bitrate it is hard to detect. This is similar to how a JPG image compresses: If you compress it a lot it starts to look worse than the original, and you can see halos and artifacts around objects in the picture.

=============
Advantages and disadvantages to different formats

AAC:
Smaller, higher-quality file than MP3 at equivalent bitrate, only works on AAC compatible players and software

MP3:
Plays on just about any portable music player, recent car stereo, DVD player, etc.

WAV/AIFF/Apple Lossless:
You can re-rip a WAV file into MP3, AAC, or future new formats without losing any audio quality. The drive space required for storage becomes enormous, though: between about 400MB for Apple Lossless to about 800MB for WAV/AIFF.

Personally, I use AAC at 160Kbps (it's under custom settings in iTunes) and it sounds much better to me than a 192Kbps MP3 file. I usually listen in the car through an Alpine stereo with an iPod interface, or through a home stereo with a line-in connector. 160Kbps AAC leaves me with a decent file size and audio quality imperceptible from the original CD.

I have used MP3 files as well, and to get equivalent quality I use 256Kbps. The AAC files take up less space.

Toshiba Satellite A75-S231 Windows XP Pro

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Answer 2

Jeff SD

Level 3

550 points

Sep 20, 2006 9:41 AM in response to artistjoh

Here is what I did to find out what worked best for me.

I took a CD and encoded one song on it (the same song) in AIFF, AAC, MP3 and Apple Loss-less.

Then I put them all on my iPod and listened to all of them. Then I chose which one sounded best to me and looked at the resulting size to decide what to encode all my music as.

I chose AAC 128 just like Apple did. However everyone hears things differently so you may decide you like a different format.

Good luck 🙂

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Answer 3

artistjoh Author

Level 2

177 points

Sep 20, 2006 10:26 AM in response to artistjoh

I am curious about Apple Lossless, how does it stack up? I want to find the best possible quality yet still have album art.

My understanding from these descriptions is that WAV and AIFF are equally good in quality but both have large file sizes, that MP3 is the worst, but has small file sizes and that AAC is in the middle for quality yet has very small file sizes. Where does the Apple Lossless fit on that scale?

I have no requirement to play the music on anything other than computer and iPod now (My CD collection is just back up now) so the issue of the format being playable only on iPod or Macintosh is not an issue for me.

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Answer 4

artistjoh Author

Level 2

177 points

Sep 20, 2006 12:09 PM in response to artistjoh

With much research on Google as well as these discussions I am gradually getting the picture here. One thing I haven't found out is what is the difference inb file size between AAC at the highest bitrate and Apple Lossless? is it similar? A little smaller? Or is it still a lot smaller?

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Answer 5

Sep 20, 2006 12:12 PM in response to artistjoh

People have been arguing about this for years. Your best bet would be to rip a song in a variety of formats and do a blind sound test to see which one you like best.

To answer your subject line question: SHN and FLAC are the best compressions to use, but not available on iPod. Even if they were, they cost you about 10MB per minute of space.

I personally use 320kbps MP3. I have an iPod compatible Alpine car deck and I also listen thru my computer speakers at work and that's usually it. I need to keep them in MP3 b/c that is also how I stream music from my office to my living room via my PC. If not for that I would have to have two different rips for every song.

Bottom line is it's all your personal preference.

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Answer 6

artistjoh Author

Level 2

177 points

Sep 20, 2006 12:51 PM in response to disilluzion

I'll be doing the ear tests in due course, but in the meanwhile I am trying to get to raw data of exactly how big the files are because if for example Apple Lossless and AAC at 320kbps are indistinguishable by ear but have significantly different file sizes then I must go with the file size. If I find a distinguishable sound difference then I will go with the sound and accept less songs. But in the end I am looking for as good a quality as possible.

I for example find most people's sound quality on MP3 to be abysmal. but what was on my computer acceptable when played through a good stereo. It is only tonight that I have discovered that is at least partly because of my large WAV files. Now I am trying to determine if I should compress or not, and how far. I am starting by collecting the empirical evidence of figures and file sizes.

I am still not certain of how big a AAC file at 320kbps is compared to an Apple Lossless file?

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Answer 7

Jeff Bryan

Level 9

61,797 points

Sep 20, 2006 12:58 PM in response to artistjoh

"I am still not certain of how big a AAC file at 320kbps is compared to an Apple Lossless file?"

Why not rip a song from a cd in both formats and compare the file size?

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Answer 8

artistjoh Author

Level 2

177 points

Sep 20, 2006 3:05 PM in response to Jeff Bryan

Done, and yes it seems to be half the Apple Lossless size, so, significantly smaller.

So, next to the subjective stuff with the ears.

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Answer 9

Jeff Bryan

Level 9

61,797 points

Sep 20, 2006 3:10 PM in response to artistjoh

"So, next to the subjective stuff with the ears."

Believe me, it'll be worth your while getting it right first time.

Take it from someone who's ripped his entire cd collection twice!!

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Answer 10

artistjoh Author

Level 2

177 points

Sep 20, 2006 9:59 PM in response to Jeff Bryan

Believe me, it'll be worth your while getting it
right first time.

Take it from someone who's ripped his entire cd
collection twice!!

Which is why I am being thorough with research, especially stuff that can be quantified rather than whether or not people simply like one format or other. (Or if they do - why)

I am starting to think that it might be wise to store a WAV or AIFF library on an external drive, mothball it, and then create a new library
that is compressed for general usage. I need to decide now because I am almost ready to start doing some compression. Unfortunately I have been using iTunes for a long time and compression was never an issue, but getting an iPod has made it imperative.

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Answer 11

hackwojr

Level 1

10 points

Sep 20, 2006 10:10 PM in response to artistjoh

Another thing you need to take into account is your iPOD battery. The larger the file, the more battery it uses up. If you use WAV files all the time, the battery will not last long. The more compression, the less battery is used because the iPOD has to access the hard drive less. So if you can barely tell a difference (if you can at all) between 320 and 160, choose the lower. Most people (and it depends on your age because teenagers hear better) can't tell a difference between original and 160 or 192. My opinion (and many experts on the matter) agree that anything above 160 is not needed.

Part of this has to do with how the file is converted. If a loud Crash and a small child's whisper is being recorded at the same time, both sound signatures will be recorded (with a good microphone) but realistically, a person would only hear the crash on playback. Compression techniques take advantage of this and get rid of certain data like "the child's wisper".

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Answer 12

Sep 20, 2006 10:18 PM in response to artistjoh

Which format is best for you really depends on what kind of music you listen to, how much you're into it and what you listen to it on.

I'm a big audio nerd and I listen to a lot of more complex/higher-range music. So I've converted nearly all of my physical CD Library to Lossless in iTunes, from MP3 320K originally.

I definitely do notice a difference.

Most people wouldn't consider a 10 fold increase in file size worth it for the ability to hear a little more backgound noise but I certainly do.

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Answer 13

artistjoh Author

Level 2

177 points

Sep 20, 2006 11:04 PM in response to MacDudeGuy

I'm a big audio nerd and I listen to a lot of more
complex/higher-range music. So I've converted nearly
all of my physical CD Library to Lossless in iTunes,
from MP3 320K originally.

I definitely do notice a difference.

Most people wouldn't consider a 10 fold increase in
file size worth it for the ability to hear a little
more backgound noise but I certainly do.

I agree on the importance of the subtleties, and for me it really is a matter of if I can discern any difference at all. I am not so sure that complexity of music is a factor, because I find I often notice differences most in simple acoustic recordings of folk music, and also in old recordings where the original is poor already and you can't afford to lose any more.

I have been using iTunes for a long time and take my music from the computer to my stereo as my primary music source. I have never liked the quality of iTunes Store music, nor any other downloaded music for that matter. I never understood the popularity of Napster because I consider music from there to be impossible to enjoy for quality reasons quite aside from the legal aspects.

So my ears thank you for your input here

I will be concentrating on whether or not I can tell the difference between 320 AAC and Apple Lossless on the iPod both with headphones and with the stereo. I have seen discussions and reviews on classical music sites where it is claimed that experienced classical listeners cannot tell the difference between high bit rate AAC and the original CD on an iPod. I remain to be convinced. My first experiments are that there is a big difference that I can notice, not in the main body of the music, but in the subtle noise in the background as you describe, but which is important to me, as it appears to be for you.

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