I've been mostly a lurker on this site for a few months now, and since then I've ripped all my CDs to FLAC. From there I had turned most of them into mp3's using EAC and LAME 3.90. Now I want to reencode them to the next format, AAC. I'm just confused about all the different types that are available, and I want to know what is best for me, and how to go about doing it. I've done a bit of a search of the foruim, but I haven't really found what I'm looking for (maybe I haven't looked hard enough ).

Okay, I have a recent version of Nero. I have iTunes and WinAmp, as well as dbPowerAmp. I also have EAC, FLAC Frontend, and foobar2000. I don't have a problem getting anything else that may be necessary.

All I want to know is the different between AAC, mp4, and m4a, and what I should use. Which formats are supported by common music players, and how to go about encoding to get the best possible quality. Hopefully one or two of you can help this poor, uneducated fool out.

what do you mean by a "common" music player? if you have a non-apple player you're most likely wasting your time converting to any of those file extensions. fortunately, the world's most dominant player (ipod) plays them just fine. as for the distinctions between the extensions, i know .aac is apple's take on mp3 in that it is another lossy compression format. apple's itunes music store uses this format. mp4 is based on mpeg 4 and can contain either audio or video files. i don't think you'd rip much music into .mp4. m4a on the other hand, is the audio only version of mpeg 4. this is the extension apple lossless files use.

I don't think AAC is the next gen lossy format. It used to enjoy a lot of big corporation backing with big promises. However only Apple really adopted it. But average people don't care about tiny differences: MP3 is CD quality for them, and most wouldn't know other possibilities even exist (DAPs are referred to as "mp3 players"). I don't really see AAC becoming more dominant in the near future. If anything, interest has faded.

Thus it all depends on what brands you feel closer to in the future and your individual needs. Use:
AAC: If you like Apple products. The VBR AAC encoders are not mature yet. And any non-VBR lossy encoder is already at a great disadvantage compared to other modern encoders to cancel out whatever theoretical advantage AAC might have.
Vorbis: If you prefer Samsung (which will soon be one of the top contenders because they're also one of the leaders in memory market) or most other asian brands (iAudio, iRiver, mpio,...). Vorbis proved to be better than AAC and MP3 in the recent tests. It is regarded as one of the top contenders along with MPC in the HA community now AFAIK. Kudos to the people who help develop this effort. This deserves an applaud because it came with no big corporate backing; pushed by only a few individuals for a relatively very short amount of time (I am not a Vorbis user; just a delighted observer).
MP3: Use for maximum compatibility and tested and established quality. Most people here would recommend you stick to this, because the difference is already quite small and the LAME encoder is quite good.
MPC: Regarded by most HA people as the highest quality at reasonable bitrates for a long time. Also very good for transcoding into popular transform codecs (MP3/Vorbis/AAC) because it's subband based. I believe it will be supported in the next gen devices on which users can run their own playback software -- where DAPs converge into PocketPCs.
WTF: Don't know about this one
Lossless: You don't need to worry about the future. Lossless is the future.
Nonperceptual lossy: If you can't afford as high bitrates as lossless but want very good transcoding results for portable playback.

BTW as far as audio is concerned mp4 and m4a are the same AFAIK, just different naming convention (m4a is used by Apple). Apart from that Nero is coming with a new version of their encoder soon. Until that is tested probably people will recommend you to use iTunes encoder. I am not an AAC user, so someone else would explain this better.

Edit: I remember rjamorim being a big AAC fan in the past and then gave up on it. I wonder what he uses now.

There are differences between *.aac, *.mp4, and *.m4a audio files. A *.aac file is a raw AAC file or raw AACplus file not contained. A *.mp4 and *.m4a audio file are AAC audio wraped in the mpeg-4 AAC encoder. Apple, Nero, and the default settings for WinAmp all utilize the mpeg-4 AAC encoder. WinAmp has the options for encoding both raw AAC files and AACplus files.

As for converting a FLAC file to a mpeg-4 AAC file, this can easily be done. I recomend dbpoweramp simply because it can use QuickTime to encode mpeg-4 AAC files, it can also use Nero. The QuickTime/iTunes mpeg-4 AAC encoder is currently the best one. However, this might change when Nero 7 is released on the 26th of October. I own a iPod and to my knowledge the iPod line are currently the most popular DAP's that support the mpeg-4 AAC format. I don't know of any other DAP's that will play mpeg-4 AAC files but I am sure they are out there.

As far as mpeg-4 AAC being a future format, I don't know. The mpeg-4 AAC file format was meant to replace the mpeg-1 layer 3 (mp3) audio strandard. The mpeg-4 AAC format (in dealing with QuickTime and Nero) is ahead of a lot of mp3 encoders. Development on the Lame mp3 encoder has really narrowed the gap between the mpeg-4 AAC and mp3 formats. In a not-so recent test, iTunes 4.8 (I bilieve it was 4.8) was tested against Lame 3.96.1 at the bitrates of 128kbps and ~132kbps VBR respectively. There was not a statistical difference between the two formats at those bitrates.

Once you get up past the 192kbps bitrate, the differences are really neglidgable (ie to most people including me, some people might be able to hear differences). If you want universal compatibility and continued development, then stick with the Lame mp3 encoder and you might want to switch to the recently recomended Lame 3.97b1 encoder. The mpeg-4 AAC format is great but I think it needs a lot of work if it wants to compete with the Lame mp3 encoder.

Cool, someone's finally done a listening test. Or not?



It was iTunes 4.2 & QT 6.5 i believe (the one before they did some major changes that resulted in ringing). It's been improved by leaps and bounds since then, but work has also been done on LAME. I think it's time for a new test

I'm confident that as soon as Nero's new AAC encoder is released (if it is ever released), Sebastian Mares will go about preparing a new test.

Correct me if I'm wrong, but here are a short description.
* AAC -> Raw AAC file
* .mp4 & .m4a -> File ending for the MPEG-4 container. Which can contain AAC, MP3 or Apple Lossless encoded audio.

So what exactly is it about .aac and .mp4/.m4a files that warrants using one over the other? I'm a bit lost with all the jargon.

Basically, there are a bunch of different formats that got developed that all do (almost) the same thing, and different large corporations chose one to support for one reason or another. This led to the current situation with lots of formats. Apple supports AAC, Samsung supports Vorbis, etc. There is really very little difference at the moment between them in term. Bascially, if you happen to support a large company and want to use a lot of their products, pick the format they support. Otherwise, I would suggest mp3 if you just want your music to play on every audio player under the sun, or Vorbis/MPC if you want your music to sound the very best at a given size of the files. Other than that, the bottom line is it really won't make a huge difference which format you choose. Pick one you think sounds cool.

All of that is pretty much inaccurate. .aac is not "Apple's take on mp3"; if you'd like to assign that label to anything, it would probably be Apple's mp3 encoder. mp4 is a container, and I think you'd store lots of music in it, as opposed to plain .aac files, as companies these days seem to be moving in the direction of complying with standards. .m4a is not the audio only version of mpeg 4, it is simply an .mp4 file renamed to .m4a. It's used by apple lossless files, but not limited to those.

While your post is accurate, I'm not sure why you're quoting Masamune's post, as you're not actually answering any of his questions.

And to answer those questions:
A .aac file is just an audio file with no additional information. It doesn't have any tags, so you're not likely to know artist info, song name, album info, etc. You could add an ID3 tag to it, which some programs do, but that's not described in any standard, and finding decent players that would support such strange combinations is unlikely. The standard solution is to put the aac file in an mp4 container. The resulting file would have a .mp4 extension, and would contain the aac file, as well as additional info about the artist, etc. If you have to choose between aac and mp4, I'd advise on .mp4, as it's part of a standard and properly supported by most decent apps.

As for .m4a, an .m4a file is exactly the same as .mp4. As far as I know, .m4a came about because Apple decided a user might want to open .mp4 files with two different programs, depending on whether they contained audio or video. So they started using the .m4a extension for mp4 files containing audio, and the .m4v extension for mp4 files containing video. Other people decided this was a good idea and began to support this practice as well. Whether you want to use .mp4 or .m4a is dependant on whether the programs you plan on using it with support the .m4a extension or not. In my experience, most serious programs claiming "AAC support" recognize .m4a as well as .mp4, in which case I would advise using .m4a, as all programs I've seen which support .m4a also support .mp4, but not all programs that support .mp4 support .m4a. Also, should you run into a program that doesn't support .m4a, you'll know it right away, rather than discovering it later.

P.S. If you plan using these files with an iPod or iTunes, I have additional advice...

*.mp4 files seem to show up with a lil' TV icon on them in iTunes 6.0.1.3

*.m4a files don't - A good thing considering the files in question ARE audio (& tags) only...


Pray tell... .. ?

I'm about to transcode an AAC copy of my extensive FLAC collection (±400Gb) via foobar2000 0.8.3 and iTunesEncode.exe (iTunes 6.0.1.3 @ AAC 160 kbps 44.1 kHz Stereo VBR) for my soon to be acquired 60Gb 5G iPod... Any recomendations / tips?

I guess it's probably a good idea to enable the "Use ReplayGain" setting in the Diskwriter "Processing" section so that I can avoid having to use Apple's ReplayGain-Track-Gain'esque "Sound Check"... I'd have to remember to apply MP3Gain to the few MP3-based albums to be included on the pod too though, otherwise the aforementioned "good idea" would in fact be a bad one!

in 99.9999999% of the cases raw aac with adts headers


yes, additionally .mp4 can store .mp1, .mp2 audio (and a few more audio formats hardly anyone uses)
it can store mpeg-1, mpeg-2, mpeg-4-2, mpeg-4-10 video
it can store .jpg and .png pictures
and it can store animated content (bifs...)

"MP3: Use for maximum compatibility and tested and established quality. Most people here would recommend you stick to this, because the difference is already quite small and the LAME encoder is quite good."

Don't know what else there is to say

Isn't AAC also the audio portion of a ripped DVD?

No. That can be AC3, LPCM or DTS.

Oh that's it. Thanks for the clarification. AAC, AC3 ... can get confusing at times. Theyre' totally different, you're right.

Don't forget about RealAudio 10 AAC (.ra and .rax).

Great, now my head is spinning.

Well, since I refuse to install any RealAudio crap, I don't have to worry about that on my PC.

Or do forget about it and stick to .m4a

This is incorrect. AAC is not what some people believe it to be "Apple Audio Codec". This is wrong. Apple had nothing to do with the develiopment of AAC. That is like saying Microsoft is responsible for MP3. No no no!

AAC stands for "Advanced Audio Coding" and is a superior format to MP3 in all aspects. It is still a lossy format like MP3 however. Here is a list of just some of the advantage AAC has over MP3 (even the newest LAME encoder):

* Sample frequencies from 8 Hz to 96 kHz (official MP3: 16 Hz to 48 kHz)
* Up to 48 channels
* Higher efficiency and simpler filterbank (hybrid → pure MDCT)
* Higher coding efficiency for stationary signals (blocksize: 576 → 1024 samples)
* Higher coding efficiency for transient signals (blocksize: 192 → 128 samples)
* Much better handling of frequencies above 16 kHz
* More flexible joint stereo (separate for every scale band)

What this all means to the listener is better and more stable quality than MP3 at equivalent or slightly lower bitrates.

Now you know. AAC > MP3. But, like many other people have stated on this forum, MP3 is still the universal standard when it comes to audio players supporting the format. AAC in the MPEG-4 container (.mp4 .m4a etc..) are rapidly gaining support though. iPod is fully compatible with AAC in MPEG-4, and I highly recommand using the latest Nero AAC codec (4.2.1.0) contained in the latest Nero 7 software for encoding your music. Do not convert your music from mp3 to aac, because your mp3 file is already lossy, and aac has different lossy properties as well. When you go directly from one format to the other you get the worst of both worlds (like making a copy of a copy... the quality will continue to suffer. The best choice is to just rip any future CD's that you will own to AAC. Keep your old mp3s, because re-ripping your entire CD collection to a newer lossy format has little advantages besides saving some space on your hard drive (AAC sounds better then MP3 at equal bitrates, so you can encode AAC as lasser bitrates, and get the same quality as MP3 at higher bitrates)

All lossy formats have there advantages and disadvantages. I don't think there will ever be a future proof lossy format. This is why I have all my audio files in a lossless format and i convert to lossy depending on the usage.

Best lossless format is probably WavPack but flac has the most support right now.

You just need to remember that aac is the raw format. mp4, m4a are only containers which can contain the raw aac file. they can also contain other formats like mp3. I am not sure about m4a but mp4 can also contain divx and xvid video along with audio files!

That's a highly inaccurate and unfounded statement. I haven't seen any listening tests so far where LC-AAC encoders do (a lot) better than Lame at =>128 kbps.


mp4 and m4a is a different extension for the same thing. They are exactly the same container.

That is not an inaccurate or unfounded statment by any stretch of the imagination. You don't need a listening test to know that AAC is a superior format. I never claimed that AAC encoders do "a lot" better then mp3 at equivalent of slightly lower bitrates, but they do do better just because of the advances of AAC format.


Did I say they were different containers? I see that I did write containers when I did in fact mean container. I thought it was obvious that both those file extensions (among others) refer to the MPEG-4 container. Thank you for clearing that up though.

You are 100% correct. The other possible extensions for MPEG-4 files are the following:

- .mp4: only official extension, for both audio and video files (and advanced content)

other related extensions:
- .m4a: introduced by apple for aac/alac audio-only files, m4a can safely be renamed to .mp4
- .m4p: DRM protected files sold in iTunes, using the DRM sheme developed by apple
- .m4e: renamed .sdp files used by Envivio for streaming
- .m4v, .mp4v, .cmp, .divx, .xvid: video-only, raw mpeg-4 video streams (Should be Video Only)
- .3gp, .3g2: used by mobile phones, stores content not defined in .mp4 too (H.263, AMR)

Sorry, a listening test is exactly what I need. I don't listen to format specifications, I do listen to music. Since I, and more people with me, cannot clearly state a preference between MP3 and AAC at afformentioned bitrates (at least not shown through any listening test) your claims about quality ARE inaccurate. So if what you say is not what you mean I think you need to rephrase it. AAC does not do better on the area I mentioned, not at all. And finding your comments inaccurate is not limited to just my person. Click


Sorry, the quote was from AlexanderTG's post. I'll fix it.

stephanV, I will try to get you a sound test for concrete evidence that AAC is a better format. I know you don't listen to format specifications. But both formats are lossy anyway so there really isn't a great arguement for either one. Believe me I used to be a big fan of LAME MP3, but I personally decided that Nero AAC-LC is better. I also believe that H.264 is superior to DivX for video encoding at equal bitrates, but that debate is for a different forum I suppose. Anyway, it's all a matter of personal preference, although with all audio tests aside, theoretically AAC is a superior format if you look at the specs. I cannot claim that all or any AAC encoders follow these specs though, which I suppose was your point.

Maybe this one:




All AAC encoders follows AAC spec. Otherwise there are something else as AAC.
Specifications mean nothing. Go to reallyrarewares and download a very old ISO encoder, and compare quality with a modern implementation of MP3: you'll easily be convinced that specifications (theoretical performance) are nothing compared to the implementation (concrete or real performance).

You can safely believe that encoder x is better (and even much much much better) than encoder y, but without proof, I suggest you to keep this belief for yourself. It's a rule on this board.

Don't forget that it should apply to the target bitrates mentioned here. I'm not questioning that HE-AAC at 64 kbps is better than MP3 at 64 kbps.


I'm not a fan of anything, but you need to base your decision on something. It would seem to me that a decision based on practice has more value than one based on theory. And if I look at practice, I can't state preference between LC-AAC and MP3, and neither can most people. (just looking at quality)


Not at all. If an AAC encoder does not follow the AAC specifications, it's not an AAC encoder. But I don't see how a standard alone can be a guarantee for quality. If that were the case, all that needs to be done is implementing it and you're finished. No further tuning needed. And that's what I meant with when I said that I don't listen to specifications, there's more to engineering a codec than just implementing the standard.

I have just re-familiarized myself with the forum rules, and I would like to appoligize to you and everyone else on this board for posting my biased opinion without giving proof to back up my claims. I am currently working on a double-blind listening test for those who are interrested. I will be using the Nero AAC codec 4.2.1.0 and LAME 3.97 beta 1 (I think that these are the most recent versions) and normal vbr settings.

It looks enjoying Thanks!

I see a lot of confusion here, so I'll try to extend what Randall311 already wrote.

MP4 is a container format, a part of MPEG-4 standard. MPEG-4 also standardises some types of compression of sound and video. The sound compression is AAL-LC (Low Complexity), AAC-HE (High Effeciency, also known as AAC SBR and AACplus) and AAC PS (Parametric Stereo). Then we have MPEG-4 video compression divided in MPEG-4 SP (DivX 3, DivX 4, QuickTime), MPEG-4 ASP (DivX 5, DivX 6, XviD, FFMPEG, 3ivX, ND ASP) and MPEG-4 AVC (x264, ND AVC, QuickTime).

Now AAC extension is commonly used for raw audio stream encoded according to MPEG-4 standard. M4V is a MPEG-4 video. MP4 is as I already said a container designed to store raw audio and video tracks and it can also contain tags, subtitles, chapters menues etc. For video files the extension MP4 is used. For audio the extension M4A should be used to distinguish video and audio-only files.

The MP4 container accepts all MPEG-4 streams. It also supports officially MPEG-1 and MPEG-2 audio/video. So you can have an M4A audio fie with AAC compression as well as MP3. Someone already mentioned this here.

So once again AAC is a sound compression with 2 possible extensions (HE, PS). MP4 (M4A, M4B) is a container, which supports storing of AAC and other compression formats.

Vlada

Great! I for one will be interested in those results!

I'm still a little lost... but less so now. I have no interest in purchasing an iPod because of the many problems that come with them. I'm probably picking up a Creative Neeon 6GB or soemthing similar, so MP3 is the go anyway. I'm fairly happy with my LAME 3.97b1 files now anyway, I like the way the developers have cut down file sizes.

My entire collection was Flac'd some time ago, so I might try and rip a few to .m4a and do a few listening tests of my own. Aside from the HA tutorials, are there any places or encoders I should look at that give a very simple step-by-step descriton of what to do?

Big thanks for clearing this up though.

Not to take away from the original topic but I am just curious, what "many problems" are you talking about?

he probably just means the vbr playback issues that occur sometimes. although ive never personally had any problems with an ipod

What's ironic is that he's passing over the iPod for a Creative -- from what I've heard (from several sources mind you) Creative players have the worst failure rates! LOL

Not what ive heard. iPods are supposed to have bad batteries... Really bad

You must be thinking of the really old models...

No problems with mine!