Author Topic: AAC vs MP3 vs MP3 VBR (Read 23776 times)

cyberdude · « **on:** May 20, 2006, 01:12:35 pm »

I was told that AAC is superior to MP3 in audio quality and space taken at equivalent bit rates. In PMM AAC max bit rate is 296 and MP3 is 320. So Would AAC at 296 still be better than MP3 at 320?

Also, I read that for MP3 it's best to use 320 VBR. In PMM there is a slider to set the VBR %. What exactly does this do and what is generally the best VBR setting?

judb · « **Reply #1 on:** May 20, 2006, 04:42:43 pm »

Well there are a few factors to have in mind when looking at encoding quality.

First off.. I am not sure that PMM has ever been tested against other audio ripping software for quality of rips and error detection / correction.

www.hydrogenaudio.org is a GREAT resource for information on various audio encoders and decoders... they do comparison testing and bitrate testing.

I am not sure if the phatbox will playback an aac file encoded at 296kb

AAC is essentially mp4, the next rev of the Moving Pictures Experts Group audio compression standard if I recall correctly so it would stand to reason that it would be slightly better than mp3, but I haven't verified that personally. Also I recall that Ogg Vorbis at much lower bitrates would beat high quality MP3s in sound quality.

check out the info on hydrogen audio.. I use Exact Audio Copy to rip my music and encode it becasue I can get better reports about the quality of the extraction etc...

cyberdude · « **Reply #2 on:** May 20, 2006, 04:59:45 pm »

Thanks Judb. I'll check out hydrogenaudio. I only started using my Phatbox a few weeks ago and up until then never ripped CDs and never listened to MP3s

Just didn't have a need for it. I always listed to CDs in my car or HiFi.

Didn't realise there were so many issues with quality

S80_UK · « **Reply #3 on:** May 20, 2006, 06:15:53 pm »

Quote

I am not sure if the phatbox will playback an aac file encoded at 296kb

Well, it works very well on my PB. One of the features of the AAC codec is that it does not require too much processing power to decode it. My music files are a mixture of FLAC and AAC at 296kbps.

As for what sounds better, probably FLAC first (because it is lossless) then AAC-296, then MP3-320. But MP3 at 320 should sound pretty good, although I have not tested that particular codec / rate combination.

Regards,

Les.

judb · « **Reply #4 on:** May 20, 2006, 10:55:23 pm »

never tried encoding aac to test it out.. i'll have to toy with it since you say it sounds so good.

A lossless AAC apple decoder would be nice too.. someone was working on one but never posted his code so I don't know if we'll ever see it happen on the phatbox.

Oh I noticed I didn't answer your question about the quality of the encoding VBR..

VBR max quality would equate to ~320Kbps max bitrate.. VBR files at max quality would be smaller than a CBR (constant bit rate) file at 320Kbps so thats a better way to go in my mind.

Does that answer that question you had? It would be something like 128Kbps - 160Kbps - 192Kbps - 224Kbps - 256Kbps - 320Kbps for the max VBR bitrate for various slider positions I think.

cyberdude · « **Reply #5 on:** May 21, 2006, 06:31:59 pm »

Quote

Oh I noticed I didn't answer your question about the quality of the encoding VBR..

VBR max quality would equate to ~320Kbps max bitrate.. VBR files at max quality would be smaller than a CBR (constant bit rate) file at 320Kbps so thats a better way to go in my mind.

Does that answer that question you had? It would be something like 128Kbps - 160Kbps - 192Kbps - 224Kbps - 256Kbps - 320Kbps for the max VBR bitrate for various slider positions I think.

Thanks that answers my question. I have now started playing with Exact Audio Copy and Lame doing VBR at max quality to compare with the Phatbox MP3 encoder. I'll also do comparisons to AAC at 296.

One thing I have noticed and can't get to the bottom of, is that some of the CD's I've encoded sound very flat and don't seem to have a very open soundstage. There seems to be a huge variation in the quality of the recording. Is the compression just highlighting a bad production. When listening to the CD on my HiFi it doesn't sound bad at all.

rob_hutton · « **Reply #6 on:** May 22, 2006, 02:17:53 pm »

Forget about Mp3 and AAC just encode to FLAC it sound even better than CDA to my ears a lot crisper sound, ok it might be large but the disks are cheep.

I went the MP3 route sounded ok but wait AAC might sound better, so encoded to AAC, now just trying to get the final tracks to FLAC and happy.

cyberdude · « **Reply #7 on:** May 22, 2006, 02:26:54 pm »

Quote

Forget about Mp3 and AAC just encode to FLAC it sound even better than CDA to my ears a lot crisper sound, ok it might be large but the disks are cheep.

I went the MP3 route sounded ok but wait AAC might sound better, so encoded to AAC, now just trying to get the final tracks to FLAC and happy.

I considered FLAC but for the amount of music I have I would need to have a 100GB disk which are not that cheap.

judb · « **Reply #8 on:** May 22, 2006, 06:05:17 pm »

Under 200 bucks for a 100 gig drive if you do the DMS hack.. not a big deal really considering the quality boost you get. Just food for thought.

cyberdude · « **Reply #9 on:** May 23, 2006, 07:29:04 am »

Quote

Under 200 bucks for a 100 gig drive if you do the DMS hack.. not a big deal really considering the quality boost you get. Just food for thought.

I guess you're right. Will a slow drive be enough, i.e. 4800 or 5400 rpm?

S80_UK · « **Reply #10 on:** May 23, 2006, 07:49:59 am »

Rotational speed of the drive is not an issue. And in laptop drives, 5400 RPM is generally regarded as fast, by the way.

If you can, get a drive with an 8 megabyte cache memory. Some drives only have 2 MB and while they work, the palyback can occasionally glitch. With a larger cache, this seems less likely.

judb · « **Reply #11 on:** May 23, 2006, 01:41:15 pm »

The faster the drive, the hotter it runs.. so keep that in mind as the DMS carts do not have air flow holes. heat causes things to quit working faster in the computer world so slower = cooler = good in this case. (don't get a 7200 rpm drive for your laptop drive for the phatbox i am saying I guess)

cyberdude · « **Reply #12 on:** May 23, 2006, 03:12:36 pm »

Yeah, that makes sense. I swapped my 4800 drive out for a 7200 drive in my laptop and the heat is significantly more with the new drive.

Slightly off topic, having just discovered that there are variations in quality between different mp3 encoders does the same apply to FLAC encoders? As FLAC is supposed to be lossless can I assume that I'll get the same quality irrespective of the FLAC encoder I use assuming everything else like CD ROM etc are the same. Is the Phatbox FLAC encoder adequate or should I use something else?

judb · « **Reply #13 on:** May 23, 2006, 07:29:36 pm »

FLAC is lossless so theres no quality variation that I am aware of... the quality settings only effect how small the file is vs encoding time.. not the decoding ability to replay the audio file exactly.

S80_UK · « **Reply #14 on:** May 23, 2006, 11:16:13 pm »

Absolutely. Lossless is just that. Should be no different to the original. The FLAC control parameters (not accessible inside PMM as far as I know) are just a trade off of processing effort versus file size. And the file size reduction is actually very limited for a big increase in processing.

This forum has an interesting comparision of the different lossless codecs (but not the lossy ones based on psycho-acoustic models, which are by definition rather subjective)

http://members.home.nl/w.speek/comparison.htm

cyberdude · « **Reply #15 on:** May 24, 2006, 09:29:08 am »

Great. I guess I'll have to re-rip all my CDs again. Tht's going to keep me busy for a while.

S80_UK · « **Reply #16 on:** May 24, 2006, 01:55:55 pm »

On the plus side, they'll sound better, and FLAC is actually much faster to encode than most algorithms. There is less maths involved, so ripping is often limited by the audio ripping speed of your CD drive rather than the processor in your PC. As an example, most CD's I rip to FLAC take under two minutes.

rob_hutton · « **Reply #17 on:** May 25, 2006, 11:09:53 am »

Anyone know of any download sites that you can get FLAC music from?

judb · « **Reply #18 on:** May 25, 2006, 01:32:45 pm »

I recall that some bands had some live audio mixboard dumps in flac format. I don't recall who though.. its been a while since I saw that.

As far as stealing music is concerened, that is not to be discussed in any way on these forums so I am assuming you were talking about free music downloads. Furthermore I don't think any priated music is currently encoded in flac and available because of the sheer size of the files.. and hopefully it wont happen that way either.

LloydDobler · « **Reply #19 on:** May 31, 2006, 03:11:06 am »

You know, you were saying some of your mp3 files sound flat... you can compare them back to back by simply re-burning the mp3's back to an audio cd. When you make an audio cd it takes the mp3 and re-encodes it to .wav but it retains the sound. It can't recover the data that was lost in the compression.

When I was going through the big internal debate that you are, I took 10 second song clips in .wav format (uncompressed, straight off the CD) and then copied each one and converted it to .mp3 using 320 VBR. I then recorded the .wav and the .mp3 of each song back to back onto an audio disc.

I have a very nice system in my convertible and I put the disc in, in my garage, with the car off so there was nothing but the music. I can honestly say the difference is completely transparent to me. Any artifacts I thought I heard on the .mp3 I'd go back and sure enough, there they were on the .wav. Any distortion or tinny cymbal crashes, identical in sound to the .wav file.

When I made my disc, I used a wide variety of genres but I picked tracks that focused on treble, with bright horns and lots of cymbal crashes. The reasoning for this is, mp3's mostly cut off treble, and the higher the bitrate the higher the frequency spectrum that is retained. From what I understand, 320 bitrate cuts off at about 18 khz for the most part, which quite frankly is right at the upper end of what humans can really hear anyway. Sure 22khz is the official number, but only like 5% of the population can actually hear in that frequency range. My ex wife couldn't hear the flyback transformer on our TV (I could) and it operates at 16khz. Treble was completely lost on her.

So give yourself a true honest side by side test, and if you want to make a blind test, have someone else pick the order in which they're burned so that you have to guess which is the mp3 and which is the .wav. If you can accurately pick out the .mp3 more than half the time, I'd say FLAC is a good call. if you can't, you're wasting your time, just use mp3.

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Author Topic: AAC vs MP3 vs MP3 VBR (Read 23776 times)