[Gaffer74]

I thought I'd try a quick experiment to test which bitrate I should encode songs onto my iPod.

I created the following versions of the song "Like A Star" by Corinne Bailey Rae (4min 3sec):
1: AIFF , 1411kbps ... 41Mb
2: WAV , 1411kbps ... 41Mb
3: Apple Lossless , 778kbps ... 22.7Mb
4: MP3 , 320kbps ... 9.4Mb
5: AAC , 320kbps ... 9.3Mb
6: AAC , 192kbps ...5.6Mb
7: AAC , 128kbps ... 3.8Mb
8: MP3 , 128kbps ... 3.8Mb

I've also included the file sizes.

I attached to line-in on my second hi-fi and sat in the other room (out of sight...where the speakers are) and got my nephew to play the songs in any order (the hi-fi is situated in the adjoining room).

Despite what I expected, it was usually quite easy to distinguish between them.

I did have trouble distinguishing between AIFF and WAV files.
The Lossless file sounded slightly "sharper", and therefore more "in your face".
Beyond these, there was a clearer reduction in quality in that guitar strings didn't sound quite right, vocals started sounding a bit harsher with the next formats:
AAC 320 sounded very good, but I again found it more difficult to distinguish between MP3 320 and AAC 192. Overall I felt the AAC 192 provided more "air" to the proceedings and was better suited to vocals, but MP3 320 provided more "depth" and gave a better picture of bass....but it was close between them.
AAC 128 was clearly rubbish with distorted vocals and a nasty "equalised boom box" feel to the music.
MP3 128....eeeuuuuurgh, the less said the better. I wouldn't call it music...I would call it noise.

To confirm, I then burnt the tracks onto a CD using Toast Titanium. This re-converted all to aiff format, but the pre-existing formats were the rate limiting step, so any deficiencies would still be heard (and be a function of the format they were converted from...ie a AAC 128 song converted to AIFF will only sound as good as the AAC 128 song did in the first place).
Same results.

So in order of preference, I had (best->worst)
1 = 2
3
5
4 = 6
7
8

...and am glad I stuck with AAC 192 when i first got my iPod a year ago. It offers the same excellent sound of MP3 320 quality, but for much less space (about 40% less).
(The reason I chose to play through the dedicated Hi-Fi is that it should be easier to pick up subtle differences in sound).

I'm also convinced that AAC sounds "good" on the iPod because it is effectively altering the sound similar to what you might get sticking an uncompressed track through an equaliser setting like "acoustic" or "treble booster". That's why it sounded more "airy" imo....but for the purposes of portable audio, it still sounds excellent.

I'm not saying this is any way definitive...just that it works for me and to show how easy it is to do. Remember, at all times, even though I couldn't always distinguish between AIFF and WAV, they were both clearly superior to the others on a dedicated Hi-Fi set-up (which is why I always buy CD's I like rather than download from iTunes/bittorrent).

It's a simple and easy way for you to try yourself to see "how low you can go" before SQ becomes unnacceptable on portable machines.

(i always stick with best SQ possible for my Hi-Fi seperates though

)

 

[Febs]

I'd be very interested in having you redo your WAV v. lossless test using an ABX program to see if you can recreate the results.

Out of curiosity, what encoder did you use for MP3, and why did you test only CBR?

 

[jagorev]

AIFF, WAV, and Apple Lossless should be equal. I would try foobar, which has a built in ABX tester.

 

[Gaffer74]

Quote:

Originally Posted by Febs Out of curiosity, what encoder did you use for MP3, and why did you test only CBR?

I used iTunes to encode everything (pretty widedly available).
I wanted to see how specific bitrates compared, with VBR I would sometimes be hearing a 320kbps part of the song at for instance, 128 at others.
This way, it all seemed simpler to me (ps I also don't think AAC vbr does anything anyway

, it still seems like cbr to me on examination)

Quote:

Originally Posted by jagorev AIFF, WAV, and Apple Lossless should be equal.

aaah, but that's a big should. AAC lossless definitely sounded "sharper" to my ears...like I mentioned, AAC sounds like you've put wav/aiff through a "treble booster" equaliser.
(Unnaceptable for hi quality seperates, but acceptable for portable use I think...I mainly use my iPod in the car)

 

[Febs]

Quote:

Originally Posted by Gaffer74 I used iTunes to encode everything (pretty widedly available).

The iTunes MP3 encoder is not particularly good. MP3 would undoubtedly fare better in your listening test if you used a first-rate encoder, like LAME 3.97b2.

Quote:

I wanted to see how specific bitrates compared, with VBR I would sometimes be hearing a 320kbps part of the song at for instance, 128 at others.

Yeah, but with VBR, you would get a substantially better quality at comparable filesizes.

Quote:

aaah, but that's a big should. AAC lossless definitely sounded "sharper" to my ears...like I mentioned, AAC sounds like you've put wav/aiff through a "treble booster" equaliser.

Unless there is something wrong with your encoder or decoder, or the volume of your lossless file is different from the .wav or .aiff versions, there should be no difference whatsoever among them. Lossless files are decoded to bit-perfect copies of the original file.

 

[Digitalbath3737]

I'd love to see the results of an blind abx test comparing lossless to original WAV. Lossless is lossless. They don't call it lossless just for the heck of it. You're most likely suffering from the almighty placebo effect.

 

[Gaffer74]

Quote:

Originally Posted by Digitalbath3737 Lossless is lossless. They don't call it lossless just for the heck of it. You're most likely suffering from the almighty placebo effect.

Could be

, my latest iTunes update might also have altered the codec?

The test was unsighted by me, and my nephew couldn't discern the type/bitrate from the track (i didn't tell him what was what)....so it was double blind.
He randomly chose whatever tracks he wanted to play so it was random.
We were unsighted from eachother.


.....yet I could stil pick out aacLossless from WAV/aiff most of the time

....as you mentioned, it must be the codec or my ears at fault (aah well, still doesn't tempt me away from the SQ c.f. practicality of 192aac though

)

 

[sxr71]

Wow. Placebo effect. If you are seeking a difference, you will find one.

Were you writing down results? You should check your answers after about 15-20 trials.

 

[Skylab]

Even I, the die-hard proponent of lossless coding, do not think that there can be an audible difference between WAV and Lossless. I have proven that Apple Lossless files are bit-perfect with the WAV files they come from. Given that, I can't see how they could sound different (unless of course they were played at even slightly different volume levels).

I do believe it's possible to hear the difference between lossless and any/all lossy coding. I know I can.

 

[Gaffer74]

Probably was Placebo then.
As I mentioned though, this test isn't about the top three codecs, more about how low you can go before SQ is unacceptable with portable use.