Axiom Home Page Forums General Discussion Technical Questions Importance of audio source?

Very interesting.

Probably these days the digital audio from and CD / DVD player will sound the same player to player for the most part.

I happen to prefer the analog output of my old Yamaha CDC-815 5 disc changer. It has soft highs and a warm middle to the sound. There is a clear difference to the sound analog vs digital on this single player, as I can switch from analog to digital by just moving a switch in the back of the player.

Hi Official Ninja,

You raise an interesting point. Since eventually the digital output from a CD player must be converted to analog either in the CD player itself or, if you are routing the digital output via digital coaxial or optical connectors to an AV receiver, then the analog portions of the circuitry in either the CD player or the AV receiver may introduce differences like the ones you cite. Minor frequency response errors might occur, and those would likely be audible.

Regards,

Alan

Hi Alan,

Thanks for reporting in more detail on those listening tests. According to Wikipedia, AAC wasn't released as a public standard until 1997, so I doubt it would have played a big role in a 1992 test. Its implementations have also been continually improved since 1997, so a test from that long ago might not show its current capabilities anyway.

Wikipedia says that 128 kbps AAC MPEG-2 is considered "transparent" for stereo; would be interesting to see if there's a believable basis for that, and also if the current MPEG-4 implementation has changed the situation. Maybe such updated codec listening tests would be a fun project for Axiom :-). You certainly have all the technology and expertise required, and it could lead to some good press since large numbers of people want to know how to encode their music as efficiently as possible without sacrificing fidelity.

For now, I think I'll stick to my Apple Lossless encoding--files are about half the size of uncompressed, though much larger than MP3 or AAC, but no worries about fidelity or the complications of determining just how to encode.

Not to be JohnK here, but it's so rare I get to correct Alan. You have one too many Fs in there. Fraunhofer.

Pedantism, thy name is...

Bren R.

"Wikipedia says that"...come on. It also said the Elephant population of Africa had swollen to insane levels - at least for a little while.

Wiki the Elephant

Hey Bren,

Just winging it. I should have looked it up. Thanks for the correction.

Alan

Hi,

I'm sure AAC and other codecs have been improved considerably, although I'm skeptical that 128 kb/s would be totally "transparent," even now. It might be for lots of uncritical material.

It really depends on how you define that. It should be noted that in the 1992 tests, even the best codecs had occasional little artifacts that some listeners heard now and then, but they weren't so bad as to be rated "annoying."

For instance, if you played some Spanish orchestral music with castinets, there might be a slight timbral change to the sound of the castinets, but not enough that it would annoy you. But do we still call that transparent? In fact, without an immediate A/B comparison to the original source, you might not even detect a tonal shift. Does it matter if everything else in the music selection sounds just fine, except for a slight tonal coloration on the castinets or the triangle (those two instruments, harpsichord and sometime vocals, were the most revealing of any audible flaws in a codec).

Regards,

Alan

128k is not transparent on AAC. I use 160 and above, now 256 VBR for my AACs.

(oops)