Rockbox Audio Quality versus Original Firmware (RMAA comparison)

[omendelovitz]

Got it.  Actually, I was thinking of two ipods set to the same settings and using the same files/equipment.  honestly, I don't think RMAA tells the entire audio picture.  With all that we've been talking about in this thread alone, we haven't mentioned how we'd measure "soundstage" presentation, never mind imaging and/or resolution measurements.  AFAIK, those audio cues can't be measured (if so, someone please correct me and teach me )

[Febs]

What exactly is "resolution"?

[omendelovitz]

What exactly is "resolution"?

resolution means instrument separation

[saratoga]

With all that we've been talking about in this thread alone, we haven't mentioned how we'd measure "soundstage" presentation,

Sound stage == stereo crosstalk.

never mind imaging

Within this context, imaging and sound stage and stereo crosstalk are the same thing.

and/or resolution measurements.  

Resolution for all of these is 16 bits.  You don't actually need to measure that.

AFAIK, those audio cues can't be measured

All things in nature can be measured.

[Febs]

resolution means instrument separation

Then what is "imaging" and how does it differ?

[Febs]

Actually, never mind.  These are futile questions and exactly the type of debate that I did not want to get into.

Omendevolitz, what do you use as your "reference" files?  

Do you use Foobar?

[omendelovitz]

imaging is the dynamics of spatial location - the 3-D'ness of audio; depending on your system, you may be able to 'follow' the music around in your head and pinpoint an instrument's virtual location, or a progression b/w channels as a particular sound moves 'through' its audio field.  

Using a headphone example - assume imaginary horizontal lines are extending in 3 directions from the centre of your head.  Label them x,y,z arbitrarily.  A well recorded (engineered) musical piece will 'locate' a sound in a  certain location (e.g. - left 3 on the x, -5 on the y and -3 on the z axes) rather than placing it all right up 'against' your ear.  Think of watching real life vs. television or imax v/s the movies.  TV and regular movies are flatter.  Hope this helps.

[omendelovitz]

my reference files are songs that I know well that have been recorded well enough to notice 'placement' of insturments, etc.  Some are in ALAC, others in AAC 320 or Lame 320.

I understand you not wanting to delve too deeply into this on this forum/thread.  These 'conversations' are better left to head-fi, etc.

[Febs]

What are the actual songs that you use as reference songs?

[omendelovitz]

Here you go:

The Be Good Tanyas - The Littlest Birds

Django Reinhardt - Minor Swing

Chris de Burgh - Spanish Train

Dave Matthews Band - The Dreaming Tree

Dave Matthews Band - Listener Supported

Dire Straits - Money For Nothing

Dixie Chicks - Landslide

Earth, Wind & Fire - September

Genesis - Jesus He Knows Me

George Michael - Fastlove

Goo Goo Dolls - Slide

Various Artists, Santaolallia Gustavo - De Usuahia A La Quiaca

Heart - Crazy On You

Heart - 15-Back to Avalon

James Taylor - Carolina In My Mind

The La's - There She Goes

Paul Simon - You Can Call Me Al

Paul Simon - Crazy Love. Vol 2

Phil Collins - Easy Lover

Phil Collins - Something Happened on the Way to Heaven

Red Hot Chili Peppers - Higher Ground

Rush - 21 - 2 Overture - The Temples Of Syrinx

Rush - The Spirit Of Radio

Sloan - Delivering Maybes

Sloan - The Other Man

The Smiths - Bigmouth Strikes Again

The Smiths - This Charming Man

STYX - Mr. Roboto

The Tea Party - The Badger

The Tea Party - Shadows On The Mountainside

Toad the Wet Sprocket - Whatever I Fear

Toad the Wet Sprocket - Nanci

Van Halen - Hot For Teacher

Dave Matthews - So Damn Lucky

Dave Matthews - Trouble

Dave Matthews Band - Stay (Wasting Time)

Pat Metheny - Sisters

Pat Metheny - New Chautauqua

Pat Metheny Group - James

Pat Metheny - Above the Treetops

Pat Metheny - Facing West

Pat Metheny - See the World

Pat Metheny Group - Part 1

Dave Matthews Band - Say Goodbye

Dave Matthews Band - Tripping Billies

Dave Matthews Band - The Stone

Phil Collins - I Cannot Believe It's True

Dave Brubeck - Take Five

Dead Can Dance - American Dreaming

[omendelovitz]

Saratoga,

While I appreciate your enthusiasm, Platitudes don't help.  I'm hoping you can be a little more specific with your statements - e.g. how does stereo crosstalk effect perceived spaciousness of the soundstage?  How does it affect imaging?  exacly what is 16 bit?  How would it affect instrument separation?

oh, and let me correct myself - I've never found an audio hobbyist whose been able to measure the above types of audio cues; I've also never had a chance to speak/interact with someone who works with these issues professionally to teach me such nuances in audio reproductions - if you have, please fill me in or at least refer me to places where I can learn all these types of goodies for myself! Yumm

[Febs]

Here you go:
...

Dixie Chicks - Landslide

Omendelovitz, since you hear a difference between the Apple FW and Rockbox, I would be greatly appreciative if you could do a test for me.  I have posted two clips of Landslide (one of your reference tracks) for you to compare:

Wave files:
Clip 1
Clip 2

WavPack Files
Clip 1
Clip 2

It doesn't matter which set you choose; they are identical except that obviously the WavPack files are smaller.  To prepare the clips, I ripped Landslide from CD using EAC.  The .wave file was placed on my iPod, and then played back using both the Apple firmware and Rockbox.  In each case, the clips were recorded to  .wav file, using the iPod's line out and a pocket dock.  In each firmware, the iPod's volume was set on maximum (i.e., +6dB in Rockbox; a "full blue line" in the Apple FW).   No EQ or other processing was enabled.  I did no post-processing other than to (1) peak normalize both files so that there would be no volume differences to skew the results, and (2) trim the starting and ending points of each clip so that as near as humanly possible, they were exactly the same length.

Please compare the two clips using an ABX program such as the one built into Foobar2000.  You should do 12 trials.  Turn off the option allowing you to view the results of each trial as the test is in progress.  When you have finished 12 trials, exit the ABX program (being sure to save the results) and post the results here.

Thanks!  Please let me know if you have any questions.

[saratoga]

Saratoga,

While I appreciate your enthusiasm, Platitudes don't help.  

Platitudes are statements such as "life is great" that don't actually mean anything.  I posted definitions of those terms, as commonly used.

I'm hoping you can be a little more specific with your statements - e.g. how does stereo crosstalk effect perceived spaciousness of the soundstage?  How does it affect imaging?

Stereo cross talk collapses the sound stage.  At 0 dB you have mono.  At negative infinity you have perfect channel speration.  In this case though, since the noise floor is roughly the same as the cross talk, its a safe assumption that the channels are not audiably coupled.

Regarding imaging verses sound stage, they really are the same thing in this context.  Heres the first random site I found googling:

http://www.electronixwarehouse.com/education/glossary/S.htm

"
Soundstage
...
 (See also Imaging above)
"

So it seems its not just me who uses them interchangably.

 exacly what is 16 bit?  How would it affect instrument separation?

The resolution of the PCM audio is 16 bits in Rockbox and Apple firmwares.  It doesn't effect imaging, it determines how well the system can resolve amplitude changes in reconstructed waveforms.  This in turn determines the dynamic range of the system.  16 bit systems typically have a maxium of 96 dB SNR.

oh, and let me correct myself - I've never found an audio hobbyist whose been able to measure the above types of audio cues; I've also never had a chance to speak/interact with someone who works with these issues professionally to teach me such nuances in audio reproductions - if you have, please fill me in or at least refer me to places where I can learn all these types of goodies for myself! Yumm

A lot of audio terminology is simply made up by hobbyists as the go along.  Its very common on the internet for people with no real understanding of audio to hide behind the equipment they use and the nebulous terms they throw around (I'm not singleing you out).  Its best to just avoid fluffy language like that entirely and say what you mean.  At least thats my preference.  

But yeah, take the ABX test and post your results.  Either way it'll be interesting.

[saratoga]

Hey Febs, I think you mean

http://jazzexplosion.com/Febs/Rockbox/Landslide1.wv
http://jazzexplosion.com/Febs/Rockbox/Landslide2.wv

are the wavepack files.

Anyway, thats a difficult test.  I tried but could not ABX it.  Though it could be that I'm not sure what to look for, which doesn't help.

[Febs]

Thanks, I fixed the links.