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Rockbox Audio Quality versus Original Firmware (RMAA comparison)
Febs:
I used Rightmark Audio Analyzer to compare Rockbox versus the original software.
The results are set forth in successive posts below.
All tests were performed on my 2.8gHz Pentium 4 PC with an Audigy 2 sound card. Other test conditions are noted in the individual posts below.
Febs:
Rockbox versus original Apple firmware.
iPod video 60GB
Headphone output
Volume at 0dB in Rockbox, matched as closely as possible in the Apple FW using RMAA's level check.
Rockbox frequency response (headphone output):
Rockbox frequency response (line output using Pocket Dock):
Apple firmware frequency response:
Rockbox dynamic range:
Apple FW dynamic range:
Febs:
I have seen speculation that the decoders in the respective firmwares could cause differences in sound, so I encoded the RMAA test sound file from .wav to .mp3 using LAME 3.97b2 -V2. All other test conditions are the same as above.
Rockbox frequency response (MP3, headphone output):
Rockbox frequency response (MP3, line output):
Apple FW frequency response (MP3,headphone output):
The RMAA test uses a sine wave sweep, which is notoriously difficult for mp3 encoders to handle, so I'm not sure how valuable this test is. Nevertheless, it is interesting to see that the results are substantially similar for both Rockbox and the original Apple firmware.
lachlan:
I would go as far as to say they are almost identical. Out of curiosity, would it better to have the line showing greater changes, or being smoother?
omendelovitz:
Hey Febs, a quick Q 4 U. What other measures of sound output would one consider in assessing SQ? I ask b/c my main beef w/ the original OS is that it seemed to sound more "congested" than Rockbox, i.e. worse instrument separation, resolution (layering) and imaging. I'm also wondering about the background hiss audible in AOS w/ high sensitivity IEM's.
I'm not trying to be facetious here, just want to learn...
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