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  #1  
Old 04-09-2007, 05:20 AM
breez breez is offline
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Default RMAA comparison: 1.02.15P vs patched RB (cpchan's compile)

UPDATE:

Check http://www.anythingbutipod.com/forum...8&postcount=26 for latest results from cpchan's 1th june build. Original audio performance reached!

-----------------------------------------------------------------------------------------------

Here's a RMAA comparison of the original firmware and patched rockbox build from cpchan (link to thread).

RMAA: http://koti.mbnet.fi/laurimel/RMAA/S...tched%20RB.htm

The frequency response chart confirms my listening impressions of tinny sound. Also note the higher distortion in THD test. Noise results are well below what Sansa is capable of (-85 to -90dB based on prev. testing), but this is intentional as output levels were kept low to guarantee no clipping occured. I didn't have the time to hunt optimal settings for rockbox. Dithering option was enabled in RB (weird and extremely bad results with the option disabled).

In case someone was wondering, you can play standard .wav files in original firmware if you put them in the record\voice directory.

To developers, you can use RMAA to find these kind of great differences with just about any sound card, no need to invest in a pricier card.

Last edited by breez; 06-02-2007 at 07:25 AM.
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  #2  
Old 04-09-2007, 07:24 AM
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Can you explain it a bit more detailed, please? Like what is THD and frequency response?
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  #3  
Old 04-09-2007, 07:32 AM
vygi vygi is offline
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THD is Total harmonic distortion; explained here: http://en.wikipedia.org/wiki/Total_harmonic_distortion
And Frequency Response: http://en.wikipedia.org/wiki/Frequency_response
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  #4  
Old 04-09-2007, 08:49 AM
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Wow, I don't really understand the wiki article. So I will really appreciate if someone can elaborate on
1. For each test, is rockbox better/worse/on par with the original firmware?
2. How to improve? Like if you use EQ, will it help?
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  #5  
Old 04-09-2007, 09:55 AM
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Since original firmware sounds way better, I guess the values of the original firmware should be aimed by Rockbox.
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  #6  
Old 04-09-2007, 11:32 AM
breez breez is offline
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While there's a difference in the THD test, it may not be an audible difference, but great variations in the frequency response are readily audible.

The ideal frequency response from an audio source is a straight line (see the original firmware). It is easily achieved by any modern audio source into line level inputs. Usage with headphones is another story, usually with portable players there is a bass rolloff.

One could try to equalize the response, but it is not the right solution to the problem. The DAC driver is still under development and there surely is a way to get a straight frequency response.
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  #7  
Old 04-09-2007, 04:11 PM
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What do you mean by a bass roll-off?
What do you mean not the right solution? I mean your explanation makes sense because I have to boost my base to 13dB to get good sound out of rockbox.
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  #8  
Old 04-09-2007, 04:15 PM
Llorean Llorean is offline
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If you actually want to achieve something, you should probably take your RMAA results to an OFFICIAL location such as the bug tracker or official forums...
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  #9  
Old 04-09-2007, 09:01 PM
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Quote:
Originally Posted by breez View Post
The frequency response chart confirms my listening impressions of tinny sound....
Yes, I know. The audio in Rockbox for Sansa haven't really been fixed and optimized yet. The audio glitch patch is only a temporary workaround. Rockbox for Sansa is only in its Alpha stage of development, please give it some time as reverse engineering is really a voodoo science. As Llorean have suggested please take your RMAA to the official Rockbox site, so the developers can see it- I am only a packager at this point. I am really new to Rockbox and I have only just started looking at the code.

Also, please try doing a complete shutdown by holding the power button for 15 seconds. I find that sometime the sound is screw up after a Rockbox update which is cured by the above procedure.

Charles

Last edited by cpchan; 04-09-2007 at 09:21 PM.
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  #10  
Old 04-10-2007, 12:10 AM
Llorean Llorean is offline
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My personal RMAA test with the anti-vinyl-effect patch from the Rockbox tracker shows VASTLY different results. I've posted them in the patch tracker thread for the patch.
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  #11  
Old 04-10-2007, 01:56 AM
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breez, since Llorean results are very different from yours, I suspect you ran into that problem that I mentioned in my previous post. Can you please reset your player by holding the power button for 15 seconds and redo the test? I can't run the test here myself since I don't have a Windows machine.

Charles
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  #12  
Old 04-10-2007, 03:58 AM
Llorean Llorean is offline
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To summarize, Rockbox's sound quality on the Sansa (with the patch) is similar overall to that of the Gigabeat according to my test results (the retail firmware on the other hand did poorly in comparison) and the only real problem with the anti-vinyl patch seems to be that the volume is still quite wrong.
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  #13  
Old 04-10-2007, 08:53 AM
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Quote:
Originally Posted by Llorean View Post
the only real problem with the anti-vinyl patch seems to be that the volume is still quite wrong.
Do you know if the anti-vinyl patch is really a proper fix? According to the patch's page it is a workaround.

Charles
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  #14  
Old 04-10-2007, 11:17 AM
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Quote:
Originally Posted by Llorean
(the retail firmware on the other hand did poorly in comparison)
Are you serious? I just wondered, because I can't enjoy music with Rockbox, but I can enjoy it with the original firmware!!!
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  #15  
Old 04-10-2007, 11:28 AM
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I tried the test and it seems that you need to connect from your player to the computer through a line-in cable. And so a test is also dependant on the quality of the cable and the connection (gold-plated jack to silver-plated socket will degrade the sound). I also figured that connecting the Sansa to my laptop microphone socket is also a bad idea because microphone socket is mono. So in another word, I can't figure out how to do my own test. My soundcard is average on noise level and dynamic range and good for the rest. And I find my laptop sound to be very reasonably good so I guess I really have very high tolerance for bad sound.

@godess: Are you using the patched rockbox (either cpchan or my version <-- see my sig) with stereowidth and crossfeed on, and also with the right EQ? If you do then we can discuss it. If not, try the option.
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Last edited by testdasi; 04-10-2007 at 11:34 AM.
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  #16  
Old 04-10-2007, 12:25 PM
Llorean Llorean is offline
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The test should be performed without any options changed from the default (like EQ or crossfeed).

The patch is the beginnings of a proper fix, but it seems it's not there yet. I suspect that with it the hardware is set right, or closer to right, but there's still the volume issue, and from the looks of it may still be some tweaking left for the hardware. It's hard to tell over all.

@goddess: It's entirely possible you've grown used to the sound quality of the original firmware. But it's also possible the original firmware is simply unhappy playing back WAV files.
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  #17  
Old 04-11-2007, 01:55 PM
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zzzz30 zzzz30 is offline
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Quote:
Originally Posted by breez View Post
Here's a RMAA comparison of the original firmware and patched rockbox build from cpchan (link to thread).

RMAA: http://koti.mbnet.fi/laurimel/RMAA/S...tched%20RB.htm

The frequency response chart confirms my listening impressions of tinny sound. Also note the higher distortion in THD test. Noise results are well below what Sansa is capable of (-85 to -90dB based on prev. testing), but this is intentional as output levels were kept low to guarantee no clipping occured. I didn't have the time to hunt optimal settings for rockbox. Dithering option was enabled in RB (weird and extremely bad results with the option disabled).

In case someone was wondering, you can play standard .wav files in original firmware if you put them in the record\voice directory.

To developers, you can use RMAA to find these kind of great differences with just about any sound card, no need to invest in a pricier card.
Great.
Does your equipment allow to measure IMD in db? A low intermodulation
(is it distance? Or offset?) offset is a common reason for "bad" sound quality. Valve amp's get an IMD 20 or 30 db better than solid state amps.
Kind regards,
Helmut
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  #18  
Old 04-11-2007, 03:04 PM
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testdasi testdasi is offline
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OMG, I don't understand all these technical stuffs
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Copy files in MTP mode
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  #19  
Old 04-13-2007, 04:10 AM
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Dont worry testdasi, your not the only one.
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  #20  
Old 04-13-2007, 11:50 AM
breez breez is offline
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Quote:
Originally Posted by cpchan View Post
Also, please try doing a complete shutdown by holding the power button for 15 seconds. I find that sometime the sound is screw up after a Rockbox update which is cured by the above procedure.
I might do just that when I find some time.

Quote:
Originally Posted by zzzz30 View Post
Great.
Does your equipment allow to measure IMD in db? A low intermodulation
(is it distance? Or offset?) offset is a common reason for "bad" sound quality. Valve amp's get an IMD 20 or 30 db better than solid state amps.
Kind regards,
Helmut
I think the dB can be calculated from the value. Eg. -10dB = 10%, -20dB = 1% and so on. This IMD test also counts noise so the result might not be very good in this particular test (best noise levels weren't achieved).
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