Rockbox Technical Forums

Support and General Use => Recording => Topic started by: markanini on December 03, 2011, 10:52:38 AM

Title: Questions about recording capabilities in Sansas
Post by: markanini on December 03, 2011, 10:52:38 AM
Is there any model which is known to be free of periodic background noise? From what I could gather the Clip+ is reported to have issues and my Fuze v2(variant 1) does exhibit enough noise to have me bothered. How about the e200's and Fuzev1? And how about the new Fuze+(if it's not too early to say)? Lastly are all the Sansas hardware limited to 24kHz(?) sample rate for the built-in mic?
Title: Re: Questions about recording capabilities in Sansas
Post by: Chronon on December 03, 2011, 07:02:52 PM
I haven't done very much recording with my v1 e280, but it does suffer noise issues with audio playback (associated with flash access), so I would not be surprised if it shows up during recording too.  24kHz limit applies to the 200 v1 too.
Title: Re: Questions about recording capabilities in Sansas
Post by: megal0maniac on December 03, 2011, 11:12:12 PM
The Clip plus records perfectly clearly on version 3.9.1, it's just the level which is low. That wouldn't be as much of an issue if the ADC didn't work at 14 bit, there isn't headroom to play with. Although, that begs the question of whether the quality would be any better if you got a 14bit file limited at 0dB instead of a 16bit file limited at -12dB...
Rough mental maths says it's not that different.
So I'd say that a track recorded at low level, normalised to use the full 16bits would be the best quality you can get from the clipplus.
Then, I'm allowed to record all the way up to 96kHz using PCM WAV. Different encoders have different limitations.
Title: Re: Questions about recording capabilities in Sansas
Post by: saratoga on December 03, 2011, 11:16:40 PM
Although, that begs the question of whether the quality would be any better if you got a 14bit file limited at 0dB instead of a 16bit file limited at -12dB...

The fix I put in for the 14 bit issue was to just shift the result 2 bits (e.g. increase the volume 12 db), so its exactly the same.  Just the volume is correct :)
Title: Re: Questions about recording capabilities in Sansas
Post by: megal0maniac on December 04, 2011, 01:27:18 AM
Noted, but where was the noise introduced? Could it be from the shift? (I don't know at which stage the shift occurs)
Title: Re: Questions about recording capabilities in Sansas
Post by: markanini on December 04, 2011, 04:02:30 AM
I haven't done very much recording with my v1 e280, but it does suffer noise issues with audio playback (associated with flash access), so I would not be surprised if it shows up during recording too.  24kHz limit applies to the 200 v1 too.
Thanks, the e200v1 is out as an option for me then.

The Clip plus records perfectly clearly on version 3.9.1, it's just the level which is low. That wouldn't be as much of an issue if the ADC didn't work at 14 bit, there isn't headroom to play with. Although, that begs the question of whether the quality would be any better if you got a 14bit file limited at 0dB instead of a 16bit file limited at -12dB...
Rough mental maths says it's not that different.
So I'd say that a track recorded at low level, normalised to use the full 16bits would be the best quality you can get from the clipplus.
Then, I'm allowed to record all the way up to 96kHz using PCM WAV. Different encoders have different limitations.
I'm talking about noise which is inherent to the hardware and shows up in OF as well Rockbox as a faint periodic noise when recording the built-in mic. It's interesting that yours is clean in this regard, I wonder if it's down to the hardware variants (http://www.rockbox.org/wiki/SansaAMSHardwareMappings#Clip_43_and_Fuzev2_variants). Mine is variant 1.
Title: Re: Questions about recording capabilities in Sansas
Post by: markanini on December 06, 2011, 02:23:57 PM
Any comment on whether hardware variants related to button light and sd card control could have an effect on background noise?