Rockbox Technical Forums

Support and General Use => Recording => Topic started by: Alex2140 on April 02, 2015, 01:10:24 PM

Title: Why Does Digital Gain Go Past 0 dB?
Post by: Alex2140 on April 02, 2015, 01:10:24 PM
"In digital recordings the decibel is referred to as dB DFS (Digital Full Scale) where 0dB DFS is the absolute upper limit and all values are measured in minus values, there is no such thing as a positive dB in Digital Full Scale." from http://wiki.librivox.org/index.php/Basic_Principles_of_Audio_Recording (http://wiki.librivox.org/index.php/Basic_Principles_of_Audio_Recording) yet Rockbox being digital allows going past 0dB in recording Line-In.  Why?

Is there a tutorial on using Rockbox as a Recorder?  Or should I just make sure the clipping indicator NEVER goes off, the clipping indicator being the far right vertical bar that becomes thicker in width on clip?  I ask because some of my recordings will be mixed with other sources so I don't want to run into problem when leveling all the sources together.

Thanks
Title: Re: Why Does Digital Gain Go Past 0 dB?
Post by: saratoga on April 02, 2015, 02:18:39 PM
"In digital recordings the decibel is referred to as dB DFS (Digital Full Scale) where 0dB DFS is the absolute upper limit and all values are measured in minus values, there is no such thing as a positive dB in Digital Full Scale."

0dBFS is the loudest possible digital sample, so all ones if unsigned integers.

yet Rockbox being digital allows going past 0dB in recording Line-In.  Why?

Thats a gain adjustment, so positive values mean the volume is increased. 

Title: Re: Why Does Digital Gain Go Past 0 dB?
Post by: Alex2140 on April 02, 2015, 02:35:32 PM
Is my understanding of the clipping indicator correct?  Thx
Title: Re: Why Does Digital Gain Go Past 0 dB?
Post by: 404_user_not_found on April 03, 2015, 06:57:02 AM
Is my understanding of the clipping indicator correct?  Thx
Your recorded waves should have a some space before they will get into 0 dB. After 0 dB your sound data will be dropped and that causes a clipping.

Rockbox being digital allows going past 0dB in recording Line-In.  Why?
You should understand that 0dB in Line-In like "Record my sound and don't touch recorded wave by applying a volume change", not "record my sound at absolute upper limit".