Could you explain the parameters "gain" and "reference" in the sox effect "loudness <gain> <reference>"?
by winger9 from LinuxQuestions.org on (#5PE3S)
SUMMARY:
1. I'd like to use the "loudness" effect in sox to set thirty mp3 files
(containing songs) to the same loudness, before I burn them to CD. This is so
that when my friend plays them, he doesn't have to keep adjusting the volume
control when some songs are quieter/louder.
2. The entry for the "loudness" effect in "man sox" is
Quote:
I've shown the full "man" entry in "Full Details" below.
3. a) But it doesn't explain properly what the "gain" parameter does, or how you
would decide what value to use, or what the difference is between a positive and
negative value,
b) As for "reference", I don't understand what this is or what it does. What
is the significance of 65dB? Why is it positive and not negative? How do I know
what value to choose if I don't want 65dB?
c) If I choose to accept the default value for JUST ONE of the parameters
("gain" or "reference"), do I still need to specify BOTH parameters; otherwise
if I specify ONE parameter, "loudness" won't know which parameter it is.
d) Am I right in thinking that a typical command would look like the following:
Code:sox infile outfile loudness -1 65Does -1 stand for -1dB, and does 65 stand for +65dB?
4. My Questions are:
a) Please could you answer my questions at "3.", and also explain the things I
don't understand at "3."?
b) Could you give me a couple of examples of "loudness <gain> <reference>", and
what the difference is in the results that I would get?
FULL DETAILS:
5. The following is the full entry for the "loudness" effect in "man sox":
Quote:
1. I'd like to use the "loudness" effect in sox to set thirty mp3 files
(containing songs) to the same loudness, before I burn them to CD. This is so
that when my friend plays them, he doesn't have to keep adjusting the volume
control when some songs are quieter/louder.
2. The entry for the "loudness" effect in "man sox" is
Quote:
| loudness [gain [reference]] |
3. a) But it doesn't explain properly what the "gain" parameter does, or how you
would decide what value to use, or what the difference is between a positive and
negative value,
b) As for "reference", I don't understand what this is or what it does. What
is the significance of 65dB? Why is it positive and not negative? How do I know
what value to choose if I don't want 65dB?
c) If I choose to accept the default value for JUST ONE of the parameters
("gain" or "reference"), do I still need to specify BOTH parameters; otherwise
if I specify ONE parameter, "loudness" won't know which parameter it is.
d) Am I right in thinking that a typical command would look like the following:
Code:sox infile outfile loudness -1 65Does -1 stand for -1dB, and does 65 stand for +65dB?
4. My Questions are:
a) Please could you answer my questions at "3.", and also explain the things I
don't understand at "3."?
b) Could you give me a couple of examples of "loudness <gain> <reference>", and
what the difference is in the results that I would get?
FULL DETAILS:
5. The following is the full entry for the "loudness" effect in "man sox":
Quote:
| loudness [gain [reference]] Loudness control - similar to the gain effect, but provides equalisation for the human auditory system. See http://en.wikipedia.org/wiki/Loudness for a detailed description of loudness. The gain is adjusted by the given gain parameter (usually negative) and the signal equalised according to ISO 226 w.r.t. a reference level of 65dB, though an alternative reference level may be given if the original audio has been equalised for some other optimal level. A default gain of -10dB is used if a gain value is not given. |