Subject: [linux-audio-user] sndfile-info and lots of questions
From: R Parker (rtp405_AT_yahoo.com)
Date: Fri Apr 16 2004 - 19:43:00 EEST
Hi,
As I've gone through my most challanging mastering
project, I've developed more questions than answers.
There's been reference, on this list, to documentation
that explains file formats-- I don't recall the
document title or where to find it. Ultimately, I need
a resouce that explains things like; the number of
available samples for the different bit depths (16bit
range from -ABC to +XYZ, 24bit...), DC offset is, peak
amplitude is, RMS is, etc.
I need to know if samples are syncronous with decibel
level, is maximum samples equal to 0db?
In the following sndfile-info report, what are Length
and Block Align?
Version : libsndfile-1.0.6
========================================
File : guajira-jam.wav
Length : 30396228
RIFF : 30396220
WAVE
fmt : 16
Format : 0x1 => WAVE_FORMAT_PCM
Channels : 2
Sample Rate : 44100
Block Align : 4
Bit Width : 16
Bytes/sec : 176400
data : 30396184
End
----------------------------------------
Sample Rate : 44100
Frames : 7599046
Channels : 2
Format : 0x00010002
Sections : 1
Seekable : TRUE
Duration : 00:02:52.313
Signal Max : 25922
Is Signal Max a measurement of used samples?
One of the problems I've confronted during mastering
is JAMin, Ardour and hardware meters tell me that a
track is peaking around -0.5db but the hardware mixer
indicates overload. Of course metering balistics being
what they are this is understandable. The mixer
documentation doesn't tell me at what level the
overloads are set to go off at and I haven't found a
configuration interface.
With this metering and overload discrepancy I'd like
to read a sndfile-info report that tells me; of the
available samples, this file uses a minimum of X and
maximum of X.
I wonder if some of qualities any of us should know
about our mastered files includes:
Min Sample Value
Max Sample Value
Peak Amplitude
Possibly Clipped
DC Offset
Minimum RMS Power
Maximum RMS Power
Average RMS Power
Total RMS Power
Of course another challange is tools like sndfile-info
assume that a file exists. This is not always the case
and in my situation it's almost never true. I return
JAMin output to an Ardour return bus and don't produce
a file until the return bus is exported. Printing a
track to the file system and then analyzing it is no
way to save time.
Anyway, I appreciate all the responses to my past
questions and am hopeful that someone can look at the
current mumbo jumbo and prescribe some effective
medications; coffee, sleep, black bear gallbladders,
urls to useful documents, etc.
ron
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