[linux-audio-user] sndfile-info and lots of questions

[Erik de Castro Lopo]

On Fri, 16 Apr 2004 09:43:00 -0700 (PDT)
R Parker <rtp405 at yahoo.com> wrote:

> 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.

Bits   Range                   DC offset
-----------------------------------------
16     [-32768, +32767]        0
24     [-8388608, +8388607]    0

> I need to know if samples are syncronous with decibel
> level, 

Que? I think you men synonymous rather than synchronous.

> is maximum samples equal to 0db?

Yes, it is usually the case that 0dB is simply the maximum
sample value.

> In the following sndfile-info report, what are Length

File length in bytes.

> and Block Align?

An internal detail of how data is stored in a WAV file. In other
words, something you should ignore.

> 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?

No it is the maximum absoulute sample value. Since this is a 
16 bit PCM file, the range of sample values is [-32768, +32767].

What I'll do is change that last line to:

    Signal max : 25922 (-2.04dB) 

Erik
-- 
+-----------------------------------------------------------+
  Erik de Castro Lopo  nospam at mega-nerd.com (Yes it's valid)
+-----------------------------------------------------------+
"In civilian equipment, such as computers, the number
of components alone makes miniaturization essential if
the computer is to be housed in a reasonable-sized
building." Electronics Oct. 1, 1957, p. 178