Package: mp3gain
Version: 1.5.1-1
Severity: wishlist
Tags: patch
Recent versions of mp3gain have an option to write gain information
in ID3v2 format instead of APEv2 format. This option is not yet documented
in the manpage.
Also, the manpage could more clearly explain the two ways of working with
mp3gain: changing the encoded stream versus writing replaygain tags.
Attached is a copy of the manpage with my suggested changes.
Greetings,
Joris.
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<!-- Fill in your name for FIRSTNAME and SURNAME. -->
<!ENTITY dhfirstname "<firstname>STEFAN</firstname>">
<!ENTITY dhsurname "<surname>FRITSCH</surname>">
<!-- Please adjust the date whenever revising the manpage. -->
<!ENTITY dhdate "<date>February 4, 2004</date>">
<!-- SECTION should be 1-8, maybe w/ subsection other parameters are
allowed: see man(7), man(1). -->
<!ENTITY dhsection "<manvolnum>1</manvolnum>">
<!ENTITY dhemail "<email>s...@sfritsch.de</email>">
<!ENTITY dhusername "Stefan Fritsch">
<!ENTITY dhucpackage "<refentrytitle>MP3GAIN</refentrytitle>">
<!ENTITY dhpackage "mp3gain">
<!ENTITY debian "<productname>Debian</productname>">
<!ENTITY gnu "<acronym>GNU</acronym>">
<!ENTITY lgpl "&gnu; <acronym>LGPL</acronym>">
]>
<refentry>
<refentryinfo>
<address>
&dhemail;
</address>
<author>
&dhfirstname;
&dhsurname;
</author>
<copyright>
<year>2004</year>
<holder>Glen Sawyer and &dhusername;</holder>
</copyright>
&dhdate;
</refentryinfo>
<refmeta>
&dhucpackage;
&dhsection;
</refmeta>
<refnamediv>
<refname>&dhpackage;</refname>
<refpurpose>lossless mp3 normalizer</refpurpose>
</refnamediv>
<refsynopsisdiv>
<cmdsynopsis>
<command>&dhpackage;</command>
<arg><option>options</option></arg>
<arg><replaceable>infile</replaceable></arg>
<arg><option><replaceable>infile 2</replaceable> ...</option></arg>
</cmdsynopsis>
</refsynopsisdiv>
<refsect1>
<title>DESCRIPTION</title>
<para>This manual page documents briefly the
<command>&dhpackage;</command>
command.</para>
<para>This manual page was written for the &debian; distribution
because the original program does not have a manual page.
</para>
<para><command>&dhpackage;</command> can analyze and adjust mp3 files
so that they have the same volume.</para>
<para><command>&dhpackage;</command> does not just do peak normalization,
as many normalizers do. Instead, it does some statistical analysis to
determine how loud the file actually sounds to the human ear. Also, the
changes <command>&dhpackage;</command> makes are completely lossless. There
is no quality lost in the change because the program adjusts the mp3 file
directly, without decoding and re-encoding.</para>
<para><command>&dhpackage;</command> optionally writes gain adjustments
directly into the encoded data. In this case, the adjustment works
with all mp3 players, i.e. no support for a special tag is required.
This mode is activated by any of the options <option>-r</option>,
<option>-a</option>, <option>-g</option>, or <option>-l</option>.</para>
<para>If none of the above options are given, the recommended gain change
is instead written to a special tag in the mp3 file. In this case, the
adjustment only works with mp3 players that support this tag.
Some mp3 players refer to this as ReplayGain.
The tag is written either in APEv2 format (default) or in ID3v2 format
(with <option>-s i</option>).
If you only want to print the recommended gain change (and not modify
the file at all) you may use the <option>-s s</option> (skip tag)
option. </para>
<para>The method mp3gain uses to determine the desired volume
is described at
<ulink url="http://www.replaygain.org/";>www.replaygain.org</ulink>.
See also <filename>/usr/share/doc/mp3gain/README.method</filename> .
</para>
</refsect1>
<refsect1>
<title>OPTIONS</title>
<variablelist>
<varlistentry>
<term><option>-?</option>
<option>-h</option>
</term>
<listitem>
<para>Show summary of options.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-g <replaceable>i</replaceable></option>
</term>
<listitem>
<para>apply gain <replaceable>i</replaceable> to mp3 without
doing any analysis</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-l 0 <replaceable>i</replaceable></option>
</term>
<listitem>
<para>apply gain <replaceable>i</replaceable> to channel 0
(left channel) of mp3
without doing any analysis (ONLY works for STEREO mp3s,
not Joint Stereo mp3s)</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-l 1 <replaceable>i</replaceable></option>
</term>
<listitem>
<para>apply gain <replaceable>i</replaceable> to channel 1
(right channel) of mp3
without doing any analysis (ONLY works for STEREO mp3s,
not Joint Stereo mp3s)</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-r</option>
</term>
<listitem>
<para>apply Track gain automatically (all files set to equal
loudness)</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-k</option>
</term>
<listitem>
<para>automatically lower Track gain to not clip audio</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-a</option>
</term>
<listitem>
<para>apply Album gain automatically (files are all from the same
album: a single gain change is applied to all files, so
their loudness relative to each other remains unchanged,
but the average album loudness is normalized)</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-m <replaceable>i</replaceable></option>
</term>
<listitem>
<para>modify suggested MP3 gain by integer
<replaceable>i</replaceable></para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-d <replaceable>n</replaceable></option>
</term>
<listitem>
<para>modify suggested dB gain by floating-point
<replaceable>n</replaceable></para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-c</option>
</term>
<listitem>
<para>ignore clipping warning when applying gain</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-o</option>
</term>
<listitem>
<para>output is a database-friendly tab-delimited list</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-t</option>
</term>
<listitem>
<para>mp3gain writes modified mp3 to temp file, then deletes original
instead of modifying bytes in original file (This is the default in
Debian)</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-T</option>
</term>
<listitem>
<para>mp3gain modifies bytes in original file instead of
writing to temp file.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-q</option>
</term>
<listitem>
<para>Quiet mode: no status messages</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-p</option>
</term>
<listitem>
<para>Preserve original file timestamp</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-x</option>
</term>
<listitem>
<para>Only find max. amplitude of mp3</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-f</option>
</term>
<listitem>
<para>Force <command>mp3gain</command> to assume input file
is an MPEG 2 Layer III file
(i.e. don't check for mis-named Layer I or Layer II files)</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-s c</option>
</term>
<listitem>
<para>only check stored tag info (no other processing)</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-s d</option>
</term>
<listitem>
<para>delete stored tag info (no other processing)</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-s i</option>
</term>
<listitem>
<para>use ID3v2 tag for gain information;
if the file contained gain data in APEv2 format, it is upgraded
to ID3v2</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-s a</option>
</term>
<listitem>
<para>use APEv2 tag for gain information (default)</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-s s</option>
</term>
<listitem>
<para>skip (ignore) stored tag info (do not read or write tags)</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-s r</option>
</term>
<listitem>
<para>force re-calculation (do not read tag info)</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-u</option>
</term>
<listitem>
<para>undo changes made by mp3gain (based on stored tag info)</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-w</option>
</term>
<listitem>
<para>"wrap" gain change if gain+change > 255 or gain+change < 0
(see below or use <option>-? wrap</option> switch for a complete
explanation)</para>
</listitem>
</varlistentry>
<varlistentry>
<term><option>-v</option>
</term>
<listitem>
<para>Show version of program.</para>
</listitem>
</varlistentry>
</variablelist>
<para>If you specify <option>-r</option> and <option>-a</option>,
only the second one will work.</para>
<para>If you do not specify <option>-c</option>, the program will
stop and ask before
applying gain change to a file that might clip</para>
<refsect2><title>The WRAP option</title>
<para>Here's the problem:
The "global gain" field that mp3gain adjusts is an 8-bit unsigned integer,
so
the possible values are 0 to 255.
</para><para>
MOST mp3 files (in fact, ALL the mp3 files I've examined so far) don't go
over 230. So there's plenty of headroom on top-- you can increase the gain
by 37dB (multiplying the amplitude by 76) without a problem.
</para><para>
The problem is at the bottom of the range. Some encoders create frames with
0 as the global gain for silent frames.
What happens when you _lower_ the global gain by 1?
Well, in the past, mp3gain always simply wrapped the result up to 255.
That way, if you lowered the gain by any amount and then raised it by the
same amount, the mp3 would always be _exactly_ the same.
</para><para>
There are a few encoders out there, unfortunately, that create 0-gain
frames
with other audio data in the frame.
As long as the global gain is 0, you'll never hear the data.
But if you lower the gain on such a file, the global gain is suddenly
_huge_.
If you play this modified file, there might be a brief, very loud blip.
</para><para>
So now the default behavior of mp3gain is to _not_ wrap gain changes.
In other words,
<orderedlist>
<listitem><para>
If the gain change would make a frame's global gain drop below 0,
then the global gain is set to 0.
</para></listitem><listitem><para>
If the gain change would make a frame's global gain grow above 255,
then the global gain is set to 255.
</para></listitem><listitem><para>
If a frame's global gain field is already 0, it is not changed, even if
the gain change is a positive number.
</para></listitem>
</orderedlist>
</para><para>
To use the original "wrapping" behavior, use the <option>-w</option>
switch.
</para>
</refsect2>
</refsect1>
<refsect1>
<title>SEE ALSO</title>
<para>The homepage of mp3gain is located at
<ulink
url="http://mp3gain.sourceforge.net/";>http://mp3gain.sourceforge.net/</ulink> .
</para>
</refsect1>
<refsect1>
<title>AUTHOR</title>
<para>This manual page was written by &dhusername; &dhemail; for
the &debian; system (but may be used by others). Permission is
granted to copy, distribute and/or modify this document under
the terms of the &gnu; Lesser General Public License, Version 2.1 or
any later version published by the Free Software Foundation.
</para>
<para>
On Debian systems, the complete text of the GNU Lesser General Public
License can be found in /usr/share/common-licenses/LGPL.
</para>
</refsect1>
</refentry>
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