![]() 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.Portable wxMP3gain is a simple to use program that allows you to modify the audio parameters for one or several MP3 at the same time. This manual page was written by Stefan Fritsch for the Debian system (but may be used by others). The homepage of mp3gain is located at (link to URL ). To use the original "wrapping" behavior, use the -w switch. If a frame's global gain field is already 0, it is not changed, even if the gain change is a positive number.If the gain change would make a frame's global gain grow above 255, then the global gain is set to 255. ![]() If the gain change would make a frame's global gain drop below 0, then the global gain is set to 0.So now the default behavior of mp3gain is to _not_ wrap gain changes. If you play this modified file, there might be a brief, very loud blip. But if you lower the gain on such a file, the global gain is suddenly _huge_. As long as the global gain is 0, you'll never hear the data. There are a few encoders out there, unfortunately, that create 0-gain frames with other audio data in the frame. 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. What happens when you _lower_ the global gain by 1? Well, in the past, mp3gain always simply wrapped the result up to 255. Some encoders create frames with 0 as the global gain for silent frames. The problem is at the bottom of the range. So there's plenty of headroom on top- you can increase the gain by 37dB (multiplying the amplitude by 76) without a problem. MOST mp3 files (in fact, ALL the mp3 files I've examined so far) don't go over 230. 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. If you do not specify -c, the program will stop and ask before applying gain change to a file that might clip The WRAP option If you specify -r and -a, only the second one will work. "wrap" gain change if gain+change > 255 or gain+change < 0 (see below or use -? wrap switch for a complete explanation) -v Undo changes made by mp3gain (based on stored tag info) -w Skip (ignore) stored tag info (do not read or write tags) -s rįorce re-calculation (do not read tag info) -u Only check stored tag info (no other processing) -s dĭelete stored tag info (no other processing) -s s don't check for mis-named Layer I or Layer II files) -s c qįorce mp3gain to assume input file is an MPEG 2 Layer III file (i.e. Mp3gain modifys bytes in original file instead of writing to temp file. Mp3gain writes modified mp3 to temp file, then deletes original instead of modifying bytes in original file (This is the default in Debian) -T Output is a database-friendly tab-delimited list -t Ignore clipping warning when applying gain -o Modify suggested dB gain by floating-point n -c Modify suggested MP3 gain by integer i -d n ![]() Options -? -hĪpply gain i to mp3 without doing any analysis -l 0 iĪpply gain i to channel 0 (left channel) of mp3 without doing any analysis (ONLY works for STEREO mp3s, not Joint Stereo mp3s) -l 1 iĪpply gain i to channel 1 (right channel) of mp3 without doing any analysis (ONLY works for STEREO mp3s, not Joint Stereo mp3s) -rĪpply Track gain automatically (all files set to equal loudness) -kĪutomatically lower Track gain to not clip audio -aĪpply 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) -m i See also /usr/share/doc/mp3gain-1.4.6/thod. The method mp3gain uses to determine the desired volume is described at (link to URL ). If you only want to print the recommended gain change (and not modify the file at all) you have to use the -s s (skip tag) option. ![]() If none of these options is given, only a tag denoting the recommended gain change is written to the file. Mp3gain actually changes your file's gain only when you use one of the options -r, -a, -g, or -l. no support for a special tag or something similar is required. Also, this works with all mp3 players, i.e. There is no quality lost in the change because the program adjusts the mp3 file directly, without decoding and re-encoding. Also, the changes mp3gain makes are completely lossless. Instead, it does some statistical analysis to determine how loud the file actually sounds to the human ear. Mp3gain does not just do peak normalization, as many normalizers do. Mp3gain can analyze and adjust mp3 files so that they have the same volume. This manual page was written for the Debian distribution because the original program does not have a manual page. This manual page documents briefly the mp3gain command.
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