MP3packer Settings

An MP3 reorganizer

Copyright © 2006 Reed Wilson ("Omion")
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Abstract

MP3packer is a program which can rearrange the data within an MP3 to fulfill specific goals. By default, the program generates the smallest MP3 possible (with the least padding). However, many people also use it to turn VBR files into CBR for use with players which don't support VBR.

License

This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. Please see gpl.txt for more details. Source code for this program should be available from the same place as the compiled version.

Usage

mp3packer [ options ] in.mp3 [ out ]
Processes in.mp3 according to options and saves the output to out. If out is a directory, mp3packer will keep the same name as in but in the out directory. If out is not given, the -a string will be appended to the file name (see below).

mp3packer [ options ] inDir [ outDir ]
Processes all files ending in ".mp3" in the directory inDir. This is not recursive. If outDir is given, all output files will have the same name in the outDir directory. If outDir is not given, the files will have the -a string appended to them, and will stay in inDir.

options, if specified, may be any of the following:

-b #

Minimum bitrate allowed for output. Defaults to 0, which means all frame sizes are allowed. If the number given is a valid bitrate, the minimum frame size will be "dithered" between padded and unpadded frames, depending on standard CBR rules. If the bitrate given is one more than a valid bitrate, all frames will be padded. Anything larger than the maximum bitrate will be clamped to a padded maximum-bitrate frame. All other bitrates will round up to the next higher unpadded frame.
For example, -b 129 will result in the smallest allowed frame size being a padded 128kbps frame. -b 117 will result in the smallest allowed frame size being an unpadded 128kbps frame. If -b 128 is used with 44100Hz files, the minimum bitrate will depend on the frame number. Assuming 44100Hz, for 2 frames out of 49 the minimum frame will be unpadded, for the other 47 it will be padded. All bitrates from 114 to 127 will result in the smallest frame being an unpadded 128kbps frame.

-t

Strip non-MP3 data at the beginning of the file. This will remove some kinds of ID3v2 tags. Use both -s and -t to remove all tags.

-s

Strip non-MP3 data at the end of the file. Using this option will remove most tags and any incomplete last frames from the file.

-z

This option makes mp3packer actually decode the audio, do a brute-force search for optimal encoding parameters, then re-encode it. It is quite a bit safer than the old -z switch, but it increases the time to repack the files dramatically. On my computer, a 4-minute file which would get repacked in the blink of an eye would take around 30 seconds with this option enabled.

-a "-vbr"

Specify the string to append to the file name if no output file name is given. If mp3packer -a "-food" in.mp3 is given, the output will be named in-food.mp3. "-vbr" is the default.

-u

Updates the input file, and stores a backup to the output file. So after mp3packer -u process.mp3 backup.mp3, the file process.mp3 will contain the packed mp3, and backup.mp3 will be the same as the original process.mp3. Note that if you don't specify an output file or change the -a option, the original will have "-vbr" appended to it, which may lead to confusion.

-f

Force overwriting of the output file, if it exists. When used with the -u option, it will force overwriting the backup file.

--keep-ok [ out | both ]

Specify which files to keep if no errors occur. out will only keep the output file and will delete the input file, whereas both will keep both files (the default)

--keep-bad [ in | out | both ]

Specify which files to keep if an error occurs. in will only leave the input file and will discard the repacked file. out does just the opposite. both keeps both files (default). Note that buffer under/overflows and sync errors are counted as errors, whereas recompression errors (if using the -z switch) are not.

-i

Print info about the input file, then exit. The output location, if specified, is ignored. See the info section for more detials.

--debug [ in | out | huff | all ]

Prints a bunch of debugging info about the files. --debug in will report frame statistics about the input file. --debug out will report on how the file was processed and written. --debug huff will print debug information about the recompression of frames if the -z option is given. --debug all does all three. It is recommended that you redirect the output to a file, as the information gets quite verbose.

Info

By specifying the -i option, the program will print data about the input file then exit. No files will be written and the output (if given) will be ignored. Example printout:

*** "test/APS.mp3"
INFO:
 MPEG1 layer 3
 21687 frames
 44100 Hz
 38.281250 frames per second
 566.517551 seconds
 12514543 bytes in file (176.722405 kbps)
 12514126 bytes in MP3 frames (176.716516 kbps) = current bitrate
 93784923 bits of payload data (165.546368 kbps)
 11732617 bytes of payload data (165.680544 kbps)
 76013 bits wasted from partially-full bytes (0.134176 kbps)
 12513349 bytes of MP3 data (176.705544 kbps) = minimum bitrate possible
 777 bytes of padding (0.010972 kbps)
 417 bytes outside MP3 frames (0.005889 kbps)
 1 sync error
 Bitrate distribution:
   32: 9,0
  128: 3641,0
  160: 7691,0
  192: 6700,0
  224: 2736,0
  256: 785,0
  320: 125,0
 Largest frame uses 8478 bits = 1060 bytes = 324.548437 kbps
 Smallest bitrate for CBR is 256

Explanation:

*** "test/APS.mp3"

Name of the file processed.

MPEG1 layer 3
21687 frames
44100 Hz
38.281250 frames per second
566.517551 seconds 

Basic properties of the file. All self-explanatory.

12514543 bytes in file (176.722405 kbps)

The number of bytes in the file and the corresponding bitrate. This bitrate includes tags and non-MP3 data which can be stripped out using the -s and -t options.

12514126 bytes in MP3 frames (176.716516 kbps) = current bitrate

The number of bytes currently in MP3 frames. This does not count tags and broken frames. This is the current bitrate of the file.

93784923 bits of payload data (165.546368 kbps)

The bits of payload data. This ignores padding, headers, side-info, and tags.

11732617 bytes of payload data (165.680544 kbps)

The bytes of payload data. This is not a direct result of the previous line, and in fact is generally going to be a higher bitrate than the previous line due to partially-full bytes.

76013 bits wasted from partially-full bytes (0.134176 kbps)

The number of bits wasted from partially-full bytes. The bitrate here is the difference between the previous two lines. Nothing can be done to "repack" this wasted data.

12513349 bytes of MP3 data (176.705544 kbps) = minimum bitrate possible

The amount of payload data plus headers and side-info. Assuming that mp3packer completely gets rid of all padding and non-mp3 data, this is the smallest bitrate that can be achieved.

777 bytes of padding (0.010972 kbps)

The total amount of padding in the file. This is the main thing that mp3pcker tries to get rid of.

417 bytes outside MP3 frames (0.005889 kbps)

The amount of padding and tags outside of MP3 frames. By default, everything before the first frame and after the last frame is kept, but all non-MP3 data between frames will be discarded.

1 sync error

The number of times when a frame is not found directly after the previous frame.

32: 9,0
128: 3641,0
160: 7691,0
192: 6700,0
224: 2736,0
256: 785,0
320: 125,0

The bitrate distribution of the file. Only the bitrates that actually appear in the file wil be listed. The two numbers given per line are the unpadded,padded frames. In the above example, there are nine unpadded 32kbps frames, and no padded frames of any bitrate.

Largest frame uses 8478 bits = 1060 bytes = 324.548437 kbps

Information about the frame with the largest amount of data. If the bit reservoir were not used, this would be the smallest CBR bitrate possible.

Smallest bitrate for CBR is 256

The smallest value for the -b option that will result in a CBR file. This number is generally much less than the previous line due to the bit reservoir. It is, however, generally much more than the average bitrate because of limitations on the bit reservoir.

Changelog:

1.13-145 (2006-10-17)

Throw out VBRI frames from the input file. They aren't actually audio data and the information wasn't saved anyway, so there's no reason to keep them.

1.12-143 (2006-10-04)

Suppressed many warnings from the -z switch when the errors had no effect on anything.

1.11-141 (2006-09-30)

Fixed an array overflow when using -z which showed up mainly for high-bitrate iTunes encodes.

1.10-139 (2006-09-28)

Re-implemented full-directory packing and support for deleting files on a successful repacking. Included the -z option for brute-force Huffman table searching.

1.09-134 (2006-08-06)

Now prints out the the number of sync errors when using the -i mode, and prints sync/buffer errors if they occur in normal mode.

1.08-133 (2006-07-27)

Added the -w switch to throw out entire frames if only one granule has a buffer error. This mirrors what Foobar does upon encountering a broken frame.

1.07-132 (2006-07-22)

Fixed the frame detection to ignore all the settings found in the XING frame's header. Also added support for files with only offset information but nothing else.

1.06-130 (2006-07-20)

Fixed a bizarre bug that occured when an XING tag has neither CRC nor encoder info, but the other frames have CRCs.

1.05-128 (2006-07-16)

Fixed another problem with a frame referencing data before the beginning of the file. All reservoir-related exceptions should now be non-fatal. Also added the -u switch.

1.04-126 (2006-06-25)

Fixed an error when a frame attempts to access data from the following frame(s). Also tweaked the silent-frame detection.

1.03-123 (2006-05-25)

Remove all data from frames which have been determined to be silent.

1.02-112 (2006-04-20)

Fixed the previous fix. Also fixed a problem when an XING tag was parsed as a LAME tag.

1.01-110 (2006-04-13)

Fixed a crash when the first frame references data from before the beginning of the file.

1.00-106 (2006-03-15)

First release of the OCaml version. I figured it's different enough to start a new changelog.