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MP3::Resample(3)      User Contributed Perl Documentation     MP3::Resample(3)

NAME
       Apache::MP3::Resample - Downsample MP3/FLAC/Shorten files during
       streaming

SYNOPSIS
	# httpd.conf or	access.conf
	AddType	audio/shorten .shn .SHN
	AddType	audio/flac .flac

	Alias /apache_mp3 /usr/share/libapache-mp3-perl

	<Location /songs>
	  SetHandler perl-script
	  PerlHandler Apache::MP3::Resample
	  PerlSetVar CacheDir	       /var/cache/Apache::MP3
	  PerlSetVar AllowDownload     no
	  PerlSetVar SortFields	       Album,Track,Title,-Duration
	  PerlSetVar Fields	       Track,Title,Artist,Album,Duration,Bitrate
	</Location>

DESCRIPTION
       Apache::MP3::Resample subclasses	Apache::MP3::Playlist to allow the
       user to downsample audio	files before streaming them.  This allows
       users on	slower connections to stream songs.  When this module is
       installed, a menu of bitrates is	presented in the upper right-hand
       corner of the screen.  The user can choose from one of the bitrates, or
       select a	mode that performs no resampling.  The selected	bitrate	is
       maintained in a persistent cookie so that resampling is performed
       whenever	the user returns to the	site.

       This module requires a command-line MP3 encoder to resample and
       reencode	the audio data.	 If not	otherwise specified,
       Apache::MP3::Resample will try to use the Open Source Lame MP3 encoder.
       This utility is available at http://www.sulaco.org/mp3.	Version	3.90
       was used	during the development of this module.	Your results with
       other versions may vary.

       When you	install	Lame (or the encoder of	your choice), be sure to place
       it in a directory located in Apache's PATH so that the module can find
       them at run time.  You may need to set the PATH environment variable
       during Apache's launch, or by explicitly	adding a SetEnv	directive to
       the Apache configuration	file.

       You should be aware that	the decoding/reencoding	process	is CPU-
       intensive, and server performance may degrade as	the number of
       simultaneous users increases.

CUSTOMIZATION
       This class recognizes the following two configuration variables in
       addition	to those recognized by its superclasses.

       MP3Encoder
	   The command to use to invoke	the MP3	encoder.  It should accept
	   CDDA	data on	standard input and write MP3 data to standard output.
	   The command should contain the replacement sequences	b<%b> and
	   b<%f>.  At run time,	b<%b> will be replaced with the	options	used
	   to set the bitrate and sampling frequency, while b<%f> will contain
	   the MP3 file	to be streamed.

	   If not present, the following default is used:

	     lame --mp3input %b	- <%f

       DecompressorPresets
	   A list of MIME types	and decompression programs to use for each.
	   The format uses a variant of	the standard Perl hash format, in
	   which the keys are the MIME types for the audio files and the
	   values are the command which	will be	used to	decompress files of
	   that	type.  The token "%f" will be replaced by the name of the
	   compressed audio file and the command should	end with a pipe	(|)
	   character.  Here is a simple	example, which is also the default
	   list:

	       PerlSetVar  DecompressorPresets	'"audio/shorten" => "shorten -x	%f -|",\
						 "audio/flac" => "flac -d -c -s	%f|"'

	   Note	the use	of quotation marks and backslashes to protect
	   whitespace and newlines respectively.

       ResamplePresets
	   A list of bitrates and the command-line options to pass to the
	   encoder.  The format	uses a variant of the standard Perl hash
	   format, in which the	keys are the bitrates to present to the	user
	   and the values are command-line options to pass to the encoder.
	   Here	is a simple example:

	       PerlSetVar  ResamplePresets  '16	kbps =>	-b16,\
					     56	kbps =>	-b56,\
					    128	kbps =>	-b128,\
					    160	kbps =>	-b160'

	   Note	the use	of quotation marks and backslashes to protect
	   whitespace and newlines respectively.

	   Here	is another example, which takes	advantage of the --preset
	   feature present in newer versions of	Lame.

	       PerlSetVar  ResamplePresets 'phone => --preset phone,\
					    voice  => --preset voice,\
					    fm	   => --preset fm, \
					    tape   => --preset tape,\
					    hifi   => --preset hifi,\
					    cd	   => --preset cd'

	   The user will see a popup menu containing the entries "16 kbps",
	   "56 kbps" and so forth, as well as a	blank ("--") entry that	is
	   provided automatically.  Upon selecting each	option the
	   corresponding command-line arguments	will be	slotted	into the "%s"
	   variable in the encoder line	specified by MP3Encoder.

	   More	complex	command	line options are possible.  For	example, to
	   invoke VBR (variable	bitrate) encoding and resample the output to
	   22.05 kHz, you could	apply these options

	       PerlSetVar  ResamplePresets  '16	=> -b16	-v --resample 22.05,\
					     56	=> -b56	-v --resample 22.05,\
					    128	=> -b128 -v --resample 22.05,\
					    160	=> -b160 -v --resample 22.05'

	   Lame	only accepts certain combinations of command-line options, and
	   I do	not fully understand the restrictions.	Please do not e-mail
	   me with Lame-related	questions.

	   The default presets are:

		24  kbps => -b24 --lowpass 4.0	--highpass 0.1	--resample 8,
		40  kbps => -b40 --lowpass 4.0	--resample 16,
		56  kbps => -b56 --lowpass 12.0	--resample 22.05,
		64  kbps => -b64 --lowpass 15.0	--resample 22.05,
		96  kbps => -b96 --lowpass 15.0,
		128 kbps => -b128 --lowpass 18,
		160 kbps => -b160,
		192 kbps => -b192

METHODS
       This module overrides the inherited run(), open_file() and
       directory_top() methods.	 It adds the following new methods:

       bitrate()
	   Set or get the command-line options to pass to the encoder for a
	   desired bitrate.

       stream_parms()
	   Return the parameters to append to an MP3 playlist entry in order
	   to activate resampling.

       presets()
	   Get the names of the	bitrate	presets	specified by the
	   ResamplePresets configuration variable, or the default names.
	   Called with an argument equal to the	name of	a preset, returns the
	   command-line	arguments to pass to the encoder.

       sample_popup()
	   Draws the popup menu	with the sample	rate options.

BUGS
       When the	external program is invoked to downsample the MP3 data,	its
       standard	error is redirected to /dev/null.  This	prevents Lame's
       informational messages from gumming up the server error log, but	also
       prevents	the system from	giving you helpful diagnostic messages,	such
       as "file	not found".  If	you are	having trouble with the	downsampling,
       set the configuration variable VerboseMP3Encoder	to a true value	in
       order to	see the	standard error messages.

       Also, the module	does not function properly unless CacheDir is set and
       points to a directory which exists and is writeable by the Apache
       server.

ACKNOWLEDGEMENTS
       Many people have	requested this feature and/or proposed
       implementations.	 Thank you all for your	help.

       FLAC and	Shorten	support	added by Caleb Epstein <cae@bklyn.org>.

AUTHOR
       Copyright 2000, Lincoln Stein <lstein@cshl.org>.

       This module is distributed under	the same terms as Perl itself.	Feel
       free to use, modify and redistribute it as long as you retain the
       correct attribution.

SEE ALSO
       Apache::MP3::Playlist, Apache::MP3, MP3::Info, Apache

perl v5.32.0			  2006-04-15		      MP3::Resample(3)

NAME | SYNOPSIS | DESCRIPTION | CUSTOMIZATION | METHODS | BUGS | ACKNOWLEDGEMENTS | AUTHOR | SEE ALSO

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