with a symmetric RC4 session key. For each user of paraslash you must
create a public/secret RSA key pair for authentication.
+If para_client is started without non-option arguments, an interactive
+session (shell) is started. Command history and command completion are
+supported through libreadline.
*para_audiod*
The client program which talks to para_audiod. Used to control
para_audiod, to receive status info, or to grab the stream at any
-point of the decoding process.
+point of the decoding process. Like para_client, para_audioc supports
+interactive sessions on systems with libreadline.
*para_recv*
git clone git://git.tuebingen.mpg.de/osl
- - XREFERENCE(ftp://ftp.gnu.org/pub/gnu/gcc, gcc). The
- EMPH(gnu compiler collection) is usually shipped with the
- distro. gcc-3.3 or newer is required.
+ - XREFERENCE(ftp://ftp.gnu.org/pub/gnu/gcc, gcc) or
+ XREFERENCE(http://clang.llvm.org, clang). All gcc versions
+ >= 3.3 are currently supported. Clang version 1.1 or newer
+ should work as well.
- XREFERENCE(ftp://ftp.gnu.org/pub/gnu/make, gnu make) is
also shipped with the disto. On BSD systems the gnu make
scripts which run during compilation require the EMPH(Bourne
again shell). It is most likely already installed.
- - XREFERENCE(http://www.openssl.org/, openssl). The EMPH(Secure
- Sockets Layer) library is needed for cryptographic routines
- on both the server and the client side. It is usually shipped
- with the distro, but you might have to install the "development
- package" (called libssl-dev on debian systems) as well.
+ - XREFERENCE(http://www.openssl.org/, openssl) or
+ XREFERENCE(ftp://ftp.gnupg.org/gcrypt/libgcrypt/, libgcrypt).
+ At least one of these two libraries is needed as the backend
+ for cryptographic routines on both the server and the client
+ side. Both openssl and libgcrypt are usually shipped with the
+ distro, but you might have to install the development package
+ (libssl-dev or libgcrypt-dev on debian systems) as well.
+
+ - XREFERENCE(ftp://ftp.gnu.org/pub/gnu/gengetopt/, gengetopt)
+ is needed to generate the C code for the command line parsers
+ of all paraslash executables.
- XREFERENCE(ftp://ftp.gnu.org/pub/gnu/help2man, help2man)
is used to create the man pages.
- XREFERENCE(http://www.speex.org/, speex). In order to stream
or decode speex files, libspeex (libspeex-dev) is required.
+ - XREFERENCE(http://flac.sourceforge.net/, flac). To stream
+ or decode files encoded with the _Free Lossless Audio Codec_,
+ libFLAC (libFLAC-dev) must be installed.
+
- XREFERENCE(ftp://ftp.alsa-project.org/pub/lib/, alsa-lib). On
Linux, you'll need to have ALSA's development package
libasound2-dev installed.
+ - XREFERENCE(http://downloads.xiph.org/releases/ao/,
+ libao). Needed to build the ao writer (ESD, PulseAudio,...).
+ Debian package: libao-dev.
+
+ - XREFERENCE(http://cnswww.cns.cwru.edu/php/chet/readline/rltop.html,
+ GNU Readline). If this library (libreadline-dev) is installed,
+ para_client and para_audioc support interactive sessions.
+
Installation
~~~~~~~~~~~~
./configure --help
to see a list of options. If the paraslash package was compiled
-successfully, execute as root,
+successfully, execute (optionally)
+
+ make test
+
+to run the paraslash test suite. If all tests pass, execute as root
make install
user=bar
target=~/.paraslash/server.users
- key=~/.paraslash/key.pub.$user
+ key=~/.paraslash/id_rsa.pub.$user
perms=AFS_READ,AFS_WRITE,VSS_READ,VSS_WRITE
mkdir -p ~/.paraslash
echo "user $user $key $perms" >> $target
Next, change to the "bar" account on client_host and generate the
key pair with the commands
- key=~/.paraslash/key.$LOGNAME
- mkdir -p ~/.paraslash
- (umask 077 && openssl genrsa -out $key 2048)
+ ssh-keygen -t rsa -b 2048
+ # hit enter twice to create a key with no passphrase
-para_server only needs to know the public key of the key pair just
-created. It can be extracted with
+This generates the two files id_rsa and id_rsa.pub in ~/.ssh. Note
+that paraslash can also read keys generated by the "openssl genrsa"
+command. However, since keys created with ssh-keygen can also be used
+for ssh, this method is recommended.
- pubkey=~/.paraslash/key.pub.$LOGNAME
- openssl rsa -in $key -pubout -out $pubkey
+Note that para_server refuses to use a key if it is shorter than 2048
+bits. In particular, the RSA keys of paraslash 0.3.x will not work
+with version 0.4.x. Moreover, para_client refuses to use a (private)
+key which is world-readable.
-Copy the public key just created to server_host (you may skip this step
-for a single-user setup, i.e. if foo=bar and server_host=client_host):
+para_server only needs to know the public key of the key pair just
+created. Copy this public key to server_host:
- scp $pubkey foo@server_host:.paraslash/
+ src=~/.ssh/id_rsa.pub
+ dest=.paraslash/id_rsa.pub.$LOGNAME
+ scp $src foo@server_host:$dest
Finally, tell para_client to connect to server_host:
We will also have to tell para_audiod that it should receive the
-audio stream from server_host:
+audio stream from server_host via http:
- para_audiod -l info -r 'mp3:http -i server_host'
+ para_audiod -l info -r '.:http -i server_host'
You should now be able to listen to the audio stream once para_server
starts streaming. To activate streaming, execute
- para_client connects to para_server and sends an
authentication request for a user. It does so by connecting
- to para_server, TCP 2990, the control port of para_server.
+ to TCP port 2990 of the server host. This port is called the
+ para_server _control port_.
- para_server accepts the connection and forks a child process
- which is supposed to handle the connection. The parent process
- keeps listening on the control port while the child process
- (also called para_server below) continues as follows.
+ which handles the incoming request. The parent process keeps
+ listening on the control port while the child process (also
+ called para_server below) continues as follows.
- para_server loads the RSA public key of that user, fills a
fixed-length buffer with random bytes, encrypts that buffer
session key.
- para_client receives the encrypted buffer and decrypts it
- using the user's private key, thereby obtaining the challenge
+ with the user's private key, thereby obtaining the challenge
buffer and the session key. It sends the SHA1 hash value of
the challenge back to para_server and stores the session key
for further use.
this point on the communication is encrypted using the RC4
stream cipher with the session key known to both peers.
-paraslash relies on the quality of openssl's cryptographically strong
-pseudo-random bytes, on the security of the implementation of the
-openssl RSA and RC4 crypto routines and on the infeasibility to invert
-the SHA1 function.
+paraslash relies on the quality of the pseudo-random bytes provided
+by the crypto library (openssl or libgcrypt), on the security of
+the implementation of the RSA and RC4 crypto routines and on the
+infeasibility to invert the SHA1 function.
Neither para_server or para_client create RSA keys on their own. This
has to be done once for each user as sketched in REFERENCE(Quick start,
The user_list file
~~~~~~~~~~~~~~~~~~
-At startup para_server reads the user list file which must contain
-one line per user. The default location of the user list file may be
+At startup para_server reads the user list file which contains one
+line per user. The default location of the user list file may be
changed with the --user_list option.
There should be at least one user in this file. Each user must have
contains in the third column the permissions needed to execute the
command.
-A new RSA key can be created with
-
- openssl genrsa -out <private_key> 2048
-
-and the public part may be extracted with
-
- openssl rsa -in <private_key> -pubout -out <public_key>
-
-Note that para_server refuses to use a key if it is shorter than 2048
-bits. In particular, the RSA keys of paraslash 0.3.x will not work
-with version 0.4.x. Moreover, para_client refuses to use a (private)
-key which is world-readable.
-
It is possible to make para_server reread the user_list file by
executing the paraslash "hup" command or by sending SIGHUP to the
PID of para_server.
maintains tables containing images (e.g. album cover art) and lyrics
that can be associated with one or more audio files.
-AFS uses libosl, the object storage layer, as the backend library
-for storing information on audio files, playlists, etc. This library
-offers functionality similar to a relational database, but is much
-more lightweight than a full database backend.
+AFS uses XREFERENCE(http://systemlinux.org/~maan/osl/, libosl), the
+object storage layer library, as the backend library for storing
+information on audio files, playlists, etc. This library offers
+functionality similar to a relational database, but is much more
+lightweight than a full database backend.
In this chapter we sketch the setup of the REFERENCE(The AFS process,
AFS process) during server startup and proceed with the description
in detail and contains pratical examples. The way REFERENCE(File
renames and content changes, file renames and content changes) are
detected is discussed briefly before the REFERENCE(Troubleshooting,
-Troubleshooting) section which concludes the chapter.
+Troubleshooting) section concludes the chapter.
The AFS process
~~~~~~~~~~~~~~~
para_client setatt test- /path/to/the/audio/file
Instead of a path you may use a shell wildcard pattern. The attribute
-is applied to all audio files matching that pattern:
+is applied to all audio files matching this pattern:
para_client setatt test+ '/test/directory/*'
Note that the images and lyrics are not interpreted at all, and also
the playlist and the mood blobs are only investigated when the mood
-or playlist is activated by using the select command.
+or playlist is activated with the select command.
*The score table*
last_played and the num_played fields in the audio file table.
The score table is recomputed by the select command which loads a
-new mood or playlist.
+mood or playlist. Audio files are chosen for streaming from the rows
+of the score table on a highest-score-first basis.
+
Playlists and moods
~~~~~~~~~~~~~~~~~~~
audio file table. As an example, a mood can define a filename pattern,
which is then matched against the names of audio files in the table.
-Selecting a mood or playlist means the generation of a ranking
-(a score table) for the set of admissible files. Audio files are
-then selected on a highest-score-first basis. The score table is
-recomputed at the moment the mood or playlist is selected.
-
*Playlists*
Playlists are accommodated in the playlist table of the afs database,
-using the aforementioned blob format for tables. A new filelist is
-created using the addpl command, by specifying the full (absolute)
-paths of all desired audio files, separated by newlines. For example
+using the aforementioned blob format for tables. A new playlist is
+created with the addpl command by specifying the full (absolute)
+paths of all desired audio files, separated by newlines. Example:
find /my/mp3/dir -name "*.mp3" | para addpl my_playlist
a set of *mood lines* containing expressions in terms of attributes
and other data contained in the database.
-At any time, at most one mood can be *active* which means that
+At any time at most one mood can be *active* which means that
para_server is going to select only files from that subset of
admissible files.
has no year tag or the content of the year tag is not a number. Such
audio files never match. Another difference is the special treatment
if the year tag is a two-digit number. In this case either 1900 or
-2000 are added to the tag value depending on whether the number is
+2000 is added to the tag value, depending on whether the number is
greater than 2000 plus the current year.
is composed of superframes, each containing one or more frames of
2048 samples. For 16 bit stereo a WMA superframe is about 8K large.
+*FLAC*
+
+The Free Lossless Audio Codec (FLAC) compresses audio without quality
+loss. It gives better compression ratios than a general purpose
+compressor like zip or bzip2 because FLAC is designed specifically
+for audio. A FLAC-encoded file consits of frames of varying size, up
+to 16K. Each frame starts with a header that contains all information
+necessary to decode the frame.
+
Meta data
~~~~~~~~~
32 characters long. ID3, version 2 is much more flexible but requires
a separate library being installed for paraslash to support it.
-Ogg vorbis files contain meta data as Vorbis comments, which are
-typically implemented as strings of the form "[TAG]=[VALUE]". Unlike
-ID3 version 1 tags, one may use whichever tags are appropriate for
-the content.
+Ogg vorbis, ogg speex and flac files contain meta data as Vorbis
+comments, which are typically implemented as strings of the form
+"[TAG]=[VALUE]". Unlike ID3 version 1 tags, one may use whichever
+tags are appropriate for the content.
AAC files usually use the MPEG-4 container format for storing meta
data while WMA files wrap meta data as special objects within the
of an audio file. For MP3 files, a chunk is the same as an MP3 frame,
while for OGG files a chunk is an OGG page, etc. Therefore the chunk
size varies considerably between audio formats, from a few hundred
-bytes (MP3) up to 8K (WMA).
+bytes (MP3) up to 16K (FLAC).
The chunk table contains the offsets within the audio file that
correspond to the chunk boundaries of the file. Like the meta data,
-> Create a minimal config for para_audiod for HTTP streams:
c=$HOME/.paraslash/audiod.conf.min; s=server.foo.com
- formats="mp3 ogg aac wma" # remove what you do not have
- for f in $formats; do echo receiver \"$f:http -i $s\"; done > $c
+ echo receiver \".:http -i $s\" > $c
para_audiod --config $c
-------
para_filter -f 'mp3dec --ignore-crc' -f 'compress --damp 1'
For para_audiod, each audio format has its own set of filters. The
-name of the audio format for which the filter should be applied is
-used as the prefix for the filter option. Example:
+name of the audio format for which the filter should be applied can
+be used as the prefix for the filter option. Example:
para_audiod -f 'mp3:prebuffer --duration 300'
+The "mp3" prefix above is actually interpreted as a POSIX extended
+regular expression. Therefore
+
+ para_audiod -f '.:prebuffer --duration 300'
+
+activates the prebuffer filter for all supported audio formats (because
+"." matches all audio formats) while
+
+ para_audiod -f 'wma|ogg:prebuffer --duration 300'
+
+activates it only for wma and ogg streams.
+
Decoders
~~~~~~~~
~~~~~~~~~~~~~~~~~~~~~~~~
As already mentioned REFERENCE(Streaming protocols, earlier),
-paraslash uses forward error correction (FEC) for the unreliable
-UDP transport. FEC is a technique which was invented already in
-1960 by Reed and Solomon and which is widely used for the parity
+paraslash uses forward error correction (FEC) for the unreliable UDP
+and DCCP transports. FEC is a technique which was invented already
+in 1960 by Reed and Solomon and which is widely used for the parity
calculations of storage devices (RAID arrays). It is based on the
algebraic concept of finite fields, today called Galois fields, in
honour of the mathematician Galois (1811-1832). The FEC implementation
FEC parameters: The slice size, the number of data slices k, and the
total number of slices n. It is crucial to choose the slice size
such that no fragmentation of network packets takes place because
-FEC only guards against losses and reodering but fails if slices are
+FEC only guards against losses and reordering but fails if slices are
received partially.
FEC decoding in paralash is performed through the fecdec filter which
it through a sound device. It is supported on all platforms and is
always compiled in.
+*AO*. _Libao_ is a cross-platform audio library which supports a wide
+variety of platforms including PulseAudio (gnome), ESD (Enlightened
+Sound Daemon), AIX, Solaris and IRIX. The ao writer plays audio
+through an output plugin of libao.
+
Examples
~~~~~~~~
paraslash development. It is necessary for cloning the git repository
and for getting updates.
-ftp://ftp.gnu.org/pub/gnu/gengetopt/ (gengetopt). The C code for
-the command line parsers of all paraslash executables is generated
-by gengetopt. The generated C files are shipped in the tarballs but
-are not contained in the git repository.
-
ftp://ftp.gnu.org/pub/gnu/m4/ (m4). Some input files for gengetopt
are generated from templates by the m4 macro processor.
"git log next"). You should be able to safely build on top of them.
However, at times "next" will be rebuilt from the tip of "master" to
-get rid of merge commits that will never be in "master. The commit
+get rid of merge commits that will never be in "master". The commit
that replaces "next" will usually have the identical tree, but it
will have different ancestry from the tip of "master".
protocol, only minimal internal state about the connection is
maintained, which means that there is no protection against packet
loss or network congestion. Error checking and correction (if at all)
-are performed in the application.'
+are performed in the application.
*DCCP*. The _Datagram Congestion Control Protocol_ combines the
connection-oriented state maintenance known from TCP with the
projects / paraslash.git / blobdiff