*para_server*
-para_server streams binary audio data (MP3, OGG/Vorbis, OGG/Speex,
-M4A, WMA files) over local and/or remote networks. It listens on a
-TCP port and accepts commands such as play, stop, pause, next from
-authenticated clients. There are many more commands though, see the
-man page of para_server for a description of all commands.
+para_server streams binary audio data (MP3, ...) over local and/or
+remote networks. It listens on a TCP port and accepts commands such
+as play, stop, pause, next from authenticated clients. There are
+many more commands though, see the man page of para_server for a
+description of all commands.
It supports three built-in network streaming protocols
(senders/receivers): HTTP, DCCP, or UDP. This is explained in more
little programming effort.
All connections between para_server and para_client are encrypted
-with a symmetric RC4 session key. For each user of paraslash you must
+with a symmetric 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
A command line HTTP/DCCP/UDP stream grabber. The http mode is
compatible with arbitrary HTTP streaming sources (e.g. icecast).
+In addition to the three network streaming modes, para_recv can also
+operate in local (afh) mode. In this mode it writes the content of
+an audio file on the local file system in complete chunks to stdout,
+optionally 'just in time'. This allows to cut an audio file without
+first decoding it, and it enables third-party software which is unaware
+of the particular audio format to send complete frames in real time.
*para_filter*
A small stand-alone program that prints tech info about the given
audio file to STDOUT. It can be instructed to print a "chunk table",
-an array of offsets within the audio file or to write the content of
-the audio file in complete chunks 'just in time'.
-
-This allows third-party streaming software that is unaware of the
-particular audio format to send complete frames in real time.
+an array of offsets within the audio file.
*para_write*
coreaudio (Mac OS). para_write can also be used as a stand-alone WAV
or raw audio player.
+*para_play*
+
+A command line audio player.
*para_gui*
Requirements
~~~~~~~~~~~~
+For the impatient:
+
+ git clone git://git.tuebingen.mpg.de/osl
+ cd osl && make && sudo make install && sudo ldconfig
+ sudo apt-get install autoconf libssl-dev help2man gengetopt \
+ libmad0-dev libid3tag0-dev libasound2-dev libvorbis-dev \
+ libfaad-dev libspeex-dev libFLAC-dev libsamplerate-dev \
+ libasound2-dev libao-dev libreadline-dev libncurses-dev
-In any case you'll need
+Detailed description: In any case you'll need
- XREFERENCE(http://systemlinux.org/~maan/osl/, libosl).
The _object storage layer_ library is used by para_server. To
scripts which run during compilation require the EMPH(Bourne
again shell). It is most likely already installed.
- - 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.
Optional:
+ - 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(http://www.underbit.com/products/mad/, libmad).
To compile in MP3 support for paraslash, the development
package must be installed. It is called libmad0-dev on
or decode files encoded with the _Free Lossless Audio Codec_,
libFLAC (libFLAC-dev) must be installed.
+ - XREFERENCE(http://www.mega-nerd.com/SRC/index.html,
+ libsamplerate). The resample filter will only be compiled if
+ this library is installed. Debian package: libsamplerate-dev.
+
- XREFERENCE(ftp://ftp.alsa-project.org/pub/lib/, alsa-lib). On
Linux, you'll need to have ALSA's development package
libasound2-dev installed.
libao). Needed to build the ao writer (ESD, PulseAudio,...).
Debian package: libao-dev.
+ - XREFERENCE(ftp://ftp.gnu.org/pub/gnu/ncurses, curses). Needed
+ for para_gui. Debian package: libncurses-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.
+ para_client, para_audioc and para_play support interactive
+ sessions.
Installation
~~~~~~~~~~~~
sudo chown $LOGNAME /var/paraslash
-Alternatively, use the --afs_socket Option to specify a different
+Alternatively, use the --afs-socket Option to specify a different
location for the AFS command socket.
For this first try, we'll use the info loglevel to make the output
para_server uses a challenge-response mechanism to authenticate
requests from incoming connections, similar to ssh's public key
authentication method. Authenticated connections are encrypted using
-the RC4 stream cipher.
+a stream cipher, either RC4 or AES in integer counter mode.
-In this chapter we briefly describe RSA and RC4 and sketch the
+In this chapter we briefly describe RSA, RC4 and AES, and sketch the
REFERENCE(Client-server authentication, authentication handshake)
between para_client and para_server. User management is discussed
in the section on REFERENCE(The user_list file, the user_list file).
-RSA and RC4
-~~~~~~~~~~~
+RSA, RC4, AES
+~~~~~~~~~~~~~
RSA is an asymmetric block cipher which is used in many applications,
including ssh and gpg. An RSA key consists in fact of two keys,
be used twice, a different, randomly-generated key is used for every
new connection.
+AES, the advanced encryption standard, is a well-known symmetric block
+cipher, i.e. a transformation operating on fixed-length blocks which
+is determined by a single key for both encryption and decryption. Any
+block cipher can be turned into a stream cipher by generating
+a pseudo-random key stream by encrypting successive values of a
+counter. The AES_CTR128 stream cipher used in paraslash is obtained
+in this way from the AES block cipher with a 128 bit block size.
+
+
Client-server authentication
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
fixed-length buffer with random bytes, encrypts that buffer
using the public key and sends the encrypted buffer to the
client. The first part of the buffer is the challenge which
- is used for authentication while the second part is the RC4
+ is used for authentication while the second part is the
session key.
- para_client receives the encrypted buffer and decrypts it
- Otherwise the user is considered authenticated and the client
is allowed to proceed by sending a command to be executed. From
- this point on the communication is encrypted using the RC4
- stream cipher with the session key known to both peers.
+ this point on the communication is encrypted using the stream
+ cipher with the session key known to both peers.
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
+the implementation of the RSA, RC4 and AES crypto routines and on the
infeasibility to invert the SHA1 function.
Neither para_server or para_client create RSA keys on their own. This
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.
+changed with the --user-list option.
There should be at least one user in this file. Each user must have
an RSA key pair. The public part of the key is needed by para_server
allow para_audiod to obtain the Unix credentials of the connecting
process.
-Use para_audiod's --user_allow option to allow connections only for
+Use para_audiod's --user-allow option to allow connections only for
a limited set of users.
-----------------------
Troubleshooting
~~~~~~~~~~~~~~~
-Use the debug loglevel (option -l debug for most commands) to show
-debugging info. Almost all paraslash executables have a brief online
-help which is displayed by using the -h switch. The --detailed-help
-option prints the full help text.
+Use the debug loglevel (-l debug) to show debugging info. All paraslash
+executables have a brief online help which is displayed when -h is
+given. The --detailed-help option prints the full help text.
If para_server crashed or was killed by SIGKILL (signal 9), it
may refuse to start again because of "dirty osl tables". In this
case you'll have to run the oslfsck program of libosl to fix your
-database. It might be necessary to use --force (even if your name
-isn't Luke). However, make sure para_server isn't running before
-executing oslfsck --force.
+database:
+
+ oslfsck -fd ~/.paraslash/afs_database-0.4
+
+However, make sure para_server isn't running before executing oslfsck.
If you don't mind to recreate your database you can start
from scratch by removing the entire database directory, i.e.
This prints out references to missing audio files as well as invalid
playlists and mood definitions.
+Similarly, para_audiod refuses to start if its socket file exists, since
+this indicates that another instance of para_audiod is running. After
+a crash a stale socket file might remain and you must run
+
+ para_audiod --force
+
+once to fix it up.
+
---------------------------------------
Audio formats and audio format handlers
---------------------------------------
over IP applications, has modest complexity and a small memory
footprint. Wideband and narrowband (telephone quality) speech are
supported. As for Vorbis audio, Speex bit-streams are often stored
-in OGG files.
+in OGG files. As of 2012 this codec is considered obsolete since the
+Oppus codec, described below, surpasses its performance in all areas.
+
+*OGG/Opus*
+
+Opus is a lossy audio compression format standardized through RFC
+6716 in 2012. It combines the speech-oriented SILK codec and the
+low-latency CELT (Constrained Energy Lapped Transform) codec. Like
+OGG/Vorbis and OGG/Speex, Opus data is usually encapsulated in OGG
+containers. All known software patents which cover Opus are licensed
+under royalty-free terms.
*AAC*
The audio format handler code is linked into para_server and executed
via the _add_ command. The same code is also available as a stand-alone
tool, para_afh, which can be used to print the technical data, the
-chunk table and the meta data of a file. Furthermore, one can use
-para_afh to cut an audio file, i.e. to select some of its chunks to
-produce a new file containing only these chunks.
+chunk table and the meta data of a file.
----------
Networking
connected to a receiver which produces the input stream and a writer
which absorbs the output stream.
-Some filters depend on a specific library being installed and are
-not compiled in if this library was not found at compile time. To
-see the list of supported filters, run para_filter and para_audiod
-with the --help option. The output looks similar to the following:
+Some filters depend on a specific library and are not compiled in
+if this library was not found at compile time. To see the list of
+supported filters, run para_filter and para_audiod with the --help
+option. The output looks similar to the following:
Available filters:
compress wav amp fecdec wmadec prebuffer oggdec aacdec mp3dec
para_audioc -- stat -p
-is executed, but this can be customized via the --stat_cmd option. In
+is executed, but this can be customized via the --stat-cmd option. In
particular it possible to use
para_client -- stat -p
Congestion Control ID 2: TCP-like Congestion Control
- XREFERENCE(http://www.ietf.org/rfc/rfc4342.txt, RFC 4342) (2006):
Congestion Control ID 3: TCP-Friendly Rate Control (TFRC)
+ - XREFERENCE(http://www.ietf.org/rfc/rfc6716.txt, RFC 6716) (2012):
+ Definition of the Opus Audio Codec
Application web pages
~~~~~~~~~~~~~~~~~~~~~
projects / paraslash.git / blobdiff