intf-cdda.txt

mips版本的VLC视频服务器

This file documents the ``Extended'' VLC CD-DA Plugin

Copyright (C) 2003, 2004 Rocky Bernstein ([e-mail])

Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.1 or
any later version published by the Free Software Foundation; with the
Invariant Sections being ``Free Software'' and ``Free Software Needs
Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
and with the Back-Cover Texts as in (a) below.

(a) The Free Software Foundation's Back-Cover Text is: ``You have
freedom to copy and modify this GNU Manual, like GNU software.  Copies
published by the Free Software Foundation raise funds for GNU
development.''

- - - - - -

Features over the older VLC CD-DA plugin

Internally I think this is much much cleaner. It uses the 
libcdio for disk reading and libcddb to get CDDB information.

MRL handling: 
-  Can specify device as well as track.
-  Because we use the libcdio library, the "device" can be a disk image
   to be burned (e.g. a cdrdao bin/cue pair and some primitive Nero
   support)

Features:
-  Can customize the what to show in the play-list title and author. 
-  Duration of each track is shown
-  Media information is shown using CDDB
-  Dynamic debugging
-  Will scan for a CD-ROM drive with a CD-DA loaded in it.

-----------------------------------------------------------------
General Info
-----------------------------------------------------------------

Much of what I write in this section can be found elsewhere. See for
example http://www.pctechguide.com/08cd-rom.htm, or the libcdio
documentation.

The Sony and Philips Corporations invented and Compact Disc (CD) in
the early 1980s. The specifications for the layout is often referred
to by the color of the cover on the specification. 

The first type of CD specification that was produced was the Compact
Disc Digital Audio (CD-DA) or just plain ``audio CD'' and is commonly
called the ``Red Book''. Music CD's are recorded in this format which
basically allows for around 74 minutes of audio per disc and for that
information to be split up into *tracks*. Tracks are broken up into
"sectors" and each sector contains 2,352 bytes. To play one 44.1 kHz
CD-DA sampled audio second, 75 sectors are used.

A CD can hold at most 99 such tracks. Between the tracks CD
specifications require a ``2 second'' in gap (called a @term{lead-in
gap}. This is unused space with no ``data'' similar to the space
between tracks on an old phonograph. The word ``second'' here really
refers to a measure of space and not really necessarily an amount of
time. However in the special case here where you have an audio CD, the
amount of time to play a gap of this size will take 2 seconds. Note
this is independent of how fast your CD drive can read a sector.

The beginning (or inner edge) of the CD is supposed to have a ``2
second'' lead-in gap and there is supposed to be another ``2 second''
*lead-out* gap at the end (or outer edge) of the CD.

CD-DA ``Red Book'' Specification

One can create and then write or "burn" a CD in the CD-DA format
and in this process sometimes one writes the bytes that will appear as
a file on a hard disk. This is called a "CD disk image". This
plugin may be able to play this file just the same as if it were
burned onto a CD.

As there are a number of CD-burning programs, there are a number of
CD-image formats. This plugin uses libcdio which currently understands
the BIN/CUE disk-image format used by a popular DOS/Window mastering
tool and a limited subset of the proprietary and unpublished form at
used by the Nero burning software. Over time however perhaps more
disk-image formats will be recognized.

Audio CD Identification Information (CDDB)

The Philips Red-Book specification allows for a Compact Disc to have a
Media Catalog Number or MCN written on it, and probably this
was how they CD's would be identified. Alas, very few audio discs
actually have a Medium Catalog Number on the box, and the way the code
is written on CD is *not* uniform across all discs!

However the listening community wanted a way to identify an audio CD,
so a database of CD information was gathered by basically making a
``signature'' or hash from the number of tracks on a disk and a
checksum of the bytes of the tracks. This is referred to as CDDB
information. Using the hash the database gives information about the
titles of the tracks, the CD album name, year it was published and so
on. This plugin has the ability to show this information courtesy of
libcddb written by Kris Verbeeck.


-----------------------------------------------------------------
MRLS:
-----------------------------------------------------------------

the vlc CD-DA plugin, identifies itself in the vlc GUI as CDDAX. It
also registers itelf to handle a class of MRL's that start with
cddax://.

The CDDAX MRL takes the following form:

  cddax://[path to file or CD-DA device][@[Tt]number]]

A simple cddax:// runs the default item: track 1 using the default CD
device (perhaps /dev/cdrom). The default default device is
user-configurable.

It is however also possible to specify both Compact Disc device/filename
and item explicitly in the MRL.

For example cddax://dev/cdrom2 specifies using device /dev/cdrom2 which
might useful if as I have /dev/cdrom is a burner and the /dev/cdrom2
is a read-only device. And cddax://test_cdda.cue specifies the
"cuesheet" file for a CD-DA image on disk created say with cdrdao.
(test_cdda.bin is the corresponding bin file, but using that won't
work.)

After the optional device name or file name, you can name the track
number unit which preceded by a @ or an @ and T in either case. A MRL
which ends in an @ is like not adding it at all.

Some examples of MRLS are given below. In the examples, we assume the
following configuration setting:

cdda.default_device:/dev/cdrom

    cddax://                   - track 1 of device: /dev/cdrom
    cddax://@                  - same as above
    cddax:///dev/cdrom         - probably same as above
    cddax:///dev/cdrom2        - track 1 of /dev/cdrom2
    cddax:///dev/cdrom2@       - same as above
    cddax://dev/cdrom2@53      - track 53 from /dev/cdrom2
    cddax://dev/cdrom2@T53     - Same as above
    cddax://dev/cdrom2@t53     - Same as above
    cddax://@2                 - track 2 from default device
    cddax://3                  - track 3 from default device
    cddax:///tmp/ntsc.cue      - track 1 from /tmp/ntsc.bin, (a bin/cue
                                 disk image)
    cddax:///tmp/ntsc.cue@     - same as above
    cddax://tmp/ntsc.cue@      - track 1 of tmp/ntsc.bin. NOT the
                                 the same as above unless the cwd is /.
    cddax://ntsc.nrg           - track 1 of ntsc.nrg (a nero disk image)
    cddax://tmp/ntsc.nrg@5     - track 5 of /tmp/ntsc.nrg

  Bad MRL's
    cddax://@x                  - x is not a number
    cddax/tmp                   - no colon
    cddax:/                     - must start cddax://

-----------------------------------------------------------------
Configuration settings:
-----------------------------------------------------------------

Configuration settings in vlc are generally put in ~/.vlc/vlcrc. A
description of the ones specific to CDDAX are listed below.

- -
cddax-cddb-title-format

This gives a format used in the playlist title string when CDDB is consulted.
Similar to the Unix date command, there are format specifiers
that start with a percent sign for which various information is filled
in dynamically.  The control specifiers are given as below

   %a : The album artist
   %A : The album information
   %C : Category
   %I : CDDB disk ID
   %G : Genre
   %M : The current MRL
   %m : The CD-DA Media Catalog Number (MCN)
   %n : The number of tracks on the CD
   %p : The artist/performer/composer in the track
   %T : The track number
   %s : Number of seconds in this track
   %t : The name
   %Y : The year 19xx or 20xx
   %% : a %

The default is
  Track %T. %t - %p 

- -
cddax-title-format

This gives a format used in the playlist title string when CDDB is
*NOT* consulted.  Similar to the Unix date command, there are format
specifiers that start with a percent sign for which various
information is filled in dynamically.  The control specifiers are
given as below

   %M : The current MRL
   %m : The CD-DA Media Catalog Number (MCN)
   %n : The number of tracks on the CD
   %T : The track number
   %s : Number of seconds in this track
   %% : a %

The default is 
  %T %M 

- -
cddax-cddb-email

# email given on cddb requests
# string, default: me@home

- -
cddax-cddb-enabled

# Do we use CDDB to retrieve CD information?
# bool, default: 1

- -
cddax-cddb-http