libcdio-osx/doc/libcdio.texi

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@c %**start of header
@setfilename libcdio.info
@set libcdio @code{libcdio}

@c A macro for defining terms variables.
@macro term{varname}
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@settitle The GNU libcdio library
@setchapternewpage on

@ifinfo
This file documents GNU CD input and control library

Copyright (C) 2003 Herbert Valerio Riedel @email{<hvr@@gnu.org>} and Rocky
Bernstein @email{<rocky@@panix.com>}

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.''
@end ifinfo

@titlepage
@title GNU libcdio library
@subtitle $Id: libcdio.texi,v 1.6 2003/10/28 16:23:49 rocky Exp $
@author Rocky Bernstein et al.
@page

@vskip 0pt plus 1filll

Copyright @copyright{} 2003 Herbert Valerio Riedel
@email{<hvr@@gnu.org>} and Rocky Bernstein @email{<rocky@@panix.com>}
@sp 1
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.''
@end titlepage
@page

@ifnottex
@node Top, History, (dir), (dir)

@top The GNU Video CD Ripping Program (@value{program})

This file documents GNU CD input and control library

Copyright (C) 2003 Herbert Valerio Riedel and Rocky Bernstein

@menu
* History::             How this came about
* Purpose::             Why this library?
* CD Formats::          A tour through the CD-specification spectrum
* CD Terms::            Limitations and terminology used in CD's and libcdio
* How to use::          Okay enough babble, lemme at the library!

Indices
* General Index::       Overall index
@end menu
@end ifnottex

@contents

@node History
@chapter History

As a result of the repressive Digital Millenium Copyright Act (DMCA)
I became aware of Video CD's (VCD's). Video CD's are not subject to
the DMCA and therefore enjoy the protection afforded by copyright but
no more. But in order for VCD's to be competitive with DVD's, good
tools (including GPL tools) are needed for authoring and playing
them. And so through VCD's I became aware of the excellent Video CD
tools by Herbert Valerio Riedel which form the @kbd{vcdimager} package.

Although vcdimager is great for authoring, examining and extracting
parts of a Video CD, it is not a VCD player. And when I looked at the
state of Video CD handling in existing VCD players: @code{xine},
@code{MPlayer}, and @code{vlc}, I was a bit disappointed. None handled
playback control, menu selections, or playing still frames and
segments from track 1.

Version 0.7.12 of vcdimager was very impressive, however it lacked
exportable libraries that could be used in other projects. So with the
blessing and encouragement of Herbert Valerio Riedel, I took to
extract and create libraries from this code base. The result was two
libraries: one to extract information from a VCD which I called
libvcdinfo, and another to do the reading and control of a VCD. Well,
actually, at this point I should say that a Video CD is really just
Video put on a existing well-established Compact Disc or CD format. So
the library for this is called @value{libcdio} rather than
@kbd{libvcdio}.

While on the topic of the name @value{libcdio}, I should also explain that
the library really doesn't handle writing or output (the final "o" in
the name). However it was felt that if I put libcdi that might be
confused with a particular CD format called CD-I.

@node Purpose
@chapter The problem and previous work

If around the year 2002 you were to look at the code for a number of
open-source CD or media players that work on several platforms such as
vlc, MPlayer, xine, or xmms to name but a few, you'd find the code to
read a CD sprinked with conditional compilation for this or that
platform. 

One CD player, @kbd{xmcd} by Ti Kan, was I think a bit better than
most in that it tried to @emph{encapsulate} the kinds of CD control
mechanisms (SCSI, Linux ioctl, Toshiba, etc.) in a "CD Audio Device
Interface Library" called libdi.  However this library is for Audio
CD's only and I don't believe this library has been used outside of
xmcd.

Another project, Simple DirectMedia Layer also encapsulates CD
reading. 

@quotation
SDL is a library that allows you portable low-level access to a video
framebuffer, audio output, mouse, and keyboard. With SDL, it is easy
to write portable games which run on ...
@end quotation

Many of the media players mentioned above do in fact can make use of
the SDL library but for @emph{video} output only. Because the encapsulation
is over @emph{many} kinds of I/O (video, joysticks, mice, as well as CD's),
I believe that the level of control provided for CD a little bit
limited. (However to be fair, it may have only been intended for games
and may be suitable for that).  Applications that just want the CD
reading and control portion I think will find quite a bit overhead.

At the OS level there is the "A Linux CD-ROM Standard" by David van
Leeuwen from around 1999. This defines a set of definitions and
ioctl's that mask hardware differences of various Compact Disc
hardware. It is a great idea and no doubt something similar exists on
other platforms. However this "standard" lacked adoption on OS's other
than GNU/Linux.

The library ``The Compact Disc Input and Control Library'' encapsulates
CD-ROM reading and control. Applications wishing to be oblivious of
the OS- and device-dependent properties of a CD-ROM can use this
library. Some support for disk image types like BIN/CUE and NRG is
available, so applications that use this library also have the ability
to read disc images as though they were CDs. 

A sample utility for displaying CD info is included.

@node CD Formats
@chapter CD Formats

Much of what I write in this section can be found elsewhere. See for
example @url{http://www.pctechguide.com/08cd-rom.htm} or
@url{http://www.pcguide.com/ref/cd/format.htm}

We give just enough background here to cover Compact Discs and Compact
Disc formats that are handled by this library.

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. 

@menu
* Red Book::        Red Book (CD-DA)
* Yellow Book::     Yellow Book (CD-ROM Digital Data)
* White Book::      White Book (Video CD)
@end menu

@node Red Book
@section Red Book
The first type of CD that was produced was the Compact Disc Digital
Audio (CD-DA) or just plain ``audio CD''. The specification 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.

In @value{libcdio} when you you want to read an audio sector, you call the
routine @code{cdio_read_audio_sector()}.

@node Yellow Book
@section Yellow Book
The CD-ROM specification or the ``Yellow Book'' followed a few years later
and describes the extension of CD's to store computer data,
i.e. CD-ROM (Compact Disk Read Only Memory).  

The specification in the Yellow Book defines two modes: Mode1 and
Mode2.

@menu
* Mode1::           Mode 1 Format
* Mode2::           Mode 2 Format
@end menu

@subsection ISO-9660
Nowhere in the Yellow Book ist specified how data is to be stored on a
CD-ROM.  It was feared that different companies would implement
proprietary data storage formats using this specification, resulting
in incompatible data CDs. To prevent this, representatives of major
manufacturers met at the High Sierra Hotel and Casino in Lake Tahoe,
NV, in 1985, to define a standard for storing data on CDs. This format
was nicknamed High Sierra Format. In a slightly modified form it was
later adopted as ISO the ISO 9660 standard. This standard is further
broken down into 3 "levels", the higher the level, the more
permissive.

@subsubsection Level1
Level 1 ISO 9660 defines names in the 8+3 convention so familiar to
MS-DOS: eight characters for the filename, a period, and
then three characters for the file type, all in upper case. The
allowed characters are A-Z, 0-9, ".", and "_".Level 1 ISO 9660
requires that files occupy a contiguous range of sectors. This allows
a file to be specified with a start block and a count. The maximum
directory depth is 8.

@subsubsection Level2
Level 2 ISO 9660 allows far more flexibility in filenames, but isn't
usable on some systems, notably MS-DOS.

@subsubsection Level3
Level 3 ISO-9660 allows non-contiguous files, useful if the file was
written in multiple packets with packet-writing software.

There have been a number of extensions to the ISO 9660 CD-ROM file
format. One extension is Microsoft's Joliet specification, designed to
resolve a number of deficiencies in the original ISO 9660 Level 1 file
system, and in particular to support the long file names used in
Windows 95 and subsequent versions of Windows.

Another extension is the Rock Ridge Interchange Protocol (RRIP), which
enables the recording of sufficient information to support POSIX File
System semantics.

@node Mode1
@subsection Mode1
Mode 1 is the data storage mode used by to store computer
data. The data is laid out in basically the same way as in and audio
CD format, except that the 2,352 bytes of data in each block are
broken down further. 2,048 of these bytes are for "real" data. The
other 304 bytes are used for an additional level of error detecting
and correcting code. This is necessary because data CDs cannot
tolerate the loss of a handful of bits now and then, the way audio
CDs can.

@node Mode2
@subsection Mode2
Mode 2 data CDs are the same as mode 1 CDs except that the error
detecting and correcting codes are omitted. This is similar to audio
CDs, i.e. the mode 2 format provides a more flexible vehicle for
storing types of data that do not require high data integrity: for
example, graphics and video can use this format. But in contrast to
the Red book standard, different modes can be mixed together; this is
the basis for the extensions to the original data CD standards known
as CD-ROM Extended Architecture, or CD-ROM XA.  CD-ROM XA formats
currently in use are CD-I Bridge formats, Photo CD and Video CD plus
Sony's Playstation.

@node White Book
@section White Book
The White Book was released by Sony, Philips, Matsushita, and JVC
in 1993, defines the Video CD specification. The White Book
is also known as Digital Video (DV). A Video CD contains one data
track recorded in CD-ROM XA Mode 2 Form 2. It is always the first
track on the disc (Track 1). The ISO-9660 file structure and a CD-i
application program are recorded in this track, as well as the Video
CD Information Area which gives general information about the Video
Compact Disc. After the data track, video is written in one or more
subsequent tracks within the same session. These tracks are also
recorded in Mode 2 Form 2.

In @value{libcdio} when you you want to read a mode2 format 2 audio
sector you call the routine @code{cdio_read_mode2_sector()}.

@node CD Terms
@chapter CD Terminology

@section tracks --- disc subdivisions
In this section we describe CD properties and terms that we make use
of in @value{libcdio}.

A CD is formated into a number of @term{tracks}, and 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 that the CD encodes an audio CD or CD-DA, the amount of
time to play a gap of this size will take 2 seconds.

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''
@term{lead-out} gap at the end (or outer edge) of the CD.

People have discovered that they can put useful data in the various
gaps and their equipment can read this, violating the standards but
allowing a CD to store more data.

In order to determine the number of tracks on a CD and where they
start, commands are used to get this table-of-contents or @term{TOC}
information. Asking about the start of the @term{lead-out track}
gives the amount of data stored on the Compact Disk. To make it easy
to specify this leadout track, special constant 0xAA (decimal 170) is
used to indicate it. This is safe since this is higher than the
largest legal track position. In @value{libcdio},
@code{CDIO_CDROM_LEADOUT_TRACK} is defined to be this special value.

@section block addressing (MSF, LSN, LBA)
A track is broken up into a number of 2352-byte @emph{blocks} which we
sometimes call @emph{sectors}. Whereas tracks have to have a gap
between them, a block or sector does not.

One can addressing a block in one of three formats. The oldest format
is by it's minute/second/frame number, also referred to as @term{MSF}
and written in time-like format MM:SS:FF (e.g. 30:01:40). In this
notation there are 75 ``frames'' in a ``second,'' and the familiar (if
awkward) 60 seconds in a minute. @emph{Frame} here is what we called a
@emph{block} above. The CD specification defines ``frame'' to be
@emph{another} unit which makes up a block. Very confusing.

Even more confusing is is using this time-like notation for an address
or for a length. Too often people confuse the MSF notation this with
an amount of time. A ``second'' (or 75 blocks) in this notation is
only a second of playing time for something encoded as CD-DA. It does
@emph{not} necessarily represent the amount time that it will take to
play a of Video CD---usually you need more blocks than this. Nor does
it represent the amount of data used to play a second of an
MP3---usually you need fewer blocks than this. It is also not the
amount of time your CD-ROM will take to read a ``second'' of data off
a Compact Disc: for example a 12x CD player will read 12x75 2352-byte
blocks in a one second of time.

Furthermore when programming, it is generally more cumbersome to use
an MSF rather than a LBA or LSN described below, since subtraction of
two MSF's has the awkwardness akin to subtraction using Roman
Numerals.

Probably the simplest way to address a block is to use its @term{LSN}
or ``logical sector number.'' This just numbers the blocks from 0
on. The Lead-in and Lead-out gaps described above have LSNs just like
any other space on a CD. The last unit of address is a @term{LBA}. It
is the same as a LSN but the 150 blocks assocated with the initial
lead-in is are not counted. So to convert a LBA into an LSN you just
add 150. Why the distinction between LBA and LSN? I don't know.

@node How to use
@chapter How to use

@section Example 1 --- list out tracks and LSNs
Here we will give an annotated example which can be found in the
distribution as @file{example/sample1.c}.

@smallexample
 1: #include <stdio.h>
 2: #include <sys/types.h>
 3: #include <cdio/cdio.h>
 4: int
 5: main(int argc, const char *argv[])
 6: @{
 7:  CdIo *cdio = cdio_open ("/dev/cdrom", DRIVER_UNKNOWN);
 8:  track_t first_track_num = cdio_get_first_track_num(cdio);
 9:  track_t num_tracks      = cdio_get_num_tracks(cdio);
10:  int j, i=first_track_num;
11:
12:  printf("CD-ROM Track List (%i - %i)\n", first_track_num, num_tracks);
13
14:  printf("  #:  LSN\n");
15:  
16:  for (j = 0; j < num_tracks; i++, j++) @{
17:    lsn_t lsn = cdio_get_track_lsn(cdio, i);
18:    if (CDIO_INVALID_LSN != lsn)
19:      printf("%3d: %06d\n", (int) i, lsn);
20:  @}
21:  printf("%3X: %06d  leadout\n", CDIO_CDROM_LEADOUT_TRACK, 
22:         cdio_get_track_lsn(cdio, CDIO_CDROM_LEADOUT_TRACK));
23:  cdio_destroy(cdio);
24:  return 0;
25: @}
@end smallexample 

Already from the beginning on line 2 we see something odd. The
@code{#include <sys/types.h>} is needed because @value{libcdio}
assumes type definitions exist for @code{uint32_t}, @code{uint16_t}
and so on.  Alternatively you change line 2to:

@smallexample
#define HAVE_SYS_TYPES_H
@end smallexample 

and @code{<cdio/cdio.h>} will insert line 2. If you use GNU autoconf
to configure your program, add @code{sys/types.h} to
@code{AC_HAVE_HEADERS} and @emph{it} will arrange for
@code{HAVE_SYS_TYPES_H} to get defined. If you don't have
@code{<sys/types.h>} but have some other include that defines these
types, put that instead of line 2. Or you could roll your own
typedefs. (Note: In the future, this will probably get ``fixed'' by
requiring glib.h.)

Okay after getting over the hurdle of line 2, the next line pretty
straightforward: you need to include this to get cdio definitions. One
of the types that is defined via line 3 is @code{CdIo} and a pointer
that is used pretty much in all operations. Line 6 initializes the
variable @code{cdio} which we will be using in all of the subsequent
libcdio calls. It does this via a call to @code{cdio_open()}. 

The second parameter of @code{cdio_open} is DRIVER_UNKNOWN. For any
given installation a number of Compact Disc device drivers may be
available. In particular it's not uncommon to have several drivers
that can read CD disk-image formats as well as a driver that handles
some CD-ROM piece of hardware. Using DRIVER_UNKNOWN as that second
parameter we let the library select a driver amongst those that are
available; generally the first hardware driver that is available is
the one selected.

Note that in contrast to what is typically done using ioctls to read a
CD, you don't issue any sort of CD-ROM read TOC command---that is all
done by the driver. Of course, the information that you get from
reading the TOC is often desired: many tracks are on the CD, or what
number the first one is called. This is done through calls on lines 8
and 9.

For each track, we call a cdio routine to get the logical sector
number, @code{cdio_get_track_lsn()} on line 17 and print the track
number and LSN value. Finally we print out the ``lead-out track''
information and we finally call @code{cdio_destroy()} in line 23 to
indicate we're done with the CD.

@section Example 2 --- lists drivers available and default CD device 

One thing that's a bit hoaky in Example 1 is hard-coding the name of
the device used: @code{/dev/cdrom}. Although often this is the name of
a CD-ROM device on GNU/Linux and possibly some other Unix derivates,
there are many OSs for which use a different device name.

In the next example, we'll let the driver give us the name of the CD-ROM
device that is right for it. 

@smallexample
 1: #include <stdio.h>
 2: #include <sys/types.h>
 3: #include <cdio/cdio.h>
 4: int
 5: main(int argc, const char *argv[])
 6: @{
 7:   CdIo *cdio = cdio_open (NULL, DRIVER_UNKNOWN);
 8:   driver_id_t driver_id;
 9:  
10:  if (NULL != cdio) @{
11:    printf("The driver selected is %s\n", cdio_get_driver_name(cdio));
12:    printf("The default device for this driver is %s\n\n", 
13:           cdio_get_default_device(cdio));
14:    cdio_destroy(cdio);
15:  @} else @{
16:    printf("Problem in trying to find a driver.\n\n");
17:  @}
18:
19:  for (driver_id=CDIO_MIN_DRIVER; driver_id<=CDIO_MAX_DRIVER; driver_id++)
20:    if (cdio_have_driver(driver_id))
21:      printf("We have: %s\n", cdio_driver_describe(driver_id));
22:    else
23:      printf("We don't have: %s\n", cdio_driver_describe(driver_id));
24:  return 0;
25: @}
@end smallexample

@emph{Fill out examples for cdio_read_xxx or cdio_seek, More on 
drivers?.}

@node General Index
@unnumbered General Index
@printindex cp

@bye