302 lines
11 KiB
TeX
302 lines
11 KiB
TeX
\section{Built-in Module \sectcode{cd}}
|
|
\label{module-cd}
|
|
\bimodindex{cd}
|
|
|
|
This module provides an interface to the Silicon Graphics CD library.
|
|
It is available only on Silicon Graphics systems.
|
|
|
|
The way the library works is as follows. A program opens the CD-ROM
|
|
device with \code{cd.open()} and creates a parser to parse the data
|
|
from the CD with \code{cd.createparser()}. The object returned by
|
|
\code{cd.open()} can be used to read data from the CD, but also to get
|
|
status information for the CD-ROM device, and to get information about
|
|
the CD, such as the table of contents. Data from the CD is passed to
|
|
the parser, which parses the frames, and calls any callback
|
|
functions that have previously been added.
|
|
|
|
An audio CD is divided into \dfn{tracks} or \dfn{programs} (the terms
|
|
are used interchangeably). Tracks can be subdivided into
|
|
\dfn{indices}. An audio CD contains a \dfn{table of contents} which
|
|
gives the starts of the tracks on the CD. Index 0 is usually the
|
|
pause before the start of a track. The start of the track as given by
|
|
the table of contents is normally the start of index 1.
|
|
|
|
Positions on a CD can be represented in two ways. Either a frame
|
|
number or a tuple of three values, minutes, seconds and frames. Most
|
|
functions use the latter representation. Positions can be both
|
|
relative to the beginning of the CD, and to the beginning of the
|
|
track.
|
|
|
|
Module \code{cd} defines the following functions and constants:
|
|
|
|
\renewcommand{\indexsubitem}{(in module cd)}
|
|
|
|
\begin{funcdesc}{createparser}{}
|
|
Create and return an opaque parser object. The methods of the parser
|
|
object are described below.
|
|
\end{funcdesc}
|
|
|
|
\begin{funcdesc}{msftoframe}{min\, sec\, frame}
|
|
Converts a \code{(minutes, seconds, frames)} triple representing time
|
|
in absolute time code into the corresponding CD frame number.
|
|
\end{funcdesc}
|
|
|
|
\begin{funcdesc}{open}{\optional{device\optional{\, mode}}}
|
|
Open the CD-ROM device. The return value is an opaque player object;
|
|
methods of the player object are described below. The device is the
|
|
name of the SCSI device file, e.g. /dev/scsi/sc0d4l0, or \code{None}.
|
|
If omited or \code{None}, the hardware inventory is consulted to
|
|
locate a CD-ROM drive. The \code{mode}, if not omited, should be the
|
|
string 'r'.
|
|
\end{funcdesc}
|
|
|
|
The module defines the following variables:
|
|
|
|
\begin{datadesc}{error}
|
|
Exception raised on various errors.
|
|
\end{datadesc}
|
|
|
|
\begin{datadesc}{DATASIZE}
|
|
The size of one frame's worth of audio data. This is the size of the
|
|
audio data as passed to the callback of type \code{audio}.
|
|
\end{datadesc}
|
|
|
|
\begin{datadesc}{BLOCKSIZE}
|
|
The size of one uninterpreted frame of audio data.
|
|
\end{datadesc}
|
|
|
|
The following variables are states as returned by \code{getstatus}:
|
|
|
|
\begin{datadesc}{READY}
|
|
The drive is ready for operation loaded with an audio CD.
|
|
\end{datadesc}
|
|
|
|
\begin{datadesc}{NODISC}
|
|
The drive does not have a CD loaded.
|
|
\end{datadesc}
|
|
|
|
\begin{datadesc}{CDROM}
|
|
The drive is loaded with a CD-ROM. Subsequent play or read operations
|
|
will return I/O errors.
|
|
\end{datadesc}
|
|
|
|
\begin{datadesc}{ERROR}
|
|
An error aoocurred while trying to read the disc or its table of
|
|
contents.
|
|
\end{datadesc}
|
|
|
|
\begin{datadesc}{PLAYING}
|
|
The drive is in CD player mode playing an audio CD through its audio
|
|
jacks.
|
|
\end{datadesc}
|
|
|
|
\begin{datadesc}{PAUSED}
|
|
The drive is in CD layer mode with play paused.
|
|
\end{datadesc}
|
|
|
|
\begin{datadesc}{STILL}
|
|
The equivalent of \code{PAUSED} on older (non 3301) model Toshiba
|
|
CD-ROM drives. Such drives have never been shipped by SGI.
|
|
\end{datadesc}
|
|
|
|
\begin{datadesc}{audio}
|
|
\dataline{pnum}
|
|
\dataline{index}
|
|
\dataline{ptime}
|
|
\dataline{atime}
|
|
\dataline{catalog}
|
|
\dataline{ident}
|
|
\dataline{control}
|
|
Integer constants describing the various types of parser callbacks
|
|
that can be set by the \code{addcallback()} method of CD parser
|
|
objects (see below).
|
|
\end{datadesc}
|
|
|
|
Player objects (returned by \code{cd.open()}) have the following
|
|
methods:
|
|
|
|
\renewcommand{\indexsubitem}{(CD player object method)}
|
|
|
|
\begin{funcdesc}{allowremoval}{}
|
|
Unlocks the eject button on the CD-ROM drive permitting the user to
|
|
eject the caddy if desired.
|
|
\end{funcdesc}
|
|
|
|
\begin{funcdesc}{bestreadsize}{}
|
|
Returns the best value to use for the \code{num_frames} parameter of
|
|
the \code{readda} method. Best is defined as the value that permits a
|
|
continuous flow of data from the CD-ROM drive.
|
|
\end{funcdesc}
|
|
|
|
\begin{funcdesc}{close}{}
|
|
Frees the resources associated with the player object. After calling
|
|
\code{close}, the methods of the object should no longer be used.
|
|
\end{funcdesc}
|
|
|
|
\begin{funcdesc}{eject}{}
|
|
Ejects the caddy from the CD-ROM drive.
|
|
\end{funcdesc}
|
|
|
|
\begin{funcdesc}{getstatus}{}
|
|
Returns information pertaining to the current state of the CD-ROM
|
|
drive. The returned information is a tuple with the following values:
|
|
\code{state}, \code{track}, \code{rtime}, \code{atime}, \code{ttime},
|
|
\code{first}, \code{last}, \code{scsi_audio}, \code{cur_block}.
|
|
\code{rtime} is the time relative to the start of the current track;
|
|
\code{atime} is the time relative to the beginning of the disc;
|
|
\code{ttime} is the total time on the disc. For more information on
|
|
the meaning of the values, see the manual for CDgetstatus.
|
|
The value of \code{state} is one of the following: \code{cd.ERROR},
|
|
\code{cd.NODISC}, \code{cd.READY}, \code{cd.PLAYING},
|
|
\code{cd.PAUSED}, \code{cd.STILL}, or \code{cd.CDROM}.
|
|
\end{funcdesc}
|
|
|
|
\begin{funcdesc}{gettrackinfo}{track}
|
|
Returns information about the specified track. The returned
|
|
information is a tuple consisting of two elements, the start time of
|
|
the track and the duration of the track.
|
|
\end{funcdesc}
|
|
|
|
\begin{funcdesc}{msftoblock}{min\, sec\, frame}
|
|
Converts a minutes, seconds, frames triple representing a time in
|
|
absolute time code into the corresponding logical block number for the
|
|
given CD-ROM drive. You should use \code{cd.msftoframe()} rather than
|
|
\code{msftoblock()} for comparing times. The logical block number
|
|
differs from the frame number by an offset required by certain CD-ROM
|
|
drives.
|
|
\end{funcdesc}
|
|
|
|
\begin{funcdesc}{play}{start\, play}
|
|
Starts playback of an audio CD in the CD-ROM drive at the specified
|
|
track. The audio output appears on the CD-ROM drive's headphone and
|
|
audio jacks (if fitted). Play stops at the end of the disc.
|
|
\code{start} is the number of the track at which to start playing the
|
|
CD; if \code{play} is 0, the CD will be set to an initial paused
|
|
state. The method \code{togglepause()} can then be used to commence
|
|
play.
|
|
\end{funcdesc}
|
|
|
|
\begin{funcdesc}{playabs}{min\, sec\, frame\, play}
|
|
Like \code{play()}, except that the start is given in minutes,
|
|
seconds, frames instead of a track number.
|
|
\end{funcdesc}
|
|
|
|
\begin{funcdesc}{playtrack}{start\, play}
|
|
Like \code{play()}, except that playing stops at the end of the track.
|
|
\end{funcdesc}
|
|
|
|
\begin{funcdesc}{playtrackabs}{track\, min\, sec\, frame\, play}
|
|
Like \code{play()}, except that playing begins at the spcified
|
|
absolute time and ends at the end of the specified track.
|
|
\end{funcdesc}
|
|
|
|
\begin{funcdesc}{preventremoval}{}
|
|
Locks the eject button on the CD-ROM drive thus preventing the user
|
|
from arbitrarily ejecting the caddy.
|
|
\end{funcdesc}
|
|
|
|
\begin{funcdesc}{readda}{num_frames}
|
|
Reads the specified number of frames from an audio CD mounted in the
|
|
CD-ROM drive. The return value is a string representing the audio
|
|
frames. This string can be passed unaltered to the \code{parseframe}
|
|
method of the parser object.
|
|
\end{funcdesc}
|
|
|
|
\begin{funcdesc}{seek}{min\, sec\, frame}
|
|
Sets the pointer that indicates the starting point of the next read of
|
|
digital audio data from a CD-ROM. The pointer is set to an absolute
|
|
time code location specified in minutes, seconds, and frames. The
|
|
return value is the logical block number to which the pointer has been
|
|
set.
|
|
\end{funcdesc}
|
|
|
|
\begin{funcdesc}{seekblock}{block}
|
|
Sets the pointer that indicates the starting point of the next read of
|
|
digital audio data from a CD-ROM. The pointer is set to the specified
|
|
logical block number. The return value is the logical block number to
|
|
which the pointer has been set.
|
|
\end{funcdesc}
|
|
|
|
\begin{funcdesc}{seektrack}{track}
|
|
Sets the pointer that indicates the starting point of the next read of
|
|
digital audio data from a CD-ROM. The pointer is set to the specified
|
|
track. The return value is the logical block number to which the
|
|
pointer has been set.
|
|
\end{funcdesc}
|
|
|
|
\begin{funcdesc}{stop}{}
|
|
Stops the current playing operation.
|
|
\end{funcdesc}
|
|
|
|
\begin{funcdesc}{togglepause}{}
|
|
Pauses the CD if it is playing, and makes it play if it is paused.
|
|
\end{funcdesc}
|
|
|
|
Parser objects (returned by \code{cd.createparser()}) have the
|
|
following methods:
|
|
|
|
\renewcommand{\indexsubitem}{(CD parser object method)}
|
|
|
|
\begin{funcdesc}{addcallback}{type\, func\, arg}
|
|
Adds a callback for the parser. The parser has callbacks for eight
|
|
different types of data in the digital audio data stream. Constants
|
|
for these types are defined at the \code{cd} module level (see above).
|
|
The callback is called as follows: \code{func(arg, type, data)}, where
|
|
\code{arg} is the user supplied argument, \code{type} is the
|
|
particular type of callback, and \code{data} is the data returned for
|
|
this \code{type} of callback. The type of the data depends on the
|
|
\code{type} of callback as follows:
|
|
\begin{description}
|
|
\item[\code{cd.audio}: ]
|
|
The argument is a string which can be passed unmodified to
|
|
\code{al.writesamps()}.
|
|
\item[\code{cd.pnum}: ]
|
|
The argument is an integer giving the program (track) number.
|
|
\item[\code{cd.index}: ]
|
|
The argument is an integer giving the index number.
|
|
\item[\code{cd.ptime}: ]
|
|
The argument is a tuple consisting of the program time in minutes,
|
|
seconds, and frames.
|
|
\item[\code{cd.atime}: ]
|
|
The argument is a tuple consisting of the absolute time in minutes,
|
|
seconds, and frames.
|
|
\item[\code{cd.catalog}: ]
|
|
The argument is a string of 13 characters, giving the catalog number
|
|
of the CD.
|
|
\item[\code{cd.ident}: ]
|
|
The argument is a string of 12 characters, giving the ISRC
|
|
identification number of the recording. The string consists of two
|
|
characters country code, three characters owner code, two characters
|
|
giving the year, and five characters giving a serial number.
|
|
\item[\code{cd.control}: ]
|
|
The argument is an integer giving the control bits from the CD subcode
|
|
data.
|
|
\end{description}
|
|
\end{funcdesc}
|
|
|
|
\begin{funcdesc}{deleteparser}{}
|
|
Deletes the parser and frees the memory it was using. The object
|
|
should not be used after this call. This call is done automatically
|
|
when the last reference to the object is removed.
|
|
\end{funcdesc}
|
|
|
|
\begin{funcdesc}{parseframe}{frame}
|
|
Parses one or more frames of digital audio data from a CD such as
|
|
returned by \code{readda}. It determines which subcodes are present
|
|
in the data. If these subcodes have changed since the last frame,
|
|
then \code{parseframe} executes a callback of the appropriate type
|
|
passing to it the subcode data found in the frame.
|
|
Unlike the C function, more than one frame of digital audio data can
|
|
be passed to this method.
|
|
\end{funcdesc}
|
|
|
|
\begin{funcdesc}{removecallback}{type}
|
|
Removes the callback for the given \code{type}.
|
|
\end{funcdesc}
|
|
|
|
\begin{funcdesc}{resetparser}{}
|
|
Resets the fields of the parser used for tracking subcodes to an
|
|
initial state. \code{resetparser} should be called after the disc has
|
|
been changed.
|
|
\end{funcdesc}
|