CDROM(3) BSD Programmer's Manual CDROM(3)NAME
cdrom - control audio functions of cdrom drives
SYNOPSIS
#include <sys/cdrom.h>
struct cdinfo *
cdopen(char *path);
int
cdclose(struct cdinfo *cdinfo);
int
cdplay(struct cdinfo *cdinfo, int start_frame, int end_frame);
int
cdstop(struct cdinfo *cdinfo);
int
cdpause(struct cdinfo *cdinfo, int pause_resume);
int
cdstatus(struct cdinfo *cdinfo, struct cdstatus *cdstatus);
int
cdeject(struct cdinfo *cdinfo);
int
cdload(struct cdinfo *cdinfo);
int
cdvolume(struct cdinfo *cdinfo, int volume);
void
frame_to_msf(int frame, int *minp, int *secp, int *framep);
int
msf_to_frame(int min, int sec, int frame);
DESCRIPTION
This library implements a device independent interface to control the au-
dio features of CD-ROM drives. First, the CD-ROM drive must be opened,
using the function cdopen(). The pathname should be the c partition of
the character device, for example /dev/rsd1c or /dev/rmcd0c. Alternative-
ly, if the file name is passed as NULL, then the value of the environment
variable CDROM is used. If this is also NULL, then /dev/rcdrom is tried.
SCSI devices may only be accessed as root. The structure returned by
cdopen() contains the following fields, which you may examine but not
change (along with some other fields for internal use):
struct cdinfo {
int ntracks;
struct track_info *tracks;
int total_frames;
};
The field ntracks tells the number of audio tracks on the disk. The
tracks field points to an array giving details about each track. The to-
tal playing time of the disk is given in the field total_frames. Each
frame contains audio data for 1/75th of a second.
The track_info structure contains the following fields (among others):
struct track_info {
int track_num;
int start_frame;
int nframes;
};
The track_num gives the track number for this entry. Normally, the first
track on a disk is number 1, but the creator of the disk may have as-
signed a different starting number. The field start_frame gives the ab-
solute frame number of the start of this track, and nframes is the length
of the track, both measured in units of 1/75th of a second.
The function cdclose() closes the associated file descriptor, and frees
any memory that was allocated by cdopen(). This function does not do any
other important work, so it is not necessary to go to extra trouble to
ensure that it is called before the process exits. For most drives play-
ing will continue if it is in progress when cdclose() is called, or when
the process exits.
The function cdplay() starts playing audio starting and ending at the
given absolute frames. The function cdstop() stops the current play op-
eration.
The function cdpause() will pause the current play operation if
pause_resume is zero(0) or resume from a pause if pause_resume is one(1).
The function cdstatus() may be used at any time to find out what the CD-
ROM drive is doing, and to determine the current frame number, if playing
is in progress. It fills in a structure that has the following fields
(among others):
struct cdstatus {
enum cdstate state;
int control;
int track_num;
int index_num;
int rel_frame;
int abs_frame;
};
The state is one of cdstate_unknown, cdstate_stopped, cdstate_playing or
cdstate_paused. It is dependent on the particular drive whether the state
will be stopped or paused after a cdstop operation. If the drive is cur-
rently playing, then the rest of the fields are valid, and give the cur-
rent position. The field abs_frame has the proper format to use as an
argument to cdplay(). For example, to implement a pause and resume fea-
ture, the current position can be recorded with a call to cdstatus(),
then the playing would be stopped with cdstop(). To resume, call
cdplay() starting at the saved position.
The function cdeject() ejects the caddy, if that makes sense for the un-
derlying drive.
The function cdload() loads the caddy, if that makes sense for the under-
lying drive.
The function cdvolume() sets the volume level of the audio output. The
second argument is an integer between 0 (lowest volume) and 100 (full
volume). Unfortunately, not all cdrom drives implement this function,
and in those that do, the sensitivity of the control varies greatly.
SEE ALSOcdctl(1)BSDI BSD/OS September 22, 1995 2
