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SGI Desktop Special Edition 1.0
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1995-09-11
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- 1 -
5. _C_D__A_u_d_i_o__/__D_A_T__A_u_d_i_o
This section describes changes, bug fixes, known problems,
and known documentation errors relating to the audio
capabilities of the SCSI CD-ROM drive and SCSI DAT drive
available as option peripherals for IRIS workstations.
The CD audio and DAT audio support in IRIS Digital Media
Execution Environment 5.5 is the same as the 5.3 version.
IRIX 5.3 subsystem _e_o_e_2._s_w._c_d_r_o_m includes the program
_c_d_p_l_a_y_e_r(1), which provides a transport control panel
interface to the audio capabilities of the CD-ROM drive. In
order to listen to the audio output of the CD-ROM drive when
controlling it with _c_d_p_l_a_y_e_r, you need to connect an
external amplifier or headphones directly to the drive.
IRIS Digital Media Tools 5.5 subsystem _d_m_e_d_i_a__t_o_o_l_s._s_w._c_d_d_a_t
includes the programs _c_d_m_a_n(1) and _d_a_t_m_a_n(1).
_c_d_m_a_n provides a CD transport control panel interface which
is similar to _c_d_p_l_a_y_e_r's interface. The key difference is
that _c_d_m_a_n transfers audio data across the SCSI bus and
plays it through the built-in audio subsystem on your IRIS
workstation. This allows you to listen to an audio CD
through speakers or headphones connected directly to your
computer. You can control the master audio output level
using _a_p_a_n_e_l(1). The audio output from _c_d_m_a_n will
automatically be mixed with the audio output from other
applications, such as the _I_n_d_i_g_o _M_a_g_i_c desktop environment
(see the _S_o_u_n_d_S_c_h_e_m_e chapter of these release notes).
_c_d_m_a_n includes a "record to disk file" menu which allows you
to record digital data directly from the CD-ROM to an AIFF-C
disk file.
_d_a_t_m_a_n provides a DAT transport control panel interface.
Like _c_d_m_a_n, _d_a_t_m_a_n transfers audio data across the SCSI bus
to and from the built-in audio subsystem on your
workstation. You can listen to an audio DAT through speakers
or headphones connected to your computer.
_d_a_t_m_a_n includes "record to disk file" and "record from disk
file" menus which allow you to transfer digital audio data
between AIFF-C disk files and DAT audio tapes.
IRIS Digital Media Development Environment 5.3 contains
programming interfaces to the audio playback capabilities of
the CD-ROM and DAT drives.
- 2 -
IRIS Digital Media Development Environment 5.3 includes the
source code for two programs called _c_d_t_o_d_a_t and _d_o_d_a_t.
_c_d_t_o_d_a_t is a command-line program which reads an audio CD
and digitally transfers the contents to an audio DAT. The
output DAT contains correct program numbers, index numbers,
program-time, absolute-time, copy-protect bits, and lead-in
and lead-out areas on the tape. _d_o_d_a_t is a DAT mastering
utility which allows you to copy tracks from an audio DAT to
disk files, and to sequence disk files to specified tracks
on a DAT tape.
IRIS Digital Media Development Environment 5.3 is included
with the standard IRIS Development Option 5.3.
5.1 _K_n_o_w_n__P_r_o_b_l_e_m_s__a_n_d__W_o_r_k_a_r_o_u_n_d_s
SGI is working with the manufacturer of the Python DAT drive
to produce a new revision of the DAT firmware which includes
fixes for each of the following problems.
+o DAT audio firmware problem: data tape at BOT.
Assume a DDS (data) tape (i.e., a tape previously
recorded in data mode) is inserted in the DAT drive.
The drive will rewind the tape to logical BOT, which on
a data tape is different than physical BOT. If you
attempt to write audio data to the drive, it begins
writing at logical BOT. When the tape is later re-
inserted into the drive, it is incorrectly recognized
as a data tape since DDS format data exists between
physical BOT and logical BOT.
Workaround: Check to see if the tape in the drive is
DDS media and at BOT. If so, in audio mode write a
frame of data to move the tape off logical BOT, then
issue a rewind. This will cause the tape to rewind
back to physical BOT.
+o DAT audio firmware problem: read position bug.
The DAT drive firmware incorrectly returns its position
via the MTGETAUDIO ioctl to the IRIX tape driver. There
are two modes to this behavior.
+o Immediately following a seek: Suppose you seek by
A-time (absolute time). Then MTGETAUDIO returns
the correct A-time, but incorrect P-time (program
time). Suppose you seek by P-time. Then MTGETAUDIO
returns the correct P-time, but incorrect A-time.
- 3 -
+o Following a read or write: Both A-time and P-time
are wrong.
Workaround: Read a frame from the tape and decode the
subcode information. This of course moves the tape, so
you may have to seek back to the previous location or
otherwise account for the resulting 1 frame difference
between the frame read and the new tape position.
+o DAT audio firmware problem: read delay bug.
If not used for 60 seconds, the DAT drive unloads the
tape from the heads. Once this happens, subsequent
reads will fail.
Workaround: Avoid 60 second delays between subsequent
operations.
+o Write following read: A write following a read is not
frame-accurate. It may go onto the tape several frames
too early, overwriting some of the data just read.
Workaround: None (because of the following bug).
+o DAT audio firmware problem: Write following seek.
A write following a seek is not frame-accurate. About
50% of the time, a write following a seek will go onto
the tape a few frames early.
Workaround: None.