
1997 Jun 16
36
Philips Semiconductors
Preliminary specification
Audio processor for VHS hi-fi
TDA9615H
The RFC output can be muted by setting of bit RFCM = 1.
When applying this mute the AGC control is reset by
discharging the capacitor at pin 11 (RFCAGC).
Audio dubbing
TDA9615H includes unparalleled functionality supporting
the audio dubbing function of hi-fi video recorders. Audio
dubbing is a feature mode for recording of new sound
material on the linear audio track (i.e. normal sound) of an
existing recording. Audio dubbing can be used in two
different ways.
O
UTPUT MIX
A new, partly, recording is made on the linear audio track;
afterwards during ‘playback’ mode the new linear audio
and the original hi-fi sound are combined. This way
hi-fi stereo quality remains and linear audio is only partly
used e.g. for speech only (commentary track). However
there is no control over the original (hi-fi) sound.
‘Playback’ mode mixing of hi-fi and normal sound is
supported by the output select function modes ‘Mix-Left’,
‘Mix-Right’ and ‘Mix-Stereo’ (OSN, OSR and OSL of the
output byte) creating a fixed output signal of
1
2
hi-fi left +
1
2
normal.
I
NPUT MIX
A new, complete, recording is made on the linear audio
track; afterwards ‘playback’ mode uses linear audio sound
only. This way hi-fi stereo quality is lost but there is total
freedom in defining the new material. Furthermore this
way ‘playback’ mode is no longer restricted to hi-fi video
recorders with output mix option.
Selection ‘Dub Mix’ mode of the input select function,
when combined with selection ‘Volume’ mode of the
normal select function, changes the circuit into a mixing
desk. A new linear audio recording can be created mixing
together new and original sound. By use of the left and
right channel volume controls continuous control is offered
over amplitude and ratio mix of the AUX input signal (e.g.
a microphone input) and the original hi-fi ‘playback’ mode
sound.
This functionality is realized by internal connection of the
AUX input pair to the left channel volume control and by
internal connection of the hi-fi output signal pair to the right
channel volume control. For output and hi-fi selection the
‘Dub Mix’ mode uses, and partly overrules, the output
select function settings. Output select function modes
‘Mix-Left’, ‘Mix-Right’ and ‘Mix-Stereo’ make the normal
sound available at the line outputs for monitoring of the
‘Dub Mix’ mode recording.
Table 37
Input select function is set to ‘Dub Mix’ mode (IS2, IS1, IS0 = 101); note 1
Note
1.
Modes shown in bold are the most used modes.
OUTPUT SELECT
MODE
OSN
OSR
OSL
DUB MIX OUTPUT
SELECTION
DUB MIX INPUT SELECTION
LEFT CHANNEL RIGHT CHANNEL
aux stereo
aux stereo
aux stereo
aux stereo
aux stereo
aux stereo
aux stereo
aux stereo
Mute
Left
Right
Stereo
Normal
Mix-Left
Mix-Right
Mix-Stereo
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
mute
hi-fi left
hi-fi right
stereo
normal
normal
normal
normal
mute
hi-fi left
hi-fi right
stereo
normal
hi-fi left
hi-fi right
hi-fi stereo
Output select function mode ‘Mix-Stereo’ is the setting
generally used for audio dubbing. In combination with
setting the normal select function to ‘Volume’ mode user
control over amplitude and ratio is offered for the AUX and
hi-fi signal as follows:(
1
4
AUXL +
1
4
AUXR)
×
volume left +
(
1
4
hi-fi left +
1
4
hi-fi right)
×
volume right.
Switching hi-fi to a mode other than ‘playback’ or selection
of output select function mode ‘Normal’ should be avoided;
using these settings a signal loop can be closed from
output to input possibly leading to audio oscillation. For the
same reason auto-normal switching is not active during
‘Dub Mix’ mode; in case no hi-fi input signal is detected the
hi-fi sound is muted.