Capture FM, DAC, and PCSpeaker to VGM
Notes from NewRisingSun2 on the vgmrips.net forum 2017-01-05, 3:51:28:
Subject: DOSBox-VGM
Attached find my patch to DOSBox which directly logs to .VGM
files instead of .DRO files. The program logs writes to the
Tandy 1000/PCjr's SN76496 chip, the Game Blaster (SAA1099), the
OPL2/Dual OPL2/OPL3 chip, the PC speaker (via an AY-3-8910),
and the Sound Blaster and Tandy SL/TL/RL DACs (via an YM2612).
DAC and PC speaker are only logged if "capturepcm" and
"capturespeaker" in the [dosbox] section of DOSBox.conf are set
to "true", respectively; they are "false" by default, and can
only be changed from the config file, not within a DOSBox
session from the command line. I have only added PC speaker
support for that one game (4D Boxing) that uses it as a fourth
PSG channel, but theoretically one could also use it to create
a .VGM pack of scratchy sound effects from Commander Keen
episodes 1-3. Similarly, I have added DAC logging only for the
few games that use it for drums; therefore, it only works with
single-cycle 8-bit transfers when the whole sample in memory at
the time that the DMA transfer is started (i.e. no
double-buffering).
The source code diff also incorporates my correction to the
Game Blaster base clock, my patch adding support for Tandy 1000
direct DAC writes, and my patch correcting the interpretation
of SN76496 frequency register value 0. As mentioned in one of
these discussion threads, when using the Tandy DAC, "sbtype="
should be set to "none" in the [sblaster] section of
DOSBox.conf. The source code diff is against SVN r4000, as
revisions r4002 and r4003 from two days ago made some changes
to the mixer code that break my Tandy DAC code. Just download
SVN r4003 and replace mixer.cpp and mixer.h with those from
r4000. As I am using a few C++14 features, before compiling,
you need to re-run "configure" with the CPPFLAGS="-std=gnu++14"
option, e.g.
Code:
./configure --enable-core-inline LDFLAGS="-static-libgcc \
-static-libstdc++ -s" CPPFLAGS="-std=gnu++14"
The default key to start capturing is still Ctrl+Alt+F7; even
the name in the key bindings ("mapper") file is still
"hand_caprawopl", so I wouldn't have to change my key binding
file. I tried to start logging in the middle of a 4-OP FM song,
and the playback still seemed correct, so I hope I did the
register cache business correctly, and I have taken care that
no OPL register writes are filtered (i.e. no implicit vgm_cmp).
Imported-from: https://vgmrips.net/forum/viewtopic.php?t=2585#p8181
Signed-off-by: kcgen <email address hidden>
