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Mimick CD players when first positioning the play head

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For example, audio CD players will typically position themselves in
preparation to play the first audio track when "Play" is pushed.
This even occurs for mixed-mode CDs, where the player will start
playing at the first audio track. Therefore, we try to find the most
viable audio track and only fall back to defaults if needed.
(instead of "all zeros" like before).
This commit is contained in:
krcroft 2020-02-05 23:23:12 -08:00
parent 7f39fe86b4
commit 7cac8e4c4f
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GPG key ID: 4AD3678F4A2C291C
1 changed files with 55 additions and 49 deletions
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104
src/dos/cdrom_image.cpp
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@ -362,57 +362,63 @@ bool CDROM_Interface_Image::GetAudioTrackInfo(uint8_t requested_track_num,
return true;
}
bool CDROM_Interface_Image::GetAudioSub(unsigned char& attr, unsigned char& track_num,
unsigned char& index, TMSF& relPos, TMSF& absPos)
{
// Guard 1: bail if the game requests playback status before actually playing
if (player.trackFile == nullptr) {
#ifdef DEBUG
LOG_MSG("CDROM: GetAudioSub => game asked for playback position "
"before playing audio (ignoring)");
#endif
return false;
}
// Convert our running tally of played *track* frames to *Redbook* frames.
// We 'ceil' because if our track-frame tally lands in the middle of a (fractional)
// Redbook frame, then that Redbook frame would have to be considered played to produce
// even the smallest amount of track-frames played. This also accurately represents
// the very end of a sequence where the last Redbook frame might only contain a couple
// PCM samples - but the entire last 2352-byte Redbook frame is needed to cover those samples.
const Bit32u playedRedbookFrames = static_cast<Bit32u>(
ceil(static_cast<float>(REDBOOK_FRAMES_PER_SECOND * player.playedTrackFrames)
/ player.trackFile->getRate()) );
// Add that to the track's starting sector to determine our absolute current sector
const Bit32u currentSector = player.startSector + playedRedbookFrames;
track_const_iter track(GetTrack(currentSector));
// Guard 2: bail if the track is invalid
if (track == tracks.end()) {
#ifdef DEBUG
LOG_MSG("CDROM: GetAudioSub => playback position lands outside of our tracks");
#endif
return false;
}
track_num = track->number;
attr = track->attr;
bool CDROM_Interface_Image::GetAudioSub(unsigned char& attr,
unsigned char& track_num,
unsigned char& index,
TMSF& relative_msf,
TMSF& absolute_msf) {
// Setup valid defaults to handle all scenarios
attr = 0;
track_num = 1;
index = 1;
absPos = frames_to_msf(currentSector + 150);
relPos = frames_to_msf(currentSector - track->start);
uint32_t absolute_sector = 0;
uint32_t relative_sector = 0;
if (!tracks.empty()) { // We have a useable CD; get a valid play-position
track_iter track = tracks.begin();
// the CDs has been played and is at a valid position
if (player.trackFile && player.startSector) {
const uint32_t sample_rate = player.trackFile->getRate();
const uint32_t played_frames = (player.playedTrackFrames
* REDBOOK_FRAMES_PER_SECOND
+ sample_rate - 1) / sample_rate;
absolute_sector = player.startSector + played_frames;
track_iter current_track = GetTrack(absolute_sector);
if (current_track != tracks.end()) {
track = current_track;
relative_sector = absolute_sector >= track->start ?
absolute_sector - track->start : 0;
} else { // otherwise fallback to the beginning track
absolute_sector = track->start;
// relative_sector is zero because we're at the start of the track
}
// the CD hasn't been played yet or has an invalid position
} else {
for (track_iter it = tracks.begin(); it != tracks.end(); ++it) {
if (it->attr == 0) { // Found an audio track
track = it;
absolute_sector = it->start;
break;
} // otherwise fallback to the beginning track
}
}
attr = track->attr;
track_num = track->number;
}
absolute_msf = frames_to_msf(absolute_sector + 150);
relative_msf = frames_to_msf(relative_sector);
#ifdef DEBUG
LOG_MSG("CDROM: GetAudioSub => playing at %02d:%02d:%02d (on sector %u) "
"in track %u at its %02d:%02d:%02d (at its sector %d)",
absPos.min,
absPos.sec,
absPos.fr,
currentSector + 150,
track->number,
relPos.min,
relPos.sec,
relPos.fr,
static_cast<int>(currentSector) - track->start);
LOG_MSG("CDROM: GetAudioSub => position at %02d:%02d:%02d (on sector %u) "
"within track %u at %02d:%02d:%02d (at its sector %u)",
absolute_msf.min,
absolute_msf.sec,
absolute_msf.fr,
absolute_sector + 150,
track_num,
relative_msf.min,
relative_msf.sec,
relative_msf.fr,
relative_sector);
#endif
return true;
}