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Simplify some combersome math statements

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With types refined, we can switch to cleaner integer
math and avoid casting (to float and back to ints), and also
avoid ceil((float) a / b) by using the pure-integer form
of (a + b - 1) / b
This commit is contained in:
krcroft 2020-02-05 23:14:56 -08:00
parent 0dd9eca6d6
commit eb1a9285fd
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GPG key ID: 4AD3678F4A2C291C
1 changed files with 23 additions and 17 deletions
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40
src/dos/cdrom_image.cpp
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@ -120,7 +120,8 @@ bool CDROM_Interface_Image::BinaryFile::seek(Bit32u offset)
uint64_t CDROM_Interface_Image::BinaryFile::decode(Bit16s *buffer, Bit32u desired_track_frames)
{
// Guard: only proceed with a valid file
if (file == nullptr) return 0;
if (file == nullptr)
return 0;
file->read((char*)buffer, desired_track_frames * BYTES_PER_REDBOOK_PCM_FRAME);
return (file->gcount() + BYTES_PER_REDBOOK_PCM_FRAME - 1) / BYTES_PER_REDBOOK_PCM_FRAME;
@ -203,9 +204,10 @@ Bit8u CDROM_Interface_Image::AudioFile::getChannels()
int CDROM_Interface_Image::AudioFile::getLength()
{
// Sound_GetDuration returns milliseconds so we covert to bytes
return sample ? static_cast<int>(round(
Sound_GetDuration(sample) * REDBOOK_PCM_BYTES_PER_MS)) : -1;
// Sound_GetDuration returns milliseconds but getLength()
// needs to return bytes, so we covert using PCM bytes/s
return sample ?
Sound_GetDuration(sample) * REDBOOK_PCM_BYTES_PER_MS : -1;
}
// initialize static members
@ -516,32 +518,36 @@ bool CDROM_Interface_Image::PlayAudioSector(uint64_t start, uint64_t len)
: &MixerChannel::AddSamples_m16_nonnative;
}
// Convert Redbook frames to Track frames, rounding up to whole integer frames.
// Round up to whole track frames because the content originated from whole redbook frames,
// which will require the last fractional frames to be represented by a whole PCM frame.
// Convert Redbook frames (len) to Track PCM frames, rounding up to whole integer frames.
// Note: the intermediate numerator in the calculation below can overflow uint32_t, so
// the variable types used must stay 64-bit.
player.playedTrackFrames = 0;
player.totalTrackFrames = static_cast<Bit32u>(ceil(static_cast<float>
(track_rate * player.totalRedbookFrames)
/ REDBOOK_FRAMES_PER_SECOND));
player.totalTrackFrames = (track_rate
* player.totalRedbookFrames
+ REDBOOK_FRAMES_PER_SECOND - 1) / REDBOOK_FRAMES_PER_SECOND;
#ifdef DEBUG
if (static_cast<int>(start) < track->start) {
LOG_MSG("CDROM: PlayAudioSector from sector %lu to %lu => "
"starting in the pregap of track %d [pregap %d, start %u, end %u]",
if (start < track->start) { //
LOG_MSG("CDROM: Play sector %lu to %lu in the pregap of track %d [pregap %d,"
" start %u, end %u] for %lu PCM frames at rate %lu",
start,
start + len,
track->number,
prev(track)->start - prev(track)->length,
track->start,
track->start + track->length);
track->start + track->length,
player.totalTrackFrames,
track_rate);
} else {
LOG_MSG("CDROM: PlayAudioSector from sector %lu to %lu => "
"in track %d [start %u, end %u]",
LOG_MSG("CDROM: Play sector %lu to %lu in track %d [start %u, end %u],"
" for %lu PCM frames at rate %lu",
start,
start + len,
track->number,
track->start,
track->start + track->length);
track->start + track->length,
player.totalTrackFrames,
track_rate);
}
#endif