github/duckstation
1
0
Fork 0
mirror of https://github.com/stenzek/duckstation.git synced 2025-06-11 22:07:20 +00:00
Code Issues Packages Projects Releases Wiki Activity

CDROM: Improve SeekL -> ReadN timing

Browse Source 
See comments - Mech stops at target Data - 2, or SubQ target.
This commit is contained in:
Stenzek 2024-12-02 17:23:46 +10:00
parent 71e1032605
commit 6756c96fa2
No known key found for this signature in database
1 changed files with 14 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

22
src/core/cdrom.cpp
View File

@ -46,6 +46,7 @@ enum : u32
SECTOR_HEADER_SIZE = CDImage::SECTOR_HEADER_SIZE,
MODE1_HEADER_SIZE = CDImage::MODE1_HEADER_SIZE,
MODE2_HEADER_SIZE = CDImage::MODE2_HEADER_SIZE,
SUBQ_SECTOR_SKEW = 2,
XA_ADPCM_SAMPLES_PER_SECTOR_4BIT = 4032, // 28 words * 8 nibbles per word * 18 chunks
XA_ADPCM_SAMPLES_PER_SECTOR_8BIT = 2016, // 28 words * 4 bytes per word * 18 chunks
XA_RESAMPLE_RING_BUFFER_SIZE = 32,
@ -2967,10 +2968,13 @@ bool CDROM::CompleteSeek()
if (seek_okay)
{
const CDImage::SubChannelQ& subq = GetSectorSubQ(s_reader.GetLastReadSector(), s_reader.GetSectorSubQ());
s_state.current_lba = s_reader.GetLastReadSector();
if (subq.IsCRCValid())
{
// seek and update sub-q for ReadP command
s_state.last_subq = subq;
s_state.last_subq_needs_update = false;
const auto [seek_mm, seek_ss, seek_ff] = CDImage::Position::FromLBA(s_reader.GetLastReadSector()).ToBCD();
seek_okay = (subq.absolute_minute_bcd == seek_mm && subq.absolute_second_bcd == seek_ss &&
subq.absolute_frame_bcd == seek_ff);
@ -2984,12 +2988,16 @@ bool CDROM::CompleteSeek()
seek_okay = (s_state.last_sector_header.minute == seek_mm && s_state.last_sector_header.second == seek_ss &&
s_state.last_sector_header.frame == seek_ff);
if (seek_okay)
if (seek_okay && !s_state.play_after_seek && !s_state.read_after_seek)
{
// after reading the target, the mech immediately does a 1T reverse
const u32 spt = GetSectorsPerTrack(s_state.current_subq_lba);
SetHoldPosition(s_state.current_subq_lba,
(spt <= s_state.current_subq_lba) ? (s_state.current_subq_lba - spt) : 0);
// This is pretty janky. The mech completes the seek when it "sees" a data header
// 2 sectors before the seek target, so that a subsequent ReadN can complete nearly
// immediately. Therefore when the seek completes, SubQ = Target, Data = Target - 2.
// Hack the SubQ back by 2 frames so that following seeks will read forward. If we
// ever properly handle SubQ versus data positions, this can be removed.
s_state.current_subq_lba =
(s_state.current_lba >= SUBQ_SECTOR_SKEW) ? (s_state.current_lba - SUBQ_SECTOR_SKEW) : 0;
s_state.last_subq_needs_update = true;
}
}
}
@ -3016,8 +3024,6 @@ bool CDROM::CompleteSeek()
}
}
}
s_state.current_lba = s_reader.GetLastReadSector();
}
return seek_okay;
@ -3234,7 +3240,7 @@ void CDROM::DoSectorRead()
// so that multiple sectors could be read in one back, in which case we could just "look ahead" to grab the
// subq, but I haven't got around to it. It'll break libcrypt, but CC doesn't use it. One day I'll get around to
// doing the refactor.... but given this is the only game that relies on it, priorities.
s_reader.GetMedia()->GenerateSubChannelQ(&s_state.last_subq, s_state.current_lba + 2);
s_reader.GetMedia()->GenerateSubChannelQ(&s_state.last_subq, s_state.current_lba + SUBQ_SECTOR_SKEW);
}
}
else