libatrac3plus picks the codec parameter from the frame size and the
header's joint stereo flag, and the channel count plays no part. We
guessed joint stereo from the frame size and channel count instead, so
LocoRoco 2's MuiMui house music never started: the game writes a 2-channel
normal-stereo header for every track it streams, and that 0xC0 track holds
one mono sound unit per frame. Taken as joint stereo, its first frame failed
during setup, and the game retried forever.
Now the joint stereo flag comes from the track header, and the decoder's
channel count from the parameter it maps to, so that track decodes as mono
into both output channels, as on hardware. Low-level decoding, which has
no header, still goes by the frame size. Atrac2 saves the flag; older
states fall back to the guess.
Fixes#8647.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Setting data decodes and throws away the frames before the first sample,
so on hardware it costs a decoder setup plus that decode, with the caller
waiting: ~900us for mono Atrac3 and ~3.5ms for stereo Atrac3+, whatever the
buffer size (pspautotests threads/scheduling/callcosts). It was charged
100us.
Decoding a frame now costs what the same frame costs through
sceAudiocodecDecode, through the shared ME queue, instead of a flat
2300us. That's about the same for stereo Atrac3+ and less for Atrac3
(685us mono, ~1100us stereo). The first Atrac3+ frames after setup still
come out ~500us short.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
