Upstream sizes the raw quantized-payload worst-case buffer at
aligned_width*aligned_height*2 bytes: real headroom for 4:2:0's 1.5
samples/px, but half of what 4:4:4's 3 samples/px can produce. Busy 4:4:4
content overruns the buffer on the GPU and corrupts the adjacent meta/bucket
suballocations — nondeterministic corrupt bitstreams and encoder crashes at
ANY target bitrate (smooth content never trips it, which is why 4:2:0 and
simple 4:4:4 both look fine). Found by the Phase-0 measurement matrix for
design/pyrowave-444-hdr.md; fix validated alone via upstream's own devel
tools on the RTX 5070 Ti: deterministic byte-identical outputs across runs,
1080p + 4K, 8- and 16-bit, PSNR at the expected operating points.
Patch lives in crates/pyrowave-sys/patches/ and vendor-pyrowave.sh now
re-applies patches on re-vendor; PUNKTFUNK-VENDOR.txt records it. Upstream
report to follow. No wire/ABI change; 4:2:0 sizing unchanged.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
