enricobuehler
75474dcc90
The vendored rate controller packs its wavelet block index into 16 bits (RDOperation.block_offset_saving), so a mode whose 32x32-block count exceeds u16::MAX wraps inside the controller and corrupts the bitstream — ~8K-class 4:4:4 territory. Compute the exact count (`block_count_32x32`, the counting walk of upstream init_block_meta, pinned against the validated Apple WaveletLayout) and expose `pyrowave_mode_fits_rdo`; the negotiator downgrades such a session to 4:2:0 before the Welcome (the honest-downgrade channel), and both encoders refuse outright if one slips through rather than emit a wrapped stream. Vendor patches: 0002-rdo-saving-clamp (analyze_rate_control.comp clamps the saving accumulation to the target, same overrun class as 0001; slangmosh.hpp regenerated), 0003-devel-encode-16bit-read (devel tool y4m 16-bit plane reads; tool-only, kept so the vendored source stays honest). Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
PyroWave
PyroWave is an intra-only video codec (practially speaking a still-image codec) that is optimized for extremely fast GPU encode (< ~0.1 ms encode and decode at 1080p, < ~0.2 ms at 4K). It is fully implemented in Vulkan compute shaders.
The targeted bit-rates are quite high (~200+ mbit/s) and the intended use case is local network game streaming over ethernet with absolute minimum latency where bandwidth is less of a concern.
It is integrated as part of my pyrofling project.
It is similar in scope to my master thesis from 2014, except the use case now is game streaming instead of adaptation of raw video to ethernet links.
Overview
Colorspace
Currently implemented YCbCr 4:2:0 and 4:4:4.
Wavelets
The images are transformed with the Discrete Wavelet Transform using CDF 9/7 filter. This is basically the exact same as JPEG2000.
Exact rate control
The encoder can target exact maximum bitrate for an encoded image.
Trivial "entropy" coding
The encoding of coefficients is trivial compared to normal image codecs, and is responsible for a large increase in bit-rate, especially at higher compression ratios. This simplicity massively improves encode/decode performance, since it's extremely parallelizable. It also makes it possible to do a single-pass exact rate control for an entire image.
It should be possible in theory to add a more proper entropy coder to the encoded bit-planes to achieve somewhat competent compression, but that has not been explored and is out of scope. High Throughput JPEG2000 is likely a good place to look for that anyway.
Robustness against packet loss
Being intra-only and encoding 64x64 blocks of coefficients in isolation ensures great recovery against packet loss. PyroWave has been battled tested over long distance streaming over fiber links.
Bitstream definition
Building
PyroWave is intended to be built alongside PyroFling with Granite in the normal case.
Standalone C API
NOTE: This API is still under development and the API/ABI is not yet quite stable.
A small portion of Granite needs to be checked out.
bash checkout_granite.sh
Build normally with CMake and a C API is installed.
$ mkdir build
$ cd build
$ cmake .. -DCMAKE_INSTALL_PREFIX=output -DCMAKE_BUILD_TYPE=Release -G Ninja
$ ninja install
[0/1] Install the project...
-- Install configuration: "Release"
-- Installing: ...../build/output/include/pyrowave/pyrowave.h
-- Installing: ...../build/output/lib/libpyrowave-shared.so.0.0.0
-- Installing: ...../build/output/lib/libpyrowave-shared.so.0
-- Installing: ...../build/output/lib/libpyrowave-shared.so
-- Installing: ...../build/output/share/pyrowave-shared/cmake/pyrowave-sharedConfig.cmake
-- Installing: ...../build/output/share/pyrowave-shared/cmake/pyrowave-sharedConfig-release.cmake
-- Installing: ...../build/output/share/pkgconfig/pyrowave-shared.pc
The build is tested on Linux, MinGW, msys2 and MSVC.
See pyrowave-c-test which unit tests the shared C API.
That test also serves as a basic user guide for the API.
build-steamrt.sh builds against the Sniper SDK and is also supported.
Local development and CLI
For the sample and test applications in this repo however, check out
the full https://github.com/Themaister/Granite before invoking CMake.
Build with -DPYROWAVE_DEVEL=ON to get the "full" build.
git clone --depth 1 --recursive --shallow-submodules https://github.com/Themaister/Granite Granite
Basic encoder/decoder CLI
The basic CLI takes a y4m and dumps out a raw bitstream. This is just intended for local testing.
pyrowave-encode test.y4m out.wave 400000
This encodes a raw bitstream where each frame consumes maximum 400 KB. To decode back to y4m:
pyrowave-decode out.wave out.y4m