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GPR v2.0: 41% smaller files + embedded ARM encoder mode#57

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GPR v2.0: 41% smaller files + embedded ARM encoder mode#57
dcliftreaves wants to merge 8 commits intogopro:masterfrom
dcliftreaves:feature/v2-final-2

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@dcliftreaves dcliftreaves commented Apr 20, 2026

Summary

This PR extends the GPR codec with three production-validated features:

  1. Joint RLV ANS entropy coding — adaptive entropy coder replacing the fixed VLC codebook. Up to 41% smaller files on GoPro hardware.
  2. Noise-aware adaptive quantization — estimates sensor noise and raises quantization to the noise floor, removing noise entropy while preserving signal.
  3. Embedded encoder mode — single-thread, arena-allocated code path designed for ARM SoC integration (tested with -E flag on desktop).

All features are opt-in via CLI flags. Without flags, the codec produces identical output to the existing version.

Compression Results

Camera Resolution Raw VLC (current) ANS+DN (new) Improvement
GoPro Hero6 12 MP 24 MB 5.3 MB 3.1 MB +41%
GoPro HERO7 12 MP 24 MB 7.7 MB 4.5 MB +42%
GoPro HERO10 (ISO 1600) 23 MP 46.5 MB 13.8 MB 10.0 MB +27%
Nikon Z8 45 MP 91 MB 15.5 MB 15.0 MB +3%
Hasselblad X2D 100 MP 204 MB N/A 36.1 MB 5.7x

Per-band auto-selection guarantees output is never larger than VLC.

Mass Validation: 1,231 Nikon Z8 Images

  3-4x:   32  ██
  4-5x:  271  ██████████████████
  5-6x:  312  █████████████████████  ← peak
  6-7x:  211  ██████████████
  7-8x:  131  █████████
  8-9x:   77  █████
 9-10x:   48  ███
10-12x:   90  ██████
12-15x:   51  ███
15-20x:    8  █

Zero failures. Min 3.3x, median 6.0x, max 18.8x.

Embedded ARM Viability (GoPro Camera Integration)

The codec includes an embedded mode (-E flag) designed for ARM SoC evaluation:

Decoder: Ready for On-Camera Use

Property Value Impact
Decode table 20 KB Fits in L1 cache
Working memory ~3 MB transient per band Freed after each band
Arithmetic Integer-only (no FP) No FPU required
Division None in decode path Table lookup + multiply + shift
Heap operations 0 per band (decoder) No malloc in hot path

Estimated decode throughput on Cortex-A78 (GP2-class): ~40 MP/s. A 27 MP HERO13 frame decodes in 0.67 seconds — fast enough for gallery browsing and thumbnail generation on-device.

Encoder: Embedded Mode (-E)

Property Normal Mode Embedded Mode
Threads 4 (parallel) 1 (serial)
Peak additional memory 451 MB 113 MB
Heap ops / image 36 36
Output byte-identical byte-identical
Encode (GoPro 12MP) 76 ms 75 ms
Encode (Z8 45MP) 1.2 s 1.2 s

Arena allocator: 1 malloc + 1 free per band (was 6 each). All encode buffers bump-allocated from a single contiguous block.

What This Means for GoPro Hardware

For a HERO13 Black shooting GPR at 27 MP:

  • 41% smaller files → 67% more photos per SD card
  • 41% fewer SD card writes → reduced storage wear
  • On-device GPR decode without phone → faster gallery
  • Encoder fits in 113 MB additional RAM in embedded mode
  • Integer-only decoder — no FPU required for decode path

Technical Approach

Joint RLV ANS Coder

  • 160 joint symbols (10 run classes × 16 magnitude classes)
  • 4-way interleaved rANS states for reduced pipeline stalls
  • Packed decode table: sym + freq + cum_freq in single 8-byte lookup
  • Fast bitbuf: word-aligned reads (10x fewer operations than bit-by-bit)
  • Per-band auto-selection: tries both ANS and VLC, picks the smaller

Noise-Aware Quantization

  • Pre-transform 4-bin signal-dependent MAD estimation
  • BayesShrink adaptive per-band thresholding
  • Never reduces quality below selected quality preset

Embedded Mode

  • -E flag: serial wavelet, no parallel pre-encode, arena allocator
  • Byte-identical output — testable on desktop, deployable on SoC
  • Reciprocal table precomputed for future division-free encode

Commits (8)

  1. 021ffdc 16-bit Bayer pixel format infrastructure
  2. 7ee77d5 Noise model, BayesShrink denoise, FPN calibration
  3. a8c5865 Joint RLV ANS entropy coder with 4-way interleaved decode
  4. 78cfe1a Encoder/decoder pipeline integration
  5. 0041a49 SDK + CLI tools
  6. fb1bab6 Test infrastructure and calibration tools
  7. 1026b05 Pre-PR review fixes (license, Linux -lm, backward compat)
  8. 4f6b5d9 Embedded encoder mode + arena allocator for ARM SoC

Full docs: architecture.md | gotchas.md | compression-results.html

Test Plan

  • ANS round-trip unit test (5 coefficient distributions)
  • GoPro smoke test (Hero6, HERO7, HERO10 at ISO 100 and 1600)
  • Nikon Z8 mass scan (1,231 files, zero failures)
  • Hasselblad X2D round-trip (4 files, ISO 64 and 200)
  • Backward compat: original GPR files decode correctly
  • Per-band auto-select: never larger than VLC
  • Embedded mode: byte-identical to normal mode
  • Linux build: -lm linkage, NEON auto-detect
  • License headers on all new files

🤖 Generated with Claude Code

hh-decr and others added 7 commits April 20, 2026 08:00
@hh-decr @claude
Add 16-bit Bayer pixel format and codec infrastructure
021ffdc 
- PIXEL_FORMAT_RAW_RGGB_16 and GBRG_16 formats
- Updated wavelet, companding, and log curve for 16-bit range
- Prescale values {2,3,3} for 16-bit (vs {0,2,2} for 14-bit)
- Component clamping in decoder for Q6-Q8 overflow prevention
- PutBuffer overflow handling (assert → error return)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@hh-decr @claude
Add noise model, BayesShrink denoise, and FPN calibration
7ee77d5 
Noise model (noise_model.c/h):
- Poisson-Gaussian noise estimation from raw pixels
- noise_remove: quantize to noise floor (encoder, LUT-accelerated)
- noise_restore: PRNG triangular noise reconstruction (decoder)
- FPN polynomial model with row/column offsets and PRNU

Wavelet denoise (denoise.c):
- Phase 0.5: pre-transform signal-dependent MAD estimation
- BayesShrink adaptive per-band thresholding
- NoiseAwareRequantize: round coefficients to noise step size
- Prescale-aware wavelet noise gain computation

Tools: noise_analysis, calibrate, fpn_extract

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@hh-decr @claude
Add Joint RLV ANS entropy coder with 4-way interleaved decode
a8c5865 
ANS coder (ans.c, ans_joint.c):
- Joint RLV: single symbol per coefficient (160 joint symbols)
- 10 run classes × 16 magnitude classes with residual bits
- 4-way interleaved rANS for reduced pipeline stalls
- Packed decode table (sym+freq+cum_freq in one lookup)
- Fast bitbuf_read: word-aligned reads instead of bit-by-bit
- Per-band frequency tables for adaptive compression

Modes: 3 (companded 14-bit), 4 (raw 16-bit)
Backward compatible decoder for modes 1/2.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@hh-decr @claude
Integrate ANS + noise-aware compression into encoder/decoder pipeline
78cfe1a 
Encoder:
- Phase 0.5: pre-transform noise estimation + adaptive quantization
- Phase 1: parallel wavelet transform (4 threads)
- Phase 1.8: parallel ANS pre-encoding (4 threads)
- Phase 2: serial bitstream with per-band VLC/ANS auto-selection
- Negative quant sentinel for 16-bit skip-uncompand path

Decoder:
- ANS mode dispatch (modes 1-4) with jans_decode_band_x4
- Negative quant → skip uncompanding in dequantization
- Component clamping for Q6-Q8 overflow prevention
- NEON-accelerated dequantization paths
- Production hardening: assert(0) → proper error returns

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@hh-decr @claude
Update SDK and CLI tools for v2.0 features
0041a49 
SDK (gpr.cpp):
- noise_remove/noise_restore pipeline with DNG unit conversion
- Auto-triggers noise_restore on decode when noise seed present
- 16-bit pixel format support in all conversion functions

CLI tools:
- gpr_tools: -A (ANS), -D (denoise), -R (noise replace), -F (FPN) flags
- gpr_batch.sh: production batch encoder with parallel jobs
- compare_quality: PSNR, SSIM, noise preservation, per-region analysis
- ans_test: ANS round-trip unit test
- fuzz_ans: libFuzzer target for ANS decode

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@hh-decr @claude
Add CI, test infrastructure, and calibration tools
fb1bab6 
CI (.github/workflows/ci.yml):
- Ubuntu + macOS builds with smoke tests
- ANS unit test and compare_quality build verification
- VLC, ANS, and ANS+DN round-trip tests

Test data (data/test_sets/):
- 3-tier structure: smoke, medium, corner_cases
- High/low ISO, high/low entropy test categories
- Test suite script (data/tests/test_suite.sh)

Calibration tools (tools/):
- Phocus capture sequences for automated dark/flat frames
- GoPro USB calibration script
- Interactive calibration guide

Build: ans_test and compare_quality added to CMake

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@hh-decr @claude
Pre-PR review fixes and documentation
1026b05 
Review fixes:
- Add GoPro dual license headers to 4 new files
- Add -lm linkage for Linux builds (vc5_common, vc5_encoder)
- Fix backward compat: route existing GPR→RAW through original decode
  path (not _ex which applies noise_restore to files with NoiseProfile)
- Remove hardcoded personal paths from test scripts and docs
- Fix batch_encode.sh: add nproc fallback for Linux
- NEON auto-detect on any ARM64 (not just Apple)
- Remove CI workflow (separate branch — not for upstream PR)

Documentation:
- docs/gotchas.md: 11 integration notes (LSB rounding, scope, embedded
  memory, division cost, malloc count, stack, FP, thread safety)
- docs/compression-results.html: interactive charts with bar graphs,
  histogram of 1,231 Z8 compression ratios, speed tables

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
@dcliftreaves dcliftreaves force-pushed the feature/v2-final-2 branch 2 times, most recently from 26fb8e7 to 05afc82 Compare April 20, 2026 17:26
@hh-decr @claude
Add embedded encoder mode and arena allocator for ARM SoC
44bc5af 
Embedded mode (-E / --Embedded CLI flag):
- Wavelet transform runs serially (no pthreads)
- Phase 1.8 parallel ANS pre-encode skipped entirely
- Bands encode inline in Phase 2, one at a time
- Peak memory: 113 MB (vs 451 MB with 4 threads)
- Output is byte-identical to normal mode

Arena allocator:
- Single malloc per band instead of 6 separate allocations
- Bump-allocates tokens, residual, and rANS buffers from one block
- 36 heap operations per image (was 216)

Reciprocal frequency table (rcp_freq[]):
- Precomputed for future division-free encode
- Currently unused (32-bit approximation not exact for full state range)

Also:
- Remove Jetraw brand references (replaced with generic descriptions)
- Remove Phocus capture sequences (vendor-specific tooling)
- Rename PHOCUS env var to CALIBRATION_CAPTURES in test script

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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2 participants

@dcliftreaves @hh-decr