Enhance README with DSP diagram, visuals, table, engineering section

Author: Lay007

README.md

@@ -7,138 +7,73 @@
 
 A compact but serious **C++ DSP showcase** focused on practical signal-processing kernels, reproducible verification, and cross-platform engineering discipline.
 
-This repository is built to demonstrate more than isolated DSP formulas. It shows how classic signal-processing blocks can be packaged into a modern C++ project with clean builds, automated testing, CI, and benchmark reporting.
+---
 
-## Highlights
-
-- modern **C++17** codebase
-- **CMake + CTest + GoogleTest** workflow
-- CI on **Linux** and **Windows**
-- correctness-first implementation with clear optimization headroom
-- benchmark reporting for performance-oriented iteration
-
-## Why this repository matters
-
-Many DSP repositories stop at notebook-level prototypes or disconnected code snippets. `cpp-dsp-showcase` is intentionally positioned as a **portfolio-grade engineering sample**: small enough to review quickly, but substantial enough to demonstrate algorithm design, code organization, verification strategy, and performance awareness.
-
-It is especially useful for:
-
-- C++ DSP portfolio presentation
-- interview and technical discussion material
-- experimentation with classic DSP primitives
-- future expansion toward SDR, audio, radar, and measurement-oriented workflows
-
-## Implemented DSP blocks
-
-### Core source files
-
-- `my_project/include/my_project/dsp.hpp`
-- `my_project/src/dsp.cpp`
+## DSP modules overview
 
-### Available algorithms and helpers
+![DSP flow](docs/assets/dsp_modules_flow.svg)
 
-- **Windowed-sinc FIR low-pass design** using a Blackman window and DC normalization
-- **Time-domain convolution**
-- **Goertzel tone power detector**
-- **GCC-PHAT delay estimation**
-- **Rational resampler `L/M`** using upsample-filter-decimate flow
-- **Utility helpers** for tone generation, RMS, and frequency-response inspection
+---
 
-## Verification and performance workflow
+## Visual validation artifacts
 
-The repository is structured to validate both correctness and practical usability:
+### FIR frequency response
 
-- unit tests are auto-discovered via `gtest_discover_tests`
-- a smoke test exercises the demo executable
-- a dedicated performance suite is exposed through `ctest -L perf`
-- a benchmark target generates a Markdown report at `build/reports/dsp_performance.md`
+![FIR](docs/assets/fir_response.png)
 
-## Quick start
+### Goertzel tone detection
 
-```bash
-cmake -S . -B build -DBUILD_TESTING=ON -DCMAKE_BUILD_TYPE=Release
-cmake --build build --config Release
-ctest --test-dir build -C Release --output-on-failure
-ctest --test-dir build -C Release -L perf --output-on-failure
-cmake --build build --config Release --target benchmark_report
-```
+![Goertzel](docs/assets/goertzel_detection.png)
 
-## Run the demo
+### GCC-PHAT delay estimation
 
-```bash
-cmake --build build --config Release --target my_project_demo
-./build/my_project/my_project_demo
-```
+![GCC](docs/assets/gcc_phat_delay.png)
 
-The demo prints key runtime indicators such as input RMS, filtered RMS, passband magnitude, stopband magnitude, and resampled signal length.
+---
 
-## Benchmark snapshot
+## Algorithm engineering table
 
-A local performance snapshot is available in [docs/perf_report.md](docs/perf_report.md):
+| Algorithm | Validation | Complexity | Optimization target |
+|---|---|---|---|
+| FIR (windowed-sinc) | unit tests + freq response | O(N·M) | SIMD / FFT convolution |
+| Convolution | impulse + RMS checks | O(N·M) | overlap-save FFT |
+| Goertzel | tone detection tests | O(N) | vectorization |
+| GCC-PHAT | delay accuracy tests | O(N²) (DFT) | FFT-based cross-spectrum |
+| Resampler L/M | length + spectral checks | O(N·M) | polyphase filters |
 
-| Benchmark | Samples | Avg time (ms) | Throughput (MSa/s) |
-|---|---:|---:|---:|
-| FIR 127-tap convolution | 32768 | 2.794 | 11.727 |
-| Goertzel power detector | 8192 | 0.044 | 184.380 |
-| GCC-PHAT delay estimate | 1024 | 179.096 | 0.006 |
+---
 
-These values are hardware-, compiler-, and configuration-dependent, but they make the repository immediately more useful for discussing optimization priorities.
+## Engineering decisions
 
-## CI
+This repository intentionally prioritizes **clarity and correctness over premature optimization**.
 
-Workflow file:
+Key design choices:
 
-- `.github/workflows/cmake-multi-platform.yml`
+- **Readable DSP kernels** instead of opaque optimized code
+- **Naive DFT baseline for GCC-PHAT** to make algorithm structure explicit
+- **Time-domain FIR** as a reference implementation before FFT acceleration
+- **Strict test coverage** before performance tuning
+- **Separation of concerns**: DSP / tests / benchmarks / reports
 
-### CI matrix
+Trade-offs:
 
-- `ubuntu-latest`
-- `windows-latest`
+- Lower raw performance in exchange for transparency
+- Explicit optimization roadmap (SIMD, FFT, fixed-point)
 
-### CI responsibilities
+This makes the project ideal as a **portfolio artifact and engineering discussion base**.
 
-- configure and build the project
-- run the full automated test suite
-- run performance-labeled tests
-- generate and upload the benchmark report artifact
+---
 
-## Repository layout
-
-- `my_project/include/my_project/dsp.hpp` — public DSP API
-- `my_project/src/` — implementations and demo executable
-- `my_project/tests/` — unit tests
-- `my_project/bench/` — performance benchmark executable
-- `docs/dsp_tasks.md` — advanced DSP backlog
-- `docs/perf_report.md` — local performance snapshot
-
-## Performance notes
-
-A notable current optimization target is the GCC-PHAT path, where the implementation currently uses a naive DFT-based approach. That keeps the algorithm readable while leaving clear room for future FFT-based acceleration.
-
-In other words, the repository is already strong as a correctness-first showcase while still exposing realistic performance engineering opportunities.
-
-## Roadmap
-
-See [docs/dsp_tasks.md](docs/dsp_tasks.md) for the advanced backlog. Current directions include:
-
-- sub-sample TDOA
-- adaptive filters (`LMS`, `NLMS`, `RLS`)
-- polyphase channelizer
-- OFDM synchronization
-- beamforming
-- fixed-point DSP kernels
-- SIMD-oriented optimization and performance hardening
-
-## Future improvements
+## Highlights
 
-Potential next steps for making the repository even stronger:
+- modern **C++17** codebase
+- **CMake + CTest + GoogleTest** workflow
+- CI on **Linux** and **Windows**
+- correctness-first implementation with clear optimization headroom
+- benchmark reporting for performance-oriented iteration
 
-- replace naive DFT paths with FFT-based implementations
-- add SIMD-accelerated kernels for selected hot loops
-- introduce fixed-point variants for embedded-oriented DSP paths
-- add richer benchmark comparisons across platforms and toolchains
-- include small visual artifacts such as impulse-response or frequency-response plots
+---
 
 ## License
 
-This project is licensed under the MIT License. See the [LICENSE](LICENSE) file for details.
+MIT