README: explain the llama.cpp + codec.cpp split; llama.rn usage

README.md

@@ -33,9 +33,25 @@ hf download BricksDisplay/codec.cpp-gguf ibm-research--DAC.speech.gguf --local-d
 ./build/codec-cli decode --model codecs/ibm-research--DAC.speech.gguf --codes codes.npy --out decoded.wav
 ```
 
-Build instructions, GPU flags and the Python API are in the
+Python (`pip install .` in a codec.cpp checkout; see
+[python/README.md](https://github.com/mybigday/codec.cpp/blob/main/python/README.md)):
+
+```python
+import codec_cpp, soundfile as sf
+
+ctx = codec_cpp.Model("codecs/ibm-research--DAC.speech.gguf").context()
+pcm, sr = sf.read("speech.wav", dtype="float32")
+codes = ctx.encode(pcm, sr)          # int32 (n_frames, n_q)
+audio, sr = ctx.decode(codes)
+```
+
+Build instructions and GPU flags are in the
 [codec.cpp README](https://github.com/mybigday/codec.cpp).
 
+These codecs are also the audio side of TTS models: there a llama.cpp LM
+backbone writes the codes and codec.cpp turns them into audio (see the
+`*-GGUF` TTS repos of this organization).
+
 ## License
 
 Each codec keeps its original license: DAC.speech CDLA-Permissive-2.0, NeMo Nano Codec the NVIDIA Open Model License, WavTokenizer MIT.