Add support for NVDEC backend in video processing and enhance README documentation. Introduce a new script for extracting EasyCom sessions on specific GPUs, detailing session management and error handling. Update requirements.txt to include PyNvVideoCodec as an optional dependency. Refactor streaming_turn_model_directly.py to accommodate multiple decoder backends and improve frame indexing with ffprobe.

README.md

@@ -651,6 +651,35 @@ python streaming_turn_model_directly.py \
   --output features/direct/Session_1.pt
 ```
 
+The direct reader defaults to Decord. On NVIDIA systems, install
+`PyNvVideoCodec` and select the NVDEC backend explicitly:
+
+```bash
+python -m pip install PyNvVideoCodec
+
+CUDA_VISIBLE_DEVICES=0 python streaming_turn_model_directly.py \
+  --model-id /path/to/Qwen2.5-Omni-3B \
+  --easycom-session-dir /path/to/Main/Video_Compressed/Session_1 \
+  --end 24 \
+  --mode open-stream-replay \
+  --memory-seconds 20 \
+  --video-fps 2 \
+  --frame-cache-size 64 \
+  --decoder pynvcodec \
+  --decoder-gpu-id 0 \
+  --flash-attention-2 \
+  --device cuda:0 \
+  --output features/direct/Session_1_24s_pynvcodec.pt
+```
+
+The NVDEC backend uses ffprobe for exact display-order PTS indexing, one
+reconfigurable `SimpleDecoder` for pixel decode, and the existing ffmpeg PCM
+audio path. `--decoder-gpu-id` is relative to `CUDA_VISIBLE_DEVICES`, so it is
+normally `0` even when the worker is assigned a nonzero host GPU. Decoder RGB
+conversion can differ slightly; validate a short Decord/PyNvVideoCodec pair
+before extracting every session, and do not mix decoder backends across
+train/test splits.
+
 Matching `states.shape[0]` to the target is necessary but not sufficient.
 The direct reader also validates EasyCom's 20-Hz source inventory, source PTS
 monotonicity, dense duration, crop bounds, audio sample count, and causal