Initial audio support

SHADER_CONTRACT.md

@@ -125,6 +125,11 @@ struct ShaderContext
     float bypass;
     int sourceHistoryLength;
     int temporalHistoryLength;
+    float2 audioRms;
+    float2 audioPeak;
+    float audioMonoRms;
+    float audioMonoPeak;
+    float4 audioBands;
 };
 ```
 
@@ -140,6 +145,11 @@ Fields:
 - `bypass`: `1.0` when the layer is bypassed, otherwise `0.0`.
 - `sourceHistoryLength`: number of usable source-history frames currently available.
 - `temporalHistoryLength`: number of usable temporal frames currently available for this layer.
+- `audioRms`: left/right RMS level for the audio block synchronized with the rendered output frame.
+- `audioPeak`: left/right peak level for the same synchronized audio block.
+- `audioMonoRms`: mono RMS level derived from left/right.
+- `audioMonoPeak`: mono peak level derived from left/right.
+- `audioBands`: four smoothed, normalized low-to-high frequency bands.
 
 ## Helper Functions
 
@@ -149,6 +159,8 @@ The wrapper provides:
 float4 sampleVideo(float2 uv);
 float4 sampleSourceHistory(int framesAgo, float2 uv);
 float4 sampleTemporalHistory(int framesAgo, float2 uv);
+float4 sampleAudioWaveform(float x);
+float4 sampleAudioSpectrum(float x);
 ```
 
 `sampleVideo` samples the live decoded source video.
@@ -157,6 +169,10 @@ float4 sampleTemporalHistory(int framesAgo, float2 uv);
 
 `sampleTemporalHistory` samples previous pre-layer input frames for temporal shaders that request `preLayerInput` history. `framesAgo` is clamped into the available range. If no temporal history is available, it falls back to `sampleVideo`.
 
+`sampleAudioWaveform` samples the current synchronized audio waveform texture. `x` is normalized `0..1`; returned waveform channels are encoded from `-1..1` into `0..1`.
+
+`sampleAudioSpectrum` samples the current synchronized audio spectrum texture. Values are normalized `0..1`.
+
 Example:
 
 ```slang