🎉 live server seems to be working now

2026-05-14 14:29:57 +02:00
commit d72e439fd9
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--- a/third_party/sendspin-go/docs/NATIVE_RATE_FIX.md
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+# Native Sample Rate Fix
+
+## Issue
+When loading a 96kHz FLAC file, the server was:
+1. Resampling it down to 48kHz "for Opus compatibility"
+2. Then negotiating with client
+3. Client advertises 96kHz/24bit support
+4. Server can't match because it already downsampled to 48kHz
+5. Falls through to Opus at 48kHz
+
+**Result:** Hi-res 96kHz FLAC delivered as Opus 48kHz 😢
+
+## Root Cause: Premature Resampling
+
+In `internal/server/audio_source.go:91-95`:
+```go
+// If source is not 48kHz, wrap with resampler for Opus compatibility
+if source.SampleRate() != 48000 {
+    log.Printf("Resampling %s from %d Hz to 48000 Hz for Opus compatibility",
+        displayName, source.SampleRate())
+    return NewResampledSource(source, 48000), nil
+}
+```
+
+This was **premature optimization** - assuming Opus would be needed before checking what the client supports!
+
+## Fix Applied
+
+### 1. Removed Auto-Resampling
+`internal/server/audio_source.go`:
+```go
+// Note: We no longer auto-resample here. Sources are kept at native sample rate.
+// If Opus encoding is needed and source isn't 48kHz, resampling happens per-client in audio engine.
+// This allows PCM clients to receive hi-res audio at native rates!
+
+return source, nil
+```
+
+### 2. Updated Format Negotiation
+`internal/server/audio_engine.go` - `negotiateCodec()`:
+
+**Before:** Would pick any codec without checking if it matches the source
+**After:** Prioritizes formats in this order:
+1. **PCM at native sample rate** (preserves hi-res quality)
+2. Opus only if source is 48kHz (Opus native rate)
+3. FLAC (not implemented yet)
+4. Fallback to PCM
+
+```go
+// Check newer support_formats array first (spec-compliant)
+// Prioritize PCM at native rate to preserve hi-res audio quality
+for _, format := range client.Capabilities.SupportFormats {
+    // Check if client supports PCM at our native sample rate
+    if format.Codec == "pcm" && format.SampleRate == sourceRate && format.BitDepth == DefaultBitDepth {
+        return "pcm"
+    }
+}
+
+// If no PCM match at native rate, consider compressed codecs
+for _, format := range client.Capabilities.SupportFormats {
+    // Only use Opus if source is 48kHz (Opus native rate)
+    // For other rates, prefer PCM to avoid resampling
+    if format.Codec == "opus" && sourceRate == 48000 {
+        return "opus"
+    }
+}
+```
+
+## Expected Behavior Now
+
+### Test Tone (192kHz/24bit)
+- Client advertises: [192kHz/24bit PCM, ..., Opus]
+- Server has: 192kHz/24bit source
+- **Match:** PCM 192kHz/24bit ✅
+- **Delivery:** `pcm 192000Hz 2ch 24bit`
+
+### 96kHz FLAC
+- Client advertises: [192kHz/24bit, 176kHz/24bit, **96kHz/24bit**, ..., Opus]
+- Server has: 96kHz/24bit FLAC
+- **Match:** PCM 96kHz/24bit ✅
+- **Delivery:** `pcm 96000Hz 2ch 24bit`
+
+### 48kHz MP3
+- Client advertises: [..., 48kHz/16bit, Opus]
+- Server has: 48kHz/16bit MP3
+- **Match:** PCM 48kHz/16bit OR Opus 48kHz ✅
+- **Delivery:** `pcm 48000Hz 2ch 16bit` (PCM prioritized)
+
+### 44.1kHz MP3
+- Client advertises: [..., 44.1kHz/16bit, Opus]
+- Server has: 44.1kHz/16bit MP3
+- **Match:** PCM 44.1kHz/16bit ✅
+- **Delivery:** `pcm 44100Hz 2ch 16bit`
+
+## What About Opus for Non-48kHz?
+
+For now, Opus is **only** used if:
+1. Source is already 48kHz, AND
+2. Client advertises Opus support
+
+If source is non-48kHz (like 96kHz FLAC):
+- Server will ALWAYS prefer PCM at native rate
+- No resampling, preserves full hi-res quality
+- Client handles any resampling needed on their end
+
+**Future:** Could add per-client resampling for Opus if client specifically requests it and doesn't support native PCM rate. But for hi-res use cases, PCM is always better anyway!
+
+## Testing
+
+```bash
+# Rebuild
+go build -o resonate-server ./cmd/resonate-server
+
+# Test 1: 192kHz test tone (should use PCM 192kHz)
+./resonate-server -debug -no-tui
+
+# Test 2: 96kHz FLAC (should use PCM 96kHz, NOT resample to 48kHz)
+./resonate-server -debug -no-tui -audio ~/Downloads/Sample_BeeMoved_96kHz24bit.flac
+
+# Player should show:
+# - Test 1: "Stream starting: pcm 192000Hz 2ch 24bit"
+# - Test 2: "Stream starting: pcm 96000Hz 2ch 24bit"
+```
+
+## Benefits
+
+✅ Hi-res audio preserved at native sample rates
+✅ No unnecessary downsampling
+✅ PCM prioritized over lossy compression
+✅ Better sound quality for hi-res files
+✅ Still supports Opus when appropriate (48kHz sources)