gurix
3dfcbbeaf5
- Change RunSynthesis signature to accept injected config map (D-10) - Replace hardcoded synth.ClassFreqConfigs with passed-in freqCfgs - Update all three RunSynthesis calls in encode tests to pass synth.ClassFreqConfigs
68 lines
2.2 KiB
Go
68 lines
2.2 KiB
Go
package encode
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import (
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"fmt"
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"os"
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lame "github.com/sjzar/go-lame"
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"github.com/netsynth/netsynth/classify"
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"github.com/netsynth/netsynth/synth"
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)
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// EncodeMP3 writes stereo PCM frames to an MP3 file at the given path.
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// Encoding parameters: sampleRate Hz, 128 kbps, stereo, quality 5.
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// Per D-13 (44100 Hz CD quality) and D-14 (128 kbps bitrate).
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// CRITICAL: InitParams() is called after all Set* calls (go-lame Pitfall 1).
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func EncodeMP3(outputPath string, frames [][2]float64, sampleRate int) error {
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f, err := os.Create(outputPath)
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if err != nil {
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return fmt.Errorf("create output file: %w", err)
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}
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defer f.Close()
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wr := lame.NewWriter(f)
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wr.Encoder.SetInSamplerate(sampleRate)
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wr.Encoder.SetOutSamplerate(sampleRate)
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wr.Encoder.SetNumChannels(2)
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wr.Encoder.SetBitrate(128)
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wr.Encoder.SetQuality(5)
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wr.Encoder.InitParams() // MUST be called after all Set* calls
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pcmBytes := synth.StereoFramesToInt16Bytes(frames)
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if _, err := wr.Write(pcmBytes); err != nil {
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return fmt.Errorf("write PCM to LAME encoder: %w", err)
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}
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if err := wr.Close(); err != nil {
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return fmt.Errorf("finalize MP3: %w", err)
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}
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return nil
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}
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// RunSynthesis consumes a slice of WindowSnapshots, renders audio via OscillatorBank,
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// and encodes to MP3 at outputPath.
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// freqCfgs is the merged config map from config.Load (D-10: injected, not hardcoded).
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// Returns an error if zero packets were captured (D-16 / OUT-03).
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// The zero-packet guard runs BEFORE file creation to avoid leaving an empty file on disk.
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func RunSynthesis(snapshots []classify.WindowSnapshot, outputPath string, freqCfgs map[classify.TrafficClass]synth.FreqConfig) error {
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// D-16 / OUT-03: Zero-packet guard — check BEFORE creating output file
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var totalPackets int64
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for _, snap := range snapshots {
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totalPackets += snap.TotalPackets
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}
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if totalPackets == 0 {
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return fmt.Errorf("no packets captured: output MP3 not written (empty capture produces no audio)")
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}
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// Render all windows to stereo frames
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bank := synth.NewBank(1.0, freqCfgs) // tau=1.0s per D-07
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var allFrames [][2]float64
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for _, snap := range snapshots {
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frames := bank.RenderWindow(snap)
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allFrames = append(allFrames, frames...)
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}
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// Encode to MP3
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return EncodeMP3(outputPath, allFrames, synth.SampleRate)
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}
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