feat(audio): support LPCM and fix waveform distortion

[edisonmartinsmkt]

This update adds automatic detection and conversion of LPCM (Linear PCM) audio files — a format commonly generated by Google Text-to-Speech — ensuring proper sample rate and compatibility.

✅ The following formats were tested and confirmed working:
m4a, mp3, mp4, wav, opus, oga, ogg, and lpcm.

🧪 During testing, the resulting audio files consistently displayed waveform previews (waves) on WhatsApp for Android, iOS, and Web.

Summary by Sourcery

Support automatic detection and conversion of LPCM audio streams in the WhatsApp integration to fix distorted waveforms and ensure cross-platform compatibility.

New Features:

• Automatically detect LPCM audio URLs and apply raw PCM ffmpeg settings for conversion

Bug Fixes:

• Fix waveform distortion in WhatsApp audio previews by correctly handling LPCM streams

Build:

• Add 'audio-decode' dependency to enable LPCM processing

[sourcery-ai]

Reviewer's Guide

Introduces automatic detection and handling of LPCM audio streams in the WhatsApp integration by adjusting the ffmpeg invocation when encountering raw PCM input, and adds a new dependency to support LPCM decoding.

Sequence Diagram for LPCM Audio Processing

sequenceDiagram
    participant AudioSource
    participant BaileysStartupService
    participant FFMpegProcess as ffmpeg

    AudioSource->>BaileysStartupService: Provides audio (e.g., URL to .lpcm file)
    BaileysStartupService->>BaileysStartupService: isLpcm = checkAudioFormat(audio)
    alt isLpcm is true
        BaileysStartupService->>BaileysStartupService: Log "Detected LPCM input"
        BaileysStartupService->>FFMpegProcess: Initialize with LPCM settings (s16le, 24000Hz, 1ch)
    else isLpcm is false
        BaileysStartupService->>FFMpegProcess: Initialize with default settings for other formats
    end
    BaileysStartupService->>FFMpegProcess: Set output to ogg/libopus, no video
    FFMpegProcess->>BaileysStartupService: Processed audio stream (OGG/Opus)
    BaileysStartupService-->>AudioSource: Returns processed OGG audio stream

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Updated Class Diagram for BaileysStartupService

classDiagram
  class ChannelStartupService {
    %% Base class placeholder
  }
  class BaileysStartupService {
    -logger: Logger
    +processAudio(audio: string | Buffer) : Promise~PassThrough~
  }
  BaileysStartupService --|> ChannelStartupService

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File-Level Changes

Change	Details	Files
Detect and convert LPCM audio streams before transcoding	Added isLpcm flag by matching .lpcm URLs Introduced conditional ffmpeg.inputFormat and inputOptions for raw PCM Wrapped ffmpeg invocation in a variable to apply LPCM-specific settings	src/api/integrations/channel/whatsapp/whatsapp.baileys.service.ts
Add audio-decode package to dependencies	Bumped package.json with "audio-decode": "^2.2.3"	package.json

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