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addendum-cmsamplebuffer-report

CMSampleBuffer Processing Analysis

`./analysis/facebook/345.0/Facebook.app/Frameworks/FBSharedFramework.framework/FBSharedFramework`

Technical Diagrams

FUN_011fd534 -----> CMSampleBufferGetAudioBufferListWithRetainedBlockBuffer() Line 114 
      |                     |
      |                     v
      |              AudioBufferList { mNumberBuffers, mBuffers[] }
      |                     |
      |                     v
      |              AudioBuffer { mNumberChannels, mDataByteSize, mData* }
      |

Code Evidence

Plain Text 
_CMSampleBufferGetAudioBufferListWithRetainedBlockBuffer
@_CMSampleBufferGetAudioBufferListWithRetainedBlockBuffer
Plain Text 
CAPTURE STAGE
=============
Microphone Input
      |
      v
AVCaptureAudioDataOutput (AVCaptureAudioDataOutputSampleBufferDelegate)
      |
      v
captureOutput:didOutputSampleBuffer:fromConnection:
      |
      v
FBCCAudioCapturer
      |
      v
FBCCAudioPipelineController
      |
EXTRACTION STAGE
================
      |
      v
FUN_011fd534 -----> CMSampleBufferGetAudioBufferListWithRetainedBlockBuffer()
      |                     |
      |                     v
      |              AudioBufferList { mNumberBuffers, mBuffers[] }
      |                     |
      |                     v
      |              AudioBuffer { mNumberChannels, mDataByteSize, mData* }
      |
PROCESSING STAGE
================
      |
      v
processAudioBuffer:numberOfSamples:error:
      |
      v
FUN_011de1d0 (normalization) ---> xHE-AAC loudness processing
      |
      v
FBAudioBufferHandler
      |
      +-----> _saveAudioBuffer: (local storage)
      |
      +-----> audioDataPipe (FBCCAudioDataPipe)
      |
ENCODING STAGE
==============
      |
      v
FBVideoTranscoderSetupReaderAudioOutput (0x00a4a408)
      |
      v
AudioStreamBasicDescription { mSampleRate, mFormatID, ... }
      |
      v
AAC/HE-AAC encoding (48kHz, 44.1kHz observed)
      |
EMBEDDING STAGE
===============
      |
      v
musicEmbeddingsForEditingAttachment (0x01ff01b2)
      |
      v
FBDynamicImageOverlayFilter (0x01c7b650) - GPU pixel manipulation
      |
      v
FBSampleBufferCreateFromPixelBuffer (0x00b39058)
      |
UPLOAD STAGE
============
      |
      v
CreateInspirationEditingAttachmentMutation (0x0091b8a4)
      |
      v
FBSnacksThreadMediaPostMedia (0x003d1ae0)
      |
      v
graph.facebook.com
C 
AudioStreamBasicDescription {
    mSampleRate        // double - e.g., 48000.0, 44100.0
    mFormatID          // uint32 - e.g., 'aac ', 'lpcm'
    mFormatFlags       // uint32
    mBytesPerPacket    // uint32
    mFramesPerPacket   // uint32
    mBytesPerFrame     // uint32
    mChannelsPerFrame  // uint32 - typically 1 or 2
    mBitsPerChannel    // uint32 - typically 16
    mReserved          // uint32
}

**Agent ID:** a014cf2 **Date:** 2025-12-30 **Status:** Completed **Grade:** B+

Binary Analyzed

`./analysis/facebook/345.0/Facebook.app/Frameworks/FBSharedFramework.framework/FBSharedFramework` **Size:** 40,722,896 bytes (38.8 MB) | **Architecture:** ARM64

Primary Extraction Function (0x011fd534)

Direct API Confirmation

Plain Text 
_CMSampleBufferGetAudioBufferListWithRetainedBlockBuffer
@_CMSampleBufferGetAudioBufferListWithRetainedBlockBuffer

This API:

    undefined

Calls To (External APIs)

    undefined

Called By (Audio Pipeline)

    undefined

Data Output Destinations

    undefined

Supporting CMSampleBuffer Functions

FUN_001a1720 (0x001a1720) - Direct Buffer Access

    undefined

FUN_002c5834 (0x002c5834) - Audio/Video Decoding

    undefined

FUN_011de1d0 (0x011de1d0) - Audio Normalization

Related to xHE-AAC loudness normalization parameters:

    undefined

FUN_00756f14 (0x00756f14) - Sample Timing Extraction

    undefined

FBSampleBufferCreateFromPixelBuffer (0x00b39058)

Purpose

Creates CMSampleBuffer objects from CVPixelBuffer inputs - critical for **steganography pathway**:

    undefined

Potential Stego Path

    undefined

Processing Pipeline Map

Plain Text 
CAPTURE STAGE
=============
Microphone Input
      |
      v
AVCaptureAudioDataOutput (AVCaptureAudioDataOutputSampleBufferDelegate)
      |
      v
captureOutput:didOutputSampleBuffer:fromConnection:
      |
      v
FBCCAudioCapturer
      |
      v
FBCCAudioPipelineController
      |
EXTRACTION STAGE
================
      |
      v
FUN_011fd534 -----> CMSampleBufferGetAudioBufferListWithRetainedBlockBuffer()
      |                     |
      |                     v
      |              AudioBufferList { mNumberBuffers, mBuffers[] }
      |                     |
      |                     v
      |              AudioBuffer { mNumberChannels, mDataByteSize, mData* }
      |
PROCESSING STAGE
================
      |
      v
processAudioBuffer:numberOfSamples:error:
      |
      v
FUN_011de1d0 (normalization) ---> xHE-AAC loudness processing
      |
      v
FBAudioBufferHandler
      |
      +-----> _saveAudioBuffer: (local storage)
      |
      +-----> audioDataPipe (FBCCAudioDataPipe)
      |
ENCODING STAGE
==============
      |
      v
FBVideoTranscoderSetupReaderAudioOutput (0x00a4a408)
      |
      v
AudioStreamBasicDescription { mSampleRate, mFormatID, ... }
      |
      v
AAC/HE-AAC encoding (48kHz, 44.1kHz observed)
      |
EMBEDDING STAGE
===============
      |
      v
musicEmbeddingsForEditingAttachment (0x01ff01b2)
      |
      v
FBDynamicImageOverlayFilter (0x01c7b650) - GPU pixel manipulation
      |
      v
FBSampleBufferCreateFromPixelBuffer (0x00b39058)
      |
UPLOAD STAGE
============
      |
      v
CreateInspirationEditingAttachmentMutation (0x0091b8a4)
      |
      v
FBSnacksThreadMediaPostMedia (0x003d1ae0)
      |
      v
graph.facebook.com

Audio Format Infrastructure

AudioStreamBasicDescription Structure

C 
AudioStreamBasicDescription {
    mSampleRate        // double - e.g., 48000.0, 44100.0
    mFormatID          // uint32 - e.g., 'aac ', 'lpcm'
    mFormatFlags       // uint32
    mBytesPerPacket    // uint32
    mFramesPerPacket   // uint32
    mBytesPerFrame     // uint32
    mChannelsPerFrame  // uint32 - typically 1 or 2
    mBitsPerChannel    // uint32 - typically 16
    mReserved          // uint32
}

Audio Queue Infrastructure (FNFAudioQueue)

States: Uninitialized, Ready, Stop, Playing, Pause, Failed

Audio Buffer Ring Buffer

    undefined

Critical Evidence Summary

1. Confirmed CMSampleBuffer API Usage

    undefined

2. Audio Data Byte Access

    undefined

3. Audio Processing Chain

FBCCAudioCapturer --> FBCCAudioPipelineController --> FBCCAudioDataPipe --> processAudioBuffer:numberOfSamples:error: --> FBAudioBufferHandler

4. Network Transmission Path

FBSampleBufferCreateFromPixelBuffer (0x00b39058) --> CreateInspirationEditingAttachmentMutation (0x0091b8a4) --> FBSnacksThreadMediaPostMedia (0x003d1ae0)

Key Findings

    undefined

*CMSampleBuffer Processing Analysis - Generated 2025-12-30*

Related Reports

Ring Buffer Infrastructure Analysis

Audio Transcoding Infrastructure Analysis

Review: Additional capture logs under `./analysis/facebook/`
Phase 2

Agent Handoff Document
A

Anti-Forensics Binary Analysis Report