Transcribing Audio Records with the Cloud Speech API

In this post I'll show how one might approach enriching their public archives with audio transcriptions provided by Google's Cloud Speech API.

First we can start with this collection of records:

Collection of Hearing Records

Simple meta-data for each file

For each of these audio files I'll have to download it, convert it, stage it, pass it to the speech api, and capture the results.  I'll craft this in powershell for the moment and then later implement this as a cloud function.  The results can then be added to the notes or as an OCR text rendition (or reviewed and then added).

The speech API will give me chunks of text with an associated confidence level, as shown below:

Which can all be mashed together for a pretty accurate transcription:

---

Step by Step

My first step is to enable the Speech API within GCP:

Then create a storage bucket to house the files.  I could skip this and upload it directly within a request, but staging them in a bucket makes it easier for me to later work with cloud functions.  

To convert the audio from mp3 to wav format with a single audio channel I used ffmpeg:

ffmpeg -hide_banner -loglevel panic -y -i %inputfile% -ac 1 %outputfile%

I like ffmpeg because it's easy to use on windows servers & workstations.  But there's also a good fluent ffmpeg module available in nodejs, which allows this to be built as a cloud function.  For now here's my powershell function to convert the audio file...

function ConvertTo-Wav {
	Param([string]$inputFile)
	#few variables for local pathing
	$newFileName = [System.IO.Path]::getfilenamewithoutextension($inputFile) + ".wav"
	$fileDir = [System.IO.Path]::getdirectoryname($inputFile)
	$newFilePath = [System.IO.Path]::combine($fileDir, $newFileName)
	#once is enough
	Write-Debug("ConvertTo-Wav Target File: " + $newFilePath)
	if ( (Test-Path $newFilePath) -eq $false ) {
		#convert using open source ffmpeg
		$convertCmd = "ffmpeg -hide_banner -loglevel panic -y -i `"$inputFile`" -ac 1 `"$newFilePath`""
		Write-Debug ("ConvertTo-Wav Command: " + $convertCmd)
		Invoke-Expression $convertCmd
	}
	return $newFilePath
}

This function queries for the audio records from content manager and caches the result to disk (simply for development of the script)...

function Get-CMAudioFilesJson {
	$localResponseFile = [System.IO.Path]::Combine($localTempPath,"audioRecords.json")
	$audioFiles = @()
	if ( (Test-Path $localResponseFile) -eq $false ) {
		#fetch if results not cached to disk
		$searchUri = ($baseCMUri + "/Record?q=container:11532546&format=json&pageSize=100000&properties=Uri,RecordNumber,Url,RecordExtension,RecordDocumentSize")
		Write-Debug "Searching for audio records: $searchUri"
		$response = Invoke-RestMethod -Uri $searchUri -Method Get -ContentType $ApplicationJson
		#flush to disk as raw json
		$response | ConvertTo-Json -Depth 6 | Set-Content $localResponseFile
	} else {
		#load and convert from json
		Write-Debug ("Loading Audio Records from local file: " + $localResponseFile)
		$response = Get-Content -Path $localResponseFile | ConvertFrom-Json
	}
	#if no results just error out
	if ( $response.Results -ne $null ) {
		Write-Debug ("Processing $($response.Results.length) audio records")
		$audioFiles = $response.Results
	} else {
		Write-Debug "Error"
		break
	}
	return $audioFiles
}

A function to submit the record's audio file to the speech api (and capture the results):

function Get-AudioText 
{
    Param($audioRecord)
    #formulate a valid path for the local file system
    $localFileName = (""+$audioRecord.Uri+"."+$audioRecord.RecordExtension.Value)
    $localPath = ($localTempPath + "\" + $localFileName)
    $sourceAudioFileUri = ($audioRecord.Url.Value + "/File/Document")
    $speechApiResultPath = ($localTempPath + "\" + $audioRecord.Uri + ".txt")  
    $speechTextPath = ($localTempPath + "\" + $audioRecord.Uri + "_text.txt")
    #download the audio file if not already done so
    if ( (Test-Path $localPath) -eq $false ) {  
        Invoke-WebRequest -Uri $sourceAudioFileUri -OutFile $localPath
    }
    #convert file if necessary
    if ( ($audioRecord.RecordExtension.Value.ToLower()) -ne "wav" ) {
        $localPath = ConvertTo-Wav $localPath
        $localFileName = [System.IO.Path]::GetfileName($localPath)
        if ( (Test-Path $localPath) -eq $false ) {
            Write-Error "Error Converting $($localPath)"
            return
        }
    }
 
    #transcribe, if not already done so
    Write-Debug ("Checking Speech API Text: "+$speechApiResultPath)
    if ( (Test-Path $speechApiResultPath) -eq $false ) {
        try {
            $bucketFilePath = "$bucketPath/$localFileName"
            Put-BucketFile -bucketFilePath $bucketFilePath -bucketPath $bucketPath -localPath $localPath
            #invoke speech api
            $speechCmd = "gcloud ml speech recognize-long-running $bucketFilePath --language-code=en-US"
            Write-Debug ("Speech API Command: "+$speechCmd)
            Invoke-Expression $speechCmd -OutVariable $speechResult | Tee-Object -FilePath $speechApiResultPath   
            Write-Debug ("Speech API Result: " + $speechResult)    
        } catch {
            Write-Error $_Write-Error $_
        }
    }
 
    #process transcription result
    if ( (Test-Path $speechApiResultPath) -eq $true ) {
        Write-Debug ("Reading Speech Results File: " + $speechApiResultPath)
		#remove previous consolidated transcription file
		if ( (Test-Path) -eq $true ) {Remove-Item $speechTextPath -Force }
		#flush each transcript result to disk
		$content.results | ForEach-Object { $_.alternatives | ForEach-Object { Add-Content $speechTextPath ($_.transcript+' ')  }  }
    } else {
        Write-Debug ("No Speech API Results: " + $speechTextPath)
    }
}

And then some logic to parse the search results and invoke the speech api:

#fetch the search results
$audioFiles = Get-CMAudioFilesJson
if ( $audioFiles -eq $null ) {
    Write-Error "No audio files found"
    exit
}
#process each
Write-Debug "Found $($audioFiles.Length) audio files"
foreach ( $audioFile in $audioFiles ) {
    Write-Host "Transcribing $($audioFile.RecordNumber.Value)"
    Get-AudioText  -audioRecord $audioFile
}

Here's the complete script:

Clear-Host
$DebugPreference = "Continue"
 
#variables and such
$AllProtocols = [System.Net.SecurityProtocolType]'Ssl3,Tls,Tls11,Tls12'
[System.Net.ServicePointManager]::SecurityProtocol = $AllProtocols
$ApplicationJson = "application/json"
$baseCMUri = "http://efiles.portlandoregon.gov"
$localTempPath = "C:\temp\speechapi"
$bucketPath = "gs://speech-api-cm-dev"
 
#create local staging area
if ( (Test-Path $localTempPath) -eq $false ) {
    New-Item $localTempPath -Type Directory
}
 
function Get-CMAudioFilesJson {
	$localResponseFile = [System.IO.Path]::Combine($localTempPath,"audioRecords.json")
	$audioFiles = @()
	if ( (Test-Path $localResponseFile) -eq $false ) {
		#fetch if results not cached to disk
		$searchUri = ($baseCMUri + "/Record?q=container:11532546&format=json&pageSize=100000&properties=Uri,RecordNumber,Url,RecordExtension,RecordDocumentSize")
		Write-Debug "Searching for audio records: $searchUri"
		$response = Invoke-RestMethod -Uri $searchUri -Method Get -ContentType $ApplicationJson
		#flush to disk as raw json
		$response | ConvertTo-Json -Depth 6 | Set-Content $localResponseFile
	} else {
		#load and convert from json
		Write-Debug ("Loading Audio Records from local file: " + $localResponseFile)
		$response = Get-Content -Path $localResponseFile | ConvertFrom-Json
	}
	#if no results just error out
	if ( $response.Results -ne $null ) {
		Write-Debug ("Processing $($response.Results.length) audio records")
		$audioFiles = $response.Results
	} else {
		Write-Debug "Error"
		break
	}
	return $audioFiles
}
 
function ConvertTo-Wav {
	Param([string]$inputFile)
	#few variables for local pathing
	$newFileName = [System.IO.Path]::getfilenamewithoutextension($inputFile) + ".wav"
	$fileDir = [System.IO.Path]::getdirectoryname($inputFile)
	$newFilePath = [System.IO.Path]::combine($fileDir, $newFileName)
	#once is enough
	Write-Debug("ConvertTo-Wav Target File: " + $newFilePath)
	if ( (Test-Path $newFilePath) -eq $false ) {
		#convert using open source ffmpeg
		$convertCmd = "ffmpeg -hide_banner -loglevel panic -y -i `"$inputFile`" -ac 1 `"$newFilePath`""
		Write-Debug ("ConvertTo-Wav Command: " + $convertCmd)
		Invoke-Expression $convertCmd
	}
	return $newFilePath
}
 
function Put-BucketFile {
	Param($bucketFilePath,$bucketPath,$localPath)
	#upload to bucket
    $checkCommand = "gsutil -q stat $bucketFilePath"
    $checkCommand += ';$?'
    Write-Debug ("GCS file check: " + $checkCommand)
    $fileCheck = Invoke-Expression $checkCommand
    #fileCheck is true if it exists, false otherwise
    if (-not $fileCheck ) {
        Write-Debug ("Uploading to bucket: gsutil cp " + $localPath + " " + $bucketPath)
        gsutil cp $localPath $bucketPath
    }
}
 
function Get-AudioText 
{
    Param($audioRecord)
    #formulate a valid path for the local file system
    $localFileName = (""+$audioRecord.Uri+"."+$audioRecord.RecordExtension.Value)
    $localPath = ($localTempPath + "\" + $localFileName)
    $sourceAudioFileUri = ($audioRecord.Url.Value + "/File/Document")
    $speechApiResultPath = ($localTempPath + "\" + $audioRecord.Uri + ".txt")  
    $speechTextPath = ($localTempPath + "\" + $audioRecord.Uri + "_text.txt")
    #download the audio file if not already done so
    if ( (Test-Path $localPath) -eq $false ) {  
        Invoke-WebRequest -Uri $sourceAudioFileUri -OutFile $localPath
    }
    #convert file if necessary
    if ( ($audioRecord.RecordExtension.Value.ToLower()) -ne "wav" ) {
        $localPath = ConvertTo-Wav $localPath
        $localFileName = [System.IO.Path]::GetfileName($localPath)
        if ( (Test-Path $localPath) -eq $false ) {
            Write-Error "Error Converting $($localPath)"
            return
        }
    }
 
    #transcribe, if not already done so
    Write-Debug ("Checking Speech API Text: "+$speechApiResultPath)
    if ( (Test-Path $speechApiResultPath) -eq $false ) {
        try {
            $bucketFilePath = "$bucketPath/$localFileName"
            Put-BucketFile -bucketFilePath $bucketFilePath -bucketPath $bucketPath -localPath $localPath
            #invoke speech api
            $speechCmd = "gcloud ml speech recognize-long-running $bucketFilePath --language-code=en-US"
            Write-Debug ("Speech API Command: "+$speechCmd)
            Invoke-Expression $speechCmd -OutVariable $speechResult | Tee-Object -FilePath $speechApiResultPath   
            Write-Debug ("Speech API Result: " + $speechResult)    
        } catch {
            Write-Error $_Write-Error $_
        }
    }
 
    #process transcription result
    if ( (Test-Path $speechApiResultPath) -eq $true ) {
        Write-Debug ("Reading Speech Results File: " + $speechApiResultPath)
		#remove previous consolidated transcription file
		if ( (Test-Path) -eq $true ) {Remove-Item $speechTextPath -Force }
		#flush each transcript result to disk
		$content.results | ForEach-Object { $_.alternatives | ForEach-Object { Add-Content $speechTextPath ($_.transcript+' ')  }  }
    } else {
        Write-Debug ("No Speech API Results: " + $speechTextPath)
    }
}
 
#fetch the search results
$audioFiles = Get-CMAudioFilesJson
if ( $audioFiles -eq $null ) {
    Write-Error "No audio files found"
    exit
}
#process each
Write-Debug "Found $($audioFiles.Length) audio files"
foreach ( $audioFile in $audioFiles ) {
    Write-Host "Transcribing $($audioFile.RecordNumber.Value)"
    Get-AudioText  -audioRecord $audioFile
}