cloudformation-audio-metadata is an AWS SAM + CloudFormation template designed to ingest audio files from an input S3 bucket and grab metadata information (currently just duration) from them. It sends this result through an SNS topic for consumption by another Lambda function, email, etc.

It utilizes serverlesspub's ffmpeg-aws-lambda-layer package for easily packaging ffmpeg with the Lambda function.

Get Started

It's simple! Click this fancy button:

Then give the stack a name, and configure it:

Parameters

Parameter	Required	Default Value	Description
InputBucketName	Yes		The name of the bucket to use for audio inputs.
DebugLevel	No	<empty string>	The DEBUG environment variable for the Lambda. Set to cloudformation-audio-metadata to enable debug messages.

Outputs

Output	Description
InputBucket	The name of the bucket where audio files should be uploaded.
InputBucketArn	The ARN for the bucket where audio files should be uploaded.
Topic	The ARN for the SNS Topic to subscribe to for metadata notifications.
S3Topic	The ARN for the SNS Topic to subscribe to for object creation notifications from the input bucket.

Usage in Another Stack or Serverless

Add something like this underneath resources:

videoThumbnailStack:
  Type: AWS::CloudFormation::Stack
  Properties:
    TemplateURL: https://sammarks-cf-templates.s3.amazonaws.com/audio-metadata/VERSION/template.yaml
    Parameters:
      InputBucketName: test-input-bucket
      DebugLevel: ''

Note: This stack will require the CAPABILITY_AUTO_EXPAND capability when deploying the parent stack with CloudFormation. If you are using the Serverless framework, you can "trick" it into adding the required capabilities by adding this to your serverless.yaml:

resources:
  Transform: 'AWS::Serverless-2016-10-31' # Trigger Serverless to add CAPABILITY_AUTO_EXPAND
  Resources:
    otherResource: # ... all of your original resources

Regions

A quick note on regions: If you are deploying this stack in a region other than us-east-1, you need to reference the proper region S3 bucket as we're deploying Lambda functions. Just add the region suffix to the template URL, so this:

https://sammarks-cf-templates.s3.amazonaws.com/audio-metadata/VERSION/template.yaml

becomes this:

https://sammarks-cf-templates-us-east-2.s3.amazonaws.com/audio-metadata/VERSION/template.yaml

Subscribing to object creation events

S3 does not allow two separate Lambda functions to be subscribed to the same event types on a single bucket. Because of this, the template creates an SNS topic to serve as the messenger for the S3 notifications, and the internal Lambda function subscribes to that SNS topic.

Because of this, if you want to subscribe to the object creation events in your own Lambda functions, simply create a Lambda function that references the S3Topic output of this stack.

What's deployed?

• One S3 buckets: one for audio input.
• A SNS topic for notifications.
• A SNS topic for object created notifications for the input bucket.
• A Lambda function to process the audio files.

How does it work?

The Lambda goes through the following process:

• Grab the length of the audio file using ffprobe
• Send a notification to SNS once we have the length of the audio file.

Accessing Previous Versions & Upgrading

Each time a release is made in this repository, the corresponding template is available at:

https://sammarks-cf-templates.s3.amazonaws.com/audio-metadata/VERSION/template.yaml

On upgrading: I actually recommend you lock the template you use to a specific version. Then, if you want to update to a new version, all you have to change in your CloudFormation template is the version and AWS will automatically delete the old stack and re-create the new one for you.

Features

• Automatically determine the length of an audio file uploaded to a S3 bucket.
• Reports the duration to a SNS topic.
• Send notifications about updates and error messages to a SNS topic.
• Deploy with other CloudFormation-compatible frameworks (like the Serverless framework).
• All functionality is self-contained within one CloudFormation template. Delete the template, and all of our created resources are removed.

Why use this?

Right now this library just reports the duration of any audio file uploaded to a specific S3 bucket. Use this if you want to automatically calculate the length of a file yourself instead of relying on clients to upload accurate information.