# AWS HealthScribe streaming
<a name="health-scribe-streaming"></a>

With AWS HealthScribe streaming, you can transcribe medical conversations in real-time. AWS HealthScribe streaming is a real-time HTTP2 based bi-directional service that accepts audio stream on one channel and vends an audio transcription on the other channel. After streaming is complete, AWS HealthScribe analyzes the stream contents and produces a transcript JSON file and a clinical note JSON file. 

 To start streaming, use the [StartMedicalScribeStream](https://docs.aws.amazon.com/transcribe/latest/APIReference/API_streaming_StartMedicalScribeStream.html) API operation. This API starts an HTTP2 based bi-directional channel that you use to stream audio events. 

When you start a stream, first specify the stream configuration in a `MedicalScribeConfigurationEvent`. This event includes channel definitions, encryption settings, and post-stream analytics settings, such as the output configuration for aggregated transcript and clinical note generation. 

After you start streaming audio, you manage the stream as follows:
+  When you are finished, to start processing the results with post-stream analytics, send a `MedicalScribeSessionControlEvent` with a `Type` of `END_OF_SESSION` and AWS HealthScribe starts the analytics.
+ To pause streaming, complete the input stream without sending the `MedicalScribeSessionControlEvent`.
+ To resume a paused stream, use the `StartMedicalScribeStream` API operation and specify the same `SessionId`. This is the `SessionId` you used when you originally started the stream.

**Topics**
+ [Guidelines and requirements](#health-scribe-streaming-requirements)
+ [ResourceAccessRoleArn role permissions](#health-scribe-data-access-role)
+ [Starting AWS HealthScribe streaming transcription](health-scribe-streaming-setting-up.md)

## Guidelines and requirements
<a name="health-scribe-streaming-requirements"></a>

The following are guidelines and requirements for AWS HealthScribe streaming:
+ Before you send audio events, you must first specify the stream configuration in a `[MedicalScribeConfigurationEvent](https://docs.aws.amazon.com/transcribe/latest/APIReference/API_streaming_MedicalScribeConfigurationEvent.html)`.
+ To run post-stream analytics, the `ResourceAccessRoleArn` in your `MedicalScribeConfigurationEvent` must have the correct permissions. For more information, see [ResourceAccessRoleArn role permissions](#health-scribe-data-access-role). 
+ You can resume a session any number of times within 5 hours from the initial stream creation.
+ You can stream at most 2 hours of audio over a session across all streaming requests.
+ By default, AWS HealthScribe provides encryption at rest to protect sensitive customer data using Amazon S3-managed keys. When you start a stream, you can specify a AWS KMS key for a second layer of encryption. Your `ResourceAccessRoleArn` must have permission to use your AWS KMS key. For more information, see [Data Encryption at rest for AWS HealthScribe](health-scribe-encryption.md). 
+ You can use AWS HealthScribe streaming with the AWS SDKs, excluding the AWS SDK for Python (Boto3) and SDK for PHP.
+ If a `LimitExceededException` exception occurs after you end a stream, you can restart the session and still generate post-stream analytics. To restart the stream, use the [StartMedicalScribeStream](https://docs.aws.amazon.com/transcribe/latest/APIReference/API_streaming_StartMedicalScribeStream.html) API and use same `SessionID`. Then send a `MedicalScribeSessionControlEvent` with a `Type` of `END_OF_SESSION` and AWS HealthScribe starts the analytics.

## ResourceAccessRoleArn role permissions
<a name="health-scribe-data-access-role"></a>

To run post-stream analytics, the `ResourceAccessRoleArn` in your `MedicalScribeConfigurationEvent` must be able to access your Amazon S3 output bucket and, if you provide it, your AWS KMS key. Also, the role's trust policy must grant the `transcribe.streaming.amazonaws.com` service permission to assume the role.

The following is an example IAM policy that grants Amazon S3 bucket permissions and AWS KMS key permissions. For more information, see [Data Encryption at rest for AWS HealthScribe](health-scribe-encryption.md).

------
#### [ JSON ]

****  

```
{
    "Version":"2012-10-17",		 	 	 
    "Statement": [
        {
            "Action": [
                "s3:PutObject"
            ],
            "Resource": [
                "arn:aws:s3:::{{amzn-s3-demo-bucket}}",
                "arn:aws:s3:::{{amzn-s3-demo-bucket}}/*"
            ],
            "Effect": "Allow"
        },
        {
            "Action": [
                "kms:DescribeKey",
                "kms:Decrypt",
                "kms:Encrypt",
                "kms:GenerateDataKey*"
            ],
            "Resource": "arn:aws:kms:us-west-2:{{123456789012}}:key/{{1234abcd-12ab-34cd-56ef-123456SAMPLE}}",
            "Effect": "Allow"
        }
    ]
}
```

------

The following is an example trust policy.

------
#### [ JSON ]

****  

```
{
    "Version":"2012-10-17",		 	 	 
    "Statement": [
        {
            "Effect": "Allow",
            "Principal": {
                "Service": [
                    "transcribe.streaming.amazonaws.com"
                ]
            },
            "Action": "sts:AssumeRole"
        }
    ]
}
```

------