# Record captions (/en/realtime-media/speech-to-text/build/process-transcription-data/record-captions)
> For AI agents: see the complete documentation index at [llms.txt](/llms.txt).
Real-Time STT enables you to record caption text, generate a .vtt file, and store it in the configured cloud storage. These recorded captions are designed for seamless playback alongside audio and video recordings. Additionally, you can use the .vtt file to generate meeting minutes and topic summaries, perform sentiment analysis and content moderation. Caption recording does not incur any additional fees.
This page explains how to record captions and synchronize them with the audio or video files generated by Cloud Recording.
Since Cloud Recording and transcription tasks operate on different servers, you must enable the NTP timestamp for Cloud Recording to synchronize the timestamps with the transcription.
## Prerequisites [#prerequisites]
To follow this procedure, you must:
* Have a valid [Agora Account](https://console.agora.io/v2).
* Have a valid Agora project with an app ID and a temporary token or a token
server. For details, see [Agora account management](/en/realtime-media/voice/manage-agora-account).
* Have a computer with access to the internet. If your network has a firewall, follow the steps in [Firewall requirements](../../reference/firewall).
* Join a Video SDK channel as a host and start streaming. Refer to the [Voice SDK quickstart](/en/realtime-media/voice/quickstart) guide.
* Make sure Real-Time STT is enabled for your app.
* Set the `enableNTPtimestamp` parameter to `true` in the body of the Cloud Recording `start` request to synchronize the timestamps with the transcription.
Sample Cloud Recording `start` request body
```json
"recordingConfig": {
"maxIdleTime": 30,
"streamTypes": 2,
"channelType": 1,
"extensionParams": {
"enableNTPtimestamp": true
},
"transcodingConfig": {
"width": 1280,
"height": 720,
"fps": 15,
"bitrate": 2400,
"mixedVideoLayout": 3,
"layoutConfig": [
{
"alpha": 1,
"height": 1,
"render_mode": 1,
"uid": "22228",
"width": 1,
"x_axis": 0,
"y_axis": 0
}
]
}
},
```
## Implementation [#implementation]
Follow these steps to record captions and synchronize them with the corresponding recordings for seamless playback.
### Record the captions [#record-the-captions]
To record the captions, follow the API call sequence from the [REST Quickstart](../../get-started/quickstart) and modify the `start` request to include caption recording parameters as follows:
```bash
curl --location --request POST 'https://api.agora.io/api/speech-to-text/v1/projects/{appId}/join' \
--header 'Content-Type: application/json' \
--header 'Authorization: Basic ' \
--data '{
"name": "unique-agent-id",
"languages": [
"en-US"
],
"maxIdleTime": 50,
"rtcConfig": {
"channelName": "",
"subBotUid": "",
"subBotToken": "",
"pubBotUid": "",
"pubBotToken": ""
},
"captionConfig": {
"storage": {
"accessKey": "",
"secretKey": "",
"bucket": "",
"vendor": ,
"region": ,
"fileNamePrefix": ["folder","sub-folder"]
},
"extensionParams": {
"endpoint": "",
"type": "s3",
"provider": ""
}
}
}'
```
When `captionConfig.storage.vendor` is `11`, you must provide S3-compatible storage access information in `captionConfig.extensionParams`.
### extensionParams fields [#extensionparams-fields]
| Field | Type | Required | Description |
| --------------- | ---------------- | ------------------------------ | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `endpoint` | string | Required when `vendor` is `11` | The access URL for the S3-compatible storage service. Provide the full URL, for example `http://host:9002`. If you use a self-signed HTTPS certificate, you must trust it in your runtime environment first, otherwise the connection may fail. |
| `provider` | string | Recommended | The name of the S3-compatible storage provider, for example `Minio` for MinIO. Usually set together with `endpoint`. The capitalization must match the provider's requirements. |
| `type` | string | Recommended | The storage type. For standard S3-compatible storage, set this to `s3`. Usually used together with `storage.vendor = 11`. |
| `region` | string | No | The storage region identifier for use by AWS SDK-compatible clients. If set in both `storage.region` and `extensionParams.region`, `extensionParams.region` takes precedence. |
| `tag` | string | No | The base value for the object tag applied after upload. Takes effect only when `storage.vendor` is Tencent Cloud, Alibaba Cloud, or Amazon S3. Does not take effect when `vendor` is `11`. |
| `tagByRule` | array | No | Automatically applies object tags based on filename rules, for example applying different tags to different file types. When both `tag` and `tagByRule` are set, `tagByRule` takes precedence. Takes effect only for Tencent Cloud, Alibaba Cloud, and Amazon S3. Does not take effect when `vendor` is `11`. |
| `sse` | string | No | The server-side encryption method. `aes256` uses AES-256 encryption; `kms` uses AWS KMS. Takes effect only for Amazon S3. Does not take effect when `vendor` is `11`. |
| `overwritekeys` | array of objects | No | Maps uploaded files to target object names by file extension, controlling the filename used in cloud storage after upload. Not subject to the vendor restrictions that apply to `tag` fields. |
### Sync the files [#sync-the-files]
The `m3u8+vtt` file generated by Real-Time STT and the `m3u8+ts` file generated by Cloud Recording are two independent files, with different time stamps. The Cloud Recording time stamp starts at `0`, while Real-Time STT uses the system time stamp. If either process starts abnormally, the media files generated by the two services may be out of sync during playback.
Agora provides a post-processing script that lets you sync the `m3u8+ts` and `m3u8+vtt` files. To run this script, take the following steps:
1. Unzip the [post-processing script](https://github.com/AgoraIO/Docs-Source/files/10931258/add_webvtt.zip) to a local folder.
2. Run the script on your transcription files:
```python
python3 insert_subtitle.py --av audio_dir/audio_ts.m3u8 --subtitle subtitle_dir/subtitle.m3u8 --output output_dir/ --overwrite
```
If `ffmpeg/ffprobe` are not in your `PATH`, use `-ffmpeg_path` to specify the path.
3. Play the synchronized files:
1. Run the following command to start the HTTP server:
```python
python3 -m http.server --bind 127.0.0.1 -d output_dir
```
2. In your browser, enter the following URL:
```bash
http://127.0.0.1:8000/player_demo.html
```
## Supported OSS vendors [#supported-oss-vendors]
`vendor`: Number. The third-party cloud storage vendor. The following are supported:
* `1`: [Amazon S3](https://aws.amazon.com/s3/?nc1=h_ls)
* `5`: [Microsoft Azure](https://azure.microsoft.com/en-us/services/storage/blobs/)
* `6`: [Google Cloud](https://cloud.google.com/storage)
* `11`: Other S3-compatible object storage, such as MinIO and some self-hosted storage services. When using this vendor, set the region in `extensionParams.region` instead of `storage.region`.services
`region`: Number. The region information specified for the third-party cloud storage. The service only supports regions in the following lists:
* Amazon S3 (`vendor` = `1`):
* `0`: `US_EAST_1`
* `1`: `US_EAST_2`
* `2`: `US_WEST_1`
* `3`: `US_WEST_2`
* `4`: `EU_WEST_1`
* `5`: `EU_WEST_2`
* `6`: `EU_WEST_3`
* `7`: `EU_CENTRAL_1`
* `8`: `AP_SOUTHEAST_1`
* `9`: `AP_SOUTHEAST_2`
* `10`: `AP_NORTHEAST_1`
* `11`: `AP_NORTHEAST_2`
* `12`: `SA_EAST_1`
* `13`: `CA_CENTRAL_1`
* `14`: `AP_SOUTH_1`
* `15`: `CN_NORTH_1`
* `16`: `CN_NORTHWEST_1`
* `17`: `US_GOV_WEST_1`
* `20`: `AP_NORTHEAST_3`
* `21`: `EU_NORTH_1`
* `22`: `ME_SOUTH_1`
* `23`: `US_GOV_EAST_1`
* `24`: `AP_SOUTHEAST_3`
* `25`: `EU_SOUTH_1`
* `28`: `IL_CENTRAL_1`
* Microsoft Azure (`vendor` = `5`): The `region` parameter has no effect, whether set or not.
* Google Cloud (`vendor` = `6`): The `region` parameter has no effect, whether set or not.