How to use live transcription

Media Services logo v3


Azure Media Services will be retired June 30th, 2024. For more information, see the AMS Retirement Guide.

Transcription delivery and playback

When you publish a live stream using MPEG-DASH or HLS/CMAF, transcribed text in IMSC1.1 compatible TTML is created along with video and audio. It is packaged into MPEG-4 Part 30 (ISO/IEC 14496-30) fragments. If you use HLS/TS, text is delivered as chunked VTT.

If you are using the Azure Media Player, use the Azure Media Player version 2.3.3 or later.


Additional charges apply when live transcription is turned on. Please review the pricing information in the Live Video section of the Media Services pricing page.


You should use GOP sizes of 2 seconds for live events. You must use GOP sizes of 4 seconds or below for passthrough live events with live transcriptions in order to get correct transcription data. If you choose to use higher GOP size, the transcription data might have defects, e.g. missing content.

Live transcription auto generated VTT file

When you enable live transcription for a live event, a WebVTT file is generated and is located in the root of the archived asset. As this file is delayed until after all speech has been broadcast, you should not delete the live output for several minutes after the broadcast has ended. You can then download the VTT file and edit it or use it for translation to other languages for subtitles. The files is named auto-generated-best_XXX.vtt.


The final auto generated live transcription VTT files are delayed for processing. Unless you wait for several minutes before deleting a live output, the content in the file will be truncated. Additionally, live transcription is not available for use with multiple input streams for a live event.

For more information about how to use the Tracks API with the generated WebVTT file, see the Tracks article.

Create a live event with live transcription

You can create a live event with live transcription using the Azure portal, with the REST API or with any of the SDKs.

The language code must match the spoken language of the video. See the language code table at the end of this article.

Start or stop transcription after the live event has started

You can start and stop, or change the language of live transcription while the live event is in running, standby or stopped state.


Turning live transcription on or off must be done before any data is written to the output asset - this is usually when a live output is created, or when the incoming input stream arrives at the live event.

To turn on live transcriptions or to update the transcription language, patch the live event to include a “transcriptions” property with the correct language code on the 'language' property. See the list above to supported language codes.

To turn off live transcriptions, remove the “transcriptions” property from the live event object.

Live transcription regions and languages

Live transcription is available in the regions as documented here.

This is the list of available languages that can be transcribed, use the language code in the API.

Language Locale (BCP-47)
Afrikaans (South Africa) af-ZA
Amharic (Ethiopia) am-ET
Arabic (Algeria) ar-DZ
Arabic (Bahrain), modern standard ar-BH
Arabic (Egypt) ar-EG
Arabic (Iraq) ar-IQ
Arabic (Israel) ar-IL
Arabic (Jordan) ar-JO
Arabic (Kuwait) ar-KW
Arabic (Lebanon) ar-LB
Arabic (Libya) ar-LY
Arabic (Morocco) ar-MA
Arabic (Oman) ar-OM
Arabic (Palestinian Authority) ar-PS
Arabic (Qatar) ar-QA
Arabic (Saudi Arabia) ar-SA
Arabic (Syria) ar-SY
Arabic (Tunisia) ar-TN
Arabic (United Arab Emirates) ar-AE
Arabic (Yemen) ar-YE
Bengali (India) bn-IN
Bulgarian (Bulgaria) bg-BG
Burmese (Myanmar) my-MM
Catalan (Spain) ca-ES
Chinese (Cantonese, Traditional) zh-HK
Chinese (Mandarin, Simplified) zh-CN
Chinese (Taiwanese Mandarin) zh-TW
Croatian (Croatia) hr-HR
Czech (Czech) cs-CZ
Danish (Denmark) da-DK
Dutch (Belgium) nl-BE
Dutch (Netherlands) nl-NL
English (Australia) en-AU
English (Canada) en-CA
English (Ghana) en-GH
English (Hong Kong) en-HK
English (India) en-IN
English (Ireland) en-IE
English (Kenya) en-KE
English (New Zealand) en-NZ
English (Nigeria) en-NG
English (Philippines) en-PH
English (Singapore) en-SG
English (South Africa) en-ZA
English (Tanzania) en-TZ
English (United Kingdom) en-GB
English (United States) en-US
Estonian (Estonia) et-EE
Filipino (Philippines) fil-PH
Finnish (Finland) fi-FI
French (Belgium) fr-BE
French (Canada) fr-CA
French (France) fr-FR
French (Switzerland) fr-CH
German (Austria) de-AT
German (Germany) de-DE
German (Switzerland) de-CH
Greek (Greece) el-GR
Gujarati (Indian) gu-IN
Hebrew (Israel) he-IL
Hindi (India) hi-IN
Hungarian (Hungary) hu-HU
Icelandic (Iceland) is-IS
Indonesian (Indonesia) id-ID
Irish (Ireland) ga-IE
Italian (Italy) it-IT
Japanese (Japan) ja-JP
Javanese (Indonesia) jv-ID
Kannada (India) kn-IN
Khmer (Cambodia) km-KH
Korean (Korea) ko-KR
Lao (Laos) lo-LA
Latvian (Latvia) lv-LV
Lithuanian (Lithuania) lt-LT
Macedonian (North Macedonia) mk-MK
Malay (Malaysia) ms-MY
Maltese (Malta) mt-MT
Marathi (India) mr-IN
Norwegian (Bokmål, Norway) nb-NO
Persian (Iran) fa-IR
Polish (Poland) pl-PL
Portuguese (Brazil) pt-BR
Portuguese (Portugal) pt-PT
Romanian (Romania) ro-RO
Russian (Russia) ru-RU
Serbian (Serbia) sr-RS
Sinhala (Sri Lanka) si-LK
Slovak (Slovakia) sk-SK
Slovenian (Slovenia) sl-SI
Spanish (Argentina) es-AR
Spanish (Bolivia) es-BO
Spanish (Chile) es-CL
Spanish (Colombia) es-CO
Spanish (Costa Rica) es-CR
Spanish (Cuba) es-CU
Spanish (Dominican Republic) es-DO
Spanish (Ecuador) es-EC
Spanish (El Salvador) es-SV
Spanish (Equatorial Guinea) es-GQ
Spanish (Guatemala) es-GT
Spanish (Honduras) es-HN
Spanish (Mexico) es-MX
Spanish (Nicaragua) es-NI
Spanish (Panama) es-PA
Spanish (Paraguay) es-PY
Spanish (Peru) es-PE
Spanish (Puerto Rico) es-PR
Spanish (Spain) es-ES
Spanish (Uruguay) es-UY
Spanish (USA) es-US
Spanish (Venezuela) es-VE
Swahili (Kenya) sw-KE
Swahili (Tanzania) sw-TZ
Swedish (Sweden) sv-SE
Tamil (India) ta-IN
Telugu (India) te-IN
Thai (Thailand) th-TH
Turkish (Turkey) tr-TR
Ukrainian (Ukraine) uk-UA
Uzbek (Uzbekistan) uz-UZ
Vietnamese (Vietnam) vi-VN
Zulu (South Africa) zu-ZA

Get help and support

You can contact Media Services with questions or follow our updates by one of the following methods: