This is the documentation for a previous version of our product. Click here to see the latest version.

Real-time Virtual Appliance

Important Notices

The legacy V1 API that the Real-time Virtual Appliance currently supports will be discontinued in a future release. We recommend that customers familiarise themselves with the configuration object as described in the Speech API Guide. Future notices will be provided to announce the end of life of the V1 API, and provide detailed instructions on migrations to the V2 API.

Currently, Speechmatics supports 2 python libraries for use with our Real-time products. smwebsocket-py is recommended for use for the Real-time Virtual Appliance, and speechmatics-python is recommended for use in both our Real-time Container and our Real-time Virtual Appliance. In a future release we will exclusively support speechmatics-python as our preferred Python library. We recommend you familiarise yourself with this library. Please contact if you require access to this library.

What's New

  • New language packs for English (en) and Spanish (es)
  • Caching support for Custom Dictionary to improve performance where the same Custom Dictionary is repeatedly used

Issues Fixed

The following issues are addressed since the previous release:

Issue IDSummaryResolution Description
REQ-10688Memory leak on client disconnect with pending buffered audioClients sending data to a worker faster than it can be processed could cause a memory leak; this has now been addressed.
REQ-11829No worker available in RTVA in unclean disconnectsThis was caused by a race condition that has now been fixed.
REQ-13430Virtual Appliance conflict of internal (docker) and customer subnetsA smaller subnet is now used to reduce the likelihood of conflicts.
REQ-14062There have been some instances of a Spanish file only being partially transcribedThe latest rebuild of Spanish (es) resolves this issue.

Known Limitations

The following are known issues in this release:

Issue IDSummaryDetailed Description and Possible Workarounds
REQ-1409Proteus HCL with <unk> causes out of memory errorA custom dictionary list that contains the word '' causes the worker to crash.
REQ-7549Memory leak affecting gRPCThere is a small memory leak in the gRPC Python server (
REQ-10160Advanced punctuation for Spanish (es) does not contain inverted marks.Inverted marks [ ¿ ¡ ] are not currently available for Spanish advanced punctuation.
REQ-10627Double full stops when acronym is at the end of the sentenceIf there is an acronym at the end of the sentence, then a double full stop will be output, for example: "team G.B.."
REQ-11087Additional white space appearing before the very last end of sentence punctuation character.Its been observed that additional white space can occur before a full-stop '.' in some transcripts. This can be parsed and removed by a post-processing step if necessary.
REQ-111353.2.0 introduced unwanted hesitations in transcripts.Due to changes in the way that training data is now ingested to improve the accuracy of spontaneous speech for English (en) there is a greater likelihood that hesitations will be included in the output transcripts. We plan to support a hesitation filtering capability in a future release for customers that do not want to see hesitations on transcripts.
REQ-11792Speaker change token positioning is incorrectWe are aware of a consistent mis-placing of the speaker change token after the first word of the new speakers' sentence rather than before it.
REQ-12202High memory usage when using custom dictionaryIt has been observed that when using custom dictionary an additional 800-1700MB of memory is required (depending on the size of the wordlist used).

Supported Platforms

Virtual Appliance image (OVA) for installation on:

  • VMware ESXi 6.5+ or VMware Workstation Player.
  • VirtualBox 5.2+
  • Amazon EC2

See the Installation and Admin Guide for details on the minimum specifications for the VM. The maximum number of concurrent jobs (maxworkers) that you can run on a single appliance is 30.

Form Factors

There are four variants of the Real-time Virtual Appliance.

VariantImage SizeMax. Disk SpaceLanguages
mini14GB40GBen, de, es
midi26GB60GBen, de, es, fr, ko, ja, nl, pt
maxi42GB80GBen, de, es, fr, ko, ja, nl, pt, it, da, pl, ca, hi, ru, sv
plus46GB80GBen, cmn, no, ar, bg, cs, el, fi, hu, hr, lt, lv, ro, sk, sl, tr, ms

Upgrade Path

Remove the license from your old appliance (see the Admin Guide), then re-import the new OVA and configure networking as per the Installation and Admin guide. You will need to re-apply the license code you have once the OVA has imported.


Upload the OVA to VMWare ESX, VMWare Workstation Player, or VirtualBox. See the Installation and Admin Guide for more information.