Add /audio/transcriptions Endpoint for OpenWebUI

[zenabius]

OpenWebUI requires an /audio/transcriptions endpoint to handle audio-to-text processing. This feature will allow users to transcribe audio input via the API.

Expected Behavior:
The endpoint should accept an audio file (e.g., MP3, WAV).
It should return the transcribed text in JSON format.

[mostlygeek]

OpenAI docs: https://platform.openai.com/docs/guides/speech-to-text#transcriptions

note: this API uses multipart forms but does support a model parameter.

@zenabius do you have a backend config that llama-swap could run for audio transcriptions? You can test it with http://server/upstream/{model}/v1/audio/transcriptions. The upstream/ path takes a model on the path and proxies everything after transparently to the upstream.

[zenabius]

🚀 It WORKS!

🔗 API Endpoint

Open WebUI API path /admin/settings/audio:
STT Settings
http://server/upstream/whisper-audio
STT Model
model: whisper-large-v3-turbo

⚙️ Configuration

Below is the configuration for the my /audio/transcriptions endpoint:

whisper-audio:
  cmd: >
    docker run --rm 
    --gpus '"device=2"'
    --init 
    -p 9797:5000 
    -v /mnt/llm/whisper.cpp/HF:/root/.cache/
    -v /mnt/llm/whisper.cpp/HF/data1:/data
    local/whisper.cpp:audio-cuda

  proxy: "http://127.0.0.1:9797"
  ttl: 0
  unlisted: false
  checkEndpoint: /health
  aliases:
    - audio

[mostlygeek]

I would like to eventually support the /v1/audio/transcriptions but if this works I'll leave this here for people to use it under /upstream/.

Could you share a bit more about how to get it working?

• where to get the container from
• where to download models from (likely here: https://huggingface.co/ggerganov/whisper.cpp/tree/main)

I think it would be fairly easy to add the endpoint.

[zenabius]

Here’s a breakdown of LLM summary how to get everything working:

1. Building the Docker Container

The Dockerfile provided ensures that all necessary dependencies are installed. To build the container, run:

docker build -t local/whisper.cpp:audio-cuda -f Dockerfile .

This will create a Docker image named local/whisper.cpp:audio-cuda with CUDA support.

2. Running the Container

Once built, you can run the container using:

docker run --gpus all -p 5000:5000 --rm -v /path/to/files:/root/.cache/ local/whisper.cpp:audio-cuda

This will:

• Expose the API on port 5000
• Ensure GPU acceleration is available
• Remove the container after stopping it

3. Downloading the Model

The model is specified as "openai/whisper-large-v3-turbo" and will be automatically downloaded from Hugging Face when the container runs. If you prefer to download it manually, you can run:

huggingface-cli download openai/whisper-large-v3-turbo

Alternatively, if using whisper.cpp, you can get models from:
https://huggingface.co/ggerganov/whisper.cpp/tree/main.

For whisper.cpp, you’d typically download and move the .bin files into a directory where your application can access them.

4. Testing the API

Once the container is running, you can test the transcription API with:

curl -X POST http://localhost:5000/audio/transcriptions \
     -F "file=@audio.mp3"

This will return a JSON response with the transcription.

5. Adding a /v1/audio/transcriptions Endpoint

If you want to support /v1/audio/transcriptions, modify backend.py:

1. Change:

   @app.post('/audio/transcriptions', tags=[transcription_tag])

   to:

   @app.post('/v1/audio/transcriptions', tags=[transcription_tag])

2. Restart the container! 🚀

Remove .txt from backend.py.txt and Dockerfile.txt
backend.py.txt
Dockerfile.txt
requirements.txt

[mostlygeek]

Excellent! thank you for the detailed write up!

[matiashegoburu]

Please add this to the main branch, having a fully compatible open ai api set of endpoints under the same base url is very handy

[mostlygeek]

@zenabius which inference server are you using? I was looking at your docs and I can't figure which python server you're dockerizing.

Edit:

Actually NM :). I got whisper.cpp's server running with:

$ CUDA_VISIBLE_DEVICES=1 ./whisper-server-5bb1d58 \
  --host 0.0.0.0 --port 9233 \
  -m /mnt/nvme/models/whisper/ggml-large-v3-turbo-q8_0.bin \
  --request-path /audio/transcriptions --inference-path ""

[mostlygeek]

Using /v1/audio/transcriptions and whisper.cpp:

Configuration example:

models:
  "whisper":
    proxy: "http://127.0.0.1:9233"
    checkEndpoint: /v1/audio/transcriptions/
    cmd: >
      path/to/whisper-server
        --host 127.0.0.1 --port 9233
        -m path/to/ggml-large-v3-turbo-q8_0.bin
        --request-path /v1/audio/transcriptions --inference-path ""

Important for OpenAI API compatibility:

1. Set flags: --request-path /v1/audio/transcriptions --inference-path ""
2. SetcheckEndpoint: /v1/audio/transcriptions/

Testing with curl:

Using samples from whisper.cpp:

curl 10.0.1.50:8080/v1/audio/transcriptions \
    -H "Content-Type: multipart/form-data" \
    -F file="@mm1.wav" \
    -F temperature="0.0" \
    -F temperature_inc="0.2" \
    -F response_format="json" \
    -F model="whisper"

Results with 3090:

$ time curl 10.0.1.50:8080/v1/audio/transcriptions \
    -H "Content-Type: multipart/form-data" \
    -F file="@mm1.wav" \
    -F temperature="0.0" \
    -F temperature_inc="0.2" \
    -F response_format="json" \
    -F model="whisper" | jq -r .text

  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100 5150k  100   991  100 5149k   1340  6967k --:--:-- --:--:-- --:--:-- 6960k

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real    0m0.752s
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Cuda Installation

$ curl -LO https://huggingface.co/ggerganov/whisper.cpp/resolve/main/ggml-large-v3-turbo-q8_0.bin

$ git clone https://github.com/ggerganov/whisper.cpp.git
$ cd whisper.cpp

# fetch samples 
$ make samples

# build 
$ CUDACXX=/usr/local/cuda-12.6/bin/nvcc cmake -B build -DBUILD_SHARED_LIBS=OFF -DGGML_CUDA=1
$ cmake --build build --config Release -j 16

# test it
$ ./build/bin/whisper-cli -m ggml-large-v3-turbo-q8_0.bin samples/jfk.wav

[mostlygeek]

Fixed in #67