Offline Pipeline API

Truebar’s offline API lets you run the same pipelines used for streaming, but as HTTP jobs. It is ideal for large audio archives, background text clean-up, and TTS workloads where real-time latency is not required.

When to choose the offline API#

Batch ingestion – Transcribe or synthesise long-form media without keeping a WebSocket connection open.
Post-processing – Re-run NLP stages on previously captured transcripts.
Automation – Integrate with schedulers or serverless jobs where HTTP fits better than persistent sockets.

Endpoint overview#

Path: POST /api/pipelines/process
Auth: Authorization: Bearer <access_token>
Pipeline: provided per request in the pipeline form part
Input data: uploaded as a second form part (data)
Async mode: append ?async=true to process large jobs asynchronously (you’ll receive a 202 ACCEPTED with a status URL)

Requests use multipart/form-data so you can send JSON metadata and binary payloads together.

cURL
Python
JavaScript (Node.js)
Java

curl --fail --location \\  --request POST "$TRUEBAR_API_BASE_URL/api/pipelines/process" \\  --header "Authorization: Bearer $TRUEBAR_ACCESS_TOKEN" \\  --form 'pipeline=@pipeline.json;type=application/json' \\  --form 'data=@sample.pcm;type=application/octet-stream'

submit_offline_job.py

import jsonimport osfrom pathlib import Path
import requests

pipeline = [    {        "task": "ASR",        "exceptionHandlingPolicy": "THROW",        "config": {"tag": "KALDI:sl-SI:COL:20221208-0800", "parameters": {"enableInterims": False}},    },    {        "task": "NLP_pc",        "exceptionHandlingPolicy": "SKIP",        "config": {"tag": "NEMO_PUNCTUATOR:sl-SI:*:*", "parameters": {"enableSplitToSentences": True}},    },]
response = requests.post(    f"{os.environ['TRUEBAR_API_BASE_URL']}/api/pipelines/process",    headers={"Authorization": f"Bearer {os.environ['TRUEBAR_ACCESS_TOKEN']}"},    files={        "pipeline": ("pipeline.json", json.dumps(pipeline), "application/json"),        "data": ("sample.pcm", Path("sample.pcm").read_bytes(), "application/octet-stream"),    },    timeout=30,)response.raise_for_status()if response.headers.get("Content-Type", "").startswith("application/json"):    print(response.json())else:    with open("result.bin", "wb") as handle:        handle.write(response.content)

submit-offline-job.mjs

import { readFileSync } from 'node:fs';import FormData from 'form-data';import axios from 'axios';
const pipeline = [  {    task: 'ASR',    exceptionHandlingPolicy: 'THROW',    config: { tag: 'KALDI:sl-SI:COL:20221208-0800', parameters: { enableInterims: false } },  },  {    task: 'NLP_pc',    exceptionHandlingPolicy: 'SKIP',    config: { tag: 'NEMO_PUNCTUATOR:sl-SI:*:*', parameters: { enableSplitToSentences: true } },  },];
const form = new FormData();form.append('pipeline', JSON.stringify(pipeline), {  filename: 'pipeline.json',  contentType: 'application/json',});form.append('data', readFileSync('sample.pcm'), {  filename: 'sample.pcm',  contentType: 'application/octet-stream',});
const response = await axios.post(  `${process.env.TRUEBAR_API_BASE_URL}/api/pipelines/process`,  form,  {    headers: {      Authorization: `Bearer ${process.env.TRUEBAR_ACCESS_TOKEN}`,      ...form.getHeaders(),    },  },);
if (response.headers['content-type']?.startsWith('application/json')) {  console.log(response.data);} else {  console.log(`Received ${response.data.length} bytes of audio.`);}

SubmitOfflineJob.java

import java.io.IOException;import java.net.URI;import java.net.http.HttpClient;import java.net.http.HttpRequest;import java.net.http.HttpResponse;import java.nio.charset.StandardCharsets;import java.nio.file.Files;import java.nio.file.Path;import java.util.UUID;
public class SubmitOfflineJob {  public static void main(String[] args) throws IOException, InterruptedException {    var boundary = "----TruebarBoundary" + UUID.randomUUID();
    String pipelineJson = """        [          {            \"task\": \"ASR\",            \"exceptionHandlingPolicy\": \"THROW\",            \"config\": { \"tag\": \"KALDI:sl-SI:COL:20221208-0800\", \"parameters\": { \"enableInterims\": false } }          },          {            \"task\": \"NLP_pc\",            \"exceptionHandlingPolicy\": \"SKIP\",            \"config\": { \"tag\": \"NEMO_PUNCTUATOR:sl-SI:*:*\", \"parameters\": { \"enableSplitToSentences\": true } }          }        ]        """;
    byte[] audioBytes = Files.readAllBytes(Path.of("sample.pcm"));
    var builder = new StringBuilder();    builder.append("--").append(boundary).append("\r\n");    builder.append("Content-Disposition: form-data; name=\"pipeline\"; filename=\"pipeline.json\"\r\n");    builder.append("Content-Type: application/json\r\n\r\n");    builder.append(pipelineJson).append("\r\n");
    builder.append("--").append(boundary).append("\r\n");    builder.append("Content-Disposition: form-data; name=\"data\"; filename=\"sample.pcm\"\r\n");    builder.append("Content-Type: application/octet-stream\r\n\r\n");
    byte[] header = builder.toString().getBytes(StandardCharsets.UTF_8);    byte[] footer = ("\r\n--" + boundary + "--\r\n").getBytes(StandardCharsets.UTF_8);
    byte[] body = new byte[header.length + audioBytes.length + footer.length];    System.arraycopy(header, 0, body, 0, header.length);    System.arraycopy(audioBytes, 0, body, header.length, audioBytes.length);    System.arraycopy(footer, 0, body, header.length + audioBytes.length, footer.length);
    HttpRequest request = HttpRequest.newBuilder()        .uri(URI.create(System.getenv("TRUEBAR_API_BASE_URL") + "/api/pipelines/process"))        .header("Authorization", "Bearer " + System.getenv("TRUEBAR_ACCESS_TOKEN"))        .header("Content-Type", "multipart/form-data; boundary=" + boundary)        .POST(HttpRequest.BodyPublishers.ofByteArray(body))        .build();
    HttpClient client = HttpClient.newHttpClient();    HttpResponse<byte[]> response = client.send(request, HttpResponse.BodyHandlers.ofByteArray());    System.out.println("Status: " + response.statusCode());    System.out.println("Content-Type: " + response.headers().firstValue("Content-Type").orElse("unknown"));  }}

pipeline.json contains the same stage definition you would send to the streaming API.

pipeline.json

[  {    "task": "ASR",    "exceptionHandlingPolicy": "THROW",    "config": {      "tag": "KALDI:sl-SI:COL:20221208-0800",      "parameters": { "enableInterims": false }    }  },  {    "task": "NLP_pc",    "exceptionHandlingPolicy": "SKIP",    "config": {      "tag": "NEMO_PUNCTUATOR:sl-SI:*:*",      "parameters": { "enableSplitToSentences": true }    }  }]

Text payload schema#

Text-based pipelines expect a JSON array of text segments. Each segment wraps one or more tokens; at minimum you must supply the token text.

[  {    "isFinal": true,    "startTimeMs": 0,    "endTimeMs": 1500,    "tokens": [      { "text": "Danes" },      { "text": "je" },      { "text": "lep" },      { "text": "dan" },      { "text": ".", "isLeftHanded": true }    ]  }]

Token fields:

text (required) – literal text.
isLeftHanded / isRightHanded – spacing hints used by the quickstarts.
startOffsetMs / endOffsetMs – token-level timings relative to the segment.
speakerCode – diarisation speaker label.
confidence – probability score returned by ASR/NLP stages.

Segment fields (isFinal, startTimeMs, endTimeMs) are optional unless you need precise alignment metadata.

Audio payloads#

Upload audio in the data form field.
The server accepts common WAV/FLAC/MP3/MP4 containers; prefer mono 16 kHz PCM for best accuracy.
Avoid multi-track media: the decoder does not auto-select an audio stream.
For large uploads, enable --compressed in curl or use resumable uploads in your HTTP client.

Response formats#

Pipelines ending in text stages (ASR, NLP) return JSON using the same segment structure as above.
Pipelines ending in audio stages (TTS) return raw audio bytes (Content-Type: application/octet-stream).
On success you’ll receive 200 OK (sync) or 202 ACCEPTED (async); failed jobs include a JSON error object with id, timestamp, and message.

Worked examples#

Punctuation-only text job#

cURL
Python
JavaScript (Node.js)
Java

curl --fail --location \  --request POST "$TRUEBAR_API_BASE_URL/api/pipelines/process" \  --header "Authorization: Bearer $TRUEBAR_ACCESS_TOKEN" \  --form 'pipeline=[{"task":"NLP_pc","exceptionHandlingPolicy":"THROW","config":{"tag":"NEMO_PC:sl-SI:*:*","parameters":{"enableSplitToSentences":false}}}];type=application/json' \  --form 'data=[{"tokens":[{"text":"Danes"},{"text":"je"},{"text":"lep"},{"text":"dan"}]}];type=application/json'

import jsonimport os
import requests

pipeline = [    {        "task": "NLP_pc",        "exceptionHandlingPolicy": "THROW",        "config": {            "tag": "NEMO_PC:sl-SI:*:*",            "parameters": {"enableSplitToSentences": False},        },    }]
text_segments = [    {"tokens": [{"text": word} for word in ["Danes", "je", "lep", "dan"]]}]
response = requests.post(    f"{os.environ['TRUEBAR_API_BASE_URL']}/api/pipelines/process",    headers={"Authorization": f"Bearer {os.environ['TRUEBAR_ACCESS_TOKEN']}"},    files={        "pipeline": ("pipeline.json", json.dumps(pipeline), "application/json"),        "data": ("segments.json", json.dumps(text_segments), "application/json"),    },    timeout=10,)response.raise_for_status()print(response.json())

import axios from 'axios';import FormData from 'form-data';
const pipeline = [  {    task: 'NLP_pc',    exceptionHandlingPolicy: 'THROW',    config: {      tag: 'NEMO_PC:sl-SI:*:*',      parameters: { enableSplitToSentences: false },    },  },];
const segments = [  { tokens: [{ text: 'Danes' }, { text: 'je' }, { text: 'lep' }, { text: 'dan' }] },];
const form = new FormData();form.append('pipeline', JSON.stringify(pipeline), {  filename: 'pipeline.json',  contentType: 'application/json',});form.append('data', JSON.stringify(segments), {  filename: 'segments.json',  contentType: 'application/json',});
const { data } = await axios.post(  `${process.env.TRUEBAR_API_BASE_URL}/api/pipelines/process`,  form,  {    headers: {      Authorization: `Bearer ${process.env.TRUEBAR_ACCESS_TOKEN}`,      ...form.getHeaders(),    },  },);console.log(data);

import java.net.URI;import java.net.http.HttpClient;import java.net.http.HttpRequest;import java.net.http.HttpResponse;
public class SubmitPunctuationJob {  public static void main(String[] args) throws Exception {    String boundary = "----TruebarBoundaryPunctuation";    String pipelineJson = """        [          {            \"task\": \"NLP_pc\",            \"exceptionHandlingPolicy\": \"THROW\",            \"config\": { \"tag\": \"NEMO_PC:sl-SI:*:*\", \"parameters\": { \"enableSplitToSentences\": false } }          }        ]        """;    String dataJson = """        [          {            \"tokens\": [              { \"text\": \"Danes\" },              { \"text\": \"je\" },              { \"text\": \"lep\" },              { \"text\": \"dan\" }            ]          }        ]        """;
    String body = "--" + boundary + "\r\n" +        "Content-Disposition: form-data; name=\"pipeline\"; filename=\"pipeline.json\"\r\n" +        "Content-Type: application/json\r\n\r\n" +        pipelineJson + "\r\n" +        "--" + boundary + "\r\n" +        "Content-Disposition: form-data; name=\"data\"; filename=\"segments.json\"\r\n" +        "Content-Type: application/json\r\n\r\n" +        dataJson + "\r\n" +        "--" + boundary + "--\r\n";
    HttpRequest request = HttpRequest.newBuilder()        .uri(URI.create(System.getenv("TRUEBAR_API_BASE_URL") + "/api/pipelines/process"))        .header("Authorization", "Bearer " + System.getenv("TRUEBAR_ACCESS_TOKEN"))        .header("Content-Type", "multipart/form-data; boundary=" + boundary)        .POST(HttpRequest.BodyPublishers.ofString(body))        .build();
    HttpClient client = HttpClient.newHttpClient();    HttpResponse<String> response = client.send(request, HttpResponse.BodyHandlers.ofString());    System.out.println(response.body());  }}

Response:

[  {    "isFinal": true,    "tokens": [      { "text": "Danes" },      { "text": "je" },      { "text": "lep" },      { "text": "dan" },      { "text": ".", "isLeftHanded": true }    ]  }]

Speech-to-text audio job#

cURL
Python
JavaScript (Node.js)
Java

curl --fail --location \  --request POST "$TRUEBAR_API_BASE_URL/api/pipelines/process" \  --header "Authorization: Bearer $TRUEBAR_ACCESS_TOKEN" \  --form 'pipeline=[{"task":"ASR","exceptionHandlingPolicy":"THROW","config":{"tag":"KALDI:sl-SI:COL:20221208-0800","parameters":{"enableInterims":false,"enableSd":false}}}];type=application/json' \  --form 'data=@sample.wav;type=audio/wav'

import jsonimport osfrom pathlib import Path
import requests

pipeline = [    {        "task": "ASR",        "exceptionHandlingPolicy": "THROW",        "config": {            "tag": "KALDI:sl-SI:COL:20221208-0800",            "parameters": {"enableInterims": False, "enableSd": False},        },    }]
response = requests.post(    f"{os.environ['TRUEBAR_API_BASE_URL']}/api/pipelines/process",    headers={"Authorization": f"Bearer {os.environ['TRUEBAR_ACCESS_TOKEN']}"},    files={        "pipeline": ("pipeline.json", json.dumps(pipeline), "application/json"),        "data": ("sample.wav", Path("sample.wav").read_bytes(), "audio/wav"),    },    timeout=30,)response.raise_for_status()print(response.json())

import { readFileSync } from 'node:fs';import FormData from 'form-data';import axios from 'axios';
const pipeline = [  {    task: 'ASR',    exceptionHandlingPolicy: 'THROW',    config: {      tag: 'KALDI:sl-SI:COL:20221208-0800',      parameters: { enableInterims: false, enableSd: false },    },  },];
const form = new FormData();form.append('pipeline', JSON.stringify(pipeline), {  filename: 'pipeline.json',  contentType: 'application/json',});form.append('data', readFileSync('sample.wav'), {  filename: 'sample.wav',  contentType: 'audio/wav',});
const { data } = await axios.post(  `${process.env.TRUEBAR_API_BASE_URL}/api/pipelines/process`,  form,  {    headers: {      Authorization: `Bearer ${process.env.TRUEBAR_ACCESS_TOKEN}`,      ...form.getHeaders(),    },  },);console.log(data);

import java.net.URI;import java.net.http.HttpClient;import java.net.http.HttpRequest;import java.net.http.HttpResponse;import java.nio.charset.StandardCharsets;import java.nio.file.Files;import java.nio.file.Path;
public class SubmitAsrJob {  public static void main(String[] args) throws Exception {    String boundary = "----TruebarBoundaryAsr";    String pipelineJson = """        [          {            \"task\": \"ASR\",            \"exceptionHandlingPolicy\": \"THROW\",            \"config\": { \"tag\": \"KALDI:sl-SI:COL:20221208-0800\", \"parameters\": { \"enableInterims\": false, \"enableSd\": false } }          }        ]        """;
    byte[] audio = Files.readAllBytes(Path.of("sample.wav"));
    var builder = new StringBuilder();    builder.append("--").append(boundary).append("\r\n");    builder.append("Content-Disposition: form-data; name=\"pipeline\"; filename=\"pipeline.json\"\r\n");    builder.append("Content-Type: application/json\r\n\r\n");    builder.append(pipelineJson).append("\r\n");    builder.append("--").append(boundary).append("\r\n");    builder.append("Content-Disposition: form-data; name=\"data\"; filename=\"sample.wav\"\r\n");    builder.append("Content-Type: audio/wav\r\n\r\n");
    byte[] header = builder.toString().getBytes(StandardCharsets.UTF_8);    byte[] footer = ("\r\n--" + boundary + "--\r\n").getBytes(StandardCharsets.UTF_8);    byte[] body = new byte[header.length + audio.length + footer.length];    System.arraycopy(header, 0, body, 0, header.length);    System.arraycopy(audio, 0, body, header.length, audio.length);    System.arraycopy(footer, 0, body, header.length + audio.length, footer.length);
    HttpRequest request = HttpRequest.newBuilder()        .uri(URI.create(System.getenv("TRUEBAR_API_BASE_URL") + "/api/pipelines/process"))        .header("Authorization", "Bearer " + System.getenv("TRUEBAR_ACCESS_TOKEN"))        .header("Content-Type", "multipart/form-data; boundary=" + boundary)        .POST(HttpRequest.BodyPublishers.ofByteArray(body))        .build();
    HttpClient client = HttpClient.newHttpClient();    HttpResponse<String> response = client.send(request, HttpResponse.BodyHandlers.ofString());    System.out.println(response.body());  }}

The response is a JSON array of text segments. To receive audio instead (e.g., TTS), end the pipeline with a TTS stage; the response body will contain PCM bytes that you can stream to a player or persist as a file.

HTTP responses & errors#

Successful operations return:

200 OK – synchronous job completed with results in the body.
202 ACCEPTED – async job accepted; poll the history API or the URL returned in the Location header.
204 NO_CONTENT – ad-hoc helper endpoints (e.g., deletes) completed successfully.

Common error codes:

400 BAD_REQUEST – malformed multipart payload or invalid pipeline definition.
401 UNAUTHORIZED / 403 FORBIDDEN – missing token or insufficient roles (PIPELINE_OFFLINE_API, STAGE_*).
404 NOT_FOUND – unknown session/job identifier when querying results.
409 CONFLICT – duplicate submission or resource already exists.
415 UNSUPPORTED_MEDIA_TYPE – decoder cannot read the uploaded audio.
500 INTERNAL_SERVER_ERROR – unexpected platform error (contact support with the id from the response body).

Error response shape

{  "id": "b7f1c8c0-3a4b-4d9b-8d2e-f2b9f8a6c1de",  "timestamp": "2024-04-22T08:15:30.123Z",  "message": "Pipeline tag KALDI:sl-SI:COL:20221208-0800 not available for this tenant."}

Related guides#

Streaming STT Guide – real-time transcription.
Streaming TTS Guide – real-time synthesis.
History API – retrieve completed jobs and recordings.