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This guide covers the three ways to submit audio for batch transcription. For endpoint details and schemas, see the Batch API reference.
The Batch API is served from https://api.batch.slng.ai, not https://api.slng.ai, and uses the same bearer API key.
Prerequisites:
  • An SLNG API key
  • Audio in a supported format: wav, mp3, flac, aac, ogg, m4a, mp4, amr, mpeg

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Placeholders

The snippets below use these placeholders. Replace them before running the code.
PlaceholderReplace with
$API_KEYAn SLNG API key from app.slng.ai/api-keys. Set with export API_KEY=…
myjob123 / job8f3a...The job_id returned by POST /v1/batch/jobs (auto-generated if omitted)
<presigned_url>The presigned upload URL returned by the mode: "presign" flow
audio.wav / s3_keyYour local file path / the S3 key the gateway returned at presign time

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Input Methods

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Method 1: File Upload

Upload the audio file directly using multipart/form-data. 
curl -X POST https://api.batch.slng.ai/v1/batch/jobs \
  -H "Authorization: Bearer $API_KEY" \
  -F file=@audio.wav \
  -F transcription_config='{"language":"en"}'

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Method 2: URL Input

Provide a publicly accessible HTTPS URL. The system downloads the file (max 1 GB). Supports presigned S3/GCS URLs for private files. 
curl -X POST https://api.batch.slng.ai/v1/batch/jobs \
  -H "Authorization: Bearer $API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "input_url": "https://example.com/audio.wav",
    "transcription_config": { "language": "en" }
  }'
FieldTypeRequiredDescription
input_urlstringyesHTTPS URL of the audio file
transcription_configobjectyesTranscription settings
job_idstringnoAlphanumeric job ID (auto-generated if omitted)
model_codestringnoModel to use (default: slng/speechmatics/batch:15.0.0)
metadataobjectnoArbitrary key-value metadata

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Method 3: Presigned Upload

Use this method for large files or when you need upload progress tracking. Three steps: request a presigned URL, upload the file directly to S3, then create the job referencing the upload.
1

Request a presigned S3 upload URL

curl -X POST https://api.batch.slng.ai/v1/batch/jobs \
  -H "Authorization: Bearer $API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "mode": "presign",
    "filename": "audio.wav",
    "transcription_config": { "language": "en" }
  }'
Returns 200 OK (no job is created yet). The response carries the job_id, the validated transcription_config (and any other config you sent, echoed back), the future S3 locations, and an upload object with the presigned PUT URL plus the headers your upload must send:
{
  "job_id": "job8f3a...",
  "transcription_config": { "language": "en", "operating_point": "standard", "diarization": "none" },
  "input_s3_uri": "s3://slng-production-batch-input/inputs/job8f3a.../audio.wav",
  "output_s3_prefix": "s3://slng-production-batch-output/outputs/job8f3a.../",
  "upload": {
    "url": "https://slng-production-batch-input.s3.amazonaws.com/...",
    "s3_key": "inputs/job8f3a.../audio.wav",
    "s3_uri": "s3://slng-production-batch-input/inputs/job8f3a.../audio.wav",
    "expires_in": 1800,
    "headers": { "Content-Type": "application/octet-stream" }
  }
}
Carry the returned transcription_config (and any echoed tracking / output_config) verbatim into step 3.
2

Upload the file to the presigned URL

Send the bytes with the exact headers from upload.headers (typically Content-Type: application/octet-stream):
curl -X PUT "<presigned_url>" \
  -H "Content-Type: application/octet-stream" \
  --data-binary @audio.wav
3

Create the job

Reference the job_id and s3_key from step 1.
curl -X POST https://api.batch.slng.ai/v1/batch/jobs \
  -H "Authorization: Bearer $API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "job_id": "job8f3a...",
    "s3_key": "inputs/job8f3a.../audio.wav",
    "transcription_config": { "language": "en" }
  }'

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Job Lifecycle

After submission, a job moves through these statuses: QUEUED → IN_PROGRESS → DECODING → POST_PROCESSING → DONE / FAILED A successfully deleted job moves to DELETED (terminal). Poll GET /v1/batch/jobs/{jobId} until the status reaches DONE or FAILED. The response includes the full job record (config, timestamps, error_message on failures); see the API reference for the schema. 
curl https://api.batch.slng.ai/v1/batch/jobs/myjob123 \
  -H "Authorization: Bearer $API_KEY"
Once DONE, retrieve the transcript: 
curl https://api.batch.slng.ai/v1/batch/jobs/myjob123/files \
  -H "Authorization: Bearer $API_KEY"
This returns signed download URLs for the input audio and the output transcripts. Each output entry carries a format field: json, txt, or srt. Signed URLs expire after roughly one hour. To list jobs instead of polling a single one, use GET /v1/batch/jobs. It supports pagination (page, page_size) plus filtering by status, model_code, and submission date range, and sorting by submitted_at, status, or model_code. See the API reference for the full parameter list.

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Transcription Config

FieldTypeDefaultDescription
languagestringenLanguage code for the audio
operating_pointstringstandardAccuracy level: standard or enhanced
diarizationstringnoneSpeaker separation: none, speaker, or channel
domainstring—Domain-specific language model
output_localestring—Locale for formatting (dates, numbers)
enable_entitiesboolean—Detect and format entities (dates, times, addresses)
additional_vocabarray—Custom words to improve recognition
Example with diarization and enhanced accuracy: 
{
  "transcription_config": {
    "language": "en",
    "operating_point": "enhanced",
    "diarization": "speaker"
  }
}

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Limits

LimitValue
Max file size1 GB
Presigned upload URL expiry30 minutes
Supported audio formatswav, mp3, flac, aac, ogg, m4a, mp4, amr, mpeg
URL input schemeHTTPS only

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Next Steps

Batch API reference

Endpoint details, request schemas, and response formats

Getting started

Set up your API key and make your first request