When you submit a task to the Upload and Extend Audio API, you can use the callBackUrl parameter to set a callback URL. When the task is completed, the system will automatically push the results to your specified address.

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Callback Mechanism Overview

The callback mechanism eliminates the need to poll the API for task status. The system will proactively push task completion results to your server.

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Callback Timing

The system will send callback notifications in the following situations:
  • Audio extension task completed successfully
  • Audio extension task failed
  • Errors occurred during task processing

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Callback Method

  • HTTP Method: POST
  • Content Type: application/json
  • Timeout Setting: 15 seconds
  • Retry Mechanism: Retry 3 times after failure, with intervals of 1 minute, 5 minutes, and 15 minutes respectively

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Callback Request Format

When the task is completed, the system will send a POST request to your callBackUrl in the following format: 
{
  "code": 200,
  "msg": "All generated successfully.",
  "data": {
    "callbackType": "complete",
    "task_id": "2fac****9f72",
    "data": [
      {
        "id": "8551****662c",
        "audio_url": "https://example.cn/****.mp3",
        "source_audio_url": "https://example.cn/****.mp3",
        "stream_audio_url": "https://example.cn/****",
        "source_stream_audio_url": "https://example.cn/****",
        "image_url": "https://example.cn/****.jpeg",
        "source_image_url": "https://example.cn/****.jpeg",
        "prompt": "[Verse] Night city lights shining bright",
        "model_name": "chirp-v3-5",
        "title": "Iron Man",
        "tags": "electrifying, rock",
        "createTime": "2025-01-01 00:00:00",
        "duration": 198.44
      }
    ]
  }
}

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Status Code Description

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code
integer
required
Callback status code indicating task processing result:
Status CodeDescription
200Success - Audio extension completed
400Bad Request - Parameter error, unsupported audio file format, content violation, etc.
451Download Failed - Unable to download source audio file
500Server Error - Please try again later
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msg
string
required
Status message providing detailed status description
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data.callbackType
string
required
Callback type indicating the current callback stage:
  • text: Text generation completed
  • first: First music track completed
  • complete: All music tracks completed
  • error: Task failed
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data.task_id
string
required
Task ID, consistent with the taskId returned when you submitted the task
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data.data
array
Audio extension result information, returned on success
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data.data[].id
string
Music unique identifier
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data.data[].audio_url
string
Extended audio file URL
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data.data[].source_audio_url
string
Original audio file URL
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data.data[].stream_audio_url
string
Streaming audio URL
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data.data[].source_stream_audio_url
string
Original streaming audio URL
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data.data[].image_url
string
Cover image URL
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data.data[].source_image_url
string
Original cover image URL
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data.data[].prompt
string
Generation prompt/lyrics
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data.data[].model_name
string
Model name used
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data.data[].title
string
Music title
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data.data[].tags
string
Music tags
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data.data[].createTime
string
Creation time
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data.data[].duration
number
Audio duration (seconds)

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Callback Reception Examples

Here are example codes for receiving callbacks in popular programming languages: 
const express = require('express');
const app = express();

app.use(express.json());

app.post('/upload-extend-callback', (req, res) => {
  const { code, msg, data } = req.body;
  
  console.log('Received audio extension callback:', {
    taskId: data.task_id,
    callbackType: data.callbackType,
    status: code,
    message: msg
  });
  
  if (code === 200) {
    // Task completed successfully
    console.log('Audio extension completed');
    const musicData = data.data || [];
    
    console.log(`Extended ${musicData.length} music tracks:`);
    musicData.forEach((music, index) => {
      console.log(`Extended music ${index + 1}:`);
      console.log(`  Title: ${music.title}`);
      console.log(`  Duration: ${music.duration} seconds`);
      console.log(`  Style tags: ${music.tags}`);
      console.log(`  Extended audio URL: ${music.audio_url}`);
      console.log(`  Cover URL: ${music.image_url}`);
    });
    
    // Process extended music
    // Can download audio files, save locally, etc.
    
  } else {
    // Task failed
    console.log('Audio extension failed:', msg);
    
    // Handle failure cases...
    if (code === 400) {
      console.log('Parameter error or content violation');
    } else if (code === 451) {
      console.log('Source audio file download failed');
    } else if (code === 500) {
      console.log('Server internal error');
    }
  }
  
  // Return 200 status code to confirm callback received
  res.status(200).json({ status: 'received' });
});

app.listen(3000, () => {
  console.log('Callback server running on port 3000');
});

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Best Practices

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Callback URL Configuration Recommendations

  1. Use HTTPS: Ensure your callback URL uses HTTPS protocol for secure data transmission
  2. Verify Source: Verify the legitimacy of the request source in callback processing
  3. Idempotent Processing: The same taskId may receive multiple callbacks, ensure processing logic is idempotent
  4. Quick Response: Callback processing should return a 200 status code as quickly as possible to avoid timeout
  5. Asynchronous Processing: Complex business logic should be processed asynchronously to avoid blocking callback response
  6. Audio Processing: Audio download and processing should be done in asynchronous tasks to avoid blocking callback response

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Important Reminders

  • Callback URL must be a publicly accessible address
  • Server must respond within 15 seconds, otherwise it will be considered a timeout
  • If 3 consecutive retries fail, the system will stop sending callbacks
  • Please ensure the stability of callback processing logic to avoid callback failures due to exceptions
  • Generated audio URLs may have time limits, recommend downloading and saving promptly
  • Pay attention to content policy compliance to avoid generation failures due to policy violations
  • Ensure uploaded audio file format is supported

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Troubleshooting

If you do not receive callback notifications, please check the following:

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Alternative Solution

If you cannot use the callback mechanism, you can also use polling:

Poll Query Results

Use the get music generation details endpoint to regularly query task status. We recommend querying every 30 seconds.