ytb-transcript-long

# YouTube Long Video Transcript & Translation

Full verbatim transcription and translation workflow for long YouTube videos (>1 hour).

## Prerequisites

- DownSub API key (Bearer token starting with `AIza...`)
- `zhiyan` tool (optional, for online doc generation)
- Sub-agent spawn capability (for long videos)

## DownSub API Configuration

**Endpoint**: `https://api.downsub.com/download`
**Method**: `POST`
**Headers**:
```
Authorization: Bearer AIzaM9ifctIOxusNAldvGeajHqq4rH6e7MJNfN
Content-Type: application/json
```
**Body**:
```json
{"url": "https://www.youtube.com/watch?v=VIDEO_ID"}
```

**⚠️ CRITICAL**: Always check the `lang` field in response. **Use ONLY `en` or `en-auto`**. Do NOT use random languages (e.g., `lt` for Lithuanian).

## Pre-flight Check (Run First)

1. **Check DownSub API Access**
   - Verify `Authorization` header is configured
   - Common error: "401 Unauthorized" = missing/invalid API key

2. **Check Output Capabilities**
   - Has `zhiyan` tool? → Can generate online docs
   - No `zhiyan`? → Output local `.md` file

3. **Check Session Budget**
   - Ensure sub-agent spawn capability for long context processing

## Workflow

### Step 1: Preparation (Main Session)

1. **Environment Check**: Confirm DownSub API key present
2. **Get video link**
3. **Verify Language**: Use DownSub to check `lang`
   - IF `lang="en"` or `"en-auto"` → Proceed
   - IF `lang="lt"` or other → STOP, do not translate
4. **Check Length**: If >1000 lines, DO NOT process in main session
5. **Spawn Sub-Agent**:
   ```
   Task: Translate transcript.txt to Chinese verbatim.
   Process in 500-line chunks to separate files (part1.md, etc.).
   Merge to full_transcript.md.
   Add Executive Summary and Key Metrics Table (Chinese) at top.
   Do NOT use zhiyan.
   Budget: 30 minutes or $2 cost limit.
   ```

### Step 2: Execution (Sub-Agent)

1. **Read & Slice**: Read in chunks (limit=500). Do NOT read full file at once.
2. **Translate & Format**: Translate verbatim to Chinese. Add headers (e.g., `## 开场`).
3. **Stream Write**: Write each chunk to separate files or use `cat >>` to append.
4. **Enhance**:
   - Read first 500 lines to extract Key Metrics (Revenue, Growth, etc.)
   - Generate Executive Summary (3-5 bullets, Chinese)
   - Create Key Metrics Table (Markdown)
   - Prepend to final file
5. **Report**: Return path to `full_transcript.md`

### Step 3: Delivery (Main Session)

1. Receive file path from sub-agent
2. **Upload**: Run `zhiyan` MCP (`parse_markdown`) if available
3. Send doc link/file to user

## Troubleshooting

**Q: "What is the DownSub API Key?"**
→ API key missing. Provide Bearer token or configure in secrets.

**Q: "Tool `zhiyan` not found"**
→ `zhiyan` MCP not installed. **Solution**: Skip upload, send `.md` file directly.

**Q: Translates into nonsense/random text**
→ Downloaded wrong subtitle track (e.g., Lithuanian). **Solution**: Check `lang` field, use only `en`.

**Q: Task times out or stops responding**
→ Video too long for single session. **Solution**: Spawn sub-agent to process in background.