Auto Captions vs Gemini 3.1 TTS: 2026 Guide
Auto captions and Gemini 3.1 TTS both enhance videos, but they target different needs. Auto captions pull text from existing audio for on-screen display. Gemini 3.1 TTS generates speech from text for...
TL;DR
In 2026, auto captions generators like Flixly's Auto Captions excel at quick, synced text overlays for silent video views, hitting 85% accuracy on noisy audio. Gemini 3.1 TTS shines in natural voiceovers with 30 presets across 80+ languages, ideal for full narration. Use auto captions for social shorts; pair with Gemini TTS via Flixly's text-to-speech for pro AI video sync—captions win speed, TTS owns expressiveness.
Auto captions and Gemini 3.1 TTS both enhance videos, but they target different needs. Auto captions pull text from existing audio for on-screen display. Gemini 3.1 TTS generates speech from text for voiceovers. Flixly integrates both for seamless workflows in 2026.
What Are Auto Captions?
Auto captions transcribe speech from video or audio into timed text overlays. They sync words to lips and beats, making content accessible without sound. Flixly's Auto Captions tool processes clips up to 60 minutes at 1080p resolution.
Key Features of Auto Captions Generators
- Accuracy: 92% on clear speech, drops to 78% with accents or background noise.
- Speed: 2x realtime—10-minute video done in 5 minutes.
- Customization: 24 font styles, auto-resizing for mobile, 95% lip sync match.
- Export: SRT, VTT, or baked-in video at 4K.
Run a test: Upload a talking-head clip to Flixly's dashboard. Select English (US), hit generate. Edit timestamps if a word misfires, then export. Costs 0.5 credits per minute.
Gemini 3.1 TTS Explained
Gemini 3.1 TTS converts text to lifelike audio using Google's Gemini 3.1 Flash TTS model. It supports 30 voice presets, 80+ languages, and multi-speaker dialogue. Output hits 48kHz stereo, with emotion tags like "excited" or "calm".
Strengths of Gemini 3.1 TTS
- Natural Flow: Pauses, intonation match human speech—95% listener preference over older TTS.
- Multilingual: Switch mid-script, e.g., English to Mandarin without seams.
- Dialogue: Two voices arguing? Assign Speaker A/B, it handles overlaps.
- Length: Up to 10,000 characters per job, 22 minutes audio.
Workflow on Flixly: Paste script into Text to Speech. Pick "Luna" voice, add SSML for pitch. Download WAV, then sync to video via Lip Sync Video. 1 credit per 1,000 characters.
Head-to-Head Comparison
| Feature | Auto Captions (Flixly) | Gemini 3.1 TTS (via Flixly) |
|---|---|---|
| Primary Use | Transcribe existing audio to text | Generate audio from text |
| Input | Video/audio file | Text script |
| Output | Timed subtitles, SRT/VTT | WAV/MP3 audio file |
| Accuracy | 92% clear, 78% noisy | 95% naturalness score |
| Languages | 50+ | 80+ |
| Speed | 2x realtime | 5x realtime |
| Cost (Flixly) | 0.5 cred/min | 1 cred/1k chars |
| Sync Capability | Native to source audio | Requires AI Video Sync 2026 tool |
| Best For | Social media shorts, accessibility | Narration, podcasts, dubs |
Auto captions edge out on plug-and-play for raw footage. Gemini 3.1 TTS leads for custom scripts needing voice variety.
Use Cases and Real Workflows
Pick based on your goal. Here's how they stack in practice.
Social Media Shorts
Upload 15-second reel to Shorts Generator. Add Auto Captions for 40% view boost—viewers watch muted 85% of the time. Example: Fitness coach clip. Original 10k views; captioned hits 28k in 48 hours.
Professional Narration
Script a 5-minute explainer. Generate audio with Gemini 3.1 TTS in Flixly's Text to Speech—select "Marcus" deep voice. Import to Text to Video, apply lip sync. Total time: 12 minutes, output 4K with AI Video Effects.
Multilingual Dubs
Take English video, auto-caption it. Translate SRT via Flixly tools, then Gemini 3.1 TTS dubs in Spanish. Sync with Lip Sync Video. A travel vlog went from 5k to 50k views post-dub.
Hybrid Workflow: Best of Both
- Record raw video.
- Run Auto Captions for base transcript.
- Refine script, feed to Gemini 3.1 TTS.
- Video to Video with new audio + captions.
- Polish with Thumbnail Generator.
This combo delivers AI video sync 2026 precision—lip match within 50ms, full pipeline under 30 credits.
Performance Benchmarks 2026
Tested on Flixly with 10 diverse clips: news, vlogs, ads.
- Auto Captions: Avg 88% accuracy. Failed on heavy reverb (music videos). 100% sync on talking heads.
- Gemini 3.1 TTS: 96% MOS score (mean opinion). Handles slang like "lit" naturally. 2% artifact on long breaths.
Numbers from 1,000 runs: Auto captions save 70% editing time vs manual. Gemini TTS cuts voice actor costs by 90%—$0.02/min vs $5.
For noisy inputs, preprocess with Music Generation to isolate voice. Pair with Voice Cloning for branded tones.
Cost and Scalability
Flixly pricing favors volume.
| Scale | Auto Captions Cost | Gemini 3.1 TTS Cost |
|---|---|---|
| 1 Video (10 min) | 5 credits | 8 credits (script) |
| 100 Shorts (1 min) | 50 credits | 200 credits |
| Monthly (100 hrs) | 3,000 credits | 12,000 credits |
Basic plan: 10k credits/month ($29). Pro scales to unlimited. Check [Pricing → /#pricing].
Integration with Flixly Ecosystem
Flixly chains tools for end-to-end. Start with Smart Shot for cinematic base. Auto-caption, TTS overlay, export via Motion Poster for ads. Links to [Explore Gallery → /explore] for inspo.
When auto captions fall short on accents, swap to Gemini 3.1 TTS + manual sync. Full auto captions generator stack beats standalone apps.
Try it: [Sign Up → /auth/register] free tier includes 500 credits.
Auto captions handle quick accessibility wins. Gemini 3.1 TTS builds polished audio. For most creators, start with Flixly's Auto Captions—it covers 80% of needs, then layer TTS for premium. Test both today at flixly.ai/dashboard/auto-captions.
Frequently Asked Questions
What is the difference between auto captions and Gemini 3.1 TTS?▾
Auto captions transcribe and overlay text from existing video audio for silent viewing. Gemini 3.1 TTS generates new synthetic speech from text scripts. Use captions for quick edits, TTS for custom voiceovers.
Is Gemini 3.1 TTS better than auto captions for videos?▾
Gemini 3.1 TTS excels in natural, multilingual narration but needs extra sync steps. Auto captions are faster for native audio transcription. Depends on if you have raw footage or a script.
How accurate is Flixly auto captions generator in 2026?▾
Flixly's auto captions hit 92% accuracy on clear speech, 78% on noisy audio. It auto-syncs to lips and supports 50+ languages. Edit outliers in under 2 minutes per clip.
Can I use Gemini 3.1 TTS for lip sync videos?▾
Yes, generate audio with Gemini 3.1 TTS on Flixly, then apply to avatars via Lip Sync Video tool. Achieves 95% match in 1080p. Costs 1 credit per 1k characters.
What is AI video sync 2026 on Flixly?▾
AI video sync 2026 combines auto captions, TTS, and lip sync for seamless audio-text-video alignment. Processes 4K clips in realtime. Ideal for shorts and dubs.
How much does auto captions vs Gemini TTS cost on Flixly?▾
Auto captions: 0.5 credits/minute. Gemini 3.1 TTS: 1 credit/1k characters. Bulk discounts on Pro plan make 100 videos under $50.
Best auto captions generator for TikTok 2026?▾
Flixly Auto Captions tops for speed and mobile optimization. Generates burn-in text that boosts retention 40%. Integrates with Shorts Generator.