best AI video generation API 2026 Veo 3.1 API Grok video API Omni Flash API video generation API comparison GenRelay video

Best AI Video Generation API in 2026 — Breakdown | GenRelay

Aug 22, 2026·9 min read

You're evaluating video generation APIs for a product feature. The marketing copy for each model says roughly the same thing. The real differences — billing structure, generation modes, audio support, resolution ceiling, and actual cost at your expected volume — are scattered across docs that don't always agree.

This article covers every video model available through GenRelay as of August 2026. For each model: what it generates, how it bills, the real pricing, what it's suited for, and where it falls short. Then a consolidated comparison table and clear per-use-case recommendations so you can make a decision and start building.

What video generation models are available on GenRelay?

As of August 2026, GenRelay provides access to four video models:

Model	Generation mode	Audio	Max resolution
Veo 3.1 Lite	t2v / i2v / ref2v	Yes	4K
Gemini Omni Flash	t2v	No	1080p
Grok Imagine 1.0	t2v	No	1080p
Grok Imagine 1.5	i2v	No	1080p

All four are accessible through a single endpoint — https://genrelay.ai/v1/videos/generations — with a consistent request structure. Switching models requires only a model field change.

Veo 3.1 Lite — highest output quality, full generation mode coverage

What it generates: Text-to-video (t2v), image-to-video (i2v), and reference-to-video (ref2v). Veo 3.1 Lite is the only video model in this set that supports ref2v — generating video from a reference clip to maintain motion style or scene continuity. It also synthesizes audio alongside the video; sound effects and ambient audio are produced in the same generation call, not as a post-processing step.

Billing: Per second of output video, tiered by resolution.

Resolution	Rate per second
720p	$0.060
1080p	$0.120
4K	$0.180

A 5-second clip at 720p costs $0.30. At 1080p the same clip is $0.60. At 4K it is $0.90.

What it's best for:
- Marketing hero videos and premium creative assets where quality matters and generation frequency is moderate
- Workflows that require all three generation modes — particularly ref2v, unavailable in any other model here
- Use cases where the output needs audio (product demos, social ads, narrated clips)
- Paid creative tools where the higher per-clip cost is passed through to end users

Where it falls short: It's the most expensive model in this set by a significant margin. For high-volume background loops, draft generation, or social filler content, the per-second rate makes it hard to justify at scale.

Verdict: Use Veo 3.1 Lite when quality, audio, or ref2v matter. Route cost-sensitive bulk workloads to Grok 1.0 or Omni Flash.

Gemini Omni Flash — flat per-generation billing, predictable unit costs

What it generates: Text-to-video. Omni Flash produces clips at a fixed price per generation, independent of clip duration. Your cost per clip is the same whether the output is 3 seconds or 15 seconds.

Billing: Per generation (flat rate per API call).

Resolution	Rate per generation
720p	$0.10
1080p	$0.15

What it's best for:
- Apps that generate variable-length clips and need a stable per-clip unit cost for billing or budgeting
- Longer clips at 720p — the effective per-second rate improves as clip length increases; a 15-second clip at $0.10 total works out to $0.0067/s, well below any per-second model
- Workloads where predicting monthly spend from a single number (clips × $0.10) is more useful than tracking seconds generated

Where it falls short: Text-to-video only. No image-to-video or reference modes. No audio output. Maximum resolution is 1080p.

Verdict: Use Omni Flash when flat per-clip billing makes budget planning easier, or when you're generating longer clips where the fixed rate becomes cost-competitive. For short clips (under 5 seconds at 720p), Grok 1.0 may be cheaper.

For a direct comparison of billing behavior between Omni Flash and Veo 3.1 Lite, see Veo 3.1 vs Omni Flash.

Grok Imagine 1.0 — lowest per-second rate, text-to-video at scale

What it generates: Text-to-video. Grok Imagine 1.0 is the most cost-efficient per-second model in this set. At $0.010 per second, it costs 6× less than Veo 3.1 Lite at 720p.

Billing: Per second of output video, flat across resolutions.

Resolution	Rate per second
720p	$0.010
1080p	$0.010

What it's best for:
- High-volume text-to-video workloads where cost efficiency is the primary constraint
- Apps with free tiers that include video generation — 1,000 five-second clips costs $50 total
- Rapid draft generation and iteration before committing to a higher-quality final render
- Short-form social content (5–8 second clips) where output volume is high

Where it falls short: Text-to-video only. No image-to-video. No audio. Output quality is lower than Veo 3.1 Lite — less coherent motion on complex prompts and weaker prompt adherence in dynamic scenes.

Verdict: Grok Imagine 1.0 is the right default for cost-sensitive bulk text-to-video. At $0.010/s, it's the lowest-cost path to any video output on GenRelay.

Grok Imagine 1.5 — image-to-video at an affordable per-second rate

What it generates: Image-to-video (i2v). Provide a source image and a motion prompt; the model animates the image into a video clip. As of August 2026, Grok Imagine 1.5 is the most affordable i2v option on GenRelay.

Billing: Per second of output video, flat across resolutions.

Resolution	Rate per second
720p	$0.022
1080p	$0.022

What it's best for:
- Product photo animation — taking static e-commerce or marketing images and generating motion clips for ads or listings
- Portrait and character animation from still photos
- Workflows that need i2v at a lower cost than Veo 3.1 Lite's i2v mode ($0.060/s vs. $0.022/s at 720p)

Where it falls short: Image-to-video only — no text-to-video support. No audio. The same output quality ceiling as Grok 1.0 relative to Veo 3.1 Lite.

Verdict: Use Grok Imagine 1.5 for i2v workloads where cost matters. If you need i2v with higher output quality or audio synthesis, Veo 3.1 Lite covers both at a higher per-second rate.

For integration code and parameters for both Grok models, see the Grok video API guide.

How do the four models compare at a 5-second 720p clip?

Model	Billing	Cost per 5-second 720p clip
Grok Imagine 1.0	$0.010/s	$0.050
Omni Flash	$0.10/clip	$0.10
Grok Imagine 1.5 (i2v)	$0.022/s	$0.110
Veo 3.1 Lite	$0.060/s	$0.30

At this clip length, Grok 1.0 is cheapest for t2v. Omni Flash's flat rate becomes more competitive as clip length increases — at 15 seconds, Omni Flash costs $0.10 versus Grok 1.0's $0.15.

Monthly cost — 1,000 clips at 5 seconds, 720p:

Model	Monthly estimate
Grok Imagine 1.0	$50
Omni Flash	$100
Grok Imagine 1.5	$110
Veo 3.1 Lite	$300

Which model should I use for my use case?

Need audio in the output? Veo 3.1 Lite is the only option.

Need ref2v (reference-to-video)? Veo 3.1 Lite is the only option.

Need i2v at the lowest per-second cost? Grok Imagine 1.5 at $0.022/s.

Need t2v at bulk scale? Grok Imagine 1.0 at $0.010/s.

Need flat per-clip billing for variable-length t2v? Omni Flash at $0.10–$0.15 per clip.

Building a premium paid creative tool? Veo 3.1 Lite — highest quality, full mode coverage.

How do I call the GenRelay video API in Python?

All four models share the same endpoint and the same Bearer token authentication. Switch models by changing the model field.

import os
import time
import requests

HEADERS = {"Authorization": f"Bearer {os.environ['GENRELAY_API_KEY']}"}
BASE = "https://genrelay.ai/v1"

def submit_video(model: str, prompt: str, duration: int = 5, resolution: str = "720p", **extra) -> str:
    """Submit a video generation job. Returns job ID."""
    payload = {"model": model, "prompt": prompt, "duration": duration, "resolution": resolution}
    payload.update(extra)
    r = requests.post(f"{BASE}/videos/generations", headers=HEADERS, json=payload, timeout=30)
    r.raise_for_status()
    return r.json()["id"]

def poll_job(job_id: str, interval: int = 5, max_wait: int = 300) -> str:
    """Poll until job succeeds. Returns video URL."""
    for _ in range(max_wait // interval):
        time.sleep(interval)
        r = requests.get(f"{BASE}/videos/generations/{job_id}", headers=HEADERS)
        r.raise_for_status()
        job = r.json()
        if job["status"] == "succeeded":
            return job["output"]["url"]
        if job["status"] == "failed":
            raise RuntimeError(f"Generation failed: {job.get('error')}")
    raise TimeoutError("Job did not complete within timeout")

# Text-to-video examples:
grok_job  = submit_video("grok-1.0",     "a wave breaking on a rocky shore at golden hour")
flash_job = submit_video("omni-flash",   "a wave breaking on a rocky shore at golden hour")
veo_job   = submit_video("veo-3.1-lite", "a wave breaking on a rocky shore at golden hour, ambient ocean sound")

# Image-to-video with Grok 1.5:
i2v_job = submit_video(
    "grok-1.5",
    "subtle ripple motion through the fabric",
    image_url="https://your-bucket.com/product.jpg",  # source image
    duration=5,
)

video_url = poll_job(veo_job)
print(video_url)

Frequently asked questions

Which model has the broadest feature coverage?
Veo 3.1 Lite. It supports three generation modes (t2v, i2v, ref2v), audio synthesis, and 4K resolution. No other model in this set covers all of these. For applications where only basic t2v is required, the other models offer more favorable cost structures.

Can I use multiple models in the same application?
Yes. Switching models is a single parameter change. A practical pattern: use Grok 1.0 for draft generation and user previews, then route approved requests through Veo 3.1 Lite for the final deliverable — paying the premium cost only when quality matters.

Is Omni Flash billed per second or per generation?
Per generation. One API call equals one charge regardless of clip length. This distinguishes it from Veo 3.1 Lite and the Grok models, which bill per second of output video.

What resolution should I target for social distribution?
720p is sufficient for most social platforms (Instagram Reels, TikTok, X). Use 1080p when targeting YouTube or when users will download the video as a final deliverable.

How long does video generation take?
Generation time varies by model and clip length, typically ranging from 15 seconds to a few minutes. All models return jobs asynchronously — poll GET /v1/videos/generations/{job_id} until status is succeeded. For detailed polling patterns, see the async video API polling guide.