[HN Gopher] Show HN: LemonSlice - Upgrade your voice agents to r...
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Show HN: LemonSlice - Upgrade your voice agents to real-time video
Hey HN, we're the co-founders of LemonSlice (try our HN playground
here: https://lemonslice.com/hn). We train interactive avatar video
models. Our API lets you upload a photo and immediately jump into a
FaceTime-style call with that character. Here's a demo:
https://www.loom.com/share/941577113141418e80d2834c83a5a0a9
Chatbots are everywhere and voice AI has taken off, but we believe
video avatars will be the most common form factor for
conversational AI. Most people would rather watch something than
read it. The problem is that generating video in real-time is hard,
and overcoming the uncanny valley is even harder. We haven't
broken the uncanny valley yet. Nobody has. But we're getting close
and our photorealistic avatars are currently best-in-class (judge
for yourself: https://lemonslice.com/try/taylor). Plus, we're the
only avatar model that can do animals and heavily stylized
cartoons. Try it: https://lemonslice.com/try/alien. Warning!
Talking to this little guy may improve your mood. Today we're
releasing our new model* - Lemon Slice 2, a 20B-parameter diffusion
transformer that generates infinite-length video at 20fps on a
single GPU - and opening up our API. How did we get a video
diffusion model to run in real-time? There was no single trick,
just a lot of them stacked together. The first big change was
making our model causal. Standard video diffusion models are
bidirectional (they look at frames both before and after the
current one), which means you can't stream. From there it was
about fitting everything on one GPU. We switched from full to
sliding window attention, which killed our memory bottleneck. We
distilled from 40 denoising steps down to just a few - quality
degraded less than we feared, especially after using GAN-based
distillation (though tuning that adversarial loss to avoid mode
collapse was its own adventure). And the rest was inference work:
modifying RoPE from complex to real (this one was cool!), precision
tuning, fusing kernels, a special rolling KV cache, lots of other
caching, and more. We kept shaving off milliseconds wherever we
could and eventually got to real-time. We set up a guest
playground for HN so you can create and talk to characters without
logging in: https://lemonslice.com/hn. For those who want to build
with our API (we have a new LiveKit integration that we're pumped
about!), grab a coupon code in the HN playground for your first Pro
month free ($100 value). See the docs: https://lemonslice.com/docs.
Pricing is usage-based at $0.12-0.20/min for video generation.
Looking forward to your feedback! EDIT: Tell us what characters
you want to see in the comments and we can make them for you to
talk to (e.g. Max Headroom) *We did a Show HN last year for our V1
model: https://news.ycombinator.com/item?id=43785044. It was
technically impressive but so bad compared to what we have today.
Author : lcolucci
Score : 51 points
Date : 2026-01-27 17:55 UTC (5 hours ago)
| zvonimirs wrote:
| We're launching a new AI assistant and I wanted to make it alive
| so I started to play around with LemonSlice and I loved it!! I
| wanted to make our assistant be like a coworker that can give it
| an ability to create Loom style videos. Here's what I created -
| https://drive.google.com/file/d/1nIpEvNkuXA0jeZVjHC8OjuJlT-3...
|
| Anyway, big thumbs up for the LemonSlice team, I'm excited to see
| it progress. I can definitely see products start coming alive
| with tools like this.
| sid-the-kid wrote:
| Very cool! Thanks for sharing. I love your use-case of turning
| an AI coding agent into more of an AI employee. Will be
| interesting to see if users can connect better with the product
| this way.
| bzmrgonz wrote:
| How did your token spend add up? I'm hesitant with evil
| customers racking up ai charges just to shit and giggles. Even
| competitors might sponsor some runaway charges.
| sid-the-kid wrote:
| hey HN! one of the founders here. as of today, we are seeing
| informational avatars + roleplaying for training as the most
| common use cases. The roleplaying use-case was surprising to us.
| Think a nurse training to triage with AI patients. Or, SDRs
| practicing lead qualification with different kinds of clients.
| buddycorp wrote:
| I'm curious if I can plug in my own OpenAI realtime voice agents
| into this.
| lcolucci wrote:
| Good question! Yes and to do this you'd want to use our "Self-
| Managed Pipeline": https://lemonslice.com/docs/self-
| managed/overview. You can combine any TTS, LLM and STT
| combination with LemonSlice as the avatar layer.
| jfaat wrote:
| I'm using an openAI realtime voice with livekit, and they said
| they have a livekit integration so it would probably be doable
| that way. I haven't used video in livekit though and I don't
| know how the plugins are setup for it
| lcolucci wrote:
| Yes this is exactly right. Using the LiveKit integration you
| can add LemonSlice as an avatar layer on top of any voice
| provider
| tmshapland wrote:
| Here's the link to the LiveKit LemonSlice plugin. It's very
| easy to get started. https://docs.livekit.io/agents/models/
| avatar/plugins/lemonsl...
| sid-the-kid wrote:
| Good question. When using the API, you can bring any voice
| agent (or LLM). Our API takes in what the agent will say, and
| then streams back the video of the agent saying it.
|
| For the fully hosted version, we are currently partnered with
| ElevenLabs.
| ed_mercer wrote:
| This looks super awesome!
| sid-the-kid wrote:
| thank you! it's by far the thing I have worked on that I am
| most proud of.
| dreamdeadline wrote:
| Cool! Do you plan to expose controls over the avatar's movement,
| facial expressions, or emotional reactions so users can fine-tune
| interactions?
| lcolucci wrote:
| Yes we do! Within the web app, there's a "action text prompt"
| section that allows you to control the overall actions of the
| character (e.g. "a fox talking with lots of arm motions").
| We'll soon expose this in the API so you can control the
| characters movements dynamically (e.g. "now wave your hand")
| sid-the-kid wrote:
| Our text control is good, especially for emotions. For example,
| you can add the text prompt: "a person talking. they are
| angry", and agent will have an angry expression.
|
| You can also control background motions (like ocean waves, or a
| waterfall or car driving).
|
| We are actively training a model that has better text control
| over hand motions.
| marieschneegans wrote:
| This is next-level!
| lcolucci wrote:
| Thanks so much! We're super proud of it
| bennyp101 wrote:
| Heads up, your privacy policy[0] does not work in dark mode - I
| was going to comment saying it made no sense, then I highlighted
| the page and more text appeared :)
|
| [0] https://lemonslice.com/privacy
| sid-the-kid wrote:
| Good catch! Working on a fix now.
| sid-the-kid wrote:
| Fix deployed! This is why it's good to launch on hacker news.
| thanks for the tip.
| bennyp101 wrote:
| Nice one - thanks :)
| benswerd wrote:
| The last year vs this year is crazy
| sid-the-kid wrote:
| thanks! it just barley worked last year, but not much else.
| this year it's actually good. we got lucky: it's both new tech
| and turned out to be good quality.
| lcolucci wrote:
| Agreed. We were so excited about the results last year and they
| are SO BAD now by comparison. Hopefully we'll say the same
| thing again in the couple months
| r0fl wrote:
| Wow this is the most impressive thing I've seen on hacker news in
| years!!!!!
|
| Take my money!!!!!!
| lcolucci wrote:
| Wow thank you so much :) We're so proud of it!!
| skandan wrote:
| Wow this team is non-stop!!! Wild that this small crew is
| dropping hit after hit. Is there an open polymarket on who
| acquires them?
| lcolucci wrote:
| haha thank you so much! The team is incredible - small but
| mighty
| r0fl wrote:
| Where's the hn playground to grab a free month?
|
| I have so many websites that would do well with this!
| lcolucci wrote:
| https://lemonslice.com/hn - There's a button for "Get 1st month
| free" in the Developer Quickstart
| dang wrote:
| (We've replaced the link to their homepage
| (https://lemonslice.com/) with the HN playground at the start
| of the text above)
| lcolucci wrote:
| Thanks Dan! The HN playground let's anyone try out for free
| without login
| r0fl wrote:
| Pricing is confusing
|
| Video Agents Unlimited agents Up to 3 concurrent calls Creative
| Studio 1min long videos Up to 3 concurrent generations
|
| Does that mean I can have a total of 1 minute of video calls? Or
| video calls can only be 1 minute long? Or does it mean I can have
| unlimited calls, 3 calls at a time all month long?
|
| Can I have different avatars or only the same avatar x 3?
|
| Can I record the avatar and make videos and post on social media?
| lcolucci wrote:
| Sorry about the confusion. Video Agents and Creative Studio are
| two entirely different products. Video Agents = interactive
| video. Creative Studio = make a video and download it. If
| you're interested in real-time video calls, then Video Agents
| is the only pricing and feature set you should look at.
| r0fl wrote:
| Wow I can't get enough of this site! This is literally all I've
| been playing with for like half an hour. Even moved a meeting!
|
| My mind is blown! It feels like the first time I used my
| microphone to chat with ai
| sid-the-kid wrote:
| glad we found somebody who likes it as much as us! BTW, biggest
| thing we are working to improve is speed of the response. I
| think we can make that much faster.
| lcolucci wrote:
| This comment made my day! So happy you're liking it
| koakuma-chan wrote:
| > You're probably thinking, how is this useful
|
| I was thinking why the quality is so poor.
| sid-the-kid wrote:
| curious what avatar you think is poor quality? Or, what you
| think is poor quality. i want to know :)
| koakuma-chan wrote:
| Low res and low fps. Not sure if lipsync is poor, or if low
| fps makes it look poor. Voice sounds low quality, as if
| recorded on a bad mic, and doesn't feel like it matches the
| avatar.
| sid-the-kid wrote:
| thanks for the feedback. that's helpful. Ya, some avatars
| have worse lip synch than others. It depends a little on
| how zoomed in you are.
|
| I am double checking now to make 100% sure we return the
| original audio (and not the encoded/decoded audio).
|
| We are working on high-res.
| wumms wrote:
| You could add a Max Headroom to the hn link. You might reach real
| time by interspersing freeze frames, duplicates, or static.
| sid-the-kid wrote:
| 1) yes on Max Headroom. we are on it. 2) it already is real
| time...?
| wumms wrote:
| Whoops! Mistook the "You're about to speak with an
| AI."-progress bar for processing delay.
| sid-the-kid wrote:
| Makes sense. The init should be about 10s. But, after that,
| it should be real time. TBH, this is probably a common
| confusion. So thanks for calling it out.
| lcolucci wrote:
| I wonder if we should make the UI a more common interface
| (e.g. "the call is ringing") to avoid this confusion?
|
| It's a normal mp4 video that's looping initially (the
| "welcome message") and then as soon as you send the bot a
| message, we connect you to a GPU and the call becomes
| interactive. Connecting to the GPU takes about 10s.
| sid-the-kid wrote:
| And, just like that, Max Headroom is back:
| https://lemonslice.com/try/agent_ccb102bdfc1fcb30
| shj2105 wrote:
| Not working on mobile iOS
| lcolucci wrote:
| what's not working for you?
| convivialdingo wrote:
| That's super impressive! Definitely one of the best quality
| conversational agents I've tried syncing A/V and response times.
|
| The text processing is running Qwen / Alibaba?
| sid-the-kid wrote:
| Thank you! Yes, right now we are using Qwen for the LLM. They
| also released a super fast TTS model that we have not tried
| yet, which is supposed to be very fast.
| lcolucci wrote:
| Qwen is the default but you can pick any LLM in the web app
| (though not the HN playground)
| pickleballcourt wrote:
| One thing I've learnt from movie production is actually what
| separates professional from amateur quality is in the audio
| itself. Have you thought about implementing personaplex from
| NVDIA or other voice models that can both talk and listen at the
| same time?
|
| Currently the conversation still feels too STT-LLM-TTS that I
| think a lot of the voice agents suffer from (Seems like only
| Sesame and NVDIA so far have nailed the natural conversation
| flow). Still, crazy good work train your own diffusion models, I
| remember taking a look at the latest literature on diffusion and
| was mind blown by the advances in last years or so since u-net
| architecture days.
|
| EDIT: I see that the primary focus is on video generation not
| audio.
| lcolucci wrote:
| This is a good point on audio. Our main priority so far has
| been reducing latency. In service of that, we were deep in the
| process of integrating Hume's two-way S2S voice model instead
| of ElevenLabs. But then we realized that ElevenLabs had made
| their STT-LLM-TTS pipeline way faster in the past month and
| left it at that. See our measurements here (they're super
| interesting):
| https://docs.google.com/presentation/d/18kq2JKAsSahJ6yn5IJ9g...
|
| But, to your point, there are many benefits of two-way S2S
| voice beyond just speed.
|
| Using our LiveKit integration you can use LemonSlice with any
| voice provider you like. The current S2S providers LiveKit
| offers include OpenAI, Gemini, and Grok and I'm sure they'll
| add Personaplex soon.
| pickleballcourt wrote:
| Thanks for sharing! Makes sense to go with latency first.
| korneelf1 wrote:
| Wow this is really cool, haven't seen real-time video generation
| that is this impressive yet!
| lcolucci wrote:
| Thank you so much! It's been a lot of fun to build
| ProjectBarks wrote:
| Removing - Realized I made a mistake
| dang wrote:
| I don't see any evidence that r0fl's comments are astroturfing.
| Sometimes people are just enthusiastic.
|
| I appreciate your concern for the quality of the site - that
| fact that the community here cares so much about protecting it
| is the main reason why it continues to survive. Still, it's
| against HN's rules to post like you did here. Could you please
| review https://news.ycombinator.com/newsguidelines.html? Note
| this part:
|
| " _Please don 't post insinuations about astroturfing,
| shilling, bots, brigading, foreign agents and the like. It
| degrades discussion and is usually mistaken. If you're worried
| about abuse, email hn@ycombinator.com and we'll look at the
| data._"
| sid-the-kid wrote:
| it's a fair concern. but, we don't know r0fl. and we are not
| astroturfing.
|
| even I am surprised with how many opnely positive comments we
| are getting. it's not been our experience in the past.
| jedwhite wrote:
| That's an interesting insight about "stacking tricks" together.
| I'm curious where you found that approach hit limits. And what
| gives you an advantage if anything against others copying it.
| Getting real-time streaming with a 20B parameter diffusion model
| and 20fps on a single GPU seems objectively impressive. It's hard
| to resist just saying "wow" looking at the demo, but I know
| that's not helpful here. It is clearly a substantial technical
| achievement and I'm sure lots of other folks here would be
| interested in the limits with the approach and how generalizable
| it is.
| sid-the-kid wrote:
| Good question! Software gets democratized so fast that I am
| sure others will implement similar approaches soon. And, to be
| clear, some of our "speed upgrades" are pieced together from
| recent DiT papers. I do think getting everything running on a
| single GPU at this resolution and speed is totally new (as far
| as i have seen).
|
| I think people will just copy it, and we just need to continue
| moving as fast as we can. I do think that a bit of a revolution
| is happening right now in real-time video diffusion models.
| There are so many great papers being published in that area in
| the last 6 months. My guess is that many DiT models will be
| real time within 1 year.
| sid-the-kid wrote:
| One thing that is interesting: LLMs pipelines have been
| highly optimize for speed (since speed is directly related to
| cost for companies). That is just not true for real-time
| DiTs. So, there is still lots of low hanging fruit for how we
| (and others) can make things faster and better.
| storystarling wrote:
| Curious about the memory bandwidth constraints here. 20B
| parameters at 20fps seems like it would saturate the
| bandwidth of a single GPU unless you are running int4. I
| assume this requires an H100?
| andrew-w wrote:
| Yep, the model is running on Hopper architecture. Anything
| less was not sufficient in our experiments.
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