* fix(producer): mix audio into a container that can record encoder delay Every rendered composition's audio landed 1024 samples (21.33 ms at 48 kHz) after its authored `data-start`, against a frame-accurate video track. The mix is AAC-encoded, and AAC encoders emit ~1024 priming samples. The mix was written to a raw ADTS `.aac` file, which has nowhere to record that delay, so it decoded as real leading silence and every stage downstream preserved it faithfully. Measuring each intermediate localises it precisely: the source WAV is exact, the mixer's own output is already 21.33 ms late, and the pad/trim and mux stages inherit it unchanged. The filter graph itself is correct - run by hand to PCM it lands on the authored start. Switch the artifact to an MP4-family container, which stores the delay as an edit list that decoders strip. Same codec, same bitrate, so no size or quality change. The filename is a contract shared by three consumers - the mux input, the distributed plan artifact, and the PNG-sequence sidecar handed to users for NLE ingest - and its extension is what selects the muxer. Give it one owner in the engine rather than five literals, so those consumers cannot drift onto different containers. Note for reviewers: this renames the distributed plan's audio artifact, which is an on-disk contract between the plan writer and the assembler. Both move together here, but a plan written by an older build would not be found by a newer assembler. Flagging in case that mixed-version window matters for how these are deployed. * fix(cloud): read the plan audio artifact name from the producer contract The aws-lambda and gcp-cloud-run adapters each restated the plan's audio filename in five places, so renaming it in the producer left them looking for a file that is no longer written. CI caught it: the gcp dispatch test asserting a plan has no audio artifact started seeing one. Export the name from `@hyperframes/producer/distributed` and consume it in both adapters. This is the same failure the constant exists to prevent, one package boundary further out: a literal that drifts from the writer's is a silently missing audio track rather than a loud error, because both call sites only ever ask whether the file exists. * fix(cloud): accept a legacy plan's audio artifact name for one release Review raised a rolling-deploy window I had flagged but left undecided: `plan` and `assemble` are separate invocations bridged by object storage, so a pre-rollout planner can be paired with a post-rollout assembler. Both readers locate the artifact by existence alone, which makes that pairing a silently muted video rather than an error. That is reachable enough to be worth two lines, so reads now accept the old name while writes only ever emit the new one. Give the fallback one owner (`resolvePlanAudioPath` / `isPlanAudioArtifactPath`) rather than four call sites, marked for deletion one release out. Also fixes a hole in the first pass of this: the plan-v2 materializer matched either name but then joined the CURRENT one, so a legacy plan resolved to a path that was never written. It now joins the artifact's own name. Review nits in the same pass: correct the pad-branch docstring, which still described a concat-copy shape the pad branch stopped using when it moved to apad + re-encode, and fix the Windows fixture's stale `.aac` output extension so it cannot model a shape that reintroduces the priming delay. * test(producer): rebake the missing-host-comp-id golden without the audio delay The pinned reference was rendered before this branch, so it carries the 1024 sample encoder-priming delay in its audio. With the delay gone the correct audio now sits ahead of the reference and the harness's envelope correlation drops below its floor. Cross-correlating the old and new references at native 48 kHz gives a lag of exactly 1024 samples (21.33 ms) at a correlation of 0.99985: same audio, moved by exactly the amount this branch removes. Regenerated inside the CI container (Dockerfile.test, ffmpeg 5.1.9) rather than natively, so the reference matches the encoder CI will compare against - the container reproduced CI's failure to the digit (correlation 0.3938764027803616, lagWindows -12) before the rebake and passes at correlation 1.0 after it. Note for archaeology: the new reference is also 3 dB louder than the old one. That gap is not from this branch - `main` and this branch render the fixture at the same level - it is pre-existing drift the reference had accumulated, which a scale-invariant correlator could never see. The rebake absorbs it. Only output.mp4 is updated. `--update` also rewrites compiled.html, but that diff is embedded-font churn with no bearing on the comparison, which reports "Failed at compilation: 0" either way. * test(producer): rebake the variables-prod golden without the audio delay Same cause as the missing-host-comp-id rebake, caught by shard-8 once the earlier shard stopped failing and the rest of the matrix could run: this reference also carries the encoder-priming delay this branch removes. Reproduced in the CI container to the digit (correlation 0.42704173048439215, lagWindows -12), rebaked there, and it now passes at correlation 1.0. Worth recording: the shift here is 2048 samples (42.67 ms) at correlation 0.99983, exactly twice the 1024 of the other fixture. The delay compounds once per un-compensated AAC generation, and this fixture's audio needs its duration normalized, so it takes the pad/trim branch's re-encode and picks up a second frame of priming on top of the mixer's. So the pre-fix error was not a fixed 21 ms - it grew with the number of times the audio was re-encoded. All nine shards ran in that CI round with only this one failing, so the matrix has now covered every fixture against this change.
@hyperframes/producer
Full HTML-to-video rendering pipeline: capture frames with Chrome's BeginFrame API, encode with FFmpeg, mix audio — all in one call.
Install
npm install @hyperframes/producer
Requirements: Node.js >= 22, Chrome/Chromium (auto-downloaded), FFmpeg
Usage
Render a video
import { createRenderJob, executeRenderJob } from "@hyperframes/producer";
const job = createRenderJob({
inputPath: "./my-composition.html",
outputPath: "./output.mp4",
width: 1920,
height: 1080,
fps: 30,
});
const result = await executeRenderJob(job, (progress) => {
console.log(`${Math.round(progress.percent * 100)}%`);
});
console.log(result.outputPath); // ./output.mp4
Run as an HTTP server
The producer can also run as a render server, accepting render requests over HTTP:
import { startServer } from "@hyperframes/producer";
await startServer({ port: 8080 });
// POST /render with a RenderConfig body
Configuration
RenderConfig controls the render pipeline:
| Option | Default | Description |
|---|---|---|
inputPath |
— | Path to the HTML composition |
outputPath |
— | Output video file path (or directory, for format: "png-sequence") |
width |
1920 | Frame width in pixels |
height |
1080 | Frame height in pixels |
fps |
30 | Frames per second (24, 30, or 60) |
quality |
"standard" |
Encoder preset ("draft", "standard", "high") |
format |
"mp4" |
Output container — "mp4", "webm", "mov", or "png-sequence". See Transparent Video Output below. |
videoFrameFormat |
"auto" |
Source video frame extraction format — "auto", "jpg", or "png". Use "png" for UI recordings, screen captures, and color-sensitive source videos. |
Transparent Video Output
The producer can render HTML compositions to formats that carry a true alpha channel — not chroma key. The same composition that renders an opaque MP4 renders a layerable overlay when you set format.
format |
Codec / pixel format | Alpha | Audio | Use case |
|---|---|---|---|---|
"mp4" (default) |
H.264 (yuv420p) or H.265 + HDR10 | No | AAC | Streaming, social, default deliverable |
"webm" |
VP9 + yuva420p | True alpha | Opus | Web playback as overlay (<video> over background); supported in Chrome, Edge, Firefox |
"mov" |
ProRes 4444 + yuva444p10le | True alpha + 10-bit | AAC | Editor ingest (Premiere, Final Cut Pro, DaVinci Resolve) |
"png-sequence" |
Numbered RGBA PNGs in a directory | Lossless alpha | Sidecar audio.aac |
After Effects / Nuke / Fusion, or pipelines that post-process frames before encoding |
Example
import { createRenderJob, executeRenderJob } from "@hyperframes/producer";
const job = createRenderJob({
inputPath: "./my-composition.html",
outputPath: "./output.webm", // or a directory for "png-sequence"
width: 1080,
height: 1920,
fps: 30,
format: "webm", // "mp4" | "webm" | "mov" | "png-sequence"
});
await executeRenderJob(job);
What "transparent background" means here
The producer captures Chrome screenshots with the page background forced transparent (html, body, [data-composition-id] { background: transparent !important }) and the CDP default background override set to RGBA 0,0,0,0. The captured PNGs carry a real alpha channel and that channel is preserved end-to-end:
- VP9 (
webm) is encoded with-pix_fmt yuva420p,-auto-alt-ref 0,-cpu-used 4by default, andalpha_mode=1metadata. Tune the speed/quality tradeoff withPRODUCER_VP9_CPU_USED(-8to8) or local CLI--vp9-cpu-used. - ProRes 4444 (
mov) is encoded with-pix_fmt yuva444p10le. - PNG sequences are written without re-encoding (zero-padded
frame_NNNNNN.png).
This is not chroma keying. There is no green/blue background to remove and no "key" tolerance to tune — pixels that were transparent in the browser are transparent in the output.
Caveats
- Linux + alpha forces screenshot capture. Chrome's BeginFrame compositor (the default deterministic capture path on Linux headless-shell) does not preserve alpha; the orchestrator falls back to
Page.captureScreenshot, which is slower per frame. macOS and Windows already use screenshot mode by default, so they are unaffected. - HDR + alpha is not supported. Setting
hdr: truetogether with an alpha-capable format logs a warning and falls back to SDR. Useformat: "mp4"for HDR10 output. png-sequencedoes not produce a single muxed file. When the composition contains audio elements, anaudio.aacsidecar is written alongside the PNGs inoutputPath.- Safari + WebM alpha is incomplete. For broad browser playback of an alpha video, ship
format: "mov"to your editor and re-encode for the codec your distribution target supports.
Authoring transparent compositions
Don't paint a fullscreen background in your HTML. The default body background is overridden to transparent automatically — any body { background: ... }, #root { background: ... }, or [data-composition-id] { background: ... } rule is force-overridden during alpha rendering. Backgrounds on inner elements (cards, scenes, components) are kept.
Distributed rendering
For renders too large for a single machine, the producer ships a public set of distributed-render primitives. They are pure functions over local file paths — networking and orchestration live in adapter packages (Temporal, AWS Lambda + Step Functions, Cloud Run Jobs, K8s Jobs).
Plan v2 is recommended for new integrations. It publishes an immutable manifest plus content-addressed artifacts and materializes only each worker's declared dependencies:
import { planV2, renderChunkV2, assembleV2 } from "@hyperframes/producer/distributed";
// Controller-side: produce a v2 manifest + local content-addressed store.
const planResult = await planV2(
projectDir,
{ fps: 30, width: 1920, height: 1080, format: "mp4" },
"/tmp/plan-v2",
);
const chunk = await renderChunkV2("/tmp/plan-v2", 0, "/tmp/chunks/0.mp4");
// Controller-side: stitch chunks into the final deliverable.
await assembleV2("/tmp/plan-v2", ["/tmp/chunks/0.mp4", "/tmp/chunks/1.mp4"], "/tmp/output.mp4");
Cloud adapters should use planV2WithPublisher() so artifacts publish
directly to object storage. The legacy plan() / renderChunk() /
assemble() v1 layout remains supported, and cloud SDKs still interpret an
omitted protocol as v1 for backwards compatibility.
The activity functions plus their result types are also re-exported from @hyperframes/producer so callers that pin the main package don't need a separate subpath import. Supported formats: mp4 SDR, mov ProRes 4444, and png-sequence. webm and HDR mp4 trip a typed FormatNotSupportedInDistributedError — use the in-process renderer (executeRenderJob) for those.
How it works
- Serve — spins up a local file server for the HTML composition
- Capture — opens the page in headless Chrome, seeks frame-by-frame via
HeadlessExperimental.beginFrame(orPage.captureScreenshotfor transparent / non-Linux renders), captures screenshots - Encode — pipes frames through FFmpeg (with GPU encoder detection and chunked concat). Skipped for
format: "png-sequence". - Mix — extracts
<audio>elements and mixes them into the final video. Forpng-sequence, audio is written as anaudio.aacsidecar. - Finalize — applies faststart for streaming-friendly MP4 (no-op for WebM, MOV, and
png-sequence)
Documentation
Full documentation: hyperframes.heygen.com/packages/producer
Related packages
@hyperframes/core— types, parsers, frame adapters@hyperframes/engine— lower-level capture and encode primitiveshyperframes— CLI