codecs

codecs is a cursor rule for Cursor from AcKeskin/contexture. It costs 0 tokens per session (1,622 once invoked), scanned A, original, MIT.

A set of coding rules for managing hardware video encoder and decoder sessions. It treats each session as a limited resource that must be opened, used, flushed, and closed in a predictable way.

In plain words
What is it for?
Use it when writing or reviewing code that uses NVENC, NVDEC, VideoToolbox, MediaCodec, or similar hardware video codecs.
Why use it?
It helps prevent leaked sessions, resource exhaustion, extra latency, and broken video output caused by creating sessions too often or failing to release them.

Cursor rule for Cursor

Written for Cursor: a Cursor rule (.mdc).

Good fit Use it when writing or reviewing code that uses NVENC, NVDEC, VideoToolbox, MediaCodec, or similar hardware video codecs.

Compare 6 cursor rules from other repositories ↓
Install with agentmods
npx agentmods add rules/ackeskin/contexture/codecs
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Clone the repo
git clone --depth 1 https://github.com/AcKeskin/contexture

Made for: Cursor.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for codecs

README.md
[![agentmods](https://agentmods.dev/badge/rules/ackeskin/contexture/codecs/github.svg)](https://agentmods.dev/rules/ackeskin/contexture/codecs)
Your own site
<a href="https://agentmods.dev/rules/ackeskin/contexture/codecs"><img src="https://agentmods.dev/badge/rules/ackeskin/contexture/codecs/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for codecs

Your own site · 80×15
<a href="https://agentmods.dev/rules/ackeskin/contexture/codecs"><img src="https://agentmods.dev/badge/rules/ackeskin/contexture/codecs.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 0 Nothing until a file matches its globs; then the whole rule loads.
When invoked 1,622 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00000 $0.01622
Opus 5.5 $0.00000 $0.00649
Sonnet 5.5 $0.00000 $0.00324
Haiku 4.5 $0.00000 $0.00162

Measured today against content hash c1f0568c1a04, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

codecs scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured today.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

cursor/rules/codecs.mdc · 44 lines

How it starts

The opening of the file, as written. The whole thing — 44 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Generated from architectural-rules/codecs/ — do not hand-edit.

Codec session lifetime

Treat each hardware encode/decode session as an explicitly-owned scarce resource with a defined create→use→destroy lifetime; release it deterministically, never on GC/finalizer timing. Hardware codec engines (NVENC/NVDEC, VideoToolbox, MediaCodec) expose a small fixed number of concurrent sessions; a leaked session starves every other consumer on the host until process exit. (VideoToolbox VTCompressionSession / VTDecompressionSession; NVENC nvEncOpenEncodeSessionEx + nvEncDestroyEncoder contract)

Open the session once for a stream and feed every frame through it; never create-and-destroy per frame. Session creation negotiates hardware, allocates the DPB/reference pool, and parses/builds parameter sets — per-frame churn destroys rate-control state, forces an IDR each time, and dominates latency. Reconfigure in place where the API allows (bitrate/framerate change) rather than tearing down. (NVENC reconfigure; VTSessionSetProperty; H.264/AVC §7.4.2 parameter-set continuity)

FLUSH/drain the codec before destroying the session and only then release. Encoders and decoders hold queued/in-flight frames (lookahead, B-frame reordering, async slots); destroying without draining silently drops trailing frames and truncates the bitstream. Submit the end-of-stream/flush sentinel, pump completions until the codec reports empty, then destroy. (VTCompressionSessionCompleteFrames; NVENC EOS NULL-input flush; MediaCodec end-of-stream BUFFER_FLAG_END_OF_STREAM)

For callback/async-completion codecs, treat submit and completion as separate events: do not assume output is ready when input returns, keep input frames/buffers alive until their completion fires, and join all outstanding completions before teardown. Releasing an input buffer or the session while a completion is pending corrupts output or faults the driver. (VTCompressionSession output handler; NVENC async event + nvEncLockBitstream; MediaCodec dequeueOutputBuffer)

Why: Hardware codec sessions are a scarce, explicitly-owned resource — leaking one degrades the whole machine, and per-frame teardown wrecks rate control and latency. Trailing frames live inside the codec's reorder/lookahead queues, so destroying without an explicit drain truncates output. Async codecs decouple submission from completion, so buffer and session lifetimes must outlive in-flight work. Source: codec specifications / platform encode-decode API contracts.

Read the full file on GitHub · 44 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. today First seen · 44 lines · 1,622 tokens per session scan A c1f0568c1a04

Subscribe to this mod's changes

codecs is a cursor rule published in the GitHub repository AcKeskin/contexture (2 stars, last pushed yesterday), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 1,622 tokens. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-10-27.