fix(rrweb): use FNV-1a hash for canvas frame dedup instead of full base64#140
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TueHaulund merged 1 commit intomainfrom Mar 4, 2026
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fix(rrweb): use FNV-1a hash for canvas frame dedup instead of full base64#140TueHaulund merged 1 commit intomainfrom
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…se64 Replace lastBlobMap (storing ~400KB base64 strings per canvas) with lastFingerprintMap (storing 8-char FNV-1a hex digests). For unchanged frames, skip the expensive encode(arrayBuffer) call entirely. This reduces worker memory per canvas from ~400KB to 8 bytes and eliminates ~400KB of temporary string allocations per unchanged frame, which helps Safari's GC keep up in high-frequency canvas capture scenarios.
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Summary
lastBlobMap: Map<number, string>(storing full ~400KB base64 strings per canvas) withlastFingerprintMap: Map<number, string>(storing 8-char FNV-1a hex digests)encode(arrayBuffer)call entirely — hash comparison is done on the raw ArrayBuffer bytescrypto.subtle/ secure context requirement)Context: investigating ~0.5MB/s memory growth in Safari with session recording enabled on canvas-heavy apps (PostHog/posthog-flutter#306). The canvas capture pipeline creates ~2-3MB of temporary allocations per frame at 2 FPS, overwhelming Safari's GC in Web Workers.
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