Achieving sub-3-second glass-to-glass latency over standard HTTP delivery requires rethinking how content distribution networks handle file caching, request volume, and the relationship between origin servers and edge nodes. The protocols designed to make this possible, LL-HLS and LL-DASH, introduce architectural demands that break many of the assumptions CDNs were originally built around.

Why Traditional CDN Caching Falls Short

Conventional CDN architecture is optimised for large, complete files. A video segment gets encoded, written to disk, cached at the edge, and served to viewers. The model works well when segments are several seconds long and requests arrive at a predictable pace.

Low-latency streaming inverts this model. Instead of waiting for complete segments, LL-DASH delivers content through chunked transfer encoding — bytes are pushed to viewers as they are generated, before the segment file is fully written. LL-HLS takes a different approach, splitting segments into tiny “parts” that are served individually, with the manifest file itself blocking until the next part becomes available.

Both approaches dramatically increase the number of requests hitting CDN edge servers. A single viewer watching a standard HLS stream might generate one request every six seconds. That same viewer on LL-HLS can generate multiple manifest and part-file requests per second. Multiply that across thousands of concurrent viewers and the request volume becomes an infrastructure problem rather than just a bandwidth problem.

The Protocol Split: LL-DASH vs LL-HLS

The two dominant low-latency protocols take meaningfully different approaches to the same problem, and supporting both simultaneously within a single delivery pipeline is one of the harder engineering challenges in modern streaming infrastructure.

LL-DASH uses a single manifest and relies on timing-based chunk requests. The player begins downloading segments while they are still being generated on the origin server. Playback can start from any key-frame, which makes key-frame placement strategy a direct lever for controlling latency. More frequent key-frames mean lower latency, but at the cost of encoding efficiency and potentially higher bandwidth consumption.

LL-HLS, developed by Apple, takes a manifest-blocking approach. The server holds the playlist request open until the next part becomes available, then delivers an updated manifest pointing to the new content. Safari handles this natively, but third-party players like hls.js have had to implement their own handling of the blocking reload mechanism and byte-range requests that LL-HLS relies on to reduce request overhead.

The practical result is that a CDN serving both protocols simultaneously needs two different data transfer strategies running in parallel — accelerated downloading of small discrete files for LL-HLS, and continuous chunked delivery of incomplete files for LL-DASH.

What This Means for Edge Infrastructure

The shift to sub-3-second delivery has downstream effects on CDN edge architecture that go beyond simply handling more requests.

Connection duration changes fundamentally. In traditional CDN operation, a connection opens, delivers a cached file, and closes within milliseconds. With chunked transfer for LL-DASH, connections stay open for the duration of a segment — potentially several seconds — while bytes trickle through. This means edge servers carry higher concurrent connection counts and sustained CPU load even when aggregate bandwidth remains similar.

Caching logic needs to be rebuilt. Standard CDN caching mechanisms were not designed for files that do not yet exist in their final form. Serving a partially-written segment from cache while simultaneously appending new bytes from the origin requires purpose-built modules that standard web server configurations like Nginx’s proxy cache cannot handle out of the box.

Monitoring changes as well. When response time is measured in segment duration rather than file download speed, traditional performance dashboards become misleading. A 500ms response time on a LL-HLS manifest request is not a performance problem — it is the protocol working as designed, holding the connection until the next part is ready. Operations teams need monitoring that understands the difference.

Key-Frame Placement as a Latency Control

One of the less obvious but most impactful variables in low-latency streaming is key-frame frequency. In both LL-DASH and LL-HLS, playback can only begin from a key-frame. If key-frames are spaced two seconds apart, that sets a floor on achievable latency regardless of how fast the CDN delivers content.

Increasing key-frame frequency reduces latency but increases the bitrate required for the same visual quality, since key-frames are significantly larger than predicted frames. This creates a direct trade-off between latency and bandwidth efficiency that must be calibrated based on the specific use case — a sports betting application has different latency requirements than a concert livestream, and the key-frame strategy should reflect that.

Where This Is Heading

The industry consensus is moving toward sub-2-second HTTP delivery as the next target. Achieving this consistently at scale will likely require further innovation in edge processing, more aggressive use of RAM-based caching for micro-segments, and potentially new approaches to manifest generation that reduce the round-trip overhead inherent in the current request-response model.

For broadcast and streaming organisations evaluating their infrastructure roadmap, the immediate takeaway is that low-latency delivery is no longer an optional premium feature. It is becoming the baseline expectation for any live content where audience engagement depends on temporal proximity to the event — sports, news, gaming, interactive entertainment, and increasingly, enterprise applications like remote production and live commerce.

The CDN is no longer just a delivery layer. It is becoming an active participant in the streaming pipeline, and the architectural decisions made at the edge now directly determine the quality of experience at the glass.

The post How CDN Architecture Is Evolving to Deliver Sub-3-Second Live Streaming appeared first on T-21.

The post How CDN Architecture Is Evolving to Deliver Sub-3-Second Live Streaming appeared first on T-21.

Category: Streaming & Broadcast Technology Slug: /av1-codec-licensing-royalty-free-over

For the better part of five years, one of the strongest arguments for deploying AV1 was the claim that it was royalty-free. That claim was never entirely accurate, but in 2025 it became something closer to financially irresponsible to plan around.

The convergence of new patent pools, high-profile enforcement actions, and a fundamental shift in how codec intellectual property is monetised means that any streaming organisation deploying advanced codecs — whether AV1, HEVC, or VVC — now faces a licensing landscape that demands attention from legal and finance teams, not just engineering.

What Changed in 2025

Three developments reshaped the codec licensing environment in ways that affect every publisher operating above a certain scale.

First, Access Advance launched its Video Distribution Patent (VDP) Pool in January 2025, covering content distribution using HEVC, VVC, AV1, and VP9. This was not a device-side licensing programme — it targets the act of encoding and delivering content itself. Royalty rates, published in July 2025, are calculated based on whichever is highest among three metrics: average monthly active video users, average monthly video subscribers, or semi-annual streaming revenue.

Second, Sisvel announced that its AV1 patent pool had licensed roughly 50% of the finished-product AV1 hardware device market — covering TVs, set-top boxes, and other consumer hardware. For a codec launched under the banner of royalty-free, having half the device market paying licensing fees fundamentally undermines that positioning.

Third, Nokia and Amazon settled a global patent dispute that included content-side royalties for H.264 and H.265 usage across Prime Video, Freevee, and Twitch. This was one of the first confirmed settlements where a tier-1 streaming service paid for the act of distributing codec-encoded content, not just for the hardware decoding it. The message to the industry was unmistakable: if Amazon can be compelled to settle, no major service is immune.

The New Licensing Landscape at a Glance

Understanding who is charging what, and for which codecs, requires tracking multiple overlapping programmes. The table below summarises the current state of the major content-side and device-side licensing pools:

Programme	Codecs Covered	Licensing Type	Notable Detail
Access Advance VDP Pool	HEVC, VVC, AV1, VP9	Content distribution	Annual cap + de minimis waiver for small services
Avanci Video Pool	HEVC, AV1	Content distribution	No cap or de minimis exception announced
Sisvel AV1 Pool	AV1	Device licensing	~50% of AV1 hardware market licensed
Access Advance / VCL Advance	HEVC, VVC	Device licensing	Consolidated from Via LA acquisition
Individual patent holders	H.264, HEVC, AV1, streaming	Direct enforcement	Nokia, InterDigital, Broadcom actively pursuing claims

What makes this landscape particularly complex is the overlap between programmes. Sixteen licensors are common to both Access Advance’s VDP Pool and Avanci’s Video Pool, which means licensees paying into both receive an offset for double royalties — but the exact offset is not publicly disclosed, making cost modelling difficult without direct engagement.

The Break-Even Math Has Changed

Before content-side licensing became enforceable, the economic case for deploying AV1 or HEVC beyond H.264 was relatively straightforward: spend more on encoding compute to save on CDN bandwidth. A 30% bitrate reduction over H.264 translated directly into CDN cost savings, with the only incremental cost being encoder complexity.

That equation has fundamentally shifted. For services above the VDP Pool thresholds, the calculation now includes encoding compute, potential content-side royalties that can reach into eight figures annually for the largest services, and the possibility of direct patent enforcement from individual holders.

Meanwhile, CDN costs have declined significantly since 2019 when these efficiency arguments were first being made. The bandwidth savings from deploying AV1 over H.264 are real, but the dollar value of those savings per gigabyte delivered is substantially lower than it was five years ago.

For services delivering HDR and 4K premium content, the codec choice remains operationally necessary — AV1 and HEVC provide capabilities that H.264 simply cannot match at those quality tiers. The royalty costs become a necessary cost of doing business. But for FAST services, ad-supported platforms, and others working primarily with 8-bit 1080p content, the efficiency argument that justified advanced codec deployment now requires a much more careful financial analysis.

Where AV1 Stands Despite the Licensing Questions

None of this means AV1 adoption is slowing. The opposite is true.

Netflix recently reported that AV1 powers roughly 30% of its streams and has expanded into HDR delivery, achieving feature parity with HEVC. On the device side, Netflix noted that 88% of large-screen devices submitted for certification between 2021 and 2025 supported AV1, with the vast majority offering full 4K at 60fps capability.

Browser support has been near-universal since AV1’s early days. Mobile remains the one platform where hardware decode lags significantly behind HEVC, though the Alliance for Open Media’s investment in the dav1d software decoder has enabled efficient AV1 playback on Android devices without dedicated hardware.

The codec itself has reached critical mass. The question is no longer whether AV1 works or whether devices support it. The question is what it costs to use it, and whether the organisations deploying it have adequately accounted for that cost.

What Comes Next: AV2 and the IP Question

The Alliance for Open Media finalised the AV2 specification in late 2025. Early testing shows compression efficiency gains in the high-20% to mid-30% range over AV1, potentially closing much of the gap with VVC.

But the more consequential signal came from InterDigital’s acquisition of AI-native compression startup Deep Render in October 2025. InterDigital — a non-practicing entity with an $8 billion market cap built on licensing codec and wireless IP — explicitly framed the acquisition as positioning for “the next generations of video technologies.” If AI-native compression techniques are being accumulated by the same organisations that monetised H.264, HEVC, and VVC, the post-AV2 generation is unlikely to reset the royalty conversation.

For publishers planning their codec roadmaps, the implication is clear: the era of assuming any advanced codec is royalty-free is over. The practical question has shifted from “can we avoid paying for codecs?” to “which codecs are worth paying for, at what scale, and with what financial provisions in place?”

That is a healthier question. It just requires different people in the room when it is being answered.

The post The Codec Licensing Shift: Why AV1’s “Royalty-Free” Era Is Effectively Over appeared first on T-21.

The post The Codec Licensing Shift: Why AV1’s “Royalty-Free” Era Is Effectively Over appeared first on T-21.