Live video reaches a viewer through a chain of separate jobs. An encoder compresses the camera or program feed, a packager cuts that feed into short media files and writes a playlist or manifest that describes them, a web server holds those files, a CDN copies and serves them close to viewers, and a player on the device requests them in order and switches quality when the connection changes. HLS and DASH are the two common specifications for the packaging and playlist step. A CDN is only the delivery step. Keeping those roles apart is the key to understanding how live streaming works and why a problem in one part can look like a problem in another.
The live streaming pipeline, step by step
Apple’s HTTP Live Streaming overview describes the workflow in terms of an encoder, segments, playlists, an HTTP distribution component, and a playback client. Those five parts map onto the following sequence.
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- Capture and encode. An encoder accepts the audio and video source and compresses it. For adaptive delivery it usually produces several renditions of the same program at different bit rates and resolutions.
- Segment and package. A segmenter or packager cuts each rendition into consecutive media segments and writes the playlist (HLS) or manifest (DASH) that lists which segments exist and which renditions are available.
- Publish to an origin. The packaged playlists and segments are written to an origin web server or an origin storage service that exposes them over HTTP.
- Distribute. A CDN or other caching layer receives viewers’ requests for playlists and segments and serves copies from edge locations, fetching from the origin when it does not have a copy.
- Fetch and play. The player reads the playlist or manifest, requests segments, chooses among the renditions as conditions change, and assembles the media into continuous playback.
Because every step after encoding is an ordinary HTTP request, the whole chain runs on web servers and caches rather than on a dedicated streaming server that holds one open connection per viewer. That design is the reason CDNs fit so naturally into live video delivery.
Encoding and renditions
The encoder turns the raw feed into compressed video and audio. The choices made here set the ceiling for everything downstream: codec, container, resolution, frame rate, and bit rate. Adaptive streaming requires more than one version of the program. A typical ladder contains several renditions, from a low bit rate suitable for a weak mobile connection to a high one for a wired television, all aligned so that a player can move from one to another without a visible break.
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Apple’s current authoring guidance lists fragmented MP4 and MPEG transport stream among its H.264 container options and says HEVC content uses fragmented MP4. Those are authoring rules, not a promise that every device plays every codec, profile, and level combination. Check the codec settings against the devices your audience actually uses before you commit to a ladder.
Segmenting and playlists
The packager divides each rendition into segments and generates the index that players rely on. In HLS, this index is a set of text playlists. In DASH, it is a manifest. Both answer the same questions for the player: what is the program, which renditions exist, and where are the files for each one.
HLS playlists
HLS uses two levels. A multivariant playlist lists the available variant streams, each with its bit rate and resolution. Each variant points to a media playlist, which lists the media resources for that rendition in order. For live programs, the media playlist is updated as new segments are produced, and the player keeps re-reading it to discover new material. HLS is designed to switch between variants as network conditions change, which Apple describes as optimizing playback for the available speed of wired and wireless connections.
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DASH manifests
DASH describes the presentation in a single manifest, the Media Presentation Description (MPD), which organizes periods, adaptation sets, and representations. Like HLS, a DASH player reads the manifest, requests media segments over HTTP, and chooses among representations. For live content the manifest changes over time, and the player re-reads it to find new segments.
The origin server
The origin is the system of record for the live program. It receives the packaged output and serves it to whatever distributes it onward. Origins are usually designed so that playlists and manifests change frequently while segments are written once and never change. That difference matters for caching, discussed below. An origin that falls behind, rejects writes, or returns errors affects every viewer, because the CDN can only pass along what the origin provides.
What a CDN does for live video
A CDN places cached copies of content at many locations so that viewers request files from a nearby server instead of the origin. For live video this reduces the load on the origin and shortens the path between the viewer and the media. Both HLS and DASH are designed for this model: the standards describe delivery over existing HTTP infrastructure, including servers, CDNs, proxies, and caches.
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A CDN does not make the program. It does not encode the source, decide which renditions exist, or determine how a player picks between them. Its job is to answer HTTP requests quickly and reliably. The practical consequence is that CDN behavior is shaped by how the origin and packager set cache headers and file lifetimes, and that choice affects playlists and segments differently.
Playlists versus segments in the cache
Live playlists and manifests change as new segments appear, so they must be refreshed frequently and should not be held in cache for long. Media segments are written once and do not change, so they can be cached for longer. Operators who give both the same cache lifetime tend to see one of two problems: viewers receive stale playlists that omit recent segments, or the origin is hit with requests it could have avoided. Set the lifetimes per file type.
HLS and DASH compared
Both specifications use HTTP delivery and adaptive renditions. They are separate standards, however, with their own manifest formats and their own ecosystems. “Both use HTTP” does not mean a playlist written for one can be read by a player built for the other.
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- Compact without compromises: The sleek design of Roku Streaming Stick won’t block neighboring HDMI ports, and it even powers from your TV alone, plugging into the back and staying out of sight. No wall outlet, no extra cords, no clutter.
- No more juggling remotes: Power up your TV, adjust the volume, and control your Roku device with one remote. Use your voice to quickly search, play entertainment, and more.
- Shows on the go: Take your TV to-go when traveling—without needing to log into someone else’s device.
- TV, simplified: With setup that only takes minutes, a simple-to-navigate Home Screen, and an uncluttered remote control that does all you need—Roku makes it easier to watch the TV you love.
| Aspect | HLS | MPEG-DASH |
|---|---|---|
| Specification | Apple’s HTTP Live Streaming; published as RFC 8216, which the RFC Editor records as informational rather than an Internet Standards Track specification. Apple’s authoring page says the specification continues to evolve and points to a newer draft. | Identified by MPEG as ISO/IEC 23009. MPEG describes it as supporting live and on-demand delivery over existing HTTP infrastructure. |
| Manifest or index | Multivariant playlist plus media playlists (text playlists) | Media Presentation Description (MPD) |
| Adaptive switching | Yes, between alternate bit-rate variants | Yes, between representations |
| Codec and container options | Authoring guidance lists fragmented MP4 and MPEG transport stream for H.264; HEVC uses fragmented MP4. Device support must be checked. | Not stated in the sources consulted; depends on the profile and the player |
| Device and player support | Varies by platform; not stated in the sources consulted | Varies by player; not stated in the sources consulted |
| Latency target | Not stated in the sources consulted | Not stated in the sources consulted |
The sources consulted establish the standards and the broad interoperability relationship. They do not provide a device-by-device or vendor-by-vendor support matrix, so any compatibility decision should be tested against the players your audience uses.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How CMAF fits in
The Common Media Application Format (CMAF) specifies a container for segmented media, built from logical objects such as tracks and switching sets. Apple’s CMAF overview describes a delivery and presentation model that can support implementations of both HLS and MPEG-DASH. In practice, this means that a single set of media segments can sometimes serve both protocols, with each protocol’s playlist or manifest pointing at the same files.
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Shared segments are not automatic. Codec, profile, encryption, timing, and player requirements all have to line up before one asset can serve both. CMAF is a format-level foundation, not a guarantee of cross-compatibility.
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- HDMI 2.1 cable required (sold separately)
- See movies and TV shows from all your services right from your home screen[2]; and find new things to watch with tailored recommendations for everyone in your home based on their interests and viewing habits
- Watch live TV and access over 800 free channels from Pluto TV, Tubi, and more[3]; if you find an interesting show or movie on your TV, mobile app, or Google search, you can easily add it to your watchlist, so it’s ready when you are[2]
- Up to 4K HDR with Dolby Vision delivers captivating, true-to-life detail[4]; and you can connect speakers that support Dolby Atmos for more immersive 3D sound
Deployment decisions that follow from the architecture
Because the chain has separate parts, most design choices map to one of them. The following checks cover the decisions that matter most.
- Encoder and ladder: Confirm that every rendition uses settings that your target devices can decode.
- Protocol choice: Decide whether HLS, DASH, or both are required by the devices and players in scope, and whether shared CMAF segments are practical for your codec and encryption setup.
- Origin: Make sure playlists and manifests update on schedule and that errors are visible to operators.
- CDN: Compare geographic coverage for your audience, cache behavior for playlists versus segments, origin integration, failover, security controls, logging, and current pricing. Pricing and features change, so confirm them with each provider.
- Latency requirements: Define the acceptable delay for your use case before choosing a configuration, since the sources consulted do not provide a general latency figure for either protocol.
Troubleshooting by symptom
- Playback stops and restarts with the same segment repeatedly: Check whether the media playlist or manifest is being updated. A stale playlist is often the cause, which points to cache settings or an origin that is not refreshing.
- Quality never rises above the lowest rendition: Check the multivariant playlist or manifest for the full list of renditions and confirm the higher ones are reachable through the CDN.
- A device fails on one stream but plays another: Compare codec, profile, and container settings against that device’s requirements, rather than assuming the protocol is the problem.
- Viewers far from the origin see delay or errors while nearby viewers do not: Review CDN coverage and edge behavior for those regions.
Each symptom above can be traced to a single stage of the pipeline. Start with the playlist or manifest, then the segments, then the CDN, then the origin.
Quick Recap
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