How IPTV works — the path of the signal from source to your screen

Most complaints about IPTV fit into two words: «it freezes» and «it lags». Behind those two words, though, stand completely different causes — some on the server, some in the router in your own home. To find the cause you have to know which road the signal travels. Below we open that road up step by step. For a general explanation of the technology: what IPTV is.

The path of the signal — seven stages

Only five of the seven stages are under the provider's control. The last two — your provider and your home network — are the user's side. When you are hunting for a problem it is more efficient to start from the end, because that is the part that is quickest to fix.

Encoding: the difference between H.264 and HEVC

Video compression determines the whole economics of IPTV. An uncompressed broadcast would need tens of gigabits; a codec fits it into a home connection. It does that by discarding detail intelligently — which is why two streams at the same resolution can look completely different.

The advantage of HEVC is clear: less bandwidth is needed for the same picture, which means 4K fits into an ordinary home connection. Its downside is compatibility — an older Smart TV or a weak box may not be able to decode HEVC in hardware, and the result is either a silent black screen or stuttering playback. That is why services often keep the mass-audience channels in H.264 and the 4K step in HEVC: 4K IPTV.

Bitrate — the number that decides quality

Users measure quality by resolution: 1080p, 2160p. In fact the main indicator is bitrate — how much data is carried per second. Resolution is the size of the picture, bitrate is the amount of detail inside it. A low-bitrate 4K stream can look worse than a well-compressed Full HD one.

• Motion demands bitrate. A news studio needs little, football a lot. Grass, fast camera movement and a crowd are the hardest scenes — the codec has no room left to «improvise».
• A low bitrate creates pixelation. Blocks in a fast scene, blurring, loss of detail — all of these are signs of insufficient bitrate.
• A high bitrate wants a share of your connection. As quality rises so does the bandwidth required; that is why every service strikes a balance.
• Adaptive steps soften the problem. If a channel is prepared at several bitrates, the player drops to a lower step when bandwidth narrows. On a single-bitrate stream there is no alternative — the picture freezes.

Why buffering happens

A player never plays «live». It first gathers a certain amount of video — that is called the buffer — and only then starts playing. The buffer is like a small reservoir: if the stream weakens for a moment, there is a reserve in the tank. When the tank empties, the screen freezes.

• The real speed drops below the stream's bitrate. The simplest and most frequent cause.
• Packet loss and jittering latency. Even when the speed is sufficient on paper, if packets arrive late or go missing the buffer does not fill.
• Wi-Fi obstacles. A wall, distance, neighbouring networks crowding onto the same channel — all of these lower the real throughput.
• Congestion on the provider's network. At peak hour the shared capacity narrows, and that does not depend on you.
• The server or an edge node is overloaded. In that case the freezing repeats on all channels and at the same hours.
• The device is not powerful enough. If a weak processor cannot cope with a 4K HEVC stream, the problem is not in the network but in the decoding.

CDN and server load

Over the open internet a separate stream is sent for every viewer. In other words, if 1,000 people watch the same channel, 1,000 separate streams leave the server side. That is the main difference from satellite broadcasting: with satellite the number of viewers has no effect on the load, whereas with IPTV every new viewer is a real cost.

The solution is to bring the content closer to the user with a distribution network and spread the load across many points. In a properly built system there is spare capacity even at the evening peak. In a system with no spare capacity, peak hour is felt immediately — the description many users give, «it freezes in the evening and it is fine during the day», is exactly a sign of that.

This is directly tied to price: server capacity, backup sources and a distribution network are a continuous expense. We have opened up the subject separately: what good-value IPTV means.

Latency and live sport

Latency is the natural consequence of segmented delivery. The player fetches several segments in advance before it can start playing; if a segment is 4 seconds long and the player gathers three of them, you are already tens of seconds behind real time. On top of that come the encoding and distribution times.

In practice it looks like this: you may hear the neighbour celebrating a goal before you see it on the screen. Latency can be reduced — shorter segments, an optimised buffer, a nearby server — but bringing it to zero goes against the nature of the protocol. So turning off social-media notifications while watching a match is practical advice. For the details of watching sport: football channels and Premier League.

Connection speed requirements

The figures below are for one stream. If several screens will run at home at the same time, the rows have to be added together — plus a reserve for everything else you do:

One nuance: an unsteady 100 Mbps line can give a worse result than a steady 20 Mbps one. Speed is a momentary measurement, while quality depends on consistency. So run the speed test at peak hour, several times.

Wi-Fi and Ethernet

Connecting the television to the router with a cable is the simplest and most effective way of improving IPTV quality. The reason is not that Wi-Fi is weak — it is that Wi-Fi is a shared medium. In the air one device talks at a time and the rest wait; and the neighbouring networks share that same air.

• Ethernet gives steady latency and steady throughput, and neither walls nor distance affect it.
• Wi-Fi 5 GHz offers wider bandwidth and less congestion, but passes through walls poorly — ideal for devices near the router.
• Wi-Fi 2.4 GHz reaches further, but it is the most crowded band: neighbouring networks, microwave ovens and household appliances all gather there.
• Repeaters are a double-edged sword. They extend coverage but often halve the throughput. A mesh system gives a better result.

If running a cable to the television is not possible, at least select the 5 GHz network and try to keep metal, mirrors and large appliances out of the way between the router and the television. Settings per device: IPTV on a Smart TV.

The role of the router

The router is the point every piece of traffic in the home passes through, so a weak router can eat up the benefit of a fast connection. The points to watch:

• Age and standard. An older-generation Wi-Fi standard cannot carry high speeds; that is very common with the simplest model a provider supplies.
• Placement. A router put inside a cupboard, on the floor or behind a wall loses half its coverage.
• Channel congestion. In a block of flats dozens of networks can sit on the same channel; changing the channel sometimes solves the problem on its own.
• The number of devices connected at once. A weak router's processor chokes on many connections — and the result is not lower speed but higher latency.
• The QoS setting. On some routers it is possible to give the television priority; that helps if there are parallel downloads in the house.
• A simple measure that works. Restarting the router from time to time clears up long-running memory and connection problems.

The role of the device — what a weak processor does

Even if the network works flawlessly, the final stage is at the device: the incoming data has to be decoded and put on the screen. A 4K HEVC stream needs a hardware decoder for that. On older Smart TVs and cheap boxes the processor may not be sufficient — and in that case the freezing looks very much like «network freezing», while the cause is something else entirely.

Telling them apart is easy: open the same channel on a phone, on the same Wi-Fi network. If it works properly on the phone, the problem is not in the network but in the television. In such cases either choosing a lower quality step or adding a small Android box settles the matter: installation and Android devices.

A sequence for localising a problem

If you go through these five steps in order, the cause is found almost every time. To avoid wasting time, work from the top down:

1. Is the problem on one channel or on all of them? If it is on one, it is a source matter — write down the channel name and report it to support.
2. Does it repeat on another device, on the same network? If it does not, it is a device or app matter.
3. Does it repeat over an Ethernet cable? If it does not, the work has to be done on the Wi-Fi and the router.
4. Does it repeat over mobile internet? If it does not, it is the home provider or the home equipment.
5. If it repeats in all three cases and at the same hours, the source is the server side and that has to be reported with concrete information.

Applying this sequence during the trial period is the most useful thing of all — the picture becomes clear before you pay: how to test a trial stream. For the buying stage: how to buy IPTV.

Frequently asked questions

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