Online video streaming services are, without a doubt, the most convenient and easy way for people to get the latest movies. When it comes to renting, streaming is often the only option. While convenience is important, we wanted to find out what you might lose along the way, so we used our HDMI capture kit to find out how Blu-ray stacks up against its online competition and if the disc still is the best format for people that really want the best quality.

The Expert Reviews testing kit allows me to grab raw footage from any HDMI-enabled device, letting me compare the actual quality with no image correction or processing. For this test, I captured footage from a PlayStation 4, using it for Blu-ray playback and for the most common video streaming services. Using the same device means that any quality differences are down to the services, not different processing from different playback devices.

The raw facts

Before we get into the testing, it’s worth looking at the specifications for Blu-ray and streaming services. On paper, Blu-ray is certainly the quality winner, with the standard supporting video encoded using H.264 at a resolution of 1,920x1,080, delivered at a bit-rate of up to 40Mbit/s.

Compare that to Netflix, which is representative of other streaming services. It also uses the H.264 codec at a resolution of 1,920x1,080, but streams at around 12Mbit/s maximum. That’s a big difference between the two. To get its streaming rate down, Netflix has to throw away more detail in its video stream compared to the Blu-ray version.

Of course, there are a couple of caveats. The figures we mentioned for Blu-ray are maximum bit-rates, not a required amount. Some discs are encoded at lower bit-rates, reducing quality, but allowing a film to fit on a single disc. This is the reason that quality can vary on Blu-ray. Even so, on average, a Blu-ray film will use higher-quality video than a streaming service, but the question is, can you really spot the detail that’s lost?

Tested image quality

Impressively, the top streaming services that we tested all managed to perform well, with a detailed Full HD picture that you’d be more than happy with. When you fire up the Blu-ray and start looking at the differences, you notice that they’re very subtle, but the disc-based format is better.

Looking at our sample shots, comparing the Blu-ray version to the Amazon Prime Instant Video (one of the best services that we’ve tested) version, you start to see some of the differences. In particular, the Blu-ray frame is sharper throughout, while Amazon (and all streaming services) look a little soft in comparison.

^The Blu-ray version (top) has more detail than the streamed Amazon version (bottom), although it's very close - click on either image to view at original resolution

Fine detail is removed from the streaming services, too. When you look at our close-up of Benedict Cumberbatch, from Star Trek Into Darkness, you can see that his hair and face are sharper and more defined in the Blu-ray version. As you go further into the distance, the differences are more pronounced: the guy on the left-hand side of the frame’s jacket loses its padded detail; the woman in the red dress’ face has more detail in the Blu-ray version.

Switching to a different part of the scene, you can see that the lady in red’s dress has less detail in the streaming version, losing some of its creases and finer detail. Colour from the Blu-ray version is better across the entire frame, with the streaming versions often looking a little drab in some areas.

All of this might not seem like much, but the combined effect when the film’s in full motion is much more. In short, the Blu-ray version looks sharper, cleaner and punchier. It’s a cumulative effect, where if you watched the Blu-ray version of a film and then switched to the streamed version, you’d notice that the latter wasn’t quite as good. The same is true for all streaming services, with Netflix, Blinkbox and the other services that we tested producing similar results.

Sound quality

This is one area where Blu-ray is ahead of the pack. While most streaming services offer at least Dolby Digital 5.1 surround sound, if not Dolby Digital Plus 7.1 sound (not on all programmes and films), the sound is compressed using lossy compression, which means that some detail is lost. Blu-ray supports Dolby TrueHD and DTS-HD Master Audio, both of which are lossless and of a higher quality. In addition, the vast majority of discs use these formats, making Blu-ray a better choice for people that want immersive surround-sound.

What about 4K and the future?

Streaming services have the advantage here, with Netflix and Amazon streaming in 4K, with a select group of applications. It requires a lot more bandwidth, with Netflix recommending that you need a staggering 25Mbit/s for Ultra HD broadcasts. Streamed 4K content looks better than Full HD content from Blu-ray, for now. The limitation is that the streaming 4K requires an H.265 - also known as a High Efficiency Video Coding (HEVC) – codec built into the receiver. This codec gives you better quality at a lower bitrate, but the downside is that video requires about three times the processing power as for H.264 and Full HD. As such, it’s not possible to just add HEVC decoding to existing devices, limiting the availability of 4K streaming to the latest TVs only for now.

While Blu-ray might lag behind for now, an Ultra HD version of the format is due out at Christmas. This will support HEVC decoding and higher-capacity discs, with movies encoded at a higher bit-rate than for streaming. In other words, 4K Blu-ray will have better image quality once again.

HEVC and Full HD

One of the benefits of HEVC is that it can be used to encode HD video. While it still requires new kit to decode it, there are two possible advantages. First, HD video can be streamed using less bandwidth; secondly, the same amount of bandwidth could be used as now, but the quality of the picture could improve to Blu-ray levels.

Conclusion

Blu-ray is the superior format for HD video at the moment, although streaming could catch up. When it comes to the future, if you want the best-quality Ultra HD films, the new Blu-ray format is the best way to get it. Streaming services manage to produce high quality video conveniently, though, making them a great choice if you just want to get content quickly on a variety of devices. Due to the difficulty of device support, though, it makes sense to choose your streaming video service carefully. Our best streaming video service article will help you make the right decision.