Data requirements between Terra and Strato

[Drhemi]

Someone asked a question of me the other day that I could not answer. He wanted to know what the speed of data transfer is from server (Terra) to player (Strato). According to him there is no way a full 18Gbps signal can pass through a single Cat 5e or Cat 6 to the player. I tried to explain that the data being transferred is not the same as playing the movie via HDMI and is more a data stream to be processed and played by the Strato. I then realized that I really had no idea of what was actually happening.

Can anyone explain what data is being transferred, at (up to) what rate, and how it is all put together in the player for HDMI output? If this has been previously discussed, please post a link if you can.

Thanks,

Wayne

 

[Montucky]

Excellent question! I have also wondered the same thing. There must be some sort of network magic happening, because I've run as many 4 simultaneous 4K streams, but apparently the system is capable of 10 4k streams! Boggles the mind.

I'm not sure about the science behind it, but the fact of the matter is that it does indeed work as advertised.

 

[Kevin D]

Compressed data vs uncompressed.

 

[andy]

Hi Wayne,

Kaleidescape's WWW site states, "Up to ten Strato/Strato C players can play 4K movies simultaneously from a single Terra server; up to 15 players can simultaneously play Blu-ray quality movies."

You can do the math, but don't assume a true 1000 Mbps connection. Even on a healthy gigabit network, I haven't seen much more than 800 Mbps. With that said, you will not approach 800 Mbps with a single connection or even 3 or 4 players (assuming your network is gigabit and healthy). You are probably looking at no more than 65-70 Mbps for each UHD stream and more like 40-60 Mbps for HD.

I suspect the 18 Gbps number your friend mentioned is specific to HDMI. That requirement doesn't come into play until the video is processed on the player side (after the data is already transferred). Assuming your display supports high frame rates, 4:4:4 color space and high color depth, then you may need the 18 Gbps on your HDMI cable.


Andy

 

[Montucky]

I suspect the 18 Gbps number your friend mentioned is specific to HDMI. That requirement doesn't come into play until the video is processed on the player side (after the data is already transferred).

That explains it. Doy. Evidently 4K Blu-Ray's bitrate is a MAXIMUM of 100Mbps, so thus the 10 streams on a gigabit network (assuming PERFECT and full usage of said network) makes sense.

So the whole 18 Gbps has zilch to do with the data being processed by the player, but rather the raw video data the TV's seeing.

 

[MikeKobb]

As others have already hinted, there are two different data rates being discussed here.

HDMI is an uncompressed signal. 4K content within the HDMI 2.0 spec can require up to 18Gbps depending on the frame rate and bit depth. So, this is the data rate of the HDMI connection between your player and the display.

But, consider, if you wanted to store that uncompressed data, a 2-hour movie would take about 16.2 terabytes!

This is why compression is used to store digital media files. In the case of 4K movies, it’s HEVC compression for video, and one of several (usually lossless) formats for audio. The data rate for these movies is not constant — more data can be used to faithfully represent fast-changing or complex scenes, while less is needed to represent, say, a static landscape. For Movie Store titles, our typical rates are on the order of 60Mbps for 4K, but peaks can exceed 100Mbps.

When playing a movie stored on a server, the compressed data is sent over the network from the server to the player, which decompresses (“decodes”) it and outputs the A/V signal as an uncompressed HDMI signal. Since the network is carrying the compressed data, it needs to be able to handle 60-100Mbps.

So, that’s why we require a Gigabit Ethernet connection between Strato players, or between Strato players and Terra servers. 100Mbit Ethernet is not fast enough to carry these signals consistently. I’ve seen this firsthand, when I forgot that I had a little 100Mbit switch behind my bedroom TV. When I added a Strato C there, it worked fine for a little while, but eventually I hit a piece of content that had enough complex and fast-changing video that the network just couldn’t keep up.

Hope this clarifies!

 

[Drhemi]

Excellent, Mike.

This is the information I was looking for. It helps clarify the issues nicely. I can use your explanation to assist my colleague in understanding the separate data streams.

Wayne