Multiple HDTV over network, bandwidth needed? (1 Viewer)

[Bulan]

Approximately how much bandwidth does one HDTV stream from a DVB-S2 tuner require on the network?

I'm guessing if I plan to have a server with 4 DVB-S2 Tuners, i need a Gigabit LAN to be able to push this out to 4 clients at once?

Also, if I now get all of these tuners, does recording on the server demand much more juice than a regular broadcast?

Just thinking ahead a bit to when I'm gonna set up my system..

And just to compare, how much bandwidth does a regular DVB-S stream need?

I'm guessing it varies with what channel your watching, but if so there must be some high/low values..

(Searched around the forum a bit but didn't find anything to my liking)

 

[Frodo]

First of all, it depends on the (hdtv) channel. The broadcaster is more or less free to choose the bitrate it wants to use for a tv channel. This means some channels are 2-3 Mbits/sec while others are 8Mbits/sec

Now about DVB-S2 H2.64
One one hand, HDTV requires a lot more bandwidth because of the higher resolution. On the other hand, much of this is compensated because H.264 compresses much better then good old mpeg-2 and because of the new modulation methods in DVB-S2.
The authors claim that a H2.64 service now takes up about the same bandwidth as a normal DVB mpeg-2 SDTV channel.

In the end this means that HDTV H2.64 wont use much more bandwidth on the LAN then a normal mpeg-2 SDTV channel.

On the client however its different. H2.64 decoding requires a LOT of cpu and gpu power. So much in fact that at the moment I dont think there is a pc yet which can perfectly display 1080p H2.64 tv.

 

[Bulan]

On the client however its different. H2.64 decoding requires a LOT of cpu and gpu power. So much in fact that at the moment I dont think there is a pc yet which can perfectly display 1080p H2.64 tv.

Thx for the answer Frodo!

But what about the server?
When it records then it doesn't need to decode the stream right?
So from the servers view it won't be so much bigger load recording a H.264 then a regular Mpeg-2 stream?

 

[Roberdin]

I'm not sure at what rate they are broadcast on cable, but I know that DVB-T HD is at around 20 MBit/s. So you should survive with up to about four streams on a megabit cable. I'd not take any chances though - when you wire up your house, use gigabit cabling anyway. It's future proofing and not significantly more expensive, although you may as well leave your clients with megabit NICs for the moment.

 

[knutinh]

On the client however its different. H2.64 decoding requires a LOT of cpu and gpu power. So much in fact that at the moment I dont think there is a pc yet which can perfectly display 1080p H2.64 tv.

http://www.anandtech.com/video/showdoc.aspx?i=2886

"Our first glimpse of the processing power required to play HD content on the PC gave us a very good indication that Blu-ray movies using MPEG-2 should have no problem on a modern system, even without GPU acceleration. The Core 2 Duo E6300 is easily capable of playing back 50-60 Mbps MPEG-2 video at 1080p. Adding a GPU to the mix did make an impact, but the small boost in performance just wasn't necessary.

Today we will turn the tables around and look at what happens when H.264/MPEG-4 AVC meets Blu-ray on the PC. This combination is much more demanding than MPEG-2 encoded Blu-ray movies, as H.264 is capable of much higher compression at better quality which requires more processing power.
...
The bookmark feature really helped out, allowing us to easily jump to the specific scene we wanted to test in Chapter 18. In this scene, the Golden Gate is being torn apart and people are running everywhere. This is one of the most stressful scenes in the movie, reaching a bitrate of over 41 Mbps at one point. "

The peak cpu usage for this HD-DVD title should be quite accurate for estimating cpu use for other applications as well, since it has a peak bitrate of 41mbps h264 for 1080p24 content. When the cpu usage reaches peak, the user will probably notice a frame-drop or slow-down. I am guessing that most broadcast material will be CBR and far lower than 41mbps.

Also, for HD-DVD content you have to do decryption, and the playback tools/codecs are probably not fine-tuned yet.

-k