[mythtv-users] Frontend Raspberry Pi setup issues

[Stephen Worthington]

On Tue, 25 Jul 2017 19:49:28 -0400, you wrote:

>
>
>On 07/25/2017 06:27 PM, DryHeat122 . wrote:
>> So I have two more questions if you guys don't mind.  First, I 
>> checked, and it now works with wifi. iperf says the rate to port 6543 
>> is 17.5 Mbps.  Is that right on the edge of what's needed or is there 
>> room for the rate to go down some?  I don't know what h.264 consumes.  
>> I ask because I am testing it in the middle of the day when the 
>> neighbors are at work and per @mike's post it might not be as good 
>> later on.
>>
>The highest rate for HD that I have seen is approx 17.7 Mb/s. This is 
>based on 8 GB/hour, which some channels use with MPEG-2. With H264 it 
>should be much less, by about a factor of 5. However wifi speed can vary 
>so that it may work fine for a while then slow down randomly, so I would 
>recommend using a wired connection. There are options for ethernet over 
>powerline and ethernet over coax which may help in your situation.

Here in New Zealand, we typically get HD recordings of around 5
Gibytes per hour for 1080i H.264.  So that factor of 5 is quite wrong.
Part of that is that the HD picture quality transmitted is quite a bit
higher than what is transmitted on MPEG2 systems, but H.264 never
produces files that are 1/5 the size of MPEG2 encoded ones.

But with H.264, what you have to watch out for is the peak bit rates.
H.264 is very variable as to how much compression it does on each
frame, so when you get a complete change of picture (eg a scene
change), you can get a very high peak bit rate for a short time.  That
can be too much for a WiFi connection.  MPEG2 recordings can be fixed
bit rate or variable bit rate, but the peak variable bit rates are not
as high as with H.264.  Still, they can be too much for an ordinary
WiFi connection.  For HD, you really need 802.11ac, not 802.11n.

If you want to play an H.265 file you have downloaded, or a 1080p
H.264 one, then the peak bit rates are again even higher than with
720p or 1080i H.264 recordings.  Let alone what is needed for 4K
H.265.