TS buffer size for TT S2-3200

Messagede crmigul01 » Jeu 16 Mar 2017 23:07

Hi Jean Pierre

First of all i want to thank you for the great work you have done.Your tools are invaluable to the DATV community.
I have some question in regards to TS buffer size.I have seen that in Minitiouner SW. you have-it adjustable.
What is the value of the buffer in TT S2-3200/TT S2-1600?
Can you estimate what is the buffer latency impact on the current implementation for the above sw version?
I ask this because i need to estimate what is the main contributor to the latency that i have and i don't know if the problem is from the encoder or from the receiver.
Do you have some experimental data in terms of minimum latency @ data rate that can be achieved using the current available encoders and the Tutioune/Minitioune receivers?

Thank you for response.

Best regards,
Cristian
crmigul01
 
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Re: TS buffer size for TT S2-3200

Messagede F6DZP » Dim 19 Mar 2017 13:10

using Tutioune1600/3200:
The minimum buffer is 512 packets of 188 bytes = 96 256 bytes
( the "frame" memory of the SAA7146A)
for DMA transfer, I ask 20 buffers by default => 96256 bytes * 20 = 1 925 120 bytes but don't get them all:
if you look at the info in Tutioune ( using "look at analyze") you will see the exact channel size
I have just run Tutioune1600 and I find : channel size = 1736704 bytes
As you can see the info for the buffer is written when you use Tutioune.
(10 buffers is the minimum where we can have some problems)

using Minitioune the buffer is 7896 bytes (can be changed in the .ini) = 6 x 1316 bytes
it is written in the Minitioune interface "TS buffer = 7896 bytes"
1316 is the unit I use for sending bytes via UDP (1316 = 7x188)
when I send data to the graph that decodes via USRC (universal source), I send data by group of 1316 bytes. by default 6 x 1316


buffer latency impact= depends of the data rate ( symbol rate) and the amount of byte waiting in the buffer

using Minitioune
- at SR2000 fec 3/4 data rate is 2764706 bytes per second => latency is 7896 /2764706 = 2.8 msec + the time taken by the codec to decod and display
- at SR250 fec 7/8 data rate is 403 184 bytes per second => latency is 7896 /403 184 = 19,6 msec + the time taken by the codec to decod and display

using Tutioune:
- at SR2000 fec 3/4 data rate is 2764706 bytes per second => latency is 1736704 /2764706 = 628 msec + the time taken by the codec to decod and display
- at SR250 fec 7/8 data rate is 403 184 bytes per second => latency is 1736704 bytes /403 184 = 4,31 sec + the time taken by the codec to decod and display

Jean-Pierre F6DZP
F6DZP
 
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