All about the software

F_Null Packet vs. Null Packet

Messagede mucsb » Dim 21 Fév 2021 16:08

Dear All,

recently I started to detect F_Null Packets in my own transmission. The picture does not build up. Does someone know what is this kind of packet for? See attached.


I am familiar with the regular Null Packet but this is somewhat different.
Fichiers joints
F_Null packets.png
F_Null packets.png (25.94 Kio) Vu 6811 fois
mucsb
 
Messages: 4
Inscription: 15 Jan 2020

Re: F_Null Packet vs. Null Packet

Messagede F6DZP » Dim 21 Fév 2021 22:02

Hello,

when you set the SR and Fec and modulation there is a TS bitrate that correspond.

If your video data + audio data + DVB tables are lower than this bitrate, the multiplexer is supposed to add null packets to give the TS bitrate needed.
If, for some reason, your multiplexer doesn't give the good TS bitrate but a lower bitrate, then, if you are using the F5OEO Pluto firmware, it adds itself Fake Null Packet to be sure that your modulator will have the good TS bitrate.

Normally you should have only Null Packets. I have added the detection of Fake Null packets in Minitioune to let people know what is happening to their final TS data.
If you have only Fake null Packets that shows that you have 2 problems :
1) no Null packets => you give too much bitrate to video + audio data so no place for Null packets. That will produce some problem with encoding datarate variations that always exist even you are in CBR mode
2) there are Fake null Packets => that indicate that you have set the TS datarate of the multiplexer too low, so it is the Pluto firmware that must add Fake Null packets to be sure that the final TS bitrate will be good.

Jean-Pierre F6DZP
F6DZP
 
Messages: 1129
Inscription: 24 Déc 2010

Re: F_Null Packet vs. Null Packet

Messagede g4saq » Ven 26 Nov 2021 12:33

Great explanation, Jean-Pierre. Thank you. I really enjoy using your excellent Minitioune. 73, Russ.
g4saq
 
Messages: 4
Inscription: 19 Juin 2017

Forums Statistiques

Qui est en ligne

Utilisateurs parcourant ce forum: Aucun utilisateur enregistré et 1 invité

Options

Retourner vers Minitioune