BATC Forum

Dear all,

I am looking for someone who has a good knowledge of GNU Radio internals and particularly the Viterbi Decoder and Convolutional Deinterleaver for DVB-T from the GNU Radio core (gr-dtv).

Those who use GNU Radio for DVB-T reception may have noticed that sometimes reception stops without a visible reason. This problem is not always related to the known difficulties in OFDM symbol acquisition. The problem I am thinking of is related to the internal processing of the stream tags that are used in the DVB-T blocks and it might be that I know the reason why it happens.

So, if anyone can help, please contact me.

Regards,

Ralf DL5EU

Bonjour Ralph,

I have written a few graphs to receive DVB-T with low SR back in 2021... You may try them and see if they have the same "problem".

73 de michel, hb9dug

https://home.swissatv.ch/2021/07/dvb-t- ... gnu-radio/

Hi Michel,

thank you very much for the information. I will test them but as long as you use the "standard" blocks from GNU Radio the problem should be there. Did you never notice it?

As you might know, the DVB-T blocks make use of GNU radio's stream tags for synchronisation. I have found out by using the Tag Debug block that (at least in my case) the Convolutional Interleaver sometimes receives a "superframe_start" tag (which is used to reset the interleaver) from the blocks upstream when there is no superframe start and that is what causes the video to freeze immediately until the next "superframe_start" that is sent when a superframe starts. I am currently working on a solution. You can find my code here: https://github.com/dl5eu/gr-dl5eu.

73 de Ralf, DL5EU