[prev in list] [next in list] [prev in thread] [next in thread] 

List:       gnuradio-discuss
Subject:    Still: adaptation of the ISDB-T blocks for DVB-T / python problem
From:       Ralf Gorholt <ralf.gorholt () gmx ! de>
Date:       2021-12-20 17:08:01
Message-ID: cc93f190-6838-c8e3-5b27-b82ebe97d94f () gmx ! de
[Download RAW message or body]


Dear all,

I have adapted Federicos blocks OFDM Synchronization and TMCC Decoder
(which is a TPS decoder now) to DVB-T. They seem to work correctly but I
am still having troubles getting a stable video.

I have added debug code to the OFDM Synchronization and TPS Decoder
blocks. Whenever I detect a problem (symbol loss, frame   loss, wrong
symbol index, change in CP position, TPS not ok and so on) I print a
message on the console and restart sync. In normal cases, when this
happens the video just stops for one or two seconds and then continues.

However, it happens that the video stops in the middle of the reception
without a visible reason. The only thing I can say is that the transport
stream that is generated is no longer recognized by VLC.

Does anybody have experienced the same or a similar problem or has an
idea what could be wrong here? Are there any DVB-T experts here on the
list who could help?

I would really be happy if I was able to find out what happens here and
why. In order to do this, I have copied the relevant blocks from the GNU
radio sources to my own module (gr-dl5eu). Unfortunately this seems to
be more difficult than I thought, certainly because I am lacking
knowledge. I have started with the DVB-T Demap block. I have adapted the
namespace and can compile and install the block without a problem. The
error I get comes from python. When I start the flowgraph in GNU Radio
Companion, python complains:

Traceback (most recent call last):
    File "/home/ralfg/Schreibtisch/GNU Radio/grc/dvbt_rx_udp_new.py",
line 431, in <module>
        main()
    File "/home/ralfg/Schreibtisch/GNU Radio/grc/dvbt_rx_udp_new.py",
line 407, in main
        tb = top_block_cls()
    File "/home/ralfg/Schreibtisch/GNU Radio/grc/dvbt_rx_udp_new.py",
line 292, in __init__
        self.dl5eu_dvbt_demap_0 = dl5eu.dvbt_demap(1512, dtv.MOD_QPSK,
dtv.NH, dtv.T2k, 1)
    File "/usr/lib/python3/dist-packages/dl5eu/dl5eu_swig.py", line 1046,
in make
        return _dl5eu_swig.dvbt_demap_make(nsize, constellation, hierarchy,
transmission, gain)
TypeError: in method 'dvbt_demap_make', argument 2 of type
'dvb_constellation_t'

Why does this type error happen in the copied block in my module
(gr-dl5eu) but not in the original block in the dtv/dvbt module? I have
attached my source code to this email. An expert will certainly see
immediately where my error is. Perhaps somebody has some time to take a
look at it?

Thank you very much for your help!

Kind regards,

Ralf

["dvbt_demap.zip" (application/x-zip-compressed)]

[prev in list] [next in list] [prev in thread] [next in thread]