Re: [Discuss-gnuradio] bit stuffing DVB-S TX example ?

Hi Ron

That formula it's very useful! Thanks. I have a silly question (sorry for it). If I understand correctly 8000000 is the symbol rate and 12901961 is the TS rate? Correct?

The multiply by 2 is because Tx signal is QPSK? If that's so then it will be 1 for BPSK, 3 for 8PSK and so on.... Am I right?

Thanks!

Raydel

El jue., 7 de feb. de 2019 7:26 PM, Ron Economos <w6rz@comcast.net> escribió:

First, you have to match the TS rate to the symbol rate. The equation is:

Symbol rate * 2 * 188/204 * code rate

For the example flow graph:

8000000 * 2 * 188/204 * 7/8 = 12.901961 Mbps

Second, you need to constrain the video bitrate to fit into the selected TS bitrate. With ffmpeg, something like this:

ffmpeg -i test.mp4 -c:v libx264 -b:v 10M -minrate 11M -maxrate 11M -bufsize 8M -c:a copy -muxrate  12901961 test.ts

For SD video, a smaller bufsize like 2M should be used.

Ron

On 2/7/19 15:15, Alban Meffre wrote:

Hi All

did some transmission test in DVB-S tonight

TX : ffmpeg + gnuradio + pluto SDR

RX : RTLSDR + sdrangel

it works but there are some gaps in the received signal because the TS stream bitrate is slightly less to the maximum usable bitrate

is it possible to add some bit stuffing at DVB-S modulator side to make to output power constant ?

Bob

--

Alban MEFFRE F4GSW

_______________________________________________  Discuss-gnuradio mailing list  Discuss-gnuradio@gnu.org  https://lists.gnu.org/mailman/listinfo/discuss-gnuradio  

_______________________________________________
Discuss-gnuradio mailing list
Discuss-gnuradio@gnu.org
https://lists.gnu.org/mailman/listinfo/discuss-gnuradio