Raydel,
You are correct on both points. QPSK (the only allowed
constellation in DVB-S) is 2 bits per symbol.
Ron
On 2/8/19 04:20, Raydel Abreu (CM2ESP) wrote:
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 <[email protected]
<mailto:[email protected]>> 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
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