Alban,
It's absolutely critical that you use the -muxrate option in
ffmpeg. If you don't, you get a variable rate Transport Stream, which is
guaranteed to cause problems.
Also, I would specify the muxrate to 1 bps of accuracy. ffmpeg supports
it. So for 300 kSyms/s, it would be 276471.
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 800 is the
hi thanks for your answers
my symbol rate is 300 ksps
using this calculator
http://www.satbroadcasts.com/DVB-S_Bitrate_and_Bandwidth_Calculator.html
and these settings : QPSK rate 1/2 FEC frame 64800
i get 276.5 kbps of TS bitrate
here are my settings for ffmpeg :
*ffmpeg -re -f lavfi -i
Hi Ron
That formula it's very useful! Thanks. I have a silly question (sorry for
it). If I understand correctly 800 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
Typo. Should be:
ffmpeg -i test.mp4 -c:v libx264 -b:v 11M -minrate 11M -maxrate 11M
-bufsize 8M -c:a copy -muxrate 12901961 test.ts
Ron
On 2/7/19 16:26, Ron Economos wrote:
First, you have to match the TS rate to the symbol rate. The equation is:
Symbol rate * 2 * 188/204 * code rate
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:
800 * 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
Hi,
I had the same issue, ffmpeg will not provide CBR for MP4 , you might
end-up with variable bit rates on the TS stream. I had some good success
with a target bit rate on ffmpeg around 150% of the bit rate set on
GNURadio. But this will only work with real time inputs like webcam,
when
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
