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

From: Ron Economos
Subject: Re: [Discuss-gnuradio] bit stuffing DVB-S TX example ?
Date: Thu, 7 Feb 2019 16:26:25 -0800
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0

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.


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 ?



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