I was looking for information regarding concurrent multistream reception and found this useful post.
I have a DVB-S2 lab setup with a Tx node directly connected to TBS 5927 and the TBS 5520SE receivers and I would like to accomplish something similar: to multiplex two streams and receive them both simultaneously.
The Tx node is sending UDP/IP traffic over MPE, over MPEG TS. At TS level, it multiplexes two PIDs, 32 and 33. All TS packets with PID 32 are sent over DVB-S2 frames using MODCOD QPSK 1/4, whereas all TS packets with PID 33 are sent over DVB-S2 frames using MODCOD 8PSK 3/5. So, in the end, in this scheme (labeled Scheme 1 below) two logical data streams are multiplexed at TS level. On the receive side, then, I instantiate two dvbnet interfaces, one for each PID, and expect to receive the UDP/IP packets sent on the corresponding PID.
In summary:
Scheme 1 (same ISI, different PID):
Stream 1: ISI = 0; PID = 32; MODCOD = QPSK 1/4
Stream 2: ISI = 0; PID = 33; MODCOD = 8PSK 3/5
Using this scheme, I've found that:
- The TBS 5927 correctly demodulates the VCM stream and decodes both MPEG TS PIDs.
- The TBS 5520SE locks randomly to one of the two streams. I don't seem to be able to control which stream/MODCOD the 5520SE locks to using dvbv5-zap.
Due to the problem with the 5520SE, I tried multiplexing at BBFRAME/ISI level. The scheme becomes:
Scheme 2 (different ISI, different PID):
Stream 1: ISI = 1; PID = 32; MODCOD = QPSK 1/4
Stream 2: ISI = 2; PID = 33; MODCOD = 8PSK 3/5
This scheme does allow me to control which stream the 5520SE locks to. All I need to do is set STREAM_ID on channel.conf used by dvbv5-zap. However, the disadvantage is that I don't seem to be able to receive both streams simultaneously when they use distinct ISI as in Scheme 2 above. Hence, although Scheme 2 solves the 5520SE problem (of choosing which MODCOD to lock to), it is a worse solution for the 5927, with which it would normally (in Scheme 1) be possible to receive both streams simultaneously.
crazycat Wrote:HW limitation, one demod path can process only one TS from S2 frames.
P.S. you can use also 6905.
So, is it possible to receive multistream simultaneously with either the TBS5927 or the TBS5520SE? If I understand correctly, the 5927 uses the STV0910 demod that was mentioned above. So I suppose it is not possible?