[linux-dvb] Re: video + net with Nexus

[Ralph Metzler <rjkm@metzlerbros.de>]

Augusto Cardoso writes:
 > I may have miss the point here, however, I have run the skystar2 cards at 38Mbps IP payload speeds without dropping any packets for more than 24 hours. With the FCII/FCIIB the maximum speed that I got is about 41Mbps. With FCIII I have tested it at 78Mbps and simulated it at 120Mbps. (Note this tests were done at B2C2 with B2C2's drivers).
 > When I used to work at B2C2, we focus on data applications. That is the main reason the B2C2 Windows driver is a NDIS driver and the B2C2 Linux driver is a network driver. Unfortunately, the B2C2 drivers are proprietary and very cumbersome.
 > 
 > We did developed a software package for testing data in Unicast and Multicast. We also run the data in the same transponder that we run the video/audio. We tested receiving all IP data and video/audio without any problems.
 > 
 > I haven't done much data tests with the linuxtv.org drivers, mainly because my use is for video/audio MPEG2 data.
 > 
 > Can this be a latency issue in the driver? How are you testing? What type of applications/protocol? What's the service provider?


What I wrote was only related to the "full-featured" Technotrend cards.
They basicaly consist of a tuner, an SAA7146 as PCI bridge, a TI AV7110 (demux,
MPEG2 decoder, ARM core, etc.) with SDRAM and DRAM and 8KB dual ported
RAM connecting the AV7110 and SAA7110. 
The transfer from the AV7110 to main memory (via SAA7146) is the
problem. The ARM core (40 MHz ARM7TDMI) has to buffer and move
the data (in software) from SDRAM to the dual ported RAM and from there
it is DMAed by the SAA7146 to main memory.
Both the buffering and the moving are very slow on the 40 MHz ARM.

The AV7110 also has internal hardware section filters. They tend
to have dropouts or even filter lockups when the data rate goes beyond
10Mbit. So, it basically does not matter if we use hardware filters or
move the whole PID to the PC memory and filter in software.


Ralph




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