[linux-dvb] Re: DVB Feature Wishlist

[Ralph Metzler <rjkm@metzlerbros.de>]

Adrian Wilkins writes:
 > > This would really depend whether USB bandwidth is per 
 > > direction or per total 
 > > of both.  Not sure which it is, but I suspect total.
 > 
 > Being a bus, I believe USB bandwidth is shared over all devices.
 > 
 > The quoted figure of 1.8 Gb per hour for storage of video for the DEC2000-t (UK version, at least) would suggest a 4Mbit/s video stream, so in theory, two streams should fit into the 12Mbit/s provided by USB 1.1
 > In practice, I don't know what is considered a high stress level for USB and at what level of saturation it starts to get unreliable. USB 2.0 would definitely have this covered, but the box is limited to 1.1 ; a brief shufty at Hauppauge.de shows their next-gen DEC3000 box alao uses 1.1 (but I couldn't read the feature list, my German is almost nonexistent).

They call their boxes DEC3000-s and DEC2000-t.
It looks like the DEC3000-s is just the DVB-S version and otherwise identical. No idea why
they use different numbers.

 
 > The performance of the ARM CPU in the DEC2000 is also of concern, but just guessing at it, I can't believe that a CPU capable of decoding MPEG2 would have any trouble managing one extra memory buffer.

The CPU (40 MHz ARM7TDMI core) definitely cannot decode MPEG2. 
There is one DSP for video and another for audio decoding on the same chip. 
The performance of the USB connection would depend on how data is
transferred internally (DMA or CPU byte shuffling).

Too bad that they did not make a box with firewire interface. The
AV7110 suports streaming of the whole TS in both directions via
firewire with minimal CPU usage.

Ralph


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