[linux-dvb] Re: DVB Feature Wishlist

["Adrian Wilkins" <Adrian.Wilkins@Ascribe.com>]

<snip>

> > 	In addition, if the first is true, would the unit be capable of
> > simultaneously streaming MPEG2 data from the tuner TO the PC, while
> > receieving an MPEG2 stream FROM the PC and decoding it to 
> the framebuffer?
> 
> 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).

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.


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