[linux-dvb] Re: [BUG] FusionHDTV5 Lite

Edgar Toernig froese at gmx.de
Mon Sep 12 08:33:43 CEST 2005


Hamish Moffatt wrote:
>
> On Mon, Sep 12, 2005 at 07:05:35AM +0200, Edgar Toernig wrote:
> > Hamish Moffatt wrote:
> > > IMHO the BT878 buffer is too small, as it's not designed for this
> > > application.
> > 
> > I'm not that sure that it's the small audio dma fifo.  It's half as
> > big as the video fifo but video dma has much more than double the
> > bandwidth and I've never seen the error with video dma.  And both
> > are sitting in the same PCI slot.
> 
> In DVB/ATSC applications the video path isn't used.

With the Pinnacle you can use both paths simultaneously - it has a
video connector on the back ...

> With regard to
> double the bit rate, for what resolution? Admittedly I don't know the
> format of the analog video data on the bus, but for a resolution of say
> 320x240 at 24 bit, that's only 1.8Mbit/sec. 3.6Mbit/sec if it's 48 bit
> (16-bit per YUV?). 

That's not per second but per field.  Multiply it by at least 25/30 (or
is it still 50/60?) to get the real bandwidth/second.  A full RGB PAL
overlay requires 768*576*32*25 = 354Mbit/sec.

> Compare that to up to 20Mbit/sec of MPEG2 data *on the audio path*.

Yeah, 20 is peanuts, isn't it ;-)

Ciao, ET.



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