[NTLUG:Discuss] HDTV card for Linux

[Paul Ingendorf]

I checked, the hardware specs do include DMA (my mistake before) this means
doing something of this nature is well within the specs for the hardware
itself the numbers you manufactured actually support this. Your numbers also
indicate a 40x cdr, not 80, do to disk to memory/memory to disk performance.
I'm sure you know about disk fragmentation and other factors that influence
disk io.  This is why these devices use 1MB or greater allocation units.
This allows the device much quicker access to contiguous data on the drive.
I don't doubt that it is pushing the physical limits of the devices but the
hardware can handle it as long as the resources are properly managed.  For
comparison, more than the cs of numbers, the series 1 tivos required ~4GB/h
of compressed video when set in their best mode.  This is with the inherent
inefficiencies in the myworld/linux architecture currently in use for at
least the tivo series.

-----Original Message-----
From: discuss-bounces at ntlug.org [mailto:discuss-bounces at ntlug.org]On
Behalf Of Bryan J. Smith
Sent: Wednesday, September 08, 2004 3:24 AM
To: pauldy at wantek.net; NTLUG Discussion List
Subject: [NTLUG:Discuss] RE: HDTV card for Linux

I'm not sure I agree.  0.125GBps is _ideal_.  Let's track the transfer.

One stream requires:
- 3MBps from I/O to memory
- 3MBps from memory to storage

That is a sustained, continuous 6MBps -- plus overhead, setup, CPU,
etc... _per_ stream.  That's 12MBps for dual-streams.  And that's
_before_ we start talking overhead.

Let's put this into more of a "tangeable" form where sustained writes
are required.  For example, CD is 1.544MBps per "speed."  12MBps is
equivalent to 80x CD-R (6MBps is 40x).

So don't be surprised if you get dropped frames -- especially a
significant chunk of a second or two.

Depends.  Some have embedded I/O controllers.

Again, depends.  A lot of uC/EuP systems have PIO/DMA programmable
lines.  UltraDMA and PCI Bus Mastering channels are _very_typical_ and
_standard_ peripherial nowdays.

In fact, more than one internal PCI bus is very common and cheap to do
in silicon.  So the ATA gets its own channel right in the stock
core+peripherial design.  About the only thing you can't put on the core
is the tuner or another EMF generating ADC/DAC (although multiple-dies
are now coming back to do just that -- but would drive costs up).  So
the tuner would get the external PCI runs -- so it should be a separate
PCI channel.

Until PCI-Express comes out, I agree.  It's not worth the cost to get
0.5GBps+ PCI/PCI-X.

Correct.  Although the LG HDTV ASTC/PVR has an IBM PowerPC 405 in it.
But it won't let you watch and record independently -- single
input-only.

After just getting my first DirecTiVO a couple of weeks ago, I'm holding
off on HDTV this year because I'm waiting for them to mature.  I'm also
hoping the LCD _projection_ (not the LCD/Plasma, but LCD _projection_)
TVs break $2K by fall of next year.