tv tuner/video

tv tuner/video

[Sacha Varma]

Some TV Tuner card/LinuxPPC questions:

1. What is the state of tv card support on LinuxPPC? I've searched the
linuxppc-dev logs and seen some announcements of bt848 support. I'm aware of the
video4linux/V4L2 work; is this supported by the PPC kernel or are there PCI
nuances that need addressing first?

2. The bt848 cards I've seen seems to offer v. limited real-time continuous
capture (320 x240 == 1/4 NTSC); I don't know if this is a limitation of the
chipset or the cards. I'm looking for full streaming PAL capture to memory. Is
this beyond the bandwidth of PCI? If so, is it usual for cards that offer this
to do hardware compression first?


Any help much appreciated. I'm largely ignorant about the architecture involved
in getting video out of the coax from my aerial and into RAM.

--
sacha varma : system simulation ltd : sacha@ssl.co.uk

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Re: tv tuner/video

[Francois.CAU]

     
> 1. What is the state of tv card support on LinuxPPC? I've searched the 
> linuxppc-dev logs and seen some announcements of bt848 support. 

The bttv driver (driver for bt848 based cards) is working on LinuxPPC.
     
> 2. The bt848 cards I've seen seems to offer v. limited real-time continuous 
> capture (320 x240 == 1/4 NTSC); I don't know if this is a limitation of the 
> chipset or the cards. I'm looking for full streaming PAL capture to memory. 
> Is this beyond the bandwidth of PCI? If so, is it usual for cards that 
> offer this to do hardware compression first?

The PCI bandwidth is large enough for video. TV applications like xawtv 
have 2 modes: 
- Overlay, where the TV card is PCI-bus-master and directly writes in the 
video memory. 
- Grabbing, where the application grabs each picture, and then displays it 
on the screen. You can even process the pictures before displaying them.

The bottle-neck for continuous capture of un-compressed, full-size video 
comes from the hard-disk.

Francois


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Re: tv tuner/video

[Gerd Knorr]

> The bottle-neck for continuous capture of un-compressed, full-size video 
> comes from the hard-disk.

... and for compressed video from the CPU.  I'd expect today's hardware
is'nt fast enouth to handle full-sized video without hand-optimized
assembler code.  xawtv 3.0 can do mjpeg compression (uses libjpeg) and
handles half-sized pal @ 25fps without much trouble on new hardware.
Hav'nt tested that code on ppc, so there might be some byte order
problems...

  Gerd

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