[mythtv] H.264 and mythtv

Wim Fokkens wimfokkens at planet.nl
Wed Aug 31 17:57:31 UTC 2005


Mike Wrote

For H.264 in high def, we really need dedicated silicon to do the 
decoding--especially if the CPU is doing other things.
Remember when we used to have hardware DVD decoders?  They're back with 
H.264...

Her is one
http://www.vdr-wiki.de/wiki/index.php/Dxr6?PHPSESSID=fce91ae9b21689bb93ba826
0dca4adda

Wim








-----Oorspronkelijk bericht-----
Van: mythtv-dev-bounces at mythtv.org [mailto:mythtv-dev-bounces at mythtv.org]
Namens Michael T. Dean
Verzonden: woensdag 31 augustus 2005 19:48
Aan: Development of mythtv
Onderwerp: Re: [mythtv] H.264 and mythtv

Bernd Paysan wrote:

>Hi,
>
>heise.de reports that from October, 26, two free-TV programs are going to
be 
>send in HDTV quality (1080i) in Germany:
>
>http://www.heise.de/newsticker/meldung/63402
>
>However, they'll use H.264, not MPEG-2. AFAIK, ffmpeg can already decode 
>H.264.
>
>Are there any plans to include H.264 support into mythtv?
>  
>
(I can't read German, but it looks to me like they're talking about 
high-def resolutions...)

Note, however, that even top-of-the-line x86-based (including 
AMD64/EMT64) chips can not keep up with H.264 decoding at high-def 
resolutions (even 720p) with acceptable frame rates.  Microsoft lists 
minimum requirements 
(http://www.microsoft.com/windows/windowsmedia/content_provider/film/Choosin
gPC.aspx  
) that in truth are way too optimistic--even with Windows drivers 
providing full support for all (sound/video) card features.

MacOS X on top-of-the-line PPC is able to decode H.264 at 1080i at 24-30fps 
iff it's QuickTime H.264.  Similarly, Windows machines have a hard time 
with QuickTime H.264, but perform much better with WMV H.264. (Perhaps 
some optimization or even reverse-optimization for the platform's 
preferred codec?)

For H.264 in high def, we really need dedicated silicon to do the 
decoding--especially if the CPU is doing other things.  The ATI R520 
will have dedicated silicon to handle H.264 decoding (to be released 
sometime in October, probably), but whether there will be support for it 
in the Linux drivers (considering today's ATI drivers don't even have 
XVMC support) and whether there will be a standard API for using it 
(don't know of any at this point), is unknown.  NVIDIA cards will not 
have the H.264 decoding built in.

However, another (more portable?) option is using OpenGL 2.0's GLSL with 
relatively-recent ATI and NVIDIA cards to use the programmable shaders 
for video decoding (semi-dedicated silicon).  This approach is less 
efficient than using dedicated silicon, but portability at the expense 
of efficiency is probably worthwhile.  Note that this requires 
relatively recent cards since older cards do not allow enough 
instructions for the PS to allow the GPU to do the decoding.  (Does 
ATI's Linux driver provide OpenGL 2.0 support?  NVIDIA's first to 
support 2.0 was 7664.  
http://www.nvidia.com/object/linux_display_ia32_1.0-7664.html )

Remember when we used to have hardware DVD decoders?  They're back with 
H.264...

If any ATI/NVIDIA guys want to provide me with a card, I'd be happy to 
add GLSL support to Myth.  :)

Mike
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