[vdr] Advice on new motherboard, xineliboutput, vdpau, hdmi video & audio, etc.

Theunis Potgieter theunis.potgieter at gmail.com
Fri Aug 20 11:36:33 CEST 2010


On 20 August 2010 00:37, Niko Mikkilä <nm at phnet.fi> wrote:
> Thu, 2010-08-19 at 20:54 +0400, Goga777 wrote:
>> > Computer hardware usually cannot provide 50.000Hz, 59.940Hz or 23.976Hz
>> > outputs to your TV/Monitor. This will cause some judder on display output
>> > as MPEG/AVC input-stream is not synchronized to output framerate.
>>
>> do you mean that all nvidia vdpau cards with existing drivers from Nvidia can't provide exact 50.000Hz,
>> 59.940Hz or 23.976Hz ??
>
> There is no graphics card, BD/DVD player or other standalone device that
> outputs those rates exactly. I don't know how much they deviate, but I'd
> guess it's usually something like 0.01 % (50.005 Hz instead of 50 Hz),
> as Jori said.
>
> However, the rate doesn't need to match exactly because the display
> device is synchronized to the video signal. The rate could be 50.1 Hz or
> maybe even 51 Hz and the display wouldn't mind. 50 fps video files would
> play slightly faster, but there would be no need to drop video frames
> because of that.
>
> Things are more problematic when receiving live broadcast. Then the
> display and the video source (graphics card and software) needs to be
> synchronized to the broadcast to avoid dropping or duplicating frames.
> Set-top digital television boxes and FF DVB cards do that, but most
> graphics cards/drivers can't because they aren't designed to follow an
> external time source.
>
> Audio playback synchronation is another issue, and somewhat difficult to
> handle properly on a PC where the audio chip's clock is almost always
> separate from the graphics card's clock. By default, many media players
> time everything according to the audio clock, and therefore they need to
> drop/duplicate video frames every now and then. The other alternative is
> to drop/duplicate audio frames or resample the audio completely.
>
> --
>
> Niko
>
>

The hardware is also running some kind of software/firmware (binary
blob). I would think that the Larabee would have been the perfect
choice, easier to create newer/maintaining firmware, since it is x86
based. If they made the Larabee propriety for the parts that we are
interested in. Then it would also defeat the purpose of having a
dynamic decoding environment. Which current hardware devices fail to
do. There for the argument to have a software based solution that can
do more than just one thing, not just live tv but also alternative
media sources/codecs.

Current hardware is good for Live TV and Recordings, software based
solutions are good for dynamic media/source input, newer codecs etc,
not so good at displaying it properly 100% all the time.

my 2c.



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