[MPlayer-dvb] New ATSC messages.

[Nico Sabbi]

Il Tuesday 18 December 2007 03:25:27 Bill Pringlemeir ha scritto:

> >
> > I suspect simply bad reception
>
> You are correct.  I had never seen these messages before and had
> just updated from SVN so I thought they were new messages just put
> in the code.  I haven't seen them since.  I am also 20km from the
> CN tower with a CM 4221, so I thought bad reception was unlikely. 
> My neighbour must have started his arc welder.
>
> I have been using atscap to capture the streams.  It seems that
> mplayer plays the "ts" stream much better than the direct V4L2
> stream. I think that this is due to the fact that the file provides
> a huge buffer.  Is there a FAQ entry somewhere on the preferred
> method to capture streams?  I imagine it is 'cat'ing some device.

you can also try to use some -cache 4096 with -speed 0.97 -af 
scaletempo -mc 10

>
>
> So, I am guessing that an external card with have dual-ported
> memory and reduce the amount of traffic on the FSB.  A card
> supporting XvMC will definitely reduce this traffic, but it cann't
> support more advanced codecs and/or filtering.  So, I am looking at
> a nVidia card that supports XvMC and has 1920x1200 DVI
> capabilities.  I know the XvMC will work, but is it correct that an
> external card will reduce the FSB memory pressure?  None of the
> HDTV faqs I have read seemed to mention anything of this.

memory pressure will decrease if you send the card a compressed
bitstream (like xvmc does) or if you send a lower resolution image.
-vc ffmpeg12 -lavcopts lowres=1 will have a significant speedup

>
> It is unfortunate that the i865g Xorg drivers don't due XvMC (it
> seems only i810 and i815 support this).  A MythTV faq seems to say
> that any card using the i810 driver will have XvMC.
>
>  http://www.mythtv.org/wiki/index.php/XvMC
>
> The i810 driver (now intel) supports many chipsets, but very few
> have XvMC support.

try with intel drivers

>
> I guess that the 533Mhz mobo docs are correct and I actually have
> 533*{4,8,16} bytes/second.  Otherwise, I don't understand how
> mplayer can play this 1080i on my system at all.  The Mpeg2 decode
> phase has to run over YUV in several interlaced blocks.  Even at
> 3.2Ghz, this is about ~60,000 instructions/pixel with dual pipline,
> but the MMX/SSE instructions would have to be all over memory with
> separate YUV iDCT per pixel (group).
>
> It did seem that the libmpeg2 might be able to do a crude scaling
> at the start of the decode.  Ie, use the frequency information to
> do a nice integer scale that would reduce the memory bw.  I am
> currently trying to play at 1280x1024 resolution.  I think if xv is
> doing the scaling, a complete 1920x1080 memory buffer must be used
> and the i865G is fitting it to the screen?  That isn't a request,
> just a query to confirm that it could be possible.

I don't have any knowledge of the decoding process, better ask
ffmpeg-devel where optimizations are generally discussed

>
> Am I smoking crack?  Is there some place to put some notes like
> this? The V4L wiki seems to be concern with getting a stream.  Not
> moving the stream onto a display.  It is quite amazing that mplayer
> does such a great job given the amount of data it is dealing with.
>
> Thanks,
> Bill Pringlemeir.
>
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