[pvrusb2] MPEG1 stream type

[Mike Isely]

On Mon, 23 Jul 2007, Mark Brand wrote:

> Hi,
> Thanks for the reply.
> 
> By the way, the formula for "watchable" at the URL has an unmatched
> parenthesis:
>     watchable = ((hres - 1) >> 1) & 1) != 0
> but we know where it goes.
> 
> The formula predicts that 352 should be OK.
> 
> 640x480 exhibits the familiar problems. 320x240 seems to hang the thing.
> 
> The funny thing is that 352x288 is standard for PAL VCDs. (352x240 is
> NTSC.) PAL VCD MPEG-1 mode works fine using Hauppauge's wintv2000.

Well I only suggested this as a possible avenue of investigation, not a 
solution :-(

I know this isn't all that helpful; the simple fact is that you're 
exploring a not-well-known area of the mpeg encoder chip.  That encoder 
is a fairly complex beast and its firmware is not exactly air-tight.  
I've learned from the ivtv maintainer that the encoder's API 
unfortunately has more than a few dark corners where dragons may hide...

If the open source community could ever get the full specs for that chip 
(Conexant cx23416), I'll bet some absolutely spectacular things could be 
done with it.  In the mean time we are stuck with the canned firmware 
and its associated "interesting" behavior.


> 
> Perhaps it's unrelated, but I notice that mplayer (unlike xine and vlc)
> wrongly detects the aspect of even mpeg-2 video:
> > VDec: vo config request - 720 x 576 (preferred colorspace: Planar YV12)
> > VDec: using Planar YV12 as output csp (no 0)
> > Movie-Aspect is 1.33:1 - prescaling to correct movie aspect.
> > VO: [xv] 720x576 => 768x576 Planar YV12

I thought that the aspect ratio of the signal was a separate parameter 
carried in the stream.  It has to be, otherwise mplayer would have to 
assume the aspect ratio based on the resolution and that definitely does 
not happen since I can capture 640x480 or 720x480 and still have the 
correct aspect ratio displayed.  In fact, there is an aspect ratio 
control in the encoder that you can tweak.  I've experimented with that 
and mplayer responds correctly when it is a different value for the 
stream that is generated.

I did those experiments a while back with just normal mpeg2 video, using 
the other capture settings at their defaults.  It sounds like this is 
not what happened for you.


> 
> Another thing about I notice is that changing the output mode to any of
> the MPEG-1 choices leaves the resolution at the default 720x576, which
> as far as I know is not possible for MPEG-1.

Can you change the resolution back to the desired value AFTER you change 
the mode?  You should still be able to change it.

  -Mike

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