[mythtv] IVTV VBI reading

[Hans Verkuil]

On Monday 11 June 2007 19:19, Bruce Markey wrote:
> Bruce Markey wrote:
> > Hans Verkuil wrote:
>
> ...
>
> >>>>  but scaling does introduce slight amount of
> >>>> ghosting. Whether this is a driver, firmware or hardware bug is
> >>>> something that I need to look into one of these days.
> >>>
> >>> This seems to be a severe issue if only the extreme maximum
> >>> resolution is considered to be acceptable. A 720x480 recording
> >>> file with the same relative bitrate as 480x480 would be 50%
> >>> larger for no (or very little) visible difference.
> >>
> >> To put this into perspective: the driver has been around for
> >> several years and I have had only a handful of complaints about
> >> this. I'm pretty sure it can be fixed somehow but it's simply not
> >> high prio at the moment.
> >
> > 1) I didn't have your email address 2) I'm complaining now and
> > 3) I could assemble a lynch mod if that's what is needed ;-).
> > There was another thread on these lists about ghosting so there
> > have been at least ten messages on this issue just this week.
> > If the response is always that you must record at 720x480 then
> > people will do what they have to do but that doesn't mean that
> > there isn't a problem.
> >
> > What if I were to tell you that you could create files two-thirds
> > the size with no visible loss in quality? That your current disks
> > could hold 50% more hours of recordings and that there would be
> > less network traffic for remote playback, lower decode CPU time,
> > faster file copy, faster deletes, less I/O contention, fewer
> > prebuffer pauses, faster commercial flagging, faster transcoding
> > or no need for transcoding, etc.? I think everyone would like that
> > even if they are not complaining now. I think a slick marketing
> > department could put out an impressive press release about the
> > vast improvements of the new version if this were fixed =).
>
> 1) I now have your email address 2) I may be about to stop
> complaining and 3) have no need for any lynch mob ;-).
>
> While doing some other unrelated testing, I set my myth recording
> profiles for "MPEG-2 Encoders (PVR-250, PVR-350)" (ivtv) to widths
> lower than 720. I noticed that I didn't notice any of the broken,
> misaligned frames described earlier in this thread. Therefore, I
> also tried different temporal_filter values and didn't see any
> ghosting for 8, 12 or 24 for resolutions 352x480, 480x480 or 544x480.
> I've made several recordings at these resolutions in recent days
> and have never seen any broken frames or ghosting.
>
> : bjm at nordtv ; uname -a
>
> Linux nordtv 2.6.21.4 #5 Sun Jun 10 17:07:26 PDT 2007 i686 GNU/Linux
>  bjm at nordtv ; modinfo ivtv | grep tagged
> version:        0.10.3 (tagged release)
>
> : bjm at nordtv ; lspci -v
>
> ...
> 00:0b.0 Multimedia video controller: Internext Compression Inc iTVC16
> (CX23416) MPEG-2 Encoder (rev 01) Subsystem: Hauppauge computer works
> Inc. WinTV PVR 250 ...
>
>
> Is there something you've done that may have affected this issue?
> Can you or anyone else verify that these issues are resolved with
> 2.6.21.x and 0.10.[23] where the ghosting or broken frames were
> seen with earlier versions?

If I remember correctly kernels 2.6.18 and 2.6.19 had a bug causing 
ghosting to appear for scaled images. This was fixed in 2.6.20. I'm not 
100% certain whether the bug was still there for 2.6.19, I'd have to 
check that, but it is certainly OK (or at least as good as I can make 
it) from 2.6.20 onwards.

Regards,

	Hans