[mythtv] IVTV VBI reading

Bruce Markey bjm at lvcm.com
Mon Jun 11 17:19:53 UTC 2007

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 #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?

--  bjm

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