[mythtv] [mythtv-commits] Ticket #2429: Autodetect video scan is confused by 1080i recordings
Yeasah Pell
yeasah at schwide.com
Wed Sep 20 18:35:44 UTC 2006
Jack Perveiler wrote:
> --- Kevin Kuphal <kuphal at dls.net> wrote:
>
>
>> MythTV wrote:
>>
>>> #2429: Autodetect video scan is confused by 1080i recordings
>>>
> <snip>
>
>>> Changes (by ijr):
>>>
>>> * status: new => closed
>>> * resolution: => wontfix
>>>
>>> Comment:
>>>
>>> That's normal.
>>>
>>>
>>>
>> Normal? I have to manually set all my NBC HD recordings to Interlaced
>> whenever I watch them because of this. It doesn't seem to be desired
>> behavior...
>>
>> Kevin
>>
>
> I get this a lot on my PBS and NBC HD recordings too. What would be nice would
> be a per-channel setting for video-scan (feature request without a patch).
> Make the default be "detect", but allow setting an override in the channel
> editor.
>
> I THOUGHT I read that Daniel was doing SOMETHING like this in the vid branch,
> but I've never looked into it so I don't know.
>
> If I'm wrong about the vid branch and nobody else implements this I may take a
> crack at it next week when my wife+kid are out of town.
>
> --Jack
>
I also get this a lot, on all sorts of channels -- both HD and SD.
There's always some combination of filters and interlace settings that
works, but it can be extremely tedious to change all that around for
different programs. It's not a per-channel thing either, it's dependent
on however the content was produced, so being able to change these
things on a per-channel basis would not totally solve the problem.
Animated material is often done at 24fps and telecined (as are most
movies that are broadcast), and the only way I can get that kind of
material to play without unnecessary interlacing artifacts or having the
video-scan detection go berserk is to include "ivtc" in the filter
chain, as well as an appropriate deinterlacer, and force video scan to
interlaced mode. (I know ivtc was primarily added to myth to allow DVDs
to be inverse telecined, but it does seem to work for some kinds of
broadcast material as well.)
Other times ivtc totally hoses the video though (causing severe
jerking), it doesn't seem to be doing sufficient cadence detection -- so
leaving that in isn't really an option. It's a real pain to have to
change that setting, since it involves changing text in a buried submenu.
Basically, I don't think myth currently has what you would call a
complete solution for deinterlacing broadcast content -- or if it does,
I have no idea how to enable it. It needs to be able to robustly detect
any telecine cadence (which can be hard, since there are crazy cadences
out there, bad edits can cause the sequence to become discontinous,
etc.), run an appropriate inverse telecine when it is needed, and then
finally deinterlace frames as required based on all that using the
deinterlacing method selected by the user.
Most digital TVs are capable of all this -- telecine pulldown and
adaptive deinterlacing is getting more common these days (my TV does do
this, anyway.) I'd like to be able to set things up so that my frontend
output in the appropriate interlaced mode (via the xrandr frontend
options) when playing interlaced content and let the TV do the
deinterlacing, but I haven't found how to set it up so that it works
with the diverse set of broadcast content out there (lots of different
resolutions and frame rates) -- in any case, that option is a "punt to
TV" option, whereas it would be much better if mythtv itself was at
least as capable as a modern TV at handling interlaced content.
Anyway, that's how I read ticket #2429, as a feature request for robust
handling of interlaced/telecined content.
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