[mythtv-users] Two odd issues with NBC DTV recordings

[Tom Dexter]

On Thu, Oct 2, 2008 at 7:25 PM, Yeechang Lee <ylee at pobox.com> wrote:
>
> I spoke too soon. I recorded another show, _Lipstick Jungle_, as a
> test, and that generated a black preview. The _Knight Rider_ recording
> generated an almost-black preview that did have a visible blue Ford
> logo in the middle so I had thought the preview was correct, but now
> am not so sure.

Well oddly enough, the few NBC shoes I recorded last night got
previews OK...first ones in a while...though I still get some
pixelation when jumping forward/back.  Maybe the success or failure of
the preview grabber depends on whether or not it's luck enough to find
a key frame.

>
> Rebuilding the seektable, as mentioned elsewhere in the thread, and
> forcing the preview to regenerate by deleting the filename.png and
> filename.100x56.png files[1]--I don't know of another way to force the
> MythWeb preview image to regenerate--created a proper preview image
> for _Lipstick Jungle_.
>
> Going back throught the start of the year, I found several other
> recordings with black preview images. Three were from Starz HD via
> FireWire and one each was from HDNet Movies via FireWire, CBS OTA, and
> PBS OTA. (Not all Starz HD recordings from 2008 had this issue.)
> Rebuilding seektable produced proper preview images from the Starz HD
> recordings but not the others.
>
> A couple of other points for those mulling over the issue:
>
> * Tom is in NYC, and I am in San Francisco. These are two of the metro
>  areas that recently gained a new SD multiplexed OTA channel,
>  Universal Sports. As a result, my NBC affiliate decreased its
>  bitrate for HD broadcasts so that formerly ~7.5GB/hour recordings
>  are now ~5.5GB/hour.

Until reading this I hadn't noticed that but yes...by newer NBC
recordings are about 5.5GB/hour.

>
> * Also, NBC recordings that came in as ~51 minutes per hour
>  (<URL:http://www.gossamer-threads.com/lists/mythtv/users/227272#227272>)
>  in the OSD over the past two years now again appear as an hour. I
>  suspect, but can't be sure, that the change occurred along with the
>  bitrate change. (The ~51-minute issue only affected prime-time
>  shows, not the videotaped late-night talk shows.)
>

That's not what I'm seeing here.  Even with the bitrate change I still
get one hour shows displaying as 52-53 minutes in the OSD as I was
before.  I don't remember for sure, but I'm not certain this is true
of all NBC shows.  It is for comedies and dramas.  Those are the ones
where they tend to mix different frame rates for commercials etc.
They may not do that on stuff like SNL for example...I have no other
saved recordings right now to check.

I know that the reason the OSD shows the incorrect length is that the
length calculation done in the remote encoder assumes one frame rate,
and can't handle the mixed frame rates NBC uses in these
shows...something very difficult to address for sure.  That's why all
this sort of stuff is related to bug 799.

Thanks for the input and the tests!

Tom