[mythtv-users] How to transcode HD recording

[John Pilkington]

On 04/01/14 10:14, mythtv at phipps-hutton.freeserve.co.uk wrote:
>
> Quoting John Pilkington <J.Pilk at tesco.net>:
>> It cuts at keyframes, and sometimes, in my HD recordings, these may be
>> several seconds apart.   I find that stepping forward or back in the
>> editor tends to get almost stuck then, too, but that may be because of
>> inadequate hardware.
>>
>> http://www.mythtv.org/wiki/MythDVBcut
>>
>
> In the UK on the FreeviewHD platform the encoders do statistical
> multiplexing ans vary the gaps between keyframes. It's usually very good
> at adding keyframes at the start and end of commercial breaks but can go
> for over 30 seconds in the end credits of films. Trying to go back one
> frame in the cutlist editor can be very slow and appear to hang. I guess
> it's also very poor if you are watching live and happen to tune in those
> times (even with a normal TV)
>
> Cheers,
> Tim.

Yes, that fits pretty well with what I see.  It's usually possible to 
find a good switch point but getting there can be tedious.  Sometimes, 
too, attempting to step by one keyframe results in no change.  I haven't 
looked hard at this but it might result from a combination of dead-zones 
and close-spaced keyframes.

I've been trying FreeviewHD > DVD to see how much difference I could see 
between that and the usual FreeviewSD > DVD.  Often not a lot.  But 
editing is less painful /after/ the necessary (and computationally 
expensive) HD > SD conversion, and the result is better.

Incidentally, MythDVBcut on the wiki applies a 188-byte offset that 
seemed to give fewer complaints from Project-X but is probably 
inappropriate for the non-mpeg2 pycut mode; I'm trying it with this 
switch at around line 407.

if ${USEPJX} ; then
    cat PXadj$$ | tr "\n" " " > bytelist$$
else
    cat PXraw$$ | tr "\n" " " > bytelist$$
fi
echo >> bytelist$$

John