[mythtv] render2019: step-length oddities in video editing

John Pilkington johnpilk222 at gmail.com
Mon Oct 7 12:35:45 UTC 2019

On 07/10/2019 12:10, Mark Kendall wrote:
> On Mon, 7 Oct 2019 at 10:12, John Pilkington <johnpilk222 at gmail.com> wrote:
>> On 07/10/2019 09:28, Mark Kendall wrote:
>>> On Sun, 6 Oct 2019 at 19:10, John Pilkington <johnpilk222 at gmail.com> wrote:
>>>> Hi Mark, thanks for the response:  I have just looked at the step
>>>> lengths in the editor in last night's ppa build of master for ubuntu
>>>> 18.04, and the 1-frame, 0.5-sec, 1-sec steps that are broken in render
>>>> 2019 all work as expected, although 1-sec is a bit elastic.
>>>> The blurriness in static frames in render 2019 is probably a mix of info
>>>> from several frames and doesn't really affect editing, but it is
>>>> different.  Normal playback seems fine.
>>> John
>>> I've pushed a fix for a regression in seeking that seems to fix the
>>> worst of the seeking issues. Editing seems fine here with software
>>> decode and VAAPI direct rendering. VAAPI decode only still gives some
>>> odd seeks for reasons I don't understand. Deinterlacing seems to be
>>> working OK and I can't see/reproduce the blurriness that you mention.
>>> Can you give me details of your decoder/deinterlacer settings?
>>> Apart from the VAAPI decode only anomaly, there is a slight oddity
>>> with 1 second seeking in a PAL recording where it seeks 24 frames
>>> instead of 25. I suspect this is a master issue as well (mythplayer
>>> actually asks to seek 24 frames). NTSC recording (imported) always
>>> seeks 30.
>>> Frame by frame seeking in videos (i.e. no seektable) still has issues
>>> when going backwards - again not sure why:)
>>> regards
>>> Mark
>> OK, thanks, I should have a build later.  The bad decoding of static
>> pictures has been most noticeable in 544x576 h264 content as from DVB-T
>> Smithsonian (99) and PBS America (91), using nvdec and 2xGLSL
>> linearblend.  I've also had segfaults while doing the tests, but haven't
>> investigated those.
> Quick test with the nvidia machine.
> The static image problem appears to be specific to nvdec when seeking
> to a keyframe. It's not deinterlacer related.
> If nvdec deinterlacing is used then seeks are erratic again. This will
> be because the frames are being filtered somewhere in the black box of
> the cuda code - not sure that is fixable, I'll have to take a look.
> The problem here is that nvdec hardware deinterlacing is a one time
> setup when the decoder is created - we lose all control of what
> cuda/nvdec is actually doing and cannot turn it off again. This is
> probably the same issue with VAAPI decode only and hardware
> deinterlacing - the frames are being filtered in the decoder which is
> throwing out the seek - although in this case it can be turned on/off
> as needed.
> Regards
> Mark

I confirm that the step-length problem has gone.  Great!

Using HDMI output on 1080 content (Strictly...) some static pictures 
remain confused, and the AOG (Audio Output Graph) often has multiple 
'append discontinuity' complaints then.  I spent some time trying to fix 
the AOG some time ago, but since it didn't break anything else I 
eventually gave up.  I'll perhaps experiment more with the deinterlacing...



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