[mythtv] framesPlayed

[Mark Kendall]

Hi Peter

Having looked at framesPlayed a little more - I think we are trying to
do too much with one variable - which is bound to fail at some point.
I plan on using a distinct variable in VideoFrame to track
discontinuities which should make things a little cleaner.

With respect to fpsMultiplier, I suspect MediaCodec is deinterlacing
adaptively - at least for some content. So in certain circumstances
(e.g. telecined material) it probably returns a mixture of raw
progressive and deinterlaced progressive frames which may result in a
variable frame rate? I've noticed that the fpsMultiplier code gets
triggered repeatedly for VAAPI decoder deinterlacing (in the render
branch) with certain material - again I think telecined.

That said, I can't think of an alternative to detecting what
MediaCodec is returning - unless there is something in the portions of
the API that FFmpeg exposes?

Regards
Mark

On Sun, 30 Jun 2019 at 19:21, Peter Bennett <pb.mythtv at gmail.com> wrote:
>
> Hi Mark
>
> I am looking into different ways to fix the bug
> https://code.mythtv.org/trac/ticket/13416
>
> There is another area that may cause you problems with framesPlayed.
>
> The shield has frame-doubling deinterlace built in, and the result was
> the elapsed time was being calculated at double the correct rate. This
> had bad consequences for many things. I added some code in
> avformatdecoder (line 4123 onwards), to detect that frame-doubling was
> being done. It sets m_fpsMultiplier to 2 and then uses logic in line
> 4160 to only increment framesPlayed on every alternate frame. Per the
> ticket, this code is not working correctly as it seems that now the
> timing is sometimes off by a factor of 1.5 instead of a factor of 2.
> This may also affect your usage of framesPlayed in the render. You may
> need to revert this code as well.
>
> Let me know if you revert that. I will probably revert it anyway when I
> have figured out a real fix for the ticket 13416.
>
> Regards
> Peter
>
>
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