[mythtv] Playback next steps

Peter Bennett pb.mythtv at gmail.com
Mon Dec 17 20:40:56 UTC 2018

On 12/17/18 3:20 PM, Mark Kendall wrote:
> On Mon, 17 Dec 2018 at 16:20, Peter Bennett <pb.mythtv at gmail.com> wrote:
>> I think it is actually about two thirds of the way across the screen that it starts. Other details -
>> The jaggies occur with both interlaced and progressive video.
>> In file mythrender_opengl2es.h there is the line
>> m_qualifiers = "precision highp float;\n";
>> This was previously set as mediump - and the jaggies occurred on the fire TV  and fire TV 4k.
>> After I changed this to highp -
>> On fire TV there was an error message that highp is not supported and it is reverting to mediump, and the jaggies remain
>> On fire TV 4K the jaggies went away and the picture is perfect
> There is an ifdef that needs to go into the shaders - platforms that
> support highp set a define. Should fix the error message.
> I don't think there is a way around the sampling issue with the UYVY
> code as it stands. Once precision is lost the shader starts to select
> the wrong texture sample - and because 2 pixels are packed into one
> sample, the sampling is highly inaccurate. It will be less obvious in
> the other methods that don't use the extra packing  - but will still
> be an issue.
>> This is mostly way over my head, but it sounds good.
>> My recommendation is that we should only commit this into master after we have created the fixes/30 branch in January. The changes sound major and they could potentially cause some unexpected issues with some configurations. I would not want the users who install from Ubuntu 19.04 to encounter problems.
> I have a patch for the UYVY code ready to go. It will fix the
> interlaced chroma issue and the precision problem. It is not at all
> invasive. If OpenGLVideo currently works without YV12 or UYVY, it will
> work after the change. It effectively removes the custom UYVY code. We
> still use UYVY but it is not as densely packed - so there is a larger
> texture in video memory but no sampling problem and no need for the
> extra filter stage.
> Regards
> Mark
> _______________________________________________
Welcome back!

It is OK with me if are confident and you want to commit it now. Let us 
know when you have either a patch or have committed it so that I can do 
some testing.


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