[mythtv-users] Fwd: Re: specific channel seek issue and acts like poor signal

John Pilkington johnpilk222 at gmail.com
Tue Apr 16 11:17:59 UTC 2019

On 16/04/2019 08:33, John wrote:
> On 15/04/2019 21:04, Tim Draper wrote:
>> ---- On Sun, 14 Apr 2019 18:20:55 +0100 Stephen Worthington 
>> <stephen_agent at jsw.gen.nz> wrote ----
>> > One obvious difference between those two channels is that, while they
>> > are both interlaced, the non-working one is bottom field first, and
>> > the working one is top field first.
>> good find. wouldn't of even thought about looking at the way the 
>> channel was rendering.
>> i took a look at playback profiles last night so see if that could 
>> help, but there doesn't appear to be a way to change profile based on 
>> channel or something useful specifically to target this issue. My 
>> primary FE is a 3-4yr old celeron so doesn't do too well with some HD 
>> content so would prefer to keep vaapi enabled if at all possible.
>> What would be the proper long term fix - is this a bug or a config issue?

> You could use Opengl playback for SD and VAAPI2 for HD. In MythTV 30 
> there is a setting in Video > Playback.
> (Setup->Video->Playback->Current Video Playback Profile->(right arrow)) 
> which allows different playback profiles to match the stream being played.
> I now use OpenGL high quality for everything. The CPU load in MythTV 30 
> (for HD) is less than 20% (per core) on a cheap celeron of the same age 
> as yours. FFmpeg has presumably been well optimised.  Check that the 
> number of process cores(Setup->Video->Playback->Current Video Playback 
> Profile->entry) Max CPUs is set to 4. I use both Freesat and Freeview 
> and find software playback is more robust across the two. The picture 
> quality is the same as VDPAU.

It's exactly 2 years since mythffmpeg first started reporting top- or 
bottom-first for me.  I believe that all my current recordings via DVB-T 
are top first, and that includes one I made recently from 4seven - but I 
mainly have post-processed recordings now and that may obscure things.

Are all programmes from DVB-S2 4seven in bottom-first format, and if so 
is that likely to be intentional?  My googling  hasn't shed much light.

John P

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