[mythtv-users] UK Freeview Mux A Jerky Playback Other Mux's Fine?

Steve Smith st3v3.sm1th at gmail.com
Mon Jan 21 17:04:49 UTC 2008

On 21/01/2008, Oliver Maunder <mail at olivermaunder.co.uk> wrote:
> On Jan 21, 2008 9:54 AM, nospam312 <nospam312 at gmail.com> wrote:
> > When I watch QVC (and other channels on this mux) I get very jerky or
> > stop start playback but other channels are generally fine.
> This could be down to the bitrate allocated to the channels. According to
> Wikipedia ( http://en.wikipedia.org/wiki/DVB-T_in_United_Kingdom) there
> are 19 channels broadcasting on MUX A but 5 TV channels on MUX 1 (plus a few
> radio channels). I've certainly noticed a big difference in picture quality
> watching QI on Dave and on BBC2.
> I've noticed some nasty artifacts with scrolling text - particularly
> horizontal scrolling credits. I assumed it was my deinterlace settings, but
> I haven't looked into it much. I'll take a look at News 24 and see if things
> are better there. Try using a different deinterlace method and see if things
> improve.
> Olly
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TIA:  It sounds like your problem is down to bad reception I'm afraid. The
fact that Mux A has more stations also means that it's less resilient to bad
reception (less room for error correction). Check your aerial. Look into
signal strengths etc.

Olly: Yes I've (and others) noticed some funny things with Channel 5 and
interlacing. They seem to fiddle with the "interlaced" flag in the stream a
lot sometimes getting it wrong (I think what they do is have the main part
of the screen progressive and the scrolling ticker interlaced but only
"detect" the progressive part). Even different scenes in programs flip
between interlaced and progressive.
The result is interlace artifacts when they broadcast the wrong flag.

Myth on my box definitely seems to be doing the right thing though (Five has
got it wrong), as the same programs show exactly the same artifacts when I
watch them on my Virgin cable box. Channel 5 news is especially bad.

Hope this helps.


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