[mythtvnz] Question about quality from satellite

[Stephen Worthington]

On Sat, 13 Jul 2013 08:00:28 +1200, you wrote:

>On 12/07/2013 22:24, ajp at cantabrian.co.nz wrote:
>>
>> Hi,
>>
>> I have recently upgraded my frontend with it now capable of full HD 
>> and it's great.
>>
>> I only record satellite in and it seems some recordings appear to be 
>> higher resolution or better quality than others. I am kinda theorizing 
>> that the good recordings are ones that are actually going out to 
>> terrestrial as full HD and obviously scaled back to SD because we 
>> don't do DVB-S2 yet -- but it's just a theory J
>>
>> Anyone know any more or have any pet theories like I'm imagining it J
>>
>> Thanks
>>
>>
>>
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>Quite correct - Sat. here is 720p while terrestrial is 1080(i - I think).
>
>I can see the differance and it's quite annoying since my "system" was 
>configure for DVB-T, but we moved into a rental that had Sky and very 
>bad analog....
>
>If you want that in writing, google "Optus D1" :)

Some Sky channels are HD if you pay them extra for an "HD ticket".  I
am not sure of the exact format used as I do not pay Sky extra for
that, but they are broadcast on DVB-S2 transponders rather than DVB-S.
But the rest of the Sky channels are SD and MPEG2 video rather than
the much better H.264 video used on DVB-T.  They are definitely not
720p = 1280x720 - the ones I watch are mostly 576i = 720x576
interlaced, or 704x576 interlaced.  720p is the lowest format
considered to be HD, although a lot of 720p broadcast programmes are
not actually HD - the source programmes have too low a bit rate.

On DVB-T, TV One and TV2 are 720p.  TV3 is 1080i = 1920x1080 but
interlaced ie half the resolution of 1080p.  The other DVB-T channels
are 576p, but with H.264 video so they are capable of rather better
than the Sky DVB-S channels if the source materiel is good enough. The
Sky DVB-S channels are limited by their older MPEG2 video format - Sky
can not change to H.264 without replacing all the old set top boxes.
MPEG2 video is rather less capable than H.264 in the same bandwidth,
but it does an OK job for SD source materiel, but less so on Sky's
576i than if they were using 576p.  But even then, some Sky channels
use lower bandwidth than others, so you get lower quality video.  I
have some programmes recorded digitally from Sky DVB-S that are just
1.3 Gibytes for 60 minutes, and others that are rather larger, up to
around 1.65 GiB.

I do not record the Freeview channels from DVB-S so I can not say for
sure what they are all broadcast as, but for testing purposes I do
have TV One set up on DVB-S so I did a short recording just now and it
is broadcasting as MPEG2 video (not H.264) inside an MPEG2 transport
stream container.  But the video is 567p instead of Sky's 576i so
better quality is possible.