[mythtv-users] BBC HD (1080) h.264 / AVC playback

Tim Small tim at buttersideup.com
Mon Feb 19 21:01:55 UTC 2007

Yeechang Lee wrote:
> Tim Small <tim at buttersideup.com> says:
>> I used mplayer to play back recordings of "Planet Earth" in 1080p - 
>> 1440x1080 16:9 25(?)fps - files which mythtv has recorded (but not 
>> transcoded).
> It's unclear whether you are saying you are playing back the
> transmission on a 1080p display, because 1440x1080 of course is not
> true 1080p (or 1080i).
OK, are you sure that this is the case?  1080 lines with square pixels 
at 16:9 does of course imply 1920*1080, and there certainly is content 
available encoded at this res, but as I understand it, the brain is more 
sensitive to vertical detail than horizontal, hence the BBC's choice of 
1440x1080 with rectangular pixels...  Is there actually a definition of 
"true 1080p" anywhere?  I couldn't find one...

As for the display, I'm using a 1280 x 1024 LCD monitor, connected by 
DVI, so I've been displaying the material both as scaled (1280 x 683 
progressive letterbox on a 1280x1024 display), and also as centred + 
cropped (scaled horizontally for square pixels) (1280x1024 progressive 
using the whole display).  Either way, all 1440x1080 of the original 
picture gets decompressed, and dumped into the frame buffer by the CPU, 
before being displayed (scaled or otherwise) by X-Video - which was 
really the point of my original posting, as I suspect that the config 
that I'm using is one of the lower power consumption options for doing 
this at the moment (without going closed source).
>> I'm pretty sure that the transmissions are 1080p - I can't see any 
>> interlacing artefacts.
> The BBC HD trials are in 1080i. See
> <URL:http://en.wikipedia.org/wiki/BBC_HD>.
Yes, I had seen that, and I certainly have seen some interlaced content 
on the BBC HD trial broadcasts, but I've had a hard stare at this 
recording, and I can't see any trace of interlacing artefacts.  Is there 
a good way to check this out programmatically?  If you like, I can make 
a clip available.  The recordings are approx 6.5G per hour.
> Of course, there certainly is a benefit to displaying 1080i
> programming on 1080p display; start reading at
> <URL:http://www.gossamer-threads.com/lists/mythtv/users/246463#246463>.
> I don't know if the GMA 950 is capable of 1080p output; if not, you
> may want to consider stepping up to an Nvidia 6xxx or higher. (I'd
> also specify "not 5xxx; see
> <URL:http://www.gossamer-threads.com/lists/mythtv/users/213177#213177>,"
> except that you almost certainly have PCI-Express slots and the
> PCX5300 is hard to find.)
I don't like non-free drivers, and won't use them if I can avoid it - as 
a result, I'll only consider buying NVidia hardware when they release 
full specs.  The 945GM will output 2048x1536 at 75 Hz according to 

In any case, my highest res output device is currently 1280x1024, and is 
likely to remain so for a while (I'm probably buying a projector at some 
point, and will look at ones with a 1080 vertical res at that time).



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