[mythtv-users] High end, state of the art Myth Frontend

Joseph Fry joe at thefrys.com
Wed Sep 18 20:36:03 UTC 2013


>> No, 1080i60 has exactly as many pixels as 1080p30.
>
> I'm not talking about 1080p30.
>
>>  the number of pixels
>> required for 1080p60 wouldn't fit into the 19.39Mbps bandwidth available
>> with sufficient picture quality
>
> Citation needed.
>
> This statement is extremely hard for me to accept.

Because it's not entirely true.

Within the limits that the ATSC allows, it's true.  Theoretically,
compressing a 1080p/60 video would use twice the bandwidth of
compressing a 1080i/60 video at the same level of quality.  In reality
that's not true because a) file size is not directly related to
resolution, b) the higher amount of detail would allow a greater
percentage of compression without a perceptible difference quality.

But the fact of the matter is, compressing a 1080p/60 signal will
result in a larger bandwidth file than compressing 1080i/60 to the
same perceptible quality level.  Your starting with double the data,
and if you try to compress it into the same bandwidth using the same
compression settings, you will introduce more artifacts.

That said, by changing the compression used, and subsequently the
capabilities of the decoder, you could definately compress a 1080p
signal into the same bandwidth without perceptible loss of quality.
But that would mean that the receiver would need to support
compression outside what the ATSC allows.  Which is why ATSC 2 is
being introduced.  It adds h264 compression and 1080p/60 to the
standard (among other things).


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