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

Joseph Fry joe at thefrys.com
Wed Sep 18 20:43:06 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).

Correction, ATSC A/72 was introduced in 2008 to add h264 and 1080p.
It is part of the ATSC standard, but has not been adopted by the FCC,
who only adopted A/53 (If I understand it correctly).  So I suppose
that in theory, any television that claims to be ATSC compliant would
need to have support for h264 and 1080p, but broadcasters are not yet
allow to transmit in that format.


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