[opendtv] Re: BBC Demonstrates HDTV Broadcasts over SD Channels
- From: Tom Barry <trbarry@xxxxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Thu, 23 Jun 2005 08:15:02 -0400
Mark Schubin wrote:
> Perhaps you know something about this that I do not, but your
reasons do
> not make sense in view of the other constraints of Table 3.
1080, for
> example, is not divisible by 16, and SMPTE standards call for
different
> production and clear apertures.
I believe ATSC (A53?) specifies that 1080 will actually be encoded
with 1088 vertical samples to get around this.
- Tom
>>The number of samples per line is further limited
>>by the ATSC standard to 704 samples.
>>
>
> Agreed.
>
>
>>The major
>>reason for this is that the ITU-R BT601 standard
>>which forms the basis for this profile includes
>>the rise times for blanking within the 720
>>samples per line. 704 is close to the active
>>picture area, and a convenient multiple of 16 for
>>MPEG-2 macroblock alignment.
>>
>>
>
> Perhaps you know something about this that I do not, but your reasons do
> not make sense in view of the other constraints of Table 3. 1080, for
> example, is not divisible by 16, and SMPTE standards call for different
> production and clear apertures. Table 3 should have said 720 x 480.
> ATSC working-group rules do not permit me to say much more about the matter.
>
> TTFN,
> Mark
>
>
>
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