[opendtv] Re: Format Independence
- From: Ron Economos <k6mpg@xxxxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Fri, 11 Nov 2005 14:32:58 -0800
The DBS folks have been using inverse telecine on their encoders
since day one, both SD and HD. The HD streams that I've
analyzed fall in and out of film mode quite often, even on
non-edited film (usually during still sequences). As Tom
suggests, this is not a problem.
Sounds like PBS had a buggy encoder.
Ron
Tom Barry wrote:
>I've written auto pulldown detection and deinterlacing for one of our
>products. Many of the bad edits do exist but typically that only causes
>one frame of bad weave, not that noticeable on interlaced TV.
>
>The problem is mostly only in software that tries to continue whatever
>mode it previously had been seeing, giving longer transition times.
>There is really no reason to expect video with repeat flags to have to
>be in any 3:2 pattern.
>
>- Tom
>
>John Shutt wrote:
>
>
>>It has been PBS's experience that MPEG 3:2 pulldown detection does not work
>>as well in the real world as it does in the lab.
>>
>>When PBS first went to Digicipher II distribution of the network feed to the
>>affiliates, they had the 3:2 detection in the Digicipher encoder (an MPEG II
>>encoder) turned on, thinking that with so many programs originally shot on
>>film, we'd save many bits and raise quality.
>>
>>What ended up happening was that yes, the programs were shot on film, but
>>edited in video. So at every scene change the 3:2 sequence was disturbed,
>>and the encoder would freeze the image as it went from film mode to regular
>>mode, then auto detect the 3:2 sequence again and freeze the image as it
>>switched back to film mode.
>>
>>3:2 pulldown detection has been turned off ever since.
>>
>>John
>>
>>
>>
>>
>>
>>>If a broadcasters sends out a 24P stream without 3:2 pull-up, it will
>>>take less space than encoding the same content at 59.94 frames per
>>>second, but not much. As Mark pointed out, an MPEG-2 encoder can
>>>simply flag repeated frames rather than encoding them.
>>>
>>>
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