[opendtv] Re: (S) DTV adaptors available for less than 50 euros in France
- From: "John Shutt" <shuttj@xxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Wed, 21 Sep 2005 10:31:45 -0400
With the typical 15 frame GOP, and a typical 30 FPS 1080i or 480i digital
video program, an I frame comes along at the rate of twice a second. For
780p and 480p, it is 4 times a second. I don't think that the several
seconds of time before an image appears during channel change is the fault
of the bitstream.
John
----- Original Message -----
From: "Craig Birkmaier" <craig@xxxxxxxxx>
>>One thing I was wondering was why not create a "default"
>>I frame in the receiver, built from the first available
>>P frame and some place fillers. So when channel surfing,
>>the receiver would sync up quickly, provide audio, a
>>bad picture at first, then improved picture as real I
>>frames show up or after a scene change?
>
> We have already discussed the limits imposed by progressive refresh.
> It takes time to build up good P frames when you don't have the
> original I-frame data from which the P-frame was predicted. With
> H.264 you can send regional Iframe updates. I suspect that this will
> eventually become a factor in how the algorithm is used, as it allows
> for new data to be added, as needed, between total I-frame updates.
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