[opendtv] Re: Finally anamorphically compressed 480i

  • From: "John Shutt" <shuttj@xxxxxxxxx>
  • To: <opendtv@xxxxxxxxxxxxx>
  • Date: Fri, 28 Jan 2011 07:58:40 -0500

Craig, the scaling is done in frame mode, because all MPEG-2 compression is frame based. There is no field encoding in MPEG-2, which is why interlaced source material compresses less efficiently than progressive source material. You end up trying to compress frames with interfield motion within them, making it harder for the encoder to find matching macroblocks from frame to frame.
As a result, what gets spit out of the scaler is progressively scanned, which is then broken up into interlace if necessary for the final baseband output, or kept progressive if that is the target output. 

John
----- Original Message ----- From: "Craig Birkmaier" <craig@xxxxxxxxx>
Even government cheese decoders have these chips. They must convert 1080i to 480i. 



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