[theora-dev] Interlazed video posibilities

[GODA-XEN at terra.es]

I don´t found any patent around this but i ned help with the patents. 
I can´t found all patents for interlazed video and I only read the
patents around MPEG , the optimization for field based video can be
aplied without problem, this is compatible whih the progresive encoding
and in a few scenarios they can be positive.

<p>process:

<p>common:
 
 -2 bits to indicate video type
    0x  Progresive
    10  interlazed bottonfieldfirst
    11  interlazed topfieldfist

 - no encoder modification needed, the proces is done
   in pre and postprocess.
 - the video hight need to be multiple of 32*

folds fields up to down
 
 - the optimization are the same for progresive video
 - if video multiple of 2 and 1/2 of resolution is not
   multiple of 16 aspect ratio avoied putin the black 
   bar in the center of the frane betwen the odd and de
   iner part for up to optain multiple of 16 resolution
   for less field-macroblock interference.
 - if the decoder is not capable to posproces de interlazed
   video, if we use the estandar cut system to indicate the
   upper field coded in the frame the decoder only show this
   field, the other is the same but start to the botton
   intested to start from the top the cut area.

field based video
  
 - opmizable modificatin P frame of the vp3/theora Macroblock
   Coding , the mode than they not only can refer to de previos
   frame or the I frame, they can refer to the second-to-previus
   frane for optimizin the encoding but this need a little more
   memory.
 - if frame resolution multiple of 2 and field isn't multiple
   of 16 is used the estandar system.
 - if the decoder is not capable to posproces de interlazed
   video, they only ned to show the iner or the odd field

<p>Avishynt test using VP3 an constat quality, comparing size:

Source:   interlaced progresive
encoded:
as progresive             100.00%    100.00%
field based video   103.74%    105.50%
folds fields up to down    99.95%          117.89%

*fiel based video is the best for mixed videos in quality.

field based video scripts

------------encoding--------------------

AVISource("source.avi").separateFields().AddBorders(0,0,0,int botton)

------------decoding--------------------

AVISource("source.avi", true , "RGB32").ConvertToYV12().AssumeFieldBased().Crop( 0, 0, -0, -int botton).Weave

()

----------------------------------------

folds fields up to down scripts

------------encoding--------------------

Clip = AVISource("source.avi").SeparateFields()
Even = SelectEven(clip).AddBorders(0,0,0,int botton)
Odd = SelectOdd(clip)
Return StackVertical( Even ,  Odd )

------------decoding--------------------

#offset is 1/2 the value of int booton in the encoding

vid = AVISource("source.avi" , true , "RGB32" ).ConvertToYV12()
Even = Crop(clip, 0, 0, -0, -offset-Height(clip)/2)
Odd = Crop(clip, 0, Height(clip)/2+offset , -0, -0)
Return Interleave( Even , Odd ).AssumeFieldBased().Weave()

----------------------------------------

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