[MPlayer-dev-eng] Re: -of mpeg

[Michael Niedermayer]

Hi

On Tuesday 21 October 2003 15:46, D Richard Felker III wrote:
> On Tue, Oct 21, 2003 at 01:15:50PM +0200, Michael Niedermayer wrote:
> > Hi
> >
> > On Saturday 18 October 2003 00:53, D Richard Felker III wrote:
> > [...]
> >
> > > I'm curious...is there any way to encode duplicate frames in mpeg
> > > output?
> >
> > mpeg2 standard:
> > ----
> > If  progressive_sequence  is  equal  to  '1',  this  flag,   combined  
> > with repeat_first_field, indicates  how  many  times  (one,  two  or 
> > three)  the reconstructed frame is output by the decoding process.
> > ----
> >
> > so yes, if the video is progresive then we can duplicate frames
>
> You can only lengthen frames by 50% (3 field duration) which doesn't
> seem very useful except for correcting minor a/v sync issues.
thats the case for interlaced streams, but for progressive u can duplicate 
frames

heres the relevant code from lavc
---
        if (s->repeat_first_field) {
            if (s->progressive_sequence) {
                if (s->top_field_first)
                    s->current_picture_ptr->repeat_pict = 4;
                else
                    s->current_picture_ptr->repeat_pict = 2;
            } else if (s->progressive_frame) {
                s->current_picture_ptr->repeat_pict = 1;
            }
        }    
---
yes they are (miss)using top_field_first here

and heres the MPEG2 standard:
---
top_field_first   --   The   meaning   of   this   element   depends    upon
picture_structure, progressive_sequence and repeat_first_field.
If progressive_sequence is equal to '0', this flag indicates what  field  of
a reconstructed frame is output first by the decoding process:
In a field picture top_field_first shall have the value '0',  and  the  only
field output by the decoding process is the decoded field picture.
In a frame picture top_field_first being set to '1' indicates that  the  top
field of the reconstructed frame is the first field output by  the  decoding
process.  top_field_first being set to '0' indicates that the  bottom  field
of the reconstructed frame is the first field output by decoding process
If  progressive_sequence  is  equal  to  '1',  this  flag,   combined   with
repeat_first_field, indicates  how  many  times  (one,  two  or  three)  the
reconstructed frame is output by the decoding process.
If repeat_first_field is set to 0,  top_field_first shall  be  set  to  '0'.
In this case the output  of  the  decoding  process  corresponding  to  this
reconstructed frame consists of one progressive frame.
If top_field_first is set to 0 and repeat_first_field is  set  to  '1',  the
output of the decoding process corresponding  to  this  reconstructed  frame
consists of two identical progressive frames.
If top_field_first is set to 1 and repeat_first_field is  set  to  '1',  the
output of the decoding process corresponding  to  this  reconstructed  frame
consists of three identical progressive frames.
---

[...]
-- 
Michael
level[i]= get_vlc(); i+=get_vlc();		(violates patent EP0266049)
median(mv[y-1][x], mv[y][x-1], mv[y+1][x+1]);	(violates patent #5,905,535)
buf[i]= qp - buf[i-1];				(violates patent #?)
for more examples, see http://mplayerhq.hu/~michael/patent.html
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