Re: [Gnash-dev] Re: Embedded video findings

[John Gilmore]

> > Basically, PlaceObject2 tag, changing the ratio of the character
> > change the video frame to play next.
> > I found a comment in Ming wondering why it needs to set a ratio,
> 
> For reference, the comment is in videostream.c:
> 
>                 /* well it isn't really clear why we need the place-block here
>                  * its not metioned in the flash-specs
>                  * but its not working without */
> 
> I hope it's clear now.

I was unable to confirm whether the (open, reverse-engineered) flash
specs now document this, because I was unable to find *any* flash
specs when starting from the Gnash or Ming home pages.  (Also, the
former openswf.org domain has disappeared and been replaced by a
domain hijacker.)

The Adobe flash spec released in May08 says, page 48, that a
PlaceObject2 tag includes:

  An optional ratio value, which controls how a morph character is
  displayed when placed.  A ratio of zero displays the character at
  the start of the morph. A ratio of 65535 displays the character at
  the end of the morph.

Also, on page 50, it says:

  The Ratio field specifies a morph ratio for the character being
  added or modified. This field applies only to characters defined
  with DefineMorphShape, and controls how far the morph has
  progressed. A ratio of zero displays the character at the start of
  the morph. A ratio of 65535 displays the character at the end of the
  morph. For values between zero and 65535 Flash Player interpolates
  between the start and end shapes, and displays an in- between shape.

These don't seem particularly clear about how this field controls the
display of frame numbers of encoded video frames!  However, in a side
reference under the VideoFrame tag on page 261, it says:

  A VideoFrame tag is not needed for every video character in every
  frame number specified. A VideoFrame tag merely sets video data
  associated with a particular frame number; it does not automatically
  display a video frame. To display a video frame, specify the frame
  number as the Ratio field in PlaceObject2 or PlaceObject3.

I hope that Gnash and Ming (and their web sites) will soon include
pointers to the spec that they implement; and that that spec will be
updated with the new info that strk has figured out.

        John