[Mplayer-cvslog] CVS: main/DOCS/tech mpcf.txt,1.7,1.8

[Michael Niedermayer]

Hi

On Friday 07 February 2003 13:57, Andreas Hess wrote:
> On Fri, Feb 07, 2003 at 01:35:23PM +0100, Michael Niedermayer wrote:
> > On Friday 07 February 2003 12:39, Andreas Hess wrote:
> > > What about VLFH (variable length frame headers ;-))? I think often
> > > there will be a long stream of frames with nearly the same header,
> > > where for example just the lsb_timestamp changes. So you can use a
> > > mask (something like 00010) to distinguish that a particular frame
> > > header consists of nothing more than the lsb_timestamp.
> >
> > yes, but there isnt that much in the frame header, its just
> > the pointers to the next/prev frames
> > 8bit flags (the zero bit is here too)
> > stream id (normally 1byte)
> > lsb_timestamp (normally 1byte)
> > the msb_timestamp & checksum are only coded for some frames so they dont
> > count
>
> Ok, but after reading your spec about MPCF the definition of and the
> difference between checksum and frame_checksum isn't clear. You say
> that frame_checksum depends on checksum_flag, but in the definition
> of frame you use checksum, when checksum_flag is set.
typo, fixed ...

>
> And what about no checksum at all in plain frames, allowing the
> checksum (or frame_checksum) just in keyframes, and there the
> checksum is the checksum (or frame_checksum) over all previous
> frames.
hmm if only the keyframes contain the checksum, then each keyframe would 
contain the checksum for the previous frames ...
the last frames after the last keyframe would have no checksum
and if we cut the stream at a keyaframe than its checksum would cover frames 
which are no longer there, this seems bad, so IMHO the current way of 
requireing the checksum to be in the last frame before a keyframe (or more 
often) is better 

[...]

Michael