[FFmpeg-soc] [soc]: r1168 - rv40/rv40.c

[Kostya]

On Thu, Aug 23, 2007 at 06:38:03PM +0200, Michael Niedermayer wrote:
> Hi
> 
> On Thu, Aug 23, 2007 at 07:18:08PM +0300, Kostya wrote:
> > On Thu, Aug 23, 2007 at 06:05:26PM +0200, kostya wrote:
> > > Author: kostya
> > > Date: Thu Aug 23 18:05:26 2007
> > > New Revision: 1168
> > > 
> > > Log:
> > > Handle case when slice tail is sent as another slice
> > 
> > Let me elaborate on it a bit.
> > 
> > Real container stores video frame by slices (controversal decision to me).
> > They decided to drop macroblock count in slice, so you need either to get
> > next slice, parse its header and set limit or just decode until end and
> > hope thet nothing goes wrong. But it appears that sometimes slice end is
> > stored as new slice so you need to add it to the end before decoding.
> > 
> > In order to workaround this err... design I keep track of last macroblock
> > decoded successfully in slice and in case of bit reader reading past
> > frame data set mode expecting frame tail, then if it arrives (without
> > correct slice header), concatenating it with the previous data and
> > decoding starting from the last successfully decoded macroblock.
> 
> you should use a parser which puts these parts back together
> how should it work with remuxing in another container lets say
> matroska, i very seriously doubt that it will work if the tail of a slice
> is in the next frame ...

Not frame, it belongs to the same frame, just resides in separate slice.
Typical RV40 intra frames contain about 11 slices, interframes - 2-4 slices.
Also I doubt that SoC Matroska muxer will be able to do this (but I will
ge happy if proven wrong).
 
> also are you sure that there are no flags/sizes at demuxer level which
> could be used to easily combine these parts into slices or frames
> without needing to look into the codec bitstream?

There seems to be something. At least MPlayer demuxer gathers slices for
one frame (including those loose tails).
 
> > 
> > I've run my decoder under FFplay and MPlayer and should note that lavf
> > demuxer drops some frames (can be clearly seen on title fade out in
> > test.rmvb), so I will try to fix it.
> 
> thanks

Can you give some hints on how to operate on slices gathered into one frame?
Setting avctx->slice_offset[] and avctx->slice_count in parser is impossible
because of race conditions.
 
> [...]
> -- 
> Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
> 
> The worst form of inequality is to try to make unequal things equal.
> -- Aristotle