[FFmpeg-devel] A few filter questions

[Clément Bœsch]

On Fri, Jul 18, 2014 at 12:38:43PM +0200, Gerion Entrup wrote:
> Am Donnerstag 17 Juli 2014, 17:24:35 schrieb Clément Bœsch:
> > On Thu, Jul 17, 2014 at 04:56:08PM +0200, Gerion Entrup wrote:
> > [...]
> > 
> > > > Also, you still have the string metadata possibility (git grep SET_META
> > > > libavfilter).
> > > 
> > > Hmm, thank you, I will take a look at it. If I see it right, it is used to
> > > fill a dictionary per frame with some kind of data?
> > 
> > Strings only, so you'll have to find a serialization somehow. Maybe simply
> > an ascii hex string or something. But yeah, it just allows you to map some
> > key → value string couples to the frames passing by in the filter.
> > 
> > How huge is the information to store per frame?
> 82 byte per frame for the finesignature
> (Could be split again in three parts: An one byte confidence, a 5 byte words 
> vector, and a 76 byte framesignature, something like:
> struct finesignature{
>     uint8_t confidence;
>     uint8_t words[5];
>     uint8_t framesignature[76]
> })
> 152 byte per 90 frames for the coursesignature
> (Note, that there are 2 coursesignatures with an offset of 45 frames:
> 0-89
> 45-134
> 90-179
> ...)
> 
> If I see it right, there are two possibilies:
> Write as chars in the output (looks crappy, but needs the same amount of 
> memory).
> Write as ascii hex in the output (looks nice, but needs twice as much memory).

It won't be encoded in the output (at least I'm not sure about which muxer
would store these meta) so the "bandwidth" issue is not a problem. An
ascii hex string would be nice IMO, it's extremely small and would appear
fine and be easily parsable.

[...]

-- 
Clément B.
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