[NUT-devel] Codec id - random notes

Michael Niedermayer michaelni at gmx.at
Fri Jun 23 23:23:57 CEST 2006


On Fri, Jun 23, 2006 at 10:17:58PM +0200, Luca Barbato wrote:
> Michael Niedermayer wrote:
> > 
> > please forget it! send a path to libnut and you will see its not feasable
> > 
> Well I believe you even if I'm missing why
> randomcodec_init(int workarounds) won't work
> the call would be something like codecs[tag].init(hints)

i have not the faintest clue what you are talking about but storing
workarund hints in nut would need you to solve the following
1. the muxer has a packet and some codec identifer (fourcc, string or other)
   next the muxer must find the workaround hints, this requires decoding 
   several frames (the muxer needs at least a mpeg4 decoder and possible some
   parsers for various headers of other codecs

are you suggesting that the nut muxer should decode frames? yes ? no ?
if no then from where do you want to find these hints? the muxer has
a bunch of "opaque" bytes which are an encoded video frame and a codec
id, things like width and height ...

2. the demuxer passes the hints to the codec, no codec in existance 
   can make any sense of such hints, they either can detect the buggy
   encoder and deal with it or they cant, if half of the info has been
   butchered (fourcc changed from xvid to mp4v) then chances are _slightly_
   lower that the detecton will work, most of the time it will, but not

you can of coarse just store the fourcc either alone or in addition to
another identifer, that of coarse will help the decoder but i wouldnt
call that "hints"


Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

In the past you could go to a library and read, borrow or copy any book
Today you'd get arrested for mere telling someone where the library is

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