[NUT-devel] Codec id - random notes

Måns Rullgård mru at inprovide.com
Sat Jun 24 15:40:56 CEST 2006

Oded Shimon <ods15 at ods15.dyndns.org> writes:

> On Sat, Jun 24, 2006 at 02:20:26PM +0100, Måns Rullgård wrote:
>> Rich Felker <dalias at aerifal.cx> writes:
>> > On Sat, Jun 24, 2006 at 01:27:24PM +0200, Michael Niedermayer wrote:
>> >> so IMHO a id system must be able to achive the following, if it doesnt
>> >> then IMHO its not worth considering
>> >> 1. streamcopy (without decoder) every valid non broken stream from
>> >> avi,mov,ogg to nut and produce a valid and playable file
>> >
>> > this is inherently impossible due to missing pts. you must have a
>> > decoder (or at least a parser) to streamcopy from avi.
>> I consider pts != dts in avi broken.
> OK, but B frames in mpeg PS files is not broken (at least according to 
> ISO...), yet still needs a decoder/parser to figure out pts for every 
> frame :)

You can get useful information from MPEG PS/TS without a decoder, but
you get nothing whatsoever from AVI.  MPEG PS/TS requires a frame to
have either no timestamp at all (in which case they can be calculated
by the decoder), only a PTS (which requires PTS == DTS), or both PTS
and DTS (which may differ).  With AVI you know nothing at all, which
is what makes it troublesome.

Måns Rullgård
mru at inprovide.com

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