[MPlayer-dev-eng] Bogus numbers for NUT overhead

[Michael Niedermayer]

Hi

On Friday 23 April 2004 01:41, D Richard Felker III wrote:
> While trying to figure out how to improve the nut design, I've been
> doing overhead calculation on paper, and discovered that most of
> Michael's numbers are totally bogus. It's IMPOSSIBLE for any container
> to have less than ~0.25% overhead for 128kbit mp3, because the packet
> size is 418 bytes, meaning that even a 1byte header gives ~0.25%
> overhead! But Michael's original "NUT preview" email on ffmpeg-devel
>
> reported:
> > -rw-r--r--    1 michael  michael   4592134 2004-04-01 19:57 test3.nut
> > -rw-r--r--    1 michael  michael   4582922 2004-04-01 19:57 test3.mp3
>
> So either his muxer was dropping some frames, or it's packing multiple
> frames together (which is illegal). Other reports since then have
> repored similarly incredible results. So what's up?
never underestimate NUT
ok, there was a bug in that early version, where various things wherent reset 
at type != 0 packets at least, maybe more, i noticed these when i implemented 
seeking ...
and the stream was 160kbit not 128, the mp3 packet size was 522/523 and with 
packet size prediction the type 0 headers should have been 1 byte each, so 
the overhead must be above 1*100%/522.5= 0.19138... %
and 
4592134 - 4582922 = 9212
9212*100% / 4582922 = 0.201%

thats pretty close, maybe there where further bugs, current nut with the same 
mp3 now gives
-rw-r--r--    1 michael  michael   4594557 2004-04-23 02:26 test3.nut
-rw-r--r--    1 michael  michael   4582922 2004-04-23 02:05 test3.mp3
4594557 - 4582922 = 11635
11635*100% / 4582922 = 0.2538...%

a simple 'ffmpeg -i test3.nut -acodec copy test3-out.mp3' gives a binary 
identical mp3 so there are certainly no droped frames

[...]

-- 
Michael
level[i]= get_vlc(); i+=get_vlc();		(violates patent EP0266049)
median(mv[y-1][x], mv[y][x-1], mv[y+1][x+1]);	(violates patent #5,905,535)
buf[i]= qp - buf[i-1];				(violates patent #?)
for more examples, see http://mplayerhq.hu/~michael/patent.html
stop it, see http://petition.eurolinux.org & http://petition.ffii.org/eubsa/en