[MPlayer-users] Re: lavc-Options for *BEST* quality?

Moritz Bunkus moritz at bunkus.org
Tue Feb 4 09:42:39 CET 2003


> My numbers were based on something I tried to do a few weeks ago:
> remux an avi file with mp3 audio into ogm. I was hoping it would save
> space, but it actually grew by 15 megs or so in the process. Perhaps
> mp3-in-ogg has more overhead than ogg vorbis for some reason though.

Depends on each packet's size. You'll never get a smaller OGM file with
the same data than it was in its AVI container, that's totally true.
And I also think that Ogg has at least one major drawback: it only
stores timestamp (called 'granulepos') for each Ogg _page_. This is not
a problem for the video stream because normalle a video stream Ogg
packet spans several Ogg pages, but for the audio there are often
several audio Ogg packets in one Ogg page. Therefore only the last
packet's granulepos can be safely recovered on demuxing. For MP3, AC3,
PCM you can easily calculate each packet's granulepos by hand, but not
for Vorbis. This makes re-merging/cutting/catting Vorbis audio rather

> In any case, even if the savings in overhead are only 2-4 megs, I
> think doing vorbis-in-avi would be much better than ogm just for the
> sake of having an index.

Several people tried to do Vorbis-in-AVI and failed. I'm pretty hopeful
that Matroska will come along in the not so far future so that we'll
finally have a rather feature-rich container format... And not that old
and totally outdated AVI.

> > zoolander.ogm  1006/80  733039525  672552326   53344661  7142538 (6.8M, 0.97%)  

I always calculate with an overhead of about 1.12% - 1.15%, and I
usually hit my desired file size within +- 800kb.

> Things will be much improved if you cache an index while playing
> the movie, but still something like mplayer -ss 1:00:00 foo.ogm will
> be very slow and painful.

Oh come on, six times page up and you're there ;) No seriously: I
agree. Perhaps I should embed an index in the OGM file and patch
mplayer to recognize it? Of course the Windows OggDS filters won't
recognize that index at all, but who cares ;)

 ==> Ciao, Mosu (Moritz Bunkus)

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