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

D Richard Felker III dalias at aerifal.cx
Tue Feb 4 17:30:48 CET 2003

On Tue, Feb 04, 2003 at 09:42:39AM +0100, Moritz Bunkus wrote:
> [Automatic answer: RTFM (read DOCS, FAQ), also read DOCS/bugreports.html]
> Hi.
> > 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
> difficult...

Yeah, tell me about it. I wrote a radio/jukebox program to stream ogg
audio from files as a continuous, and the nonsense to handle pages was
ridiculous. I don't even understand what the motivation was behind
making a container for audio-only files when the container doesn't
even facilitate proper seeking!

> > 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 and totally outdated AVI.

I don't want a "feature-rich" container format. I want something that
handles vbr audio properly, that has an index, that's recoverable
without the index (perhaps even somewhat seekable), and that supports
subtitle streams. I don't know too much about Matroska, but MCF has
all kindsa idiotic nonsense about menus and tags and its own idea of
how codec plugins should work and other crap that doesn't belong in a
movie file and that just wastes space and delays implementation so
that we never get around to having a working standard. *sigh* Also it
seems both these projects are led by Windows kids who think DShow is
the coolest thing and probably have no idea about the proper way to
design a media container.

> > 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 ;)

Well, by the time you do that, I think the ogm file will be so much
bigger that there'll be no savings over avi with mp3... :(


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