[Theora] OGG/OGM media container

illiminable ogg
Tue Jul 6 23:15:13 PDT 2004

<Pine.LNX.4.60.0407061837530.9433 at okanagan.cs.ubc.ca>
Message-ID: <009a01c463e9$e5e77ea0$0100000a at tiger>

----- Original Message -----
From: "Nilesh Bansal" <bansal at cs.ubc.ca>
To: <advocacy at xiph.org>; <theora at xiph.org>
Sent: Wednesday, July 07, 2004 9:42 AM
Subject: Re: [Theora] OGG/OGM media container

> Hi all,
> First of all, Thanks everybody for replying(on theora mailing list) to my
> earlier questions.
> Here is what I understood, and I have some doubts, so please read on and
> correct if anything is wrong.
> Ogg is a container format, which is designed to wrap any kind of
> video/audio. But, presently because of lack of developers, oggmerge
> supports only MNG video(not even theora) with vorbis audio. But, specs of
> Ogg are final and usable but it requires some developer to code that in C?

Also the current head version of my directshow project, can create
theora+vorbis files or transcode from YUY2(mpeg) or YV12 video sources and
any audio format known to windows, well really any combination of codecs,
however i use a different mux/demux that i wrote in C++, which i haven't got
around to building for any other platform... but most non-windows developers
prefer C to C++ anyway, so that's not much help !

In my proejct it's the library called libOOOgg, which is a seperate
independant implementation of ogg. It doesn't however do the packet
bit-level functions because all the codecs are pretty much hardwired to
libogg to do that.

> Suppose while downloading a file, after half the download connection
> closes. I was easily able to play ogm, but with mkv i had to provide -idx
> switch to mplayer to make it seekable (so ogm is better than mkv in that
> sense). Simmiliarly what if while downloading file gets corrupt? I expect
> mplayer to skip corrupt frames and continue playing.

Again thats a matter of opinion... ogg has no seek index... on the plus side
it means it is better for streaming, and it doesn't care if you get the
whole file... on the downside, the binary search you have to use for ogg can
be less acurate and less efficient  particularly with large files and high
latency to the source, ie over a slow network or running a large file from a
CD drive.

> Also, someone said mencoder can produce mkv files but I wasn't able to
> find a option (I installed mkvtoolsnix and recompiled mplayer, but
> mencoder -of help lists mpeg, avi and rawvideo only). No support for
> encoding to Ogg(audio only) either (I don't know if oggenc provides a
> library or not that mencoder can link to).

In windows at least you can do it in directshow... heres a page of graphedit
graphs for transcoding some known audio types...
www.illiminable.com/ogg/graphedit.html The how to encode theora how to i'm
writing for the next binary release (hopefully today) is still in svn at
http://svn.xiph.org/trunk/oggdsf/website/enc_theora_graphedit.html but will
go online at www.illiminable.com/ogg/enc_theora_graphedit.html hopefully
sometime today when i get the last few changes done for a release, and fix
up all the typos and missing/wrong images in it.


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