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Old 14th February 2002, 11:31   #1  |  Link
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New A/V Formats Q&A

Q: I get confused with the two expressions 'Ogg' and 'Vorbis' all the time ! What are their meanings and why do they get mixed up all the time ?

A: If you want to playback a video or an audio stream you have to put them into a container to be able to transport them without getting corrupted or loosing data, like putting your money in your wallet.
'Ogg' is the general container format that the guys from Xiphophorus ( Monty and his team ) were developing for their new audio and video codecs, being 'Vorbis' and 'Tarkin'. But the Ogg container can hold more than only those, its a very general container format, so it can hold other video and audio streams also like DivX, XviD or MP3, even subtitles are possible, making it a potential replacement for the good old AVI container. As Vorbis was designed also for music, and this is what it is most commonly used right now, you will find that most of the encoding tools existing will always place a Vorbis audio stream into an Ogg container ... resulting in an Ogg Vorbis file !

Q : What is the hassle about this other new format, being called TMF, MCS or MCF ? When are first implementations to be expected ?

A: MCF, the Multimedia Container Format, was TMF ( The Movie Format ) in the beginning. It was designed by a talented coder from Finland called Tronic, a lot of input came from Avery Lee, the creator of Virtualdub. The basic idea behind it was to replace AVI with a new format with a more modern structure, supplying the user with a lot more features and possibilities. The detailled specs are to be found here : http://solidhardware.com/sn/?tmf . We expect the first alpha version of a muxing tool coded in C to be released end of february.
Ogg and MCF are competing in one way or the other. As the Ogg format can be used for streaming and is very flexible, MCF is promising higher compatibility because of the very tight specs.

Q: How can i split an Ogg container movie in 2 parts for a nice 2 CD rip ? I cant open the Ogg in Nandub RC2 ...

A: There is no splitting tool available for the Ogg container format, so its hard to make 2 CD files for now. Doom9 came up with a good ( interim ) solution :
1. Get nandub RC2, exchange all dll's with ogg or vorbis in the name by latest versions coming with the actual Vorbis SDK ( www.xiph.org ). Now you can handle RC3 Ogg Vorbis in nandub, but the result will be an AVI !
2. Create such an AVI in Nandub, containing your complete video and Ogg Vorbis audio stream ( 1400 MB ). Use the 'save segmented AVI' function with segment size 704 MB to find out where about in the movie you will have to cut to get two equally sized parts. Play the 1st part ( named movie.01 ) in any player and note the total playing time it has. Now jump to the closest keyframe to this time point in nandub and use the 'Save AVI function' 2 times to create 2 AVIs, one being your 1st and other being your 2nd part ( CD ). If you dont know how to cut movies in Vdub/Nandub, see according Doom9 Guide. Note that this is only an interims solution, you have AVIs now with bad Vorbis support, seeking in the movie is impossible ! Next step is important !!
3. Now, having 2 AVIs each about 700 MB in size, being 1st and 2nd part, use nandub again to demux the video ( DivX/XviD/whatever ) and the Vorbis audio streams from these AVIs again. You should have 2 Ogg Vorbis audio ( named as WAV, so rename them to .ogg ) and 2 AVI video streams now.
4. Now you can use Tobias muxing filter as you are used to finally create 2 Ogg files, being CD1 and CD2 ...
5. As an alternaitve to 3. and 4. you may try to use philippas method of transmuxing the two AVIs to Oggs directly ( see Graph below ). This method may not work on every OS, mainly 98 and ME users reported about problems.
We admit this is big hassle, but the only alternative to this is to
- cut the VOBs into several parts ( by time .. no good solution )
- cut the WAV file ( after AC3 was decoded ) into 2 parts in Cooledit or similar
- encode both VOBs as separate and both WAVs as separate
- mux the 1st and 2nd part of your movie
This 2nd method will never give you two equally sized and similar quality parts ... the 1st CD may turn out as 710 MB and the 2nd as 685 MB f.e. , depending on content .
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