问题
I have an ogg vorbis file and I have to do two operations with it:
- cutting a part of a file from one position to another
- merging another file with existing one
How can I realize these two operations in C#?
回答1:
I'd look into the c documentation for libogg, and figure out how to do this with c. And then write almost the same code in C# using a wrapper over libogg.
I've created a low level wrapper over libogg and libvorbis using the interop assistant: https://github.com/CodesInChaos/Xiph/blob/master/LowLevel.cs
That project also contains some higher level constructs, but I don't think they'll be useful for what you're doing.
BTW if the stream IDs between the files differ, you can simply append a file to another creating a valid file that plays both streams in sequence.
You probably need to read the input files packet wise using the decoding API, and then write the combined data out packet wise. Possibly replacing the stream ID and granulepos in between.
StreamID is an integer that identifies substreams in an ogg file. To append multiple such substreams you can simply ensure that they have a different ID and then write the data.
Splitting is a bit more annoying, since granulepos is a codec dependent timestamp, and I don't remember how it is defined for vorbis. Another problem here is that you can't simply split in the middle of a packet without reencoding.
回答2:
You can do this with libzplay http://libzplay.sourceforge.net/ The steps needed to do what is being asked about:
- OpenFile
- Seek
- SetWaveOutFile(this supports .ogg exporting as well as other formats)
- StartPlayback
- StopPlayback(at time needed)
Everything is extremely well documented on the linked site for multiple languages, including c#.
This answer is for all the other people that spent hours searching and weren't helped by the previous answers. This isn't a very efficient solution to the problem here, but while searching this question came up many times, and this might be helpful to others. :)
来源：https://stackoverflow.com/questions/8152847/working-with-ogg-vorbis