From: Matthew Berg <galt@...>
Date: 2003-11-23T05:13:01+09:00
Subject: Re: Ruby classes for MP3 de-/encoding

On Sat, 2003-11-22 at 14:15, Dennis Oelkers wrote:
> On Sun, Nov 23, 2003 at 04:03:55AM +0900, Matthew Berg wrote:
> > You can do metadata extraction with GStreamer as well, though the
> > bundled bindings for libgstmediainfo can be slow in certain
> > circumstances.  I have the extraction code I've been working on up here
> > though:
> > 
> > 	http://www.gothpoodle.com/~galt/info.rb
> > 
> > This should allow you to read id3 or ogg tags at minimum, and i think
> > wav riff headers though I haven't tested it on that yet.
> 
> Thanks for all your help, but it seems as if you misunderstood my question
> a bit. I'm not looking for classes to extract metadata information, I want
> to encode/decode MP3 data.

I think you misunderstood my answer.  The metadata stuff was meant to be
a "you can do this as well" thing.  GStreamer is a full multimedia
framework, which *does* do encoding and decoding of mp3 data.

For example, a program to play a music file would look something like
this: (note, this is off the top of my head, I haven't tested it, but if
you need example code there's some up on the Ruby-GNOME2 site and
included with the distribution)

	require 'gst'

	Gst.init

	# element to read a file
	src = Gst::ElementFactory.make("filesrc")
	# element to decode autodetect and decode formats
	spider = Gst::ElementFactory.make("spider")
	# element to output to a media decide
	sink = Gst::ElementFactory.make("osssink")


	# create a pipeline
	pipeline = Gst::Pipeline.new
	# add the elements
	pipeline.add(src, spider, sink)
	# link them together
	src >> spider >> sink

	src.location = ARGV.first

	# reset the pipeline and set the state to playing
	pipeline.clear
	pipeline.play

	# keep processing the pipeline until it's finished
	while pipeline.iterate do end

	exit!

That example will actually handle any supported media type (mp3, ogg,
wav, au, flac, etc), but if you wanted to limit it to mp3 data you could
just use the "mad" element instead of "spider".

Want to output to a file instead?  Use a "filesink" element.  Want to
reencode to ogg maybe?  Put a "oggenc" element before the "filesink".

In other words you can do most anything you want with audio and video
files you'd ever want to do.  :)

Matt