22.7. Recorded sounds

| Chapter 22: Figures, Sounds and Files |

| 22.7. Recorded sounds

Inform also supports the playing back of recorded sounds, which might be anything from a three-second sound effect for a creaking door to an epic orchestral symphony. Sound support is very newly added to the system and work is still in progress. In particular, sounds are not played by Inform for OS X (although it does produce valid blorbed Glulx story files), though they should be audible from within the Inform application for Windows.

Once again, only Glulx-based works can incorporate sound effects, and we must be prepared for the fact that not all interpreters will be able to play them back. We must also bear in mind that a sound recording is a large pile of bits, and that adding any kind of sounds will greatly increase the size of the Blorb file for the released Glulx story file.

The sound files provided must have one of two formats: AIFF or Ogg Vorbis. AIFF is a traditional format in the recording industry, though it is more familiar to Mac OS X users than Windows users. It is uncompressed, giving what can be excellent audio quality, but at the cost of sometimes enormous file sizes - perhaps as much as 10 MB per minute, though this can be greatly reduced by lowering the sampling frequency, and halved again by dropping from stereo to mono.

Except for very short sound effects, we recommend using Ogg Vorbis instead. This is a compressed format whose file sizes will typically be more like 1 MB per minute. Inform uses Ogg Vorbis as the only format safe from licencing and patent disputes. (We would very much have liked to provide MP3 support, but this is no longer legally possible for free software.)

Support for Ogg Vorbis is not built in to either Windows or Mac OS X, and any sound recording you make will probably have to be made first to another format (perhaps AIFF or WAV), and then converted. See www.vorbis.com for encoding software which can convert from other sound formats to Vorbis.

Lastly, it must be remembered that recording industry bodies are very hostile to established copyright law covering fair use, parody, quotation of insubstantial passages, etc., when it comes to mixing or using commercially released music. They are well-resourced and highly litigious. If you use sound effects not originated by yourself, you do so at your own risk, even if what you do is perfectly legal on any reading of the statutes.

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