Sound Clips

Feature Design Document

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Functional Spec

• 10 seconds max
• PCM WAV format, 16-bit, 44.1kHz, mono.

Second Life supports in-world sound clips, which can be played to all residents within range. The maximum time any clip can be is 10 seconds, requiring longer sounds to be stitched together. There are various LSL functions that can be used to play sound clips, as well as a built-in system for gestures. Uploading a sound clip costs $10l, and the clip must be compatible with SL. As the Knowledge Base says, "Valid sounds are any .WAV file in standard PCM format, 16-bit/44.1kHz/mono or stereo (which will be converted to mono anyway), less than or exactly 10 seconds in length. (10.000 seconds is fine, but 10.001 will fail to upload; to the degree of one sample makes a difference.) Sounds cannot be saved as 8-bit, 22.05 kHz, or any other frequency. Sounds in other formats can be converted in most sound programs. There is currently no support for compression formats such as MP3."

Audio software

Windows

An example of a free quality converter is r8brain.

Another very useful application for converting your sound clips to 44.1kHz .wav format is Audacity, which is available free for download at https://www.audacityteam.org/download/. Torley Linden also did a video tutorial on creating and uploading sounds, viewable at http://www.youtube.com/watch?v=QBVmFafFatE

An online converter which provides complete control over converting the specs can be viewed at http://audio.online-convert.com/convert-to-wav.

An alternate online converter was http://www.mp3care.com, but as of this update isn't available.

Linux

The following section assumes some familiarity with the Linux operations system and bash scripting. One of the best tools for audio conversion under Linux is the tool ffmpeg. It is a command line tool that can convert both video and audio from one supported format to other supported formats. Source code for ffmpeg can be downloaded from the link but most modern linux distributions come with modern version already installed or ready for download in a package management system. Consult your distributions documents on how to install packages and what package management system is supported.

The following command will use ffmpeg to convert a sound file to a Second Life compatible wav file while cutting it just under 10 second segments for instant upload.

$ ffmpeg -i <filename> -f segment -segment_time 9.9 -ac 1 -ar 44100 <output filename>.%03d.wav

Command line explanation as follows.

• -i <filename> The input file to convert.
• -f segment -segment_time 9.9 Save the output file in 9.9 second segments. You can specify any time in segment_time option, including 10 for 10 seconds. But experimenting using 10 as a segment size sometimes produces file sizes to large for uploading. The 9.9 entry seems to be the perfect size for uploading with out issues.
• -ac 1 Converts a multi channel, stereo, stream into a single, mono, output stream.
• -ar 44100 Makes sure the output frequency is 44100 hz.
• <output filename>.%03d.wav Specifies the output name and format for the numbering of each segment. The %03d format will save the output stream in sequential 3 digit segments. example: mozart.000.wav, mozart.001.wav, mozart.002.wav.

Once complete the resulting wav files should be ready to upload in to Second Life.

Batch conversion
The following batch command can be used to convert a entire directory of mp3 files in to segmented wav files for direct upload.

$ for i in *.mp3; do ffmpeg -i ${i} -f segment -segment_time 9.9 -ac 1 -ar 44100 ${i/mp3/}%03d.wav ; done

Test scripts

Audio Test

Discussion for future improvements

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Relationship to other features

List of features that need to be tested when this feature changes, and why.

Upload Assets - Upload a sound clip and make sure it still works.

User Guides

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