SD2 to MP3: Convert Audio from SD2(Sound Designer 2) to MP3(MPEG Layer-3) with River Past Audio Converter, SD22MP3 converter, conversion

What is SD2?

SDII (Sound Designer II, sometimes seen abbreviated as SD2) is a monophonic/stereophonic audio file format, originally developed by Digidesign for their Macintosh-based recording/editing products. It is the successor to the original monophonic Sound Designer I audio file format.

An SDII file can be monophonic or stereophonic. When stereo is used, the tracks are interleaved (sample-001-left, sample-001-right, sample-002-left, sample-002-right, etc.) Files also store sample rate and bit depth information.

The SDII file has become a widely accepted standard for transferring audio files between editing applications. Most Mac CD-ROM writer software, for example, specifies SDII or Audio Interchange File Format as the file format needed when making audio CDs.

The SDII file has also become accepted among personal computer audio application developers. This makes transferring audio from Mac to PC platforms much easier. When used on a PC, the file must use the extension of ".sd2".

To convert SD2 files to other audio formats, please make sure Apple QuickTime is installed.

What is MP3?

MP3 is a digital audio compression algorithm that acheives a compression factor of about twelve while preserving sound quality. It does this by optimising the compression according to the range of sound that people can actually hear. MP3 is currently (July 1999) the most powerful algorithm in a series of audio encoding standards developed under the sponsorship of the Moving Picture Experts Group (MPEG) and formalised by the International Organization for Standardization (ISO).

MP3 is very different from Layer 2, using an additional MDCT layer to increase frequency resolution. Its scale factor groups are more optimised for the human ear, and it uses nonlinear sample quantisation and Huffman coding. MP3 files (filename extension ".mp3") can be downloaded from many World-Wide Web sites and can be played using software available for most operating systems (also downloadable), e.g. Winamp for PC, MacAmp for Macintosh, and mpeg123 for Unix. MP3 files are usually downloaded completely before playing but streaming MP3 is also possible. A program called a "ripper" can be used to copy a selection from a music CD onto your hard disk and another program called an encoder can convert it to an MP3 file.

Windows ships with limited MP3 encoding support. The output sample rate is limited to 24khz and the bitrate is limited 56kbps. However, many add-on packages from open source community make it possible to encode at higher sample rate and bitrate.

A commonly used open source codec is LAME. LAME comes in different forms, including a ACM (Audio compression manager) codec and a DLL (lame_enc.dll). Caution: LAME ACM does not work well on many computers, regardless which software is loading it. It is best to avoid installing LAME ACM and use lame_enc.dll instead.

MPEG.ORG is an excellent source for additional information on MPEG format and usage.

When you encode MP3 audio, we recommend you to install lame_enc.dll.

Launch River Past Audio Converter

Once River Past Audio Converter is installed properly, launch Audio Converter.

Add File

Click on the "Add" button on the tool bar. The standard file open dialog appears. Select "SD2 - Sound Designer 2" in its "Files of type" combo box.

Select the file you want to convert and click "Open". The file will be added to the conversion file list.

Note: To convert from SD2 files, you must have Apple QuickTime installed.

River Past Audio Converter

Select output format

Use the setting panel on the bottom of the window to control the output format. Click on the toggle to the left of the "Format" label to expand the panel. Select "MP3 - MPEG Layer-3" as the "Audio Type".

You can change the sample rate, channel (stereo or mono) and bitrate.

Note: The standard MPEG Layer-3 audio compressor is limited to maximum 24khz and 56kbps. Please install Lame_enc.dll for higher sample rate and bitrate.