How to Use Sound Recorder to Change Compression Settings

MORE INFORMATION

To change the audio codec used to compress a .wav file, follow these steps:

1. Click the Start button, point to Programs, point to Accessories, point to Multimedia (or Entertainment in Windows 98), and then click Sound Recorder.
2. On the File menu, click Open.
3. Type the path and file name for the .wav file you want to modify in the File Name box, and then click Open.
4. On the File menu, click Save As.
5. If you want to overwrite the original version of the file with the new version, click Change. If you do not want to overwrite the original version of the file with the new version, type a name for the new version in the File Name box, and then click Change.
6. Click the codec that you want to use to compress the new version of the file in the Format box, and then click OK.
7. Click Save.

Compressing a .wav file makes the file smaller. Because the file is smaller, it takes less time to transfer the file across a network or between two computers using modems. Not all audio codecs provide the same compression ratio, which makes some audio codecs more useful than others for a particular purpose. However, many audio codecs that provide higher compression ratios do not provide the additional features that other audio codecs provide (such as higher compression speeds and a greater number of sampling rates). When you are deciding which codec to use in compressing a .wav file, all of these factors must be taken into consideration.

For example, the Microsoft Adaptive Delta Pulse Code Modulation (ADPCM) and Microsoft Interactive Multimedia Association (IMA) ADPCM codecs can both achieve a 4:1 compression ratio, but the IMA ADPCM codec compresses files faster. The Microsoft Groupe Special Mobile (GSM) 6.10 codec can achieve only a 2:1 compression ratio, but offers a greater number of sampling rates. The Microsoft Consultative Committee for International Telephone and Telegraph (CCITT) G.711 A-Law and u-Law codec can also achieve only a 2:1 compression ratio, but is best when compatibility with current Telephony Application Programming Interface (TAPI) standards is a concern. The DSP Group Truespeech Software codec achieves the highest compression ratio, and is best in voice sampling applications.

Changing the attributes associated with a .wav file may cause the file to increase or decrease in size, but does not normally make the file sound better. In particular, compressing a .wav file or increasing the compression ratio used on a .wav file does not usually make the file sound better.

Note that GSM is primarily designed for the efficient compression of speech. Using GSM to compress music an result in poor audio quality.