Voice Codec Support
Contents
- 1 Which CODECs are supported for file recording/playback?
- 2 Which compression format does recording use, and at what rate?
- 3 How to play WAV files recorded by a sound card with a Synway voice board?
- 4 Why are noises sometimes heard in the process of file playback?
- 5 How to play or record GSM, MP3 voice files?
Which CODECs are supported for file recording/playback?
Play/record function supports the following CODECs at a sampling rate of 8000 times per second:
1) For standard wav files: Single-channel A-Law, μ-Law and 8-/16-bit linear PCM, IMA-ADPCM, Dialogic-ADPCM (VOX), MP3, GSM and G.729A are supported. For stereophonic recording which is invoked by SsmRecStereoToFile, A-Law and μ-Law are supported.
2) For plain files (i.e. files without header information): Single-channel A-law, μ-law, 8-/16-bit linear PCM, IMA-ADPCM, Dialogic-ADPCM(VOX), MP3, GSM and G.729A are supported.
3) For standard MP3 files: Single-channel MP3 is supported.
Which compression format does recording use, and at what rate?
The following recording compression formats are supported:
1) IMA-ADPCM or Dialogic-ADPCM (VOX): Compression rate of 2:1, i.e. voice data are generated at 4kbps.
2) GSM: Compression rate of 5:1, i.e. voice data are generated at 1.6kbps.
3) MP3: Compression rate of 8:1, i.e. voice data are generated at 1kbps.
4) G.729A: Compression rate of 8:1, i.e. voice data are generated at 1kbps.
How to play WAV files recorded by a sound card with a Synway voice board?
The files can be directly played by Synway voice boards if the file format is supported by our product. Otherwise, they have to be converted into a supported wav format with third-party software tools such as Cooledit.
Why are noises sometimes heard in the process of file playback?
This generally happens when voice data are corrupted or when incorrect play-format is used to decode an unformatted voice file. Another reason is the voice codec being used to play files is unsupported by Synway boards.
How to play or record GSM, MP3 voice files?
To play or record GSM, MP3 voice files, you should first modify the configuration item under Section [SystemConfig] in the file ShConfig.ini to GsmCodecEnable=1, and be sure to install necessary codec engines (The engine for GSM is usually carried by Windows operating system while that for MP3 could be acquired from the DEMO package released at our website).
