HH
VS1005 VSOS A
UDIO
S
UBSYSTEM
VS1005g
14
Audio Encoders
There are currently two Audio Encoders. They are for Ogg Vorbis and MP3 formats.
Both are intended to operate properly at the 60 MHz standard operating speed. For
details of how to use them, see the source code for the VSIDE solution Rec (more
information for Rec is available in the
VSOS Shell document
).
14.1
ENCVORB.DL3 - Ogg Vorbis Encoder
ENCVORB.DL3 offers a high-quality encoder for the free end open Ogg Vorbis audio
format. This is the recommended format for those users that don’t specifically need the
MP3 format, and for whom the variable bitrate property of Ogg Vorbis is not a problem.
The Ogg Vorbis encoder is a Variable BitRate encoder, and works best when given an
encoding quality value. The range for the quality is from 0 and 10 (10 is the best; qualities
above 6 may require a higher clock speed than 60 MHz). If set to Constant bitrate, the
encoder will convert that to an approximate quality value, and still use Variable BitRate.
14.2
ENCMP3.DL3 - MP3 Encoder (VS1205 only)
ENCMP3.DL3 offers a high-quality encoder for the popular MP3 audio format. While
not capable of getting quite the same quality as Ogg Vorbis when using similar bit-rates,
the MP3 encoder still offers high fidelity sound at bit-rates between 160-192 kbit/s, and
acceptable speech quality at very much lower bitrates.
The MP3 encoder can operate either with a Variable BitRate or Constant BitRate en-
coder depending on whether a quality or bitrate value is set. For best quality per bit,
Variable BitRate is recommended.
14.3
ENCFLAC.DL3 - FLAC Encoder
ENCFLAC.DL3 offers a lossless encoder for 16-bit audio up to 48 kHz. Typically a 48 kHz
16-bit stream is compressed from 1.536 Mbit/s to 0.8-1.3 Mbit/s. Because encoding is
lossless, compression efficiency depends on the audio data.
Because the bitrates are much higher than for the Ogg Vorbis or MP3 encoders, storing
the result to e.g. an SD card may require a separate buffer memory.
Rev. 3.57
2019-04-10
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