Convert to MP3

Constant bitrate

Specifies constant bitrate value in the range from 32 kbps to 320 kbps.

Variable bitrate

• VBR method
  • Default - Invokes the default VBR algorithm.
  • Old - Invokes the oldest, most tested VBR algorithm. It produces very good quality files, though is not very fast.
  • New - Invokes the newest VBR algorithm. It has the added advantage of being very fast (over twice as fast as the old method).
  • ABR - Turns on encoding with a targeted average bitrate.

• Min bitrate - Specifies the minimum bitrate to be used. However, in order to avoid wasted space, the smallest frame size available will be used during silences.

• Max bitrate - Specifies the maximum bitrate to be used. The use of Max bitrate is NOT RECOMMENDED.

Quality - Bitrate is of course the main influence on quality. The higher the bitrate, the higher the quality. But for a given bitrate, we have a choice of algorithms to determine the best scalefactors and Huffman encoding (noise shaping).

• 9: use slowest & best possible version of all algorithms. 8 and 9 modes are slow and may not produce significantly higher quality.

• 7: recommended.

• 5: default value. Good speed, reasonable quality.

• 3: very fast, ok quality. Psycho acoustics are used for pre-echo & M/S, but no noise shaping is done.

• 0: disables almost all algorithms including psy-model. Poor quality.

Stereo mode

• Stereo - In this mode, the encoder makes no use of potentially existing correlations between the two input channels. It can, however, negotiate the bit demand between both channel, i.e. give one channel more bits if the other contains silence or needs less bits because of a lower complexity.
• Joint stereo - In this mode, the encoder will make use of correlation between both channels. The signal will be matrixed into a sum (“mid”), computed by L+R, and difference (“side”) signal, computed by L-R, and more bits are allocated to the mid channel. This will effectively increase the bandwidth if the signal does not have too much stereo separation, thus giving a significant gain in encoding quality. In joint stereo, the encoder can select between Left/Right and Mid/Side representation on a frame basis. Joint-stereo is the default mode for input files featuring two channels.
• Dual channels - In this mode, the 2 channels will be totally independently encoded. Each channel will have exactly half of the bitrate. This mode is designed for applications like dual languages encoding (ex: English in one channel and French in the other). Using this encoding mode for regular stereo files will result in a lower quality encoding.
• Mono - The input will be encoded as a mono signal. If it was a stereo signal, it will be downsampled to mono. The downmix is calculated as the sum of the left and right channel, attenuated by 6 dB.