Bitrate denotes the average number of bits that one second of audio data will take up in your compressed bitstream. Generally speaking, the higher the bitrate achieved, the better the sound quality will be in the end - and vice versa. The following table gives you an overview about quality achievable.
Table 1.1: Bitrate versus sound quality
||Quality comparable to or better than
In MP3 Bitrate mode you can provide a bitrate that should be used, either in CBR (Constant Bitrate) or in VBR (Variable Bitrate) mode. If you want VBR mode, check the "Use Variable Bitrate mode". Note that CBR mode is recommended.
Select ouptut sampling frequency. There are three options: 32000 Hz, 44100 Hz and 48000 Hz. 44100 Hz means that you have 44100 values per second coming in from your sound card (or input file).
Free Video MP3 Extractor is able to encode audio using one of its 4 channel modes: Dual Channels, Stero, Joint Stero and Mono. Joint Stereo is the default mode.
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 a 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.
- dual channels
In this mode, the 2 channels will be totally indenpendently 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.
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.
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