Settings for LAME MP3 Encoder

Standard Settings

Version (Default Value MPEG-I):

The difference between MPEG-I and MPEG-II are the sample frequencies of the input file. MPEG-I can handle input streams (WAV files) with a sample frequency of 48000, 44100 and 32000 Hz. MPEG-II on the other hand will support stream for 24000, 22050 16000 Hz. Basically, use MPEG-II when you want to encode with low bitrates (e.g. for voice files, or if you need small MP3 files with reduced quality). As you can see, the lowest bitrate for MPEG-II is 8 Kbits/sec while for MPEG-I the lowest bitrate is 32 Kbits/s.

On-the-fly Encoding

Bitrate (Default Value 128 Kbits/s):

Determines the number of bits per second.

Output Samplerate (Default Value 44100 Hz)

Determines the number of samples per second.

Mode (Default Value Stereo):

With LAME MP3 Encoder, you can specify how the file is encoded. The default Stereo option is recommended, but at lower bitrates, the Joint Stereo or Forced Joint Stereo can yield better sound quality.

Stereo: In this mode, the encoder makes no use of potential similarity between the two input channels. It can, however, negotiate the bit demand between both channels, i.e. give one channel more bits if the other contains silence.

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") and difference ("side") signal. For quasi-mono signals, this will give a significant gain in encoding quality. This mode does not destroy phase information like IS stereo that may be used by other encoders. This setting can be used to encode DOLBY ProLogic surround signals.

Force Joint Stereo: This mode will force MS Joint Stereo on all frames. It's faster and it uses some special mid and side masking threshold.

Mono: This option will forcibly generate a mono file, if the input file is a stereo file, the input stream will be read as a mono by averaging the left and right channels.

Advanced Settings

Quality (Default Value Normal):

With LAME MP3 Encoder, you can specify the output quality, thus you can trade off encoding time against sound quality. The default (Normal) is recommended for the lower bitrates (<160 kbps), high quality for bitrates >160 kbps. The voice quality is more or less optimized to generate the best quality for voice. Details of the R3Mix quality option can be found at http://www.r3mix.net.

VBR Quality Setting

This option allows you to set the Variable Bitrate option. Variable Bitrate encoding will enable dynamically determined bitrates that depend on the music content of the current frame. This improves the overall quality of the encoded file without increasing the file size. This option sets the criteria used to determine when to increase the bitrate for a frame. The lower the number, the lower the criteria will be. Thus VBR_0 will yield the best quality (but the largest file size) while VBR_9 will have less sound quality but the file size will be the smallest. The recommended variable bitrate option is VBR_4. If you don't want VBR encoding, set this option to None.

VBR Method Setting

The VBR method setting allows you the change the VBR algorithm which is used for the encoding (detailed information can be found in the LAME user documentation - see http://www.sulaco.org/mp3/doc/html/index.html). The following selections are available

• Disabled: Don't use VBR, instead encode with a Constant Bitrate (CBR)
• VBR-Default: Use the default VBR method (currently set to VBR-MTRH)
• VBR-Old: LAME's first functional approach, based on masking, bisection in the bit domain
• VBR-New: LAME's second approach, based on masking and direct noise allocation
• VBR-MTRH: a combination of old and new (VBR) routines
• VBR-ABR: The Average Bitrate (ABR) setting, the encoding principle is similar to what AAC uses as VBR encoding, it is based on perceptual entropy, but more like CBR than VBR. When you select the ABR option in the VBR Settings box, the ABR edit box will be enabled. In this edit box you can specify the target average bitrate. Of course, a larger bitrate will yield generally better-sounding (but larger) MP3 files.

ABR Settings

Private

When enabled, it will set the private flag in the MP3 stream.

Original

When enabled, it will set the original flag in the MP3 stream.

Copyright

When enabled, it will set the copyright flag in the MP3 stream.

Checksum

When enabled, it will add a cyclic redundancy check (CRC) code in each frame, allowing [the decoding software] to detect transmission errors that could occur on the MP3 stream. However, it takes 16 bits per frame that would otherwise be used for encoding, and therefore will slightly (probably imperceptibly) reduce the sound quality.

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