Helix MP3 Encoder: Difference between revisions
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{{Software Infobox | |||
| name = Helix MP3 Encoder | |||
| logo = | |||
| screenshot = | |||
| caption = | |||
| developer = {{ha user|1312|maikmerten}} | |||
| released = <!-- {{start date and age|YYYY|MM|DD}} --> | |||
| stable_release = | |||
| stable_release_date = <!-- {{start date and age|YYYY|MM|DD}} --> | |||
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| preview_release_date = <!-- {{start date and age|YYYY|MM|DD}} --> | |||
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| operating_system = Linux, Windows | |||
| use = Encoder | |||
| license = [https://github.com/maikmerten/hmp3/blob/main/hmp3/LICENSE.txt RPSL] | |||
| website = [https://github.com/maikmerten/hmp3 github] | |||
}} | |||
The Helix MP3 Encoder was open-sourced by RealNetworks ca. 2005 via the (long-defunct) Helix community project. It originated from the [[Xing]] MP3 encoder, which was purchased by RealNetworks. | The Helix MP3 Encoder was open-sourced by RealNetworks ca. 2005 via the (long-defunct) Helix community project. It originated from the [[Xing]] MP3 encoder, which was purchased by RealNetworks. | ||
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| -V || Quality setting for '''VBR''' encoding. Ranges from 0 to 150. Default is 50. || -V115 for a ~180-200 kbps stereo VBR file | | -V || Quality setting for '''VBR''' encoding. Ranges from 0 to 150. Default is 50. || -V115 for a ~180-200 kbps stereo VBR file | ||
|} | |} | ||
[[Category:Software]] | |||
[[Category:Encoder/Decoder]] | |||
[[Category:MP3]] | |||
Revision as of 11:47, 25 March 2024
| Developer(s) |  maikmerten
|
| Release information | |
|---|---|
| Stable release | |
| Compatibility | |
| Operating system | Linux, Windows |
| Additional information | |
| Use | Encoder |
| License | RPSL |
| Website | github |
The Helix MP3 Encoder was open-sourced by RealNetworks ca. 2005 via the (long-defunct) Helix community project. It originated from the Xing MP3 encoder, which was purchased by RealNetworks.
A current version ("hmp3"), with contributions from HydrogenAudio members, is available as source code over at https://github.com/maikmerten/hmp3. This Wiki page discusses that version.
Features
- Supports MPEG-1 and MPEG-2 modes
- 48 kHz, 44.1 kHz, 32 kHz (MPEG-1)
- 24 kHz, 22.05 kHz, 16 kHz (MPEG-2)
- LAME headers for gapless playback
- CBR and VBR encoding
Listening tests
The Helix MP3 encoder participated in several listening tests and demonstrated to be amongst the highest-quality encoders for MP3 available.
- Public MP3 listening test, October 2008
- Personal listening test by Kamedo2, ~224 kbps, May 2013
- Personal listening test by Kamedo2, ~192 kbps, December 2016
Encoder switches
hmp3 is a command-line operated application. The most basic invocation to generate a MP3 file from WAV:
hmp3 input.wav output.mp3
This creates a ~128 kbps VBR file for 44.1 kHz stereo input.
| Switch | Function | Example |
|---|---|---|
| -B | Set per-channel bitrate. Selects CBR encoding. | -B64 for a 128 kbps stereo CBR file |
| -F | Frequency cutoff for the encoder lowpass filter. To actually encode anything beyond 16 kHz, also specify the -HF switch. | -F19000 for a 19 kHz lowpass |
| -HF | Controls encoding of high frequency content (> 16 kHz). Disabled by default. Valid values are 0 (disabled), 1 (partial, only "mode-1 granules"), 2 (full, "all granules"). Note that high-frequency content will only be encoded if the psychoacoustic model deems encoding high frequencies as beneficial for the given bitrate/quality settings. | -HF2 for unrestricted high-frequency encoding |
| -SBT | Threshold for short-block decisions. Lower values mean more short-block usage. Default is 700. | -SBT500 for more short-blocks (more responsive to transients, might increase bitrate in VBR) |
| -V | Quality setting for VBR encoding. Ranges from 0 to 150. Default is 50. | -V115 for a ~180-200 kbps stereo VBR file |