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Features
mpg123 the player
We all know that mpg123 is the fast console mpeg audio decoder/player, don't we? But here are some things that go beyond simple decoding:
- support for many platforms (many Unices, MacOSX, Windows) and audio subsystems
- simple but powerful control mode for frontends (commands via STDIN)
- realtime control of efficient equalizer (because built into decoder)
- built-in terminal control keys
- support for gapless playback of mp3 files (skipping encoder/decoder padding/junk)
- many audio data settings: resampling, choose channel, mono, ...
- really efficient with a growing number of assembler optimizations (pentium, MMX, AltiVec, ...)
- support for Relative Volume Adjustment / ReplayGain
- … see the feature list of libmpg123
- several audio output options using libout123
libmpg123
The decoder part of mpg123 is usable as a library in your application. Features include:
- decoding of MPEG 1.0/2.0/2.5 layer I/II/III audio streams to interleaved PCM, also free-format bitrates over 320 kbit/s
- sample-accurate seeking and gapless playback (via LAME Info frame)
- choice of sample encoding (from 8 bit µlaw to 32 bit float), mono mix
- build-time choice for integer or floating-point synth
- assembly/SIMD optimisations for common sample encodings and decoding modes
- choices between accuracy and efficiency (rounding modes, dithering)
- efficient 2:1 or 4:1 downsampling, sparing decoder work to evaluate the dropped samples
- n:m pseudo-resampler (repeat/drop samples without interpolation) as last resort to enable playback with enforced sample rate
- tune frequency scale factors for zero-cost equaliser (with 32 linearly-spaced bands given my MPEG; not pretty, but hey, it's free!)
- tune volume via scale factors, again without extra CPU cost
- parse and apply relative volume adjustment read from metadata (RVA2, ReplayGain)
- parse ID3v1, ID3v2 and ICY stream metadata (with configured interval), silenty skip other stuff
- graceful handling of stream errors (silence instead of whiny twittering)
- disabling of features to enable smaller builds for embedded systems
(a generic x86-64 float-output binary of from mpg123-1.23.0
using gcc-4.9.2 with
-Osis 118 KiB stripped, still with all the essential sample-accurate codec functionality)
libout123
The mpg123 output library (libout123) supports a wide range of audio interfaces, including:
- ALSA (Advanced Linux Sound Architecture)
- CoreAudio (Mac OS X)
- EsounD (The Enlightened Sound Daemon)
- JACK (Jack Audio Connection Kit)
- NAS (Network Audio System)
- OSS (Open Sound System)
- PortAudio (Portable cross-platform Audio API)
- PulseAudio (sound server for POSIX and Win32)
- SDL (Simple DirectMedia Layer)
- Sun Audio (/dev/audio)
- Win32 (Windows WaveOut)
It also wraps over an optional buffer process to ensure continuous playback without having to deal with concurrency in the application itself.
