Ecasound Audio Format Libraries

Ecasound is a powerful command-line multitrack audio processing tool for Unix-like systems that relies heavily on external libraries to read, process, and write various audio file types. While it provides native support for raw PCM data and basic headerless streams, compiling Ecasound against dedicated third-party libraries significantly expands its compatibility with standard, compressed, and high-resolution container formats. This article details the primary external libraries Ecasound can link against to enhance its audio format support.

libsndfile

libsndfile is the most critical format library for Ecasound. Developed by Erik de Castro Lopo, this C library provides comprehensive read and write support for a vast array of uncompressed and compressed audio formats. When Ecasound is compiled with libsndfile support (enabled via --enable-sndfile), it gains access to:

• WAV / RIFF (including 16-bit, 24-bit, 32-bit float, and multi-channel configurations)
• AIFF (Apple Interchange File Format)
• AU / SND (Sun/NeXT audio)
• FLAC (Free Lossless Audio Codec, depending on the libsndfile compile options)
• OGG / Vorbis (when bundled within libsndfile)
• PAF, IFF/SVX, VOC, and various telephony formats such as G.711 µ-law and A-law

libaudiofile

Before libsndfile became the de facto standard, Silicon Graphics' libaudiofile (Audio File Library) served as an alternative backend. Ecasound can link against libaudiofile using the --enable-audiofile flag. It provides support for standard formats including:

• AIFF and AIFF-C
• WAVE
• NeXT/Sun .snd/.au
• IRCAM Soundfiles
• Audio Visual Research (AVR) formats

While functional, libsndfile is generally preferred over libaudiofile in modern installations due to more active maintenance and broader format coverage.

libvorbis and libogg

For direct Ogg Vorbis compressed audio processing without wrapping through other libraries, Ecasound can be linked directly against the official Xiph.Org Foundation libraries:

• libogg: Handles container bitstream manipulation.
• libvorbis / libvorbisenc: Handles decoding and encoding of Vorbis streams.

Enabling direct Vorbis integration allows Ecasound to encode real-time output straight to .ogg files or decode them directly into signal chains with optimized memory buffering.

libmad

The MPEG Audio Decoder (libmad) is a high-quality integer-based MPEG audio decoder library. Linking Ecasound against libmad (--enable-libmad) allows native decoding of MPEG audio streams, notably:

• MP3 (MPEG-1 Audio Layer III)
• MPEG-2 Audio Layer III

Because libmad is exclusively a decoder, it only provides MP3 playback and reading support inside Ecasound. For MP3 output and encoding, Ecasound relies on spawning external command-line encoders like LAME rather than direct linking.

libsamplerate (Secret Rabbit Code)

Although technically an audio processing library rather than a container parser, libsamplerate is closely tied to format support during import and export. Linking against libsamplerate allows Ecasound to convert non-matching sampling rates on the fly when reading input files or preparing streams for output formats that require specific standard rates (such as 44.1 kHz for CD audio or 48 kHz for broadcast media).