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libmp3lame_for_esp32

Experiments to port lame mp3 encoder to esp32

Original sources by the authors of LAME: http://www.sourceforge.net/projects/lame

================================================================================= First benchmark: Encode Sample16kHz.raw (little-endian) data, 16 bit, stereo 16000 Hz 10 seconds

  1. Without CFLAGS: 7925057 microseconds

  2. With CFLAGS += -O3 -ffast-math: 7885191 microseconds

  3. With CFLAGS (see above) and TAKEHIRO_IEEE754_HACK: 8468706 microseconds

  4. With CFLAGS and release mode: 7220642 microseconds

So, the best option is (4): 1,38x realtime.

================================================================================= Encode the same file for more than an hour:

LOOP: free mem8bit: 11720 mem32bit: 19992 frames encoded: 139 bytes:99084

...

LOOP: free mem8bit: 11720 mem32bit: 19992 frames encoded: 88543 bytes:63669828

Isn't such a exhaustive test but enough for now.

================================================================================= TODO:

  • Encode something infinite to check memory leaks (partially done)
  • Investigate why CONFIG_ENABLE_MEMORY_DEBUG=y crashes the system
  • Profile to find the heaviest parts
  • Investigate esp32 dsp features: Vectra LX DSP Engine, MAC16
  • Streaming over tcp and http

=================================================================================

Using the LAME encoding engine (or other mp3 encoding technology) in your software may require a patent license in some countries.

As LAME may contain software for which some companies may claim software patents, if you are in a location where software patents are recognized, it is suggested that you seek legal advice before deploying and/or redistributing LAME.

In particular, it is suggested to visit

http://www.mp3licensing.com/

if it applies to your jurisdiction.