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minimp3 Decoder

This project provides the minimp3 MP1/MP2/MP3 decoder optimized for Nuclei CPUs.

The source code comes from the upstream lieff/minimp3 project.

File Structure

Directory Description
data test data, generated headers, and helper scripts
minimp3.h core decoder implementation
minimp3_ex.h extended streaming and file decoding interfaces
minimp3_test.c test and benchmark entry

Prerequests

Please refer to the Prerequests section in the parent directory's README.

Build

Switch to the directory containing the Makefile.
Below are build examples for the Nuclei N900 CPU.

Build without extension:

make CORE=n900 ARCH_EXT= all

Build with B and P extension:

make CORE=n900 ARCH_EXT=_zba_zbb_zbc_zbs_xxldspn1x all

Build with a specific test pattern:

make CORE=n900 PATTERN=1 all

When PATTERN is not specified, the build uses the pre-generated test data in data/. When PATTERN is set, the build regenerates bit_input.h, pcm_output.h, and args.h before compiling.

For details about Nuclei CPU architecture extensions, see the ARCH_EXT section in the Nuclei SDK documentation.

Performance Test

Generate Test Data

The test program compares decoded PCM output against reference data embedded in the build. A helper script is provided to switch among the bundled test patterns:

👉 data/bin/gendata.sh

To view usage details:

./data/bin/gendata.sh -h

To generate data from a specific pattern line in pattern.txt:

./data/bin/gendata.sh -p 1

The script updates:

  • data/bit_input.h: embedded MP3 bitstream input
  • data/pcm_output.h: embedded PCM reference output
  • data/args.h: default decode command arguments

Expected Output

A typical output looks like this:

Nuclei SDK Build Time: Sep 29 2025, 09:40:40
Download Mode: DDR
CPU Frequency 50303907 Hz
CPU HartID: 0
rate=44100 samples=4608 max_diff=0 PSNR=99.000000
PASS

The key validation metric is PSNR. The test is considered successful when the decoded PCM matches the embedded reference closely enough and the program prints PASS.

The PATTERN build variable can be used to benchmark multiple bundled vectors. The CI configuration currently covers a large set of patterns from data/bin/pattern.txt.