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A November 3 report describes using the Ultra Low Complexity Codec (ULC) to play 44.1 kHz stereo audio on Nintendo 64 hardware at bitrates the author compares with Opus, while using about 4% of the console’s CPU time. The result is a developer’s report, not an independently verified benchmark; details such as test conditions and the specific bitrate are not provided.
A developer says the Ultra Low Complexity Codec (ULC) can play 44.1 kHz stereo audio on Nintendo 64 hardware at bitrates described as near those of Opus, using about 4% of the console’s CPU time. The report, published November 3, outlines a potential alternative to the N64’s space-hungry ADPCM audio and its more demanding Opus decoder, though the performance figures have not been independently verified in the material provided.
The developer tested ULC for music in Xibalba 64, an N64 game built with Libdragon, an open-source development platform. The report says the game had used ADPCM audio that occupied about 31 MB of a 32 MB ROM. The author describes that as wasteful, even though modern development makes cartridge storage less restrictive than it was for commercial N64 releases.
Libdragon already includes an RSP-accelerated Opus decoder, but the author says it runs too slowly for use during gameplay. ULC is presented as a lighter alternative: a transform codec that uses a modified discrete cosine transform, then stores coefficients through a simple, nibble-based format. Its design avoids the Huffman decoding used by MP3 and does not require arbitrary bit-level reads, which the report says helps keep decoding work low.
The article credits codec creator Aikku93, who has worked on ULC since 2019 and previously made a Game Boy Advance demo that played recorded music at around 70 kbps. The N64 report gives no exact ULC bitrate for its 44.1 kHz stereo claim, and does not specify a testing method for the estimate of about 4% CPU use. Those figures should be read as the author’s account rather than as a published, independent benchmark.
More Music Within N64 Limits
If the reported performance holds across different tracks and game conditions, ULC could make continuous recorded music more practical on N64 projects without consuming most of a cartridge or leaving too little processing time for gameplay. That could expand the audio choices available to hobbyist developers and preservation projects working with the console.
The claim is not that ULC removes the N64’s technical limits. It is a possible way to work within them: a smaller audio stream can save ROM space, while a low decoding cost may leave more CPU capacity for the game. The practical value will depend on sound quality, encoder support, and whether the decoder remains efficient in real game builds.
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Why N64 Audio Was Constrained
The N64’s cartridge-based storage made lengthy recordings costly. The report estimates that five minutes of uncompressed, 44.1 kHz stereo audio would require about 12 MB even with ADPCM, while it says the full Super Mario 64 ROM was 8 MB. Developers generally generated music from short samples rather than storing complete tracks.
Nintendo’s Libultra library used the console’s Reality Signal Processor, or RSP, for audio tasks, including ADPCM decompression. According to the report, third-party developers did not initially have direct access to the RSP. Some later games, including Conker’s Bad Fur Day, used it to decode MP3 speech, but the author says MP3 decoding was too demanding for continuous audio during gameplay.
Libdragon provides an alternative for modern N64 development, including RSP-assisted ADPCM and Opus decoding. The report’s account of ULC builds on that work and on Aikku93’s earlier GBA implementation, where the codec was designed for a much slower processor than the N64.
“44100 Hz stereo with near-Opus bitrates using about 4% of the N64’s CPU time.”
— The developer writing in the November 3 report
Performance Still Needs Verification
The report does not give the exact bitrate used for the N64 audio test, the method used to calculate CPU time, or a comparison of quality across a range of music. It also does not say whether the 4% figure applies to a particular track, a particular playback setup, or broader gameplay conditions.
It remains unclear how the codec performs with varied audio, how much ROM space a full game soundtrack would require, and whether the reported results will be reproduced by other developers. The available information supports a promising technical report, not a general guarantee that ULC will outperform other codecs in every N64 project.
Testing Across N64 Projects
The immediate next step is further testing of ULC in real N64 game builds, including comparisons of bitrate, sound quality, ROM use and CPU load against ADPCM and Opus. The source report does not announce a release date, formal benchmark, or planned platform update.
Developers interested in the result can watch for implementation details and independent tests from the Libdragon community. Until those are available, the reported 44.1 kHz stereo playback and CPU figure remain claims from the developer’s report.
Key Questions
What is ULC?
ULC stands for Ultra Low Complexity Codec. It is a transform audio codec created by Aikku93, using a modified discrete cosine transform and a simple nibble-based format for storing coefficients.
What N64 audio result does the report describe?
The author reports 44.1 kHz stereo playback at bitrates described as near Opus, with about 4% of the N64’s CPU time. The provided report does not specify the exact bitrate or a benchmarking method.
Why is this relevant to N64 games?
N64 cartridges had limited storage, and the report says conventional ADPCM audio can take substantial ROM space. A codec that uses less storage and modest processing could make recorded music more practical in homebrew projects.
Has ULC been independently benchmarked on the N64?
The source material provides the developer’s report, but no independent verification or separate benchmark results. The CPU-use and bitrate claims should be treated as reported figures pending further testing.
Source: phoboslab.org
