SPCPresenter

SPCPresenter is a tool I wrote to generate visualizations of SNES/SFC chiptunes, based on snes-apu, FFmpeg, and Slint. The visualization design is essentially a port of the piano roll from RusticNES.

Functionality

SPCPresenter runs your input SPC in a custom fork of snes-apu and tracks the state of the emulated S-DSP chip every frame. It then generates a visualization and feeds it to FFmpeg to be encoded as a video.

Features

• Supports SPC modules.
  • Support for songs that require 5A22/65816 emulation (SMC/SNSF) are planned.
• Based on a custom fork of snes-apu with a much more accurate S-DSP:
  • Reorders operations to more closely match a cycle-accurate implementation.
  • Properly emulates internal register sizes and wraps/clamps values accurately.
  • Implements all S-DSP register reads and writes, many of which were previously missing.
  • Reimplements the FIR filter to properly overflow and use the correct taps.
  • Correctly mixes negative channel volumes (SNES "surround").
  • Fixes a race condition that is triggered when dynamically resizing the echo buffer.
  • Remaining inaccuracies to be fixed:
    • BRR samples are decoded one block at a time instead of 4 samples at a time.
    • ENDX latch timing is slightly inaccurate which can lead to timing errors in some drivers.
    • S-DSP is not yet cycle-accurate. It instead runs in 64 SMP-clock periods.
• Automatic BRR sample analysis:
  • Rips samples from the S-DSP as the song plays.
  • Samples are tuned using a custom implementation of the pYIN pitch detection algorithm.
    • Works quite well for monophonic pitched samples and some percussion.
  • Sample loudness is also computed to be factored in to the channel volume calculation.
  • Manual tuning parameters can be specified per source index:
    • As a fundamental frequency in Hz
    • As an AddMusicK tuning multiplier and submultiplier
    • From Super MIDI Pak session JSON files.
    • Support is planned for automatic imports from AddMusicK TXT files and XM/IT files.
  • The UI displays ripped samples and allows you to play them.
    • Useful for fine-tuning sample fundamental pitch...
    • ...or just to play around with the samples a bit.
  • Support is planned for automatic percussion classification.
  • Support is planned for automatic polyphonic sample pitch detection.
• Outputs a video file:
  • Customizable resolution (default 1080p) at 60 FPS.
  • MPEG-4 container with fast-start (moov atom at beginning of file).
  • Matroska (MKV) and QuickTime (MOV) containers are also supported.
  • yuv420p H.264 video stream encoded with libx264, crf: 16.
  • If using QuickTime, ProRes 4444 streams encoded with prores_ks are also supported.
  • Stereo AAC LC audio stream encoded with FFmpeg's aac encoder, bitrate: 384k.
• Video files are suitable for direct upload to most websites:
  • Outputs the recommended format for YouTube, Twitter, and Discord (w/ Nitro).
  • Typical H.264 exports (1080p, up to 3 minutes) are usually below 100MB.
• Video files have metadata based on SPC Id666 tags (title, artist, game name).
  • Support for extended Id666 is planned.

Installation

Windows: head to the Releases page and grab the latest binary release. Simply unzip and run the executable, and you're all set.

Linux: no binaries yet, but you can compile from source. You'll need to have ffmpeg and optionally Qt6 development packages installed, then clone the repo and run cargo build --release to build.

Usage

GUI

1. Click Browse... to select an input module.
2. The module's metadata will be displayed.
3. Select the duration of the output video. Available duration types are:
   • Seconds: explicit duration in seconds.
   • Frames: explicit duration in frames (1/60 of a second).
   • SPC duration: if present, the duration specified in the Id666 tags of the SPC file.
4. Select the duration of the fadeout in frames. This is not included in the video duration above, rather it's added on to the end.
5. Select the output video resolution. You can enter a custom resolution or use the 1080p/4K presets.
6. Optionally select a background for the visualization. You can select many common image and video formats to use as a background.
   • You can also elect to export a transparent video later if you would like to use a video editor.
   • Note: Video backgrounds must be 60 FPS, or they will play at the wrong speed. A fix for this is planned.
7. Select additional rendering options:
   • Blargg's DSP post-filter: applies the band-pass filter from snes_spc/SPC_Filter.cpp.
   • Sample interpolation: determines the filter used to stretch/compress samples in the DSP.
8. Click Render! to select the output video filename and begin rendering the visualization.
   • If you would like to render a transparent video for editing, then choose a filename ending in .mov to export in a QuickTime container. When asked if you would like to export using ProRes 4444, select OK.
9. Once the render is complete, you can select another track or even change modules to render another tune.

CLI

If SPCPresenter is started with command line arguments, it runs in CLI mode. This allows for the automation of rendering visualizations which in turn allows for batch rendering and even automated uploads.

The most basic invocation is this:

spc-presenter-rs path/to/music.spc path/to/output.mp4

Additional options:

• -R [rate]: set the sample rate of the audio (default: 44100)
• -s [condition]: select the output duration (default: time:300):
  • time:[seconds]
  • frames:[frames]
  • time:spc (if supported)
• -S [fadeout]: select the fadeout duration in frames (default: 180).
• --ow [width]: select the output resolution width (default: 1920)
• --oh [height]: select the output resolution height (default: 1080)
• -t [source_index]:[tuning_type]:[params]: Specify manual tuning for a sample by source index:
  • 0:hz:500.0 tunes source index 0 to 500.0 Hz at pitch $1.000
  • $12:amk:$03,0x32 tunes source index 18 like an AddMusicK instrument with a tuning multiplier of $03 and a submultiplier of $32.
  • You can use this flag multiple times to tune more than one sample.
• --super-midi-pak-session [json_path]: load tuning parameters from a Super MIDI Pak session JSON file.
• -P [sample_index]:[css_color]: Specify a color to be associated with a sample.
  • -P 0:#ff9800 sets the color for source index 0 to #ff9800.
  • -P $12:hsl(120, 100%, 63%) sets the color for source index 18 to #40ff40.
  • Colors are parsed with the csscolorparser crate.
• -B [background_file]: add a background to the rendered video.
• -h: Additional help + options
  • Note: options not listed here are unstable and may cause crashes or other errors.