Multi Channel File Mixing

Multiple-channel file mixing

FLAC files support up to eight channels and OGG Vorbis supports up to 255. It would be interesting to extend Mixxx to allow DJs to work with these channels individually within a virtual deck so as to be able to create live remixes from stems. Doing this from a single multi-channel file greatly simplifies the workflow and eliminates synchronization problems.

Overview of required changes

• FLAC and OGG SoundSources need to find out how many channels the loaded file offers, get meta-data for each (whether any are stereo pairs/other groups,) and report this information to their parent Deck. (Let's limit Vorbis to 8 channels as well for now.)
• Decks need to:
• Ask for this information
• Manage the supplied number of channels
• Offer additional controls for each mono channel or channel group: Mute, Solo, Volume, and Pan controls
• Tell the Analyzer which channel(s) to use for BPM detection
• Analyzer(Queue) needs to:
• Handle multiple-channel files
• Handle channel groups from 1-8 channels and render each group to a single mono signal for display
• Extend its API so it can be told about how channel groups and which channel(s) are to be used for BPM analysis
• Tell the waveform GUI widget how many streams to display (due to channel grouping, this number may not be equal to the number of discrete channels in the file.)
• CachingReader needs to be extended to support up to eight channels
• The GUI needs to:
• Include additional parallel summary waveforms for each mono channel or stereo pair
• Display Mute, Solo, Volume, and Pan controls as the Deck reports
• Overlap all (active) channels' waveforms in the detailed waveform display
• The waveform needs to change the way it renders:
• Single value, 0 at bottom, max at top.

SoundSource API changes

    int getNumberOfChannels(); // Number of mono channels in the loaded file
    QString[] getChannelNames(); // Name for each channel - from FLAC/OGG tags
    QList(int[]) getLinkedChannels(); // List of channel groups to treat as one unit (Stereo pairs, surround channels)