Add multichannel audio tests and example (stereo, 5.1, 7.1)#150
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Add multichannel audio tests and example (stereo, 5.1, 7.1)#150alexeymohr wants to merge 1 commit into
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Add tests and an example demonstrating how to create AAF files with multichannel audio tracks that Pro Tools recognizes as native stereo, 5.1, and 7.1 tracks. Pro Tools uses an "Audio Channel Combiner" OperationGroup to represent multichannel clips. Each channel gets its own mono mob chain (MasterMob -> SourceMob with PCMDescriptor -> TapeDescriptor SourceMob), and the OperationGroup wraps N SourceClip inputs together. A _TRACK_FORMAT tagged value on the TimelineMobSlot indicates the layout (2=stereo, 3=5.1, 4=7.1). The pattern was discovered by analyzing Pro Tools AAF exports and has been verified to round-trip through both pyaaf2 and Pro Tools. Relates to markreidvfx#145, markreidvfx#102, markreidvfx#93. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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Summary
tests/test_multichannel.py— write/read round-trip tests for stereo (2ch), 5.1 (6ch), and 7.1 (8ch) multichannel audio tracks using the Audio Channel Combiner OperationGroup patternexamples/multichannel_audio.py— standalone example script showing how to create multichannel AAFs that Pro Tools imports as native multichannel tracksBackground
Pro Tools represents multichannel audio clips using an "Audio Channel Combiner" OperationGroup (
6b46dd7a-132d-4856-ab21-8b751d8462ec). Each multichannel track has one composition slot containing a Sequence of OperationGroups. Each OperationGroup wraps N mono SourceClips (one per channel), and each channel has its own independent mob chain: MasterMob → SourceMob (PCMDescriptor, mono) → SourceMob (TapeDescriptor).A
_TRACK_FORMATtagged value on the TimelineMobSlot indicates the channel layout:2= stereo (2 InputSegments: L, R)3= 5.1 surround (6 InputSegments: L, C, R, Ls, Rs, LFE)4= 7.1 surround (8 InputSegments: L, C, R, Lss, Rss, Lsr, Rsr, LFE)This is the same OperationDef, same parameters, and same structure for all three formats — only the number of InputSegments and the
_TRACK_FORMATvalue differ.This pattern was discovered by analyzing Pro Tools AAF exports created with "Enforce Media Composer Compatibility" and "Export stereo, 5.1 and 7.1 tracks as multi-channel" enabled.
Notes
NumberInputs=1despite having 2, 6, or 8 actual InputSegments. This matches Pro Tools' own exports. The existingtest_transitions.pyalready registers the sameAvidParameterByteOrderandAvidEffectIDParameterDefs used here.Test plan
python -m unittest tests.test_multichannel -v— all 4 tests passtest_tagged_value,test_dictionarystill pass)python examples/multichannel_audio.pyruns and produces valid AAFsRelates to #145, #102, #93.
🤖 Generated with Claude Code