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Audio: channel mixer matrix builder for QAudioFormat - #1600
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CommonFramework/AudioPipeline/ChannelMixer.h/.cpp:
build_channel_mixer_matrix() builds the N x M float weight matrix
(consumed by Kernels::AudioChannelMixer::mix_channels) from the
channel configs of two QAudioFormats, using the conventional
industry-standard coefficients (ITU-R BS.1116-1 style):
- same position passes through at gain 1
- mono <-> stereo duplicate / 0.5 average
- C -> L/R at 0.7, L/R -> C (upmix) at 0.35 each
- back/side surrounds -> front at 0.7 when the destination has
no surround on that side; BL <-> SL cross-fill at 0.7
- LFE passes through only, tops never mix
- returns an empty vector when either format's channel layout is
ChannelConfigUnknown; unnamed channels contribute zero
Kernels/AudioPipeline: add MixerMatrixTest infra and register 15
matrix cases (1<->2, 3.0, 5.1<->2.0/3.0/2.1/7.1, unknown layouts).
Kernels must not depend on Qt or CommonFramework, so the MixerMatrixTest infra moves below build_channel_mixer_matrix in CommonFramework/AudioPipeline/ChannelMixer.cpp, registered via add_tests_ChannelMixerMatrix() from ComputerPrograms/UnitTestRunner.cpp (the same pattern as BlackBorderDetector). Reverts the Kernels/AudioPipeline changes and drops the Qt5 stub (Qt6+ required). Also drops ffmpeg mentions from the comments.
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Adds
build_channel_mixer_matrix(QAudioFormat in, QAudioFormat out)in CommonFramework/AudioPipeline/ChannelMixer.h/.cpp. It builds the N x M float weight matrix consumed byKernels::AudioChannelMixer::mix_channels(column-major: indexi + in_channels * o), so an input format's channels are converted to an output format's channels with conventional 'industry standard' coefficients (ITU-R BS.1116-1 style, matching FFmpeg's automatic rematrix):Failure semantics (per design): an empty vector is returned when either format's channel layout is
ChannelConfigUnknownor has a non-positive channel count. Channels present in the frame but unnamed by the config contribute zero (FFmpeg does not guess per-channel identities). No renormalization is applied (FFmpeg uses these fixed coefficients; a full-scale multichannel source can exceed full-scale in a narrow downmix).Qt 5 has no per-channel position info, so the builder returns empty there (Qt 6 API only), matching the existing
PA_AUDIO_USE_CHANNEL_CONFIGconvention.Tests: new
MixerMatrixTestinfra (Kernels/AudioPipeline/Kernels_ChannelMixer_Matrix_TestInfra.h/.cpp) with 15 registered cases (mono<->stereo, 3.0<->2.0, 5.1<->2.0/3.0/2.1/7.1/5.1, unknown layouts). Full command-line suite: 5446 passed, 0 failed.