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| author | John Novak <jnovak@skedulo.com> | 2022-09-17 03:16:44 +0300 |
|---|---|---|
| committer | John Novak <jnovak@skedulo.com> | 2022-09-17 03:21:38 +0300 |
| commit | 50dc5fc3ccdd7c91f6131b09b179401d86174b78 (patch) | |
| tree | e64023a4da8479f72f85604170647004c6e5e6f4 | |
| parent | f44124df9d099540cb165c49767c7c59835563ab (diff) | |
Add explanatory comment about resampling methodsjn/zoh-fixes
Only ZoH upsample is channel rate is below ZoH target rate
| -rw-r--r-- | src/hardware/mixer.cpp | 27 |
1 files changed, 26 insertions, 1 deletions
diff --git a/src/hardware/mixer.cpp b/src/hardware/mixer.cpp index da6658d6b..281987a22 100644 --- a/src/hardware/mixer.cpp +++ b/src/hardware/mixer.cpp @@ -631,6 +631,31 @@ void MixerChannel::Enable(const bool should_enable) MIXER_UnlockAudioDevice(); } +// Depending on the resampling method and the channel, mixer and ZoH upsampler +// rates, the following scenarios are possible: +// +// LinearInterpolation +// ------------------- +// - Linear interpolation resampling only if channel_rate != mixer_rate +// +// ZeroOrderHoldAndResample +// ------------------------ +// - neither ZoH upsampling nor Speex resampling if: +// channel_rate >= zoh_target_rate AND channel_rate == mixer_rate +// +// - ZoH upsampling only if: +// channel_rate < zoh_target_freq AND zoh_target_rate == mixer_rate +// +// - Speex resampling only if: +// channel_rate >= zoh_target_freq AND channel_rate != mixer_rate +// +// - both ZoH upsampling and Speex resampling if: +// channel_rate < zoh_target_rate AND zoh_target_rate != mixer_rate +// +// Resample +// -------- +// - Speex resampling only if channel_rate != mixer_rate +// void MixerChannel::ConfigureResampler() { const auto channel_rate = sample_rate; @@ -650,7 +675,7 @@ void MixerChannel::ConfigureResampler() break; case ResampleMethod::ZeroOrderHoldAndResample: - do_zoh_upsample = (channel_rate != zoh_upsampler.target_freq); + do_zoh_upsample = (channel_rate < zoh_upsampler.target_freq); if (do_zoh_upsample) { InitZohUpsamplerState(); // DEBUG_LOG_MSG("%s: Zero-order-hold upsampler is on, target rate: %d Hz ", |