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LibAudio: Use channel coupling for stereo FLAC encoding

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The estimation for this is fast but not very accurate, meaning we save
around 5-10% storage space. (We also don’t try other channel coupling
methods, but I am sceptical of how much benefit that actually provides.)
This commit is contained in:
kleines Filmröllchen 2023-08-13 14:14:23 +02:00 • committed by Jelle Raaijmakers
parent 3d0da734ee
commit 1a1cba1c3f
2 changed files with 71 additions and 21 deletions
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9
Userland/Libraries/LibAudio/FlacWriter.h
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@ -87,15 +87,16 @@ private:
ErrorOr<void> write_header();
ErrorOr<void> write_frame();
ErrorOr<void> write_subframe(ReadonlySpan<i64> subframe, BigEndianOutputBitStream& bit_stream);
ErrorOr<void> write_lpc_subframe(FlacLPCEncodedSubframe lpc_subframe, BigEndianOutputBitStream& bit_stream);
ErrorOr<void> write_verbatim_subframe(ReadonlySpan<i64> subframe, BigEndianOutputBitStream& bit_stream);
ErrorOr<void> write_frame_for(ReadonlySpan<Vector<i64, block_size>> subblock, FlacFrameChannelType channel_type);
ErrorOr<void> write_subframe(ReadonlySpan<i64> subframe, BigEndianOutputBitStream& bit_stream, u8 bits_per_sample);
ErrorOr<void> write_lpc_subframe(FlacLPCEncodedSubframe lpc_subframe, BigEndianOutputBitStream& bit_stream, u8 bits_per_sample);
ErrorOr<void> write_verbatim_subframe(ReadonlySpan<i64> subframe, BigEndianOutputBitStream& bit_stream, u8 bits_per_sample);
// Assumes 4-bit k for now.
ErrorOr<void> write_rice_partition(u8 k, ReadonlySpan<i64> residuals, BigEndianOutputBitStream& bit_stream);
// Aborts encoding once the costs exceed the previous minimum, thereby speeding up the encoder's parameter search.
// In this case, an empty Optional is returned.
ErrorOr<Optional<FlacLPCEncodedSubframe>> encode_fixed_lpc(FlacFixedLPC order, ReadonlySpan<i64> subframe, size_t current_min_cost);
ErrorOr<Optional<FlacLPCEncodedSubframe>> encode_fixed_lpc(FlacFixedLPC order, ReadonlySpan<i64> subframe, size_t current_min_cost, u8 bits_per_sample);
NonnullOwnPtr<SeekableStream> m_stream;
WriteState m_state { WriteState::HeaderUnwritten };