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LibAudio: Remove frame-wise copys from FlacLoader

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Previously, FlacLoader would read the data for each frame into a
separate vector, which are then combined via extend() in the end. This
incurs an avoidable copy per frame. By having the next_frame() function
write into a given Span, there's only one vector allocated per call to
get_more_samples().

This increases performance by at least 100% realtime, as measured by
abench, from about 1200%-1300% to (usually) 1400% on complex test files.
This commit is contained in:
kleines Filmröllchen 2021-12-17 18:42:36 +01:00 committed by Andreas Kling
parent 30130904f5
commit b48badc3b6
Notes: sideshowbarker 2024-07-17 21:46:34 +09:00 
Author: https://github.com/kleinesfilmroellchen
Commit: https://github.com/SerenityOS/serenity/commit/b48badc3b63
Pull-request: https://github.com/SerenityOS/serenity/pull/11290
2 changed files with 42 additions and 30 deletions
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65
Userland/Libraries/LibAudio/FlacLoader.cpp
View File

@ -5,6 +5,7 @@
*/
#include <AK/Debug.h>
#include <AK/FixedArray.h>
#include <AK/FlyString.h>
#include <AK/Format.h>
#include <AK/Math.h>
@ -13,6 +14,7 @@
#include <AK/String.h>
#include <AK/StringBuilder.h>
#include <AK/Try.h>
#include <AK/TypedTransfer.h>
#include <AK/UFixedBigInt.h>
#include <LibAudio/Buffer.h>
#include <LibAudio/FlacLoader.h>
@ -190,41 +192,41 @@ MaybeLoaderError FlacLoaderPlugin::seek(const int position)
LoaderSamples FlacLoaderPlugin::get_more_samples(size_t max_bytes_to_read_from_input)
{
Vector<Sample> samples;
ssize_t remaining_samples = static_cast<ssize_t>(m_total_samples - m_loaded_samples);
if (remaining_samples <= 0)
return Buffer::create_empty();
size_t samples_to_read = min(max_bytes_to_read_from_input, remaining_samples);
samples.ensure_capacity(samples_to_read);
while (samples_to_read > 0) {
if (!m_current_frame.has_value())
TRY(next_frame());
auto samples = FixedArray<Sample>(samples_to_read);
size_t sample_index = 0;
// Do a full vector extend if possible
if (m_current_frame_data.size() <= samples_to_read) {
samples_to_read -= m_current_frame_data.size();
samples.extend(move(m_current_frame_data));
m_current_frame_data.clear();
m_current_frame.clear();
} else {
samples.unchecked_append(m_current_frame_data.data(), samples_to_read);
m_current_frame_data.remove(0, samples_to_read);
if (m_current_frame_data.size() == 0) {
m_current_frame.clear();
}
samples_to_read = 0;
}
if (m_unread_data.size() > 0) {
size_t to_transfer = min(m_unread_data.size(), samples_to_read);
dbgln_if(AFLACLOADER_DEBUG, "Reading {} samples from unread sample buffer (size {})", to_transfer, m_unread_data.size());
AK::TypedTransfer<Sample>::move(samples.data(), m_unread_data.data(), to_transfer);
if (to_transfer < m_unread_data.size())
m_unread_data.remove(0, to_transfer);
else
m_unread_data.clear_with_capacity();
sample_index += to_transfer;
}
m_loaded_samples += samples.size();
while (sample_index < samples_to_read) {
TRY(next_frame(samples.span().slice(sample_index)));
sample_index += m_current_frame->sample_count;
if (m_stream->handle_any_error())
return LoaderError { LoaderError::Category::IO, m_loaded_samples, "Unknown I/O error" };
}
m_loaded_samples += sample_index;
auto maybe_buffer = Buffer::create_with_samples(move(samples));
if (maybe_buffer.is_error())
return LoaderError { LoaderError::Category::Internal, m_loaded_samples, "Couldn't allocate sample buffer" };
return maybe_buffer.release_value();
}
MaybeLoaderError FlacLoaderPlugin::next_frame()
MaybeLoaderError FlacLoaderPlugin::next_frame(Span<Sample> target_vector)
{
#define FLAC_VERIFY(check, category, msg) \
do { \
@ -293,13 +295,14 @@ MaybeLoaderError FlacLoaderPlugin::next_frame()
for (u8 i = 0; i < subframe_count; ++i) {
FlacSubframeHeader new_subframe = TRY(next_subframe_header(bit_stream, i));
Vector<i32> subframe_samples = TRY(parse_subframe(new_subframe, bit_stream));
current_subframes.append(move(subframe_samples));
current_subframes.unchecked_append(move(subframe_samples));
}
bit_stream.align_to_byte_boundary();
// TODO: check checksum, see above
[[maybe_unused]] u16 footer_checksum = static_cast<u16>(bit_stream.read_bits_big_endian(16));
dbgln_if(AFLACLOADER_DEBUG, "Subframe footer checksum: {}", footer_checksum);
Vector<i32> left;
Vector<i32> right;
@ -352,17 +355,25 @@ MaybeLoaderError FlacLoaderPlugin::next_frame()
break;
}
VERIFY(left.size() == right.size());
VERIFY(left.size() == right.size() && left.size() == m_current_frame->sample_count);
double sample_rescale = static_cast<double>(1 << (pcm_bits_per_sample(m_current_frame->bit_depth) - 1));
dbgln_if(AFLACLOADER_DEBUG, "Sample rescaled from {} bits: factor {:.1f}", pcm_bits_per_sample(m_current_frame->bit_depth), sample_rescale);
m_current_frame_data.clear_with_capacity();
m_current_frame_data.ensure_capacity(left.size());
// zip together channels
for (size_t i = 0; i < left.size(); ++i) {
auto samples_to_directly_copy = min(target_vector.size(), m_current_frame->sample_count);
for (size_t i = 0; i < samples_to_directly_copy; ++i) {
Sample frame = { left[i] / sample_rescale, right[i] / sample_rescale };
m_current_frame_data.unchecked_append(frame);
target_vector[i] = frame;
}
// move superflous data into the class buffer instead
auto result = m_unread_data.try_grow_capacity(m_current_frame->sample_count - samples_to_directly_copy);
if (result.is_error())
return LoaderError { LoaderError::Category::Internal, static_cast<size_t>(samples_to_directly_copy + m_current_sample_or_frame), "Couldn't allocate sample buffer for superflous data" };
for (size_t i = samples_to_directly_copy; i < m_current_frame->sample_count; ++i) {
Sample frame = { left[i] / sample_rescale, right[i] / sample_rescale };
m_unread_data.unchecked_append(frame);
}
return {};

7
Userland/Libraries/LibAudio/FlacLoader.h
View File

@ -111,8 +111,8 @@ private:
// Either returns the metadata block or sets error message.
// Additionally, increments m_data_start_location past the read meta block.
ErrorOr<FlacRawMetadataBlock, LoaderError> next_meta_block(InputBitStream& bit_input);
// Fetches and sets the next FLAC frame
MaybeLoaderError next_frame();
// Fetches and writes the next FLAC frame
MaybeLoaderError next_frame(Span<Sample>);
// Helper of next_frame that fetches a sub frame's header
ErrorOr<FlacSubframeHeader, LoaderError> next_subframe_header(InputBitStream& bit_input, u8 channel_index);
// Helper of next_frame that decompresses a subframe
@ -151,7 +151,8 @@ private:
u64 m_data_start_location { 0 };
OwnPtr<FlacInputStream<FLAC_BUFFER_SIZE>> m_stream;
Optional<FlacFrameHeader> m_current_frame;
Vector<Sample> m_current_frame_data;
// Whatever the last get_more_samples() call couldn't return gets stored here.
Vector<Sample, FLAC_BUFFER_SIZE> m_unread_data;
u64 m_current_sample_or_frame { 0 };
};