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LibAudio: Use symbolic constants for MP3 frame and granule size

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kleines Filmröllchen 2023-02-28 22:53:19 +01:00 committed by Jelle Raaijmakers
parent 264cc76ab4
commit 4420e48dc3
Notes: sideshowbarker 2024-07-18 02:47:59 +09:00 
Author: https://github.com/kleinesfilmroellchen
Commit: https://github.com/SerenityOS/serenity/commit/4420e48dc3
Pull-request: https://github.com/SerenityOS/serenity/pull/17642
Reviewed-by: https://github.com/Hendiadyoin1
Reviewed-by: https://github.com/gmta ✅
Reviewed-by: https://github.com/trflynn89
2 changed files with 24 additions and 19 deletions
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37
Userland/Libraries/LibAudio/MP3Loader.cpp
View File

@ -5,6 +5,7 @@
*/ */
#include "MP3Loader.h" #include "MP3Loader.h"
#include "LibAudio/MP3Types.h"
#include "MP3HuffmanTables.h" #include "MP3HuffmanTables.h"
#include "MP3Tables.h" #include "MP3Tables.h"
#include <AK/FixedArray.h> #include <AK/FixedArray.h>
@ -93,7 +94,7 @@ ErrorOr<Vector<FixedArray<Sample>>, LoaderError> MP3LoaderPlugin::load_chunks(si
int samples_to_read = samples_to_read_from_input; int samples_to_read = samples_to_read_from_input;
Vector<FixedArray<Sample>> frames; Vector<FixedArray<Sample>> frames;
while (samples_to_read > 0) { while (samples_to_read > 0) {
FixedArray<Sample> samples = LOADER_TRY(FixedArray<Sample>::create(1152)); FixedArray<Sample> samples = LOADER_TRY(FixedArray<Sample>::create(MP3::frame_size));
if (!m_current_frame.has_value()) { if (!m_current_frame.has_value()) {
auto maybe_frame = read_next_frame(); auto maybe_frame = read_next_frame();
@ -109,16 +110,16 @@ ErrorOr<Vector<FixedArray<Sample>>, LoaderError> MP3LoaderPlugin::load_chunks(si
} }
bool const is_stereo = m_current_frame->header.channel_count() == 2; bool const is_stereo = m_current_frame->header.channel_count() == 2;
auto current_frame_read = 0; size_t current_frame_read = 0;
for (; current_frame_read < 576; current_frame_read++) { for (; current_frame_read < MP3::granule_size; current_frame_read++) {
auto const left_sample = m_current_frame->channels[0].granules[0].pcm[current_frame_read / 32][current_frame_read % 32]; auto const left_sample = m_current_frame->channels[0].granules[0].pcm[current_frame_read / 32][current_frame_read % 32];
auto const right_sample = is_stereo ? m_current_frame->channels[1].granules[0].pcm[current_frame_read / 32][current_frame_read % 32] : left_sample; auto const right_sample = is_stereo ? m_current_frame->channels[1].granules[0].pcm[current_frame_read / 32][current_frame_read % 32] : left_sample;
samples[current_frame_read] = Sample { left_sample, right_sample }; samples[current_frame_read] = Sample { left_sample, right_sample };
samples_to_read--; samples_to_read--;
} }
for (; current_frame_read < 1152; current_frame_read++) { for (; current_frame_read < MP3::frame_size; current_frame_read++) {
auto const left_sample = m_current_frame->channels[0].granules[1].pcm[(current_frame_read - 576) / 32][(current_frame_read - 576) % 32]; auto const left_sample = m_current_frame->channels[0].granules[1].pcm[(current_frame_read - MP3::granule_size) / 32][(current_frame_read - MP3::granule_size) % 32];
auto const right_sample = is_stereo ? m_current_frame->channels[1].granules[1].pcm[(current_frame_read - 576) / 32][(current_frame_read - 576) % 32] : left_sample; auto const right_sample = is_stereo ? m_current_frame->channels[1].granules[1].pcm[(current_frame_read - MP3::granule_size) / 32][(current_frame_read - MP3::granule_size) % 32] : left_sample;
samples[current_frame_read] = Sample { left_sample, right_sample }; samples[current_frame_read] = Sample { left_sample, right_sample };
samples_to_read--; samples_to_read--;
} }
@ -146,7 +147,7 @@ MaybeLoaderError MP3LoaderPlugin::build_seek_table()
continue; continue;
} }
frame_count++; frame_count++;
sample_count += 1152; sample_count += MP3::frame_size;
if (frame_count % 10 == 0) if (frame_count % 10 == 0)
m_seek_table.append({ frame_pos, sample_count }); m_seek_table.append({ frame_pos, sample_count });
@ -269,7 +270,7 @@ ErrorOr<MP3::MP3Frame, LoaderError> MP3LoaderPlugin::read_frame_data(MP3::Header
for (size_t channel_index = 0; channel_index < header.channel_count(); channel_index++) { for (size_t channel_index = 0; channel_index < header.channel_count(); channel_index++) {
auto& granule = frame.channels[channel_index].granules[granule_index]; auto& granule = frame.channels[channel_index].granules[granule_index];
for (size_t i = 0; i < 576; i += 18) { for (size_t i = 0; i < MP3::granule_size; i += 18) {
MP3::BlockType block_type = granule.block_type; MP3::BlockType block_type = granule.block_type;
if (i < 36 && granule.mixed_block_flag) { if (i < 36 && granule.mixed_block_flag) {
// ISO/IEC 11172-3: if mixed_block_flag is set, the lowest two subbands are transformed with normal window. // ISO/IEC 11172-3: if mixed_block_flag is set, the lowest two subbands are transformed with normal window.
@ -357,9 +358,9 @@ MaybeLoaderError MP3LoaderPlugin::read_side_information(MP3::MP3Frame& frame)
} }
// From ISO/IEC 11172-3 (2.4.3.4.7.1) // From ISO/IEC 11172-3 (2.4.3.4.7.1)
Array<float, 576> MP3LoaderPlugin::calculate_frame_exponents(MP3::MP3Frame const& frame, size_t granule_index, size_t channel_index) Array<float, MP3::granule_size> MP3LoaderPlugin::calculate_frame_exponents(MP3::MP3Frame const& frame, size_t granule_index, size_t channel_index)
{ {
Array<float, 576> exponents; Array<float, MP3::granule_size> exponents;
auto fill_band = [&exponents](float exponent, size_t start, size_t end) { auto fill_band = [&exponents](float exponent, size_t start, size_t end) {
for (size_t j = start; j <= end; j++) { for (size_t j = start; j <= end; j++) {
@ -396,7 +397,7 @@ Array<float, 576> MP3LoaderPlugin::calculate_frame_exponents(MP3::MP3Frame const
float const gain1 = (gain - 8 * granule.sub_block_gain[1]) / 4.0; float const gain1 = (gain - 8 * granule.sub_block_gain[1]) / 4.0;
float const gain2 = (gain - 8 * granule.sub_block_gain[2]) / 4.0; float const gain2 = (gain - 8 * granule.sub_block_gain[2]) / 4.0;
while (sample_count < 576 && band_index < scale_factor_bands.size()) { while (sample_count < MP3::granule_size && band_index < scale_factor_bands.size()) {
float const exponent0 = gain0 - (scale_factor_multiplier * channel.scale_factors[band_index + 0]); float const exponent0 = gain0 - (scale_factor_multiplier * channel.scale_factors[band_index + 0]);
float const exponent1 = gain1 - (scale_factor_multiplier * channel.scale_factors[band_index + 1]); float const exponent1 = gain1 - (scale_factor_multiplier * channel.scale_factors[band_index + 1]);
float const exponent2 = gain2 - (scale_factor_multiplier * channel.scale_factors[band_index + 2]); float const exponent2 = gain2 - (scale_factor_multiplier * channel.scale_factors[band_index + 2]);
@ -411,7 +412,7 @@ Array<float, 576> MP3LoaderPlugin::calculate_frame_exponents(MP3::MP3Frame const
band_index += 3; band_index += 3;
} }
while (sample_count < 576) while (sample_count < MP3::granule_size)
exponents[sample_count++] = 0; exponents[sample_count++] = 0;
} }
return exponents; return exponents;
@ -496,7 +497,7 @@ MaybeLoaderError MP3LoaderPlugin::read_huffman_data(MP3::MP3Frame& frame, BigEnd
bool const is_short_granule = granule.window_switching_flag && granule.block_type == MP3::BlockType::Short; bool const is_short_granule = granule.window_switching_flag && granule.block_type == MP3::BlockType::Short;
size_t const region1_start = is_short_granule ? 36 : scale_factor_bands[scale_factor_band_index1].start; size_t const region1_start = is_short_granule ? 36 : scale_factor_bands[scale_factor_band_index1].start;
size_t const region2_start = is_short_granule ? 576 : scale_factor_bands[scale_factor_band_index2].start; size_t const region2_start = is_short_granule ? MP3::granule_size : scale_factor_bands[scale_factor_band_index2].start;
auto requantize = [](int const sample, float const exponent) -> float { auto requantize = [](int const sample, float const exponent) -> float {
int const sign = sample < 0 ? -1 : 1; int const sign = sample < 0 ? -1 : 1;
@ -560,7 +561,7 @@ MaybeLoaderError MP3LoaderPlugin::read_huffman_data(MP3::MP3Frame& frame, BigEnd
// until we've exhausted the granule's bits. We know the size of // until we've exhausted the granule's bits. We know the size of
// the granule from part2_3_length, which is the number of bits // the granule from part2_3_length, which is the number of bits
// used for scaleactors and huffman data (in the granule). // used for scaleactors and huffman data (in the granule).
while (granule_bits_read < granule.part_2_3_length && count <= 576 - 4) { while (granule_bits_read < granule.part_2_3_length && count <= MP3::granule_size - 4) {
auto const entry = MP3::Tables::Huffman::huffman_decode(reservoir, count1table, granule.part_2_3_length - granule_bits_read); auto const entry = MP3::Tables::Huffman::huffman_decode(reservoir, count1table, granule.part_2_3_length - granule_bits_read);
granule_bits_read += entry.bits_read; granule_bits_read += entry.bits_read;
if (!entry.code.has_value()) if (!entry.code.has_value())
@ -619,7 +620,7 @@ MaybeLoaderError MP3LoaderPlugin::read_huffman_data(MP3::MP3Frame& frame, BigEnd
void MP3LoaderPlugin::reorder_samples(MP3::Granule& granule, u32 sample_rate) void MP3LoaderPlugin::reorder_samples(MP3::Granule& granule, u32 sample_rate)
{ {
float tmp[576] = {}; float tmp[MP3::granule_size] = {};
size_t band_index = 0; size_t band_index = 0;
size_t subband_index = 0; size_t subband_index = 0;
@ -635,7 +636,7 @@ void MP3LoaderPlugin::reorder_samples(MP3::Granule& granule, u32 sample_rate)
} }
} }
while (subband_index < 576 && band_index <= 36) { while (subband_index < MP3::granule_size && band_index <= 36) {
for (size_t frequency_line_index = 0; frequency_line_index < scale_factor_bands[band_index].width; frequency_line_index++) { for (size_t frequency_line_index = 0; frequency_line_index < scale_factor_bands[band_index].width; frequency_line_index++) {
tmp[subband_index++] = granule.samples[scale_factor_bands[band_index + 0].start + frequency_line_index]; tmp[subband_index++] = granule.samples[scale_factor_bands[band_index + 0].start + frequency_line_index];
tmp[subband_index++] = granule.samples[scale_factor_bands[band_index + 1].start + frequency_line_index]; tmp[subband_index++] = granule.samples[scale_factor_bands[band_index + 1].start + frequency_line_index];
@ -644,7 +645,7 @@ void MP3LoaderPlugin::reorder_samples(MP3::Granule& granule, u32 sample_rate)
band_index += 3; band_index += 3;
} }
for (size_t i = 0; i < 576; i++) for (size_t i = 0; i < MP3::granule_size; i++)
granule.samples[i] = tmp[i]; granule.samples[i] = tmp[i];
} }
@ -738,7 +739,7 @@ void MP3LoaderPlugin::process_stereo(MP3::MP3Frame& frame, size_t granule_index)
} }
} }
void MP3LoaderPlugin::transform_samples_to_time(Array<float, 576> const& input, size_t input_offset, Array<float, 36>& output, MP3::BlockType block_type) void MP3LoaderPlugin::transform_samples_to_time(Array<float, MP3::granule_size> const& input, size_t input_offset, Array<float, 36>& output, MP3::BlockType block_type)
{ {
if (block_type == MP3::BlockType::Short) { if (block_type == MP3::BlockType::Short) {
size_t const N = 12; size_t const N = 12;

6
Userland/Libraries/LibAudio/MP3Types.h
View File

@ -12,6 +12,10 @@
namespace Audio::MP3 { namespace Audio::MP3 {
constexpr size_t const frame_size = 1152;
// 576 samples.
constexpr size_t const granule_size = frame_size / 2;
enum class Mode { enum class Mode {
Stereo = 0, Stereo = 0,
JointStereo = 1, JointStereo = 1,
@ -61,7 +65,7 @@ struct Header {
}; };
struct Granule { struct Granule {
Array<float, 576> samples; Array<float, MP3::granule_size> samples;
Array<Array<float, 18>, 32> filter_bank_input; Array<Array<float, 18>, 32> filter_bank_input;
Array<Array<float, 32>, 18> pcm; Array<Array<float, 32>, 18> pcm;
u32 part_2_3_length; u32 part_2_3_length;