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LibAudio: Handle all integer PCM sample formats "correctly" in WavWriter

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WavWriter needs a TON of modernization work, but for now this commit
just tackles two FIXMEs by converting samples correctly into all
supported integer PCM formats. The supported formats are only signed
16-bit and unsigned 8-bit for now, but can be expanded later. At least
we don't produce horrible speaker-destroying noise when writing any
other format.
This commit is contained in:
kleines Filmröllchen 2023-03-08 15:25:56 +01:00 • committed by Jelle Raaijmakers
parent 102fdf6305
commit cd2e890304
2 changed files with 44 additions and 23 deletions
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56
Userland/Libraries/LibAudio/WavWriter.cpp
View file

@ -5,21 +5,23 @@
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/Endian.h>
#include <LibAudio/WavLoader.h>
#include <LibAudio/WavWriter.h>
namespace Audio {
ErrorOr<NonnullOwnPtr<WavWriter>> WavWriter::create_from_file(StringView path, int sample_rate, u16 num_channels, u16 bits_per_sample)
ErrorOr<NonnullOwnPtr<WavWriter>> WavWriter::create_from_file(StringView path, int sample_rate, u16 num_channels, PcmSampleFormat sample_format)
{
auto wav_writer = TRY(adopt_nonnull_own_or_enomem(new (nothrow) WavWriter(sample_rate, num_channels, bits_per_sample)));
auto wav_writer = TRY(adopt_nonnull_own_or_enomem(new (nothrow) WavWriter(sample_rate, num_channels, sample_format)));
TRY(wav_writer->set_file(path));
return wav_writer;
}
WavWriter::WavWriter(int sample_rate, u16 num_channels, u16 bits_per_sample)
WavWriter::WavWriter(int sample_rate, u16 num_channels, PcmSampleFormat sample_format)
: m_sample_rate(sample_rate)
, m_num_channels(num_channels)
, m_bits_per_sample(bits_per_sample)
, m_sample_format(sample_format)
{
}
@ -39,15 +41,32 @@ ErrorOr<void> WavWriter::set_file(StringView path)
ErrorOr<void> WavWriter::write_samples(Span<Sample> samples)
{
m_data_sz += samples.size() * sizeof(Sample);
for (auto const& sample : samples) {
// FIXME: This only really works for 16-bit samples.
u16 left = static_cast<i16>(sample.left * static_cast<float>(1 << m_bits_per_sample));
u16 right = static_cast<i16>(sample.right * static_cast<float>(1 << m_bits_per_sample));
// FIXME: This ignores endianness.
TRY(m_file->write_value(left));
TRY(m_file->write_value(right));
switch (m_sample_format) {
// FIXME: For non-float formats, we don't add good quantization noise, leading to possibly unpleasant quantization artifacts.
case PcmSampleFormat::Uint8: {
constexpr float scale = static_cast<float>(NumericLimits<u8>::max()) * .5f;
for (auto const& sample : samples) {
u8 left = static_cast<u8>((sample.left + 1) * scale);
u8 right = static_cast<u8>((sample.right + 1) * scale);
TRY(m_file->write_value(left));
TRY(m_file->write_value(right));
}
m_data_sz += samples.size() * 2 * sizeof(u8);
break;
}
case PcmSampleFormat::Int16: {
constexpr float scale = static_cast<float>(NumericLimits<i16>::max());
for (auto const& sample : samples) {
u16 left = AK::convert_between_host_and_little_endian(static_cast<i16>(sample.left * scale));
u16 right = AK::convert_between_host_and_little_endian(static_cast<i16>(sample.right * scale));
TRY(m_file->write_value(left));
TRY(m_file->write_value(right));
}
m_data_sz += samples.size() * 2 * sizeof(u16);
break;
}
default:
VERIFY_NOT_REACHED();
}
return {};
@ -93,21 +112,22 @@ ErrorOr<void> WavWriter::write_header()
static u32 fmt_size = 16;
TRY(m_file->write_value(fmt_size));
// 1 for PCM
static u16 audio_format = 1;
static u16 audio_format = to_underlying(RIFF::WaveFormat::Pcm);
TRY(m_file->write_value(audio_format));
TRY(m_file->write_value(m_num_channels));
TRY(m_file->write_value(m_sample_rate));
u32 byte_rate = m_sample_rate * m_num_channels * (m_bits_per_sample / 8);
VERIFY(m_sample_format == PcmSampleFormat::Int16 || m_sample_format == PcmSampleFormat::Uint8);
u16 bits_per_sample = pcm_bits_per_sample(m_sample_format);
u32 byte_rate = m_sample_rate * m_num_channels * (bits_per_sample / 8);
TRY(m_file->write_value(byte_rate));
u16 block_align = m_num_channels * (m_bits_per_sample / 8);
u16 block_align = m_num_channels * (bits_per_sample / 8);
TRY(m_file->write_value(block_align));
TRY(m_file->write_value(m_bits_per_sample));
TRY(m_file->write_value(bits_per_sample));
// "data"
static u32 chunk_id = 0x61746164;