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LibAudio: Make MP3LoaderPlugin::read_header() static

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This will allow us to use the function when sniffing for an MP3 file to
enable consistent checks for valid frame headers.
This commit is contained in:
Zaggy1024 2023-08-25 23:04:05 -05:00 • committed by Tim Flynn
parent e087d35cd8
commit 1847155b12
2 changed files with 21 additions and 21 deletions
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40
Userland/Libraries/LibAudio/MP3Loader.cpp
View file

@ -88,7 +88,7 @@ MaybeLoaderError MP3LoaderPlugin::initialize()
TRY(seek(0)); TRY(seek(0));
TRY(synchronize()); TRY(synchronize());
auto header = TRY(read_header()); auto header = TRY(read_header(*m_bitstream, 0));
if (header.id != 1 || header.layer != 3) if (header.id != 1 || header.layer != 3)
return LoaderError { LoaderError::Category::Format, "Only MPEG-1 layer 3 supported." }; return LoaderError { LoaderError::Category::Format, "Only MPEG-1 layer 3 supported." };
@ -181,7 +181,7 @@ MaybeLoaderError MP3LoaderPlugin::build_seek_table()
while (!synchronize().is_error()) { while (!synchronize().is_error()) {
auto const frame_pos = -2 + TRY(m_stream->seek(0, SeekMode::FromCurrentPosition)); auto const frame_pos = -2 + TRY(m_stream->seek(0, SeekMode::FromCurrentPosition));
auto error_or_header = read_header(); auto error_or_header = read_header(*m_bitstream, m_loaded_samples);
if (error_or_header.is_error() || error_or_header.value().id != 1 || error_or_header.value().layer != 3) { if (error_or_header.is_error() || error_or_header.value().id != 1 || error_or_header.value().layer != 3) {
continue; continue;
} }
@ -202,30 +202,30 @@ MaybeLoaderError MP3LoaderPlugin::build_seek_table()
return {}; return {};
} }
ErrorOr<MP3::Header, LoaderError> MP3LoaderPlugin::read_header() ErrorOr<MP3::Header, LoaderError> MP3LoaderPlugin::read_header(BigEndianInputBitStream& stream, size_t sample_index)
{ {
MP3::Header header; MP3::Header header;
header.id = TRY(m_bitstream->read_bit()); header.id = TRY(stream.read_bit());
header.layer = MP3::Tables::LayerNumberLookup[TRY(m_bitstream->read_bits(2))]; header.layer = MP3::Tables::LayerNumberLookup[TRY(stream.read_bits(2))];
if (header.layer <= 0) if (header.layer <= 0)
return LoaderError { LoaderError::Category::Format, m_loaded_samples, "Frame header contains invalid layer number." }; return LoaderError { LoaderError::Category::Format, sample_index, "Frame header contains invalid layer number." };
header.protection_bit = TRY(m_bitstream->read_bit()); header.protection_bit = TRY(stream.read_bit());
header.bitrate = MP3::Tables::BitratesPerLayerLookup[header.layer - 1][TRY(m_bitstream->read_bits(4))]; header.bitrate = MP3::Tables::BitratesPerLayerLookup[header.layer - 1][TRY(stream.read_bits(4))];
if (header.bitrate <= 0) if (header.bitrate <= 0)
return LoaderError { LoaderError::Category::Format, m_loaded_samples, "Frame header contains invalid bitrate." }; return LoaderError { LoaderError::Category::Format, sample_index, "Frame header contains invalid bitrate." };
header.samplerate = MP3::Tables::SampleratesLookup[TRY(m_bitstream->read_bits(2))]; header.samplerate = MP3::Tables::SampleratesLookup[TRY(stream.read_bits(2))];
if (header.samplerate <= 0) if (header.samplerate <= 0)
return LoaderError { LoaderError::Category::Format, m_loaded_samples, "Frame header contains invalid samplerate." }; return LoaderError { LoaderError::Category::Format, sample_index, "Frame header contains invalid samplerate." };
header.padding_bit = TRY(m_bitstream->read_bit()); header.padding_bit = TRY(stream.read_bit());
header.private_bit = TRY(m_bitstream->read_bit()); header.private_bit = TRY(stream.read_bit());
header.mode = static_cast<MP3::Mode>(TRY(m_bitstream->read_bits(2))); header.mode = static_cast<MP3::Mode>(TRY(stream.read_bits(2)));
header.mode_extension = static_cast<MP3::ModeExtension>(TRY(m_bitstream->read_bits(2))); header.mode_extension = static_cast<MP3::ModeExtension>(TRY(stream.read_bits(2)));
header.copyright_bit = TRY(m_bitstream->read_bit()); header.copyright_bit = TRY(stream.read_bit());
header.original_bit = TRY(m_bitstream->read_bit()); header.original_bit = TRY(stream.read_bit());
header.emphasis = static_cast<MP3::Emphasis>(TRY(m_bitstream->read_bits(2))); header.emphasis = static_cast<MP3::Emphasis>(TRY(stream.read_bits(2)));
header.header_size = 4; header.header_size = 4;
if (!header.protection_bit) { if (!header.protection_bit) {
header.crc16 = TRY(m_bitstream->read_bits<u16>(16)); header.crc16 = TRY(stream.read_bits<u16>(16));
header.header_size += 2; header.header_size += 2;
} }
header.frame_size = 144 * header.bitrate * 1000 / header.samplerate + header.padding_bit; header.frame_size = 144 * header.bitrate * 1000 / header.samplerate + header.padding_bit;
@ -259,7 +259,7 @@ ErrorOr<MP3::MP3Frame, LoaderError> MP3LoaderPlugin::read_next_frame()
// In the second case, the error will bubble up from read_frame_data(). // In the second case, the error will bubble up from read_frame_data().
while (true) { while (true) {
TRY(synchronize()); TRY(synchronize());
MP3::Header header = TRY(read_header()); MP3::Header header = TRY(read_header(*m_bitstream, m_loaded_samples));
if (header.id != 1 || header.layer != 3) { if (header.id != 1 || header.layer != 3) {
continue; continue;
} }

2
Userland/Libraries/LibAudio/MP3Loader.h
View file

@ -43,9 +43,9 @@ private:
MaybeLoaderError initialize(); MaybeLoaderError initialize();
static MaybeLoaderError skip_id3(SeekableStream& stream); static MaybeLoaderError skip_id3(SeekableStream& stream);
static MaybeLoaderError synchronize(BigEndianInputBitStream& stream, size_t sample_index); static MaybeLoaderError synchronize(BigEndianInputBitStream& stream, size_t sample_index);
static ErrorOr<MP3::Header, LoaderError> read_header(BigEndianInputBitStream& stream, size_t sample_index);
MaybeLoaderError synchronize(); MaybeLoaderError synchronize();
MaybeLoaderError build_seek_table(); MaybeLoaderError build_seek_table();
ErrorOr<MP3::Header, LoaderError> read_header();
ErrorOr<MP3::MP3Frame, LoaderError> read_next_frame(); ErrorOr<MP3::MP3Frame, LoaderError> read_next_frame();
ErrorOr<MP3::MP3Frame, LoaderError> read_frame_data(MP3::Header const&); ErrorOr<MP3::MP3Frame, LoaderError> read_frame_data(MP3::Header const&);
MaybeLoaderError read_side_information(MP3::MP3Frame&); MaybeLoaderError read_side_information(MP3::MP3Frame&);