244 lines
7.4 KiB
C++
244 lines
7.4 KiB
C++
#include <packager/media/formats/mp2t/mpeg1_header.h>
|
|
|
|
#include <packager/media/base/bit_reader.h>
|
|
#include <packager/media/base/bit_writer.h>
|
|
#include <packager/media/formats/mp2t/mp2t_common.h>
|
|
|
|
// Parsing is done according to
|
|
// https://www.datavoyage.com/mpgscript/mpeghdr.htm
|
|
namespace {
|
|
const size_t kMpeg1HeaderMinSize = 4;
|
|
|
|
const uint8_t kMpeg1V_INV = 0b01; /* Invalid version */
|
|
const uint8_t kMpeg1L_INV = 0b00; /* Invalid layer */
|
|
|
|
const uint8_t kMpeg1L_3 = 0b01;
|
|
const uint8_t kMpeg1L_2 = 0b10;
|
|
const uint8_t kMpeg1L_1 = 0b11;
|
|
|
|
const size_t kMpeg1SamplesPerFrameTable[] = {
|
|
// L1, L2, L3
|
|
384, 1152, 1152};
|
|
|
|
const uint32_t kMpeg1SampleRateTable[][3] = {
|
|
// clang-format off
|
|
// V1, V2, V2.5
|
|
{44100, 22050, 11025},
|
|
{48000, 24000, 12000},
|
|
{32000, 16000, 8000}};
|
|
// clang-format on
|
|
const size_t kMpeg1SampleRateTableSize = std::size(kMpeg1SampleRateTable);
|
|
|
|
static inline uint32_t Mpeg1SampleRate(uint8_t sr_idx, uint8_t version) {
|
|
static int sr_version_indexes[] = {2, -1, 1, 0}; // {V2.5, RESERVED, V2, V1}
|
|
DCHECK_NE(version, 1);
|
|
DCHECK_LT(sr_idx, kMpeg1SampleRateTableSize);
|
|
return kMpeg1SampleRateTable[sr_idx][sr_version_indexes[version]];
|
|
}
|
|
|
|
const uint32_t kMpeg1BitrateTable[][5] = {
|
|
// clang-format off
|
|
// V1:L1, V1:L2, V1:L3, V2:L1, V2&V2.5:L2&L3
|
|
{ 0, 0, 0, 0, 0},
|
|
{ 32, 32, 32, 32, 8},
|
|
{ 64, 48, 40, 48, 16},
|
|
{ 96, 56, 48, 56, 24},
|
|
{ 128, 64, 56, 64, 32},
|
|
{ 160, 80, 64, 80, 40},
|
|
{ 192, 96, 80, 96, 48},
|
|
{ 224, 112, 96, 112, 56},
|
|
{ 256, 128, 112, 128, 64},
|
|
{ 288, 160, 128, 144, 80},
|
|
{ 320, 192, 160, 160, 96},
|
|
{ 352, 224, 192, 176, 112},
|
|
{ 384, 256, 224, 192, 128},
|
|
{ 416, 320, 256, 224, 144},
|
|
{ 448, 384, 320, 256, 160}};
|
|
// clang-format on
|
|
const size_t kMpeg1BitrateTableSize = std::size(kMpeg1BitrateTable);
|
|
|
|
static inline uint32_t Mpeg1BitRate(uint8_t btr_idx,
|
|
uint8_t version,
|
|
uint8_t layer) {
|
|
static int btr_version_indexes[] = {1, -1, 1, 0}; // {V2.5, RESERVED, V2, V1}
|
|
static int btr_layer_indexes[] = {-1, 2, 1, 0}; // {RESERVED, L3, L2, L1}
|
|
|
|
DCHECK_NE(version, 1);
|
|
DCHECK_NE(layer, 0);
|
|
int vidx = btr_version_indexes[version];
|
|
int lidx = btr_layer_indexes[layer];
|
|
if (vidx == 1 && lidx > 1)
|
|
lidx = 1;
|
|
|
|
DCHECK_LT(vidx * 3 + lidx, 5);
|
|
DCHECK_LT(btr_idx, kMpeg1BitrateTableSize);
|
|
return kMpeg1BitrateTable[btr_idx][vidx * 3 + lidx] * 1000;
|
|
}
|
|
|
|
static inline size_t Mpeg1FrameSize(uint8_t layer,
|
|
uint32_t bitrate,
|
|
uint32_t sample_rate,
|
|
uint8_t padded) {
|
|
DCHECK_GT(sample_rate, static_cast<uint32_t>(0));
|
|
if (layer == kMpeg1L_1)
|
|
return (12 * bitrate / sample_rate + padded) * 4;
|
|
return 144 * bitrate / sample_rate + padded;
|
|
}
|
|
|
|
} // namespace
|
|
|
|
namespace shaka {
|
|
namespace media {
|
|
namespace mp2t {
|
|
|
|
bool Mpeg1Header::IsSyncWord(const uint8_t* buf) const {
|
|
return (buf[0] == 0xff) &&
|
|
((buf[1] & 0b11100000) == 0b11100000)
|
|
// Version 01 is reserved
|
|
&& ((buf[1] & 0b00011000) != 0b00001000)
|
|
// Layer 00 is reserved
|
|
&& ((buf[1] & 0b00000110) != 0b00000000);
|
|
}
|
|
|
|
size_t Mpeg1Header::GetMinFrameSize() const {
|
|
return kMpeg1HeaderMinSize + 1;
|
|
}
|
|
|
|
size_t Mpeg1Header::GetSamplesPerFrame() const {
|
|
static int spf_layer_indexes[] = {-1, 2, 1, 0}; // {RESERVED, L3, L2, L1}
|
|
DCHECK_NE(layer_, 0);
|
|
return kMpeg1SamplesPerFrameTable[spf_layer_indexes[layer_]];
|
|
}
|
|
|
|
bool Mpeg1Header::Parse(const uint8_t* mpeg1_frame, size_t mpeg1_frame_size) {
|
|
DCHECK(mpeg1_frame);
|
|
|
|
if (mpeg1_frame_size < kMpeg1HeaderMinSize)
|
|
return false;
|
|
|
|
BitReader frame(mpeg1_frame, mpeg1_frame_size);
|
|
// Verify frame starts with sync bits (0x7ff).
|
|
uint32_t sync;
|
|
RCHECK(frame.ReadBits(11, &sync));
|
|
RCHECK(sync == 0x7ff);
|
|
// MPEG version and layer.
|
|
RCHECK(frame.ReadBits(2, &version_));
|
|
RCHECK(version_ != kMpeg1V_INV);
|
|
RCHECK(frame.ReadBits(2, &layer_));
|
|
RCHECK(layer_ != kMpeg1L_INV);
|
|
RCHECK(frame.ReadBits(1, &protection_absent_));
|
|
|
|
uint8_t btr_idx;
|
|
RCHECK(frame.ReadBits(4, &btr_idx));
|
|
RCHECK(btr_idx > 0);
|
|
bitrate_ = Mpeg1BitRate(btr_idx, version_, layer_);
|
|
|
|
uint8_t sr_idx;
|
|
RCHECK(frame.ReadBits(2, &sr_idx));
|
|
RCHECK(sr_idx < 0b11);
|
|
sample_rate_ = Mpeg1SampleRate(sr_idx, version_);
|
|
|
|
RCHECK(frame.ReadBits(1, &padded_));
|
|
// Skip private stream bit.
|
|
RCHECK(frame.SkipBits(1));
|
|
|
|
RCHECK(frame.ReadBits(2, &channel_mode_));
|
|
// Skip Mode extension
|
|
RCHECK(frame.SkipBits(2));
|
|
// Skip copyright, origination and emphasis info.
|
|
RCHECK(frame.SkipBits(4));
|
|
|
|
return true;
|
|
}
|
|
|
|
size_t Mpeg1Header::GetHeaderSize() const {
|
|
// Unlike ADTS, for MP3, the whole frame is included in the media sample, so
|
|
// return 0 header size.
|
|
return 0;
|
|
}
|
|
|
|
size_t Mpeg1Header::GetFrameSize() const {
|
|
return Mpeg1FrameSize(layer_, bitrate_, sample_rate_, padded_);
|
|
}
|
|
|
|
size_t Mpeg1Header::GetFrameSizeWithoutParsing(const uint8_t* data,
|
|
size_t num_bytes) const {
|
|
DCHECK_GT(num_bytes, static_cast<size_t>(2));
|
|
uint8_t version = (data[1] & 0b00011000) >> 3;
|
|
uint8_t layer = (data[1] & 0b00000110) >> 1;
|
|
uint8_t btr_idx = (data[2] & 0b11110000) >> 4;
|
|
uint8_t sr_idx = (data[2] & 0b00001100) >> 2;
|
|
uint8_t padded = (data[2] & 0b00000010) >> 1;
|
|
|
|
if ((version == kMpeg1V_INV) || (layer == kMpeg1L_INV) || (btr_idx == 0) ||
|
|
(sr_idx == 0b11))
|
|
return 0;
|
|
|
|
uint32_t bitrate = Mpeg1BitRate(btr_idx, version, layer);
|
|
uint32_t samplerate = Mpeg1SampleRate(sr_idx, version);
|
|
return Mpeg1FrameSize(layer, bitrate, samplerate, padded);
|
|
}
|
|
|
|
void Mpeg1Header::GetAudioSpecificConfig(std::vector<uint8_t>* buffer) const {
|
|
// The following conversion table is extracted from ISO 14496 Part 3 -
|
|
// Table 1.16 - Sampling Frequency Index.
|
|
static const size_t kConfigFrequencyTable[] = {
|
|
96000, 88200, 64000, 48000, 44100, 32000, 24000,
|
|
22050, 16000, 12000, 11025, 8000, 7350};
|
|
static const size_t kConfigFrequencyTableSize =
|
|
std::size(kConfigFrequencyTable);
|
|
uint8_t cft_idx;
|
|
|
|
for (cft_idx = 0; cft_idx < kConfigFrequencyTableSize; cft_idx++)
|
|
if (sample_rate_ == kConfigFrequencyTable[cft_idx])
|
|
break;
|
|
|
|
DCHECK(buffer);
|
|
buffer->clear();
|
|
BitWriter config(buffer);
|
|
|
|
// ISO/IEC 14496:3 Table 1.16 Syntax of GetAudioObjetType()
|
|
auto object_type = GetObjectType();
|
|
if (object_type <= 31) {
|
|
config.WriteBits(object_type, 5);
|
|
} else {
|
|
config.WriteBits(31, 5);
|
|
config.WriteBits(object_type - 32, 6);
|
|
}
|
|
|
|
config.WriteBits(cft_idx, 4);
|
|
/*
|
|
* NOTE: Number of channels matches channel_configuration index,
|
|
* since mpeg1 audio has only 1 or 2 channels
|
|
*/
|
|
config.WriteBits(GetNumChannels(), 4);
|
|
config.Flush();
|
|
}
|
|
|
|
uint8_t Mpeg1Header::GetObjectType() const {
|
|
/*
|
|
* ISO14496-3:2009 Table 1.17 - Audio Object Types
|
|
*/
|
|
if (layer_ == kMpeg1L_1)
|
|
return 32;
|
|
if (layer_ == kMpeg1L_2)
|
|
return 33;
|
|
|
|
DCHECK_EQ(layer_, kMpeg1L_3);
|
|
return 34;
|
|
}
|
|
|
|
uint32_t Mpeg1Header::GetSamplingFrequency() const {
|
|
return sample_rate_;
|
|
}
|
|
|
|
uint8_t Mpeg1Header::GetNumChannels() const {
|
|
if (channel_mode_ == 0b11)
|
|
return 1;
|
|
return 2;
|
|
}
|
|
|
|
} // namespace mp2t
|
|
} // namespace media
|
|
} // namespace shaka
|