diff options
Diffstat (limited to 'Src/replicant/nsmp3/MPEGHeader.cpp')
| -rw-r--r-- | Src/replicant/nsmp3/MPEGHeader.cpp | 170 |
1 files changed, 170 insertions, 0 deletions
diff --git a/Src/replicant/nsmp3/MPEGHeader.cpp b/Src/replicant/nsmp3/MPEGHeader.cpp new file mode 100644 index 00000000..1971577e --- /dev/null +++ b/Src/replicant/nsmp3/MPEGHeader.cpp @@ -0,0 +1,170 @@ +#include "MPEGHeader.h" +#include <math.h> + +// [mpeg_version][layer][index] +static const int bitrates[4][4][15] = +{ + { + // MPEG-2.5 + { 0,}, + { 0, 8000, 16000, 24000, 32000, 40000, 48000, 56000, 64000, 80000, 96000, 112000, 128000, 144000, 160000}, // Layer 3 + { 0, 8000, 16000, 24000, 32000, 40000, 48000, 56000, 64000, 80000, 96000, 112000, 128000, 144000, 160000}, // Layer 2 + { 0, 32000, 48000, 56000, 64000, 80000, 96000, 112000, 128000, 144000, 160000, 176000, 192000, 224000, 256000}, // Layer 1 + }, + + { + // invalid + { 0, }, + { 0, }, + { 0, }, + { 0, }, + }, + + { + // MPEG-2 + { 0,}, + { 0, 8000, 16000, 24000, 32000, 40000, 48000, 56000, 64000, 80000, 96000, 112000, 128000, 144000, 160000}, // Layer 3 + { 0, 8000, 16000, 24000, 32000, 40000, 48000, 56000, 64000, 80000, 96000, 112000, 128000, 144000, 160000}, // Layer 2 + { 0, 32000, 48000, 56000, 64000, 80000, 96000, 112000, 128000, 144000, 160000, 176000, 192000, 224000, 256000}, // Layer 1 + }, + + { + // MPEG-1 + { 0,}, + { 0, 32000, 40000, 48000, 56000, 64000, 80000, 96000, 112000, 128000, 160000, 192000, 224000, 256000, 320000}, // Layer 3 + { 0, 32000, 48000, 56000, 64000, 80000, 96000, 112000, 128000, 160000, 192000, 224000, 256000, 320000, 384000}, // Layer 2 + { 0, 32000, 64000, 96000, 128000, 160000, 192000, 224000, 256000, 288000, 320000, 352000, 384000, 416000, 448000}, // Layer 1 + }, +}; + +// [mpeg_version][index] +static const int sample_rates[4][4] = +{ + {11025, 12000, 8000, 0}, // MPEG-2.5 + {0, }, + {22050, 24000, 16000, 0}, // MPEG-2 + {44100, 48000, 32000, 0}, // MPEG-1 +}; + +// [mpeg_version][layer] +static const int samples_per_frame[4][4] = +{ + // Layer 3, Layer 2, Layer 1 + { 0, 576, 1152, 384}, // MPEG2.5 + { 0, }, + { 0, 576, 1152, 384}, // MPEG2 + { 0, 1152, 1152, 384}, // MPEG1 +}; + +// [layer] +static const int bits_per_slot[4] = { 0, 8, 8, 32 }; + +void MPEGHeader::ReadBuffer(const uint8_t *buffer) +{ + sync = ((uint16_t)buffer[0] << 3) | (buffer[1] >> 5); + mpeg_version = (buffer[1] >> 3) & 3; + layer = (buffer[1] >> 1) & 3; + protection = (buffer[1]) & 1; + bitrate_index = (buffer[2] >> 4) & 0xF; + sample_rate_index = (buffer[2] >> 2) & 3; + padding_bit = (buffer[2] >> 1) & 1; + private_bit = buffer[2] & 1; + channel_mode = (buffer[3] >> 6) & 3; + mode_extension = (buffer[3] >> 4) & 3; + copyright = (buffer[3] >> 3) & 1; + original = (buffer[3] >> 2) & 1; + emphasis = (buffer[3]) & 3; +} + +bool MPEGHeader::IsSync() const +{ + return sync == 0x07FF + && layer != LayerError + && mpeg_version != MPEG_Error + && bitrate_index != 15 + && bitrate_index != 0 + && sample_rate_index != 3 + && !(mpeg_version == MPEG2 && layer != Layer3) + && !(mpeg_version == MPEG2_5 && layer != Layer3); +} + +int MPEGHeader::GetBitrate() const +{ + return bitrates[mpeg_version][layer][bitrate_index]; +} + +int MPEGHeader::HeaderSize() const +{ + if (protection == CRC) + return 4 + 2; // 32bits frame header, 16bits CRC + else + return 4; // 32bits frame ehader +} + +int MPEGHeader::GetSampleRate() const +{ + return sample_rates[mpeg_version][sample_rate_index]; +} + +bool MPEGHeader::IsCopyright() const +{ + return copyright == 1; +} +bool MPEGHeader::IsCRC() const +{ + return protection == CRC; +} + +bool MPEGHeader::IsOriginal() const +{ + return original == 1; +} + +int MPEGHeader::GetSamplesPerFrame() const +{ + return samples_per_frame[mpeg_version][layer]; +} + +int MPEGHeader::FrameSize() const +{ + int nBitsPerSlot; + int nAvgSlotsPerFrame; + + nBitsPerSlot = bits_per_slot[layer]; + + nAvgSlotsPerFrame = (GetSamplesPerFrame() * (bitrates[mpeg_version][layer][bitrate_index] / nBitsPerSlot)) / sample_rates[mpeg_version][sample_rate_index]; + + return (nAvgSlotsPerFrame + padding_bit) * nBitsPerSlot / 8; +} + +int MPEGHeader::GetLayer() const +{ + switch(layer) + { + case Layer1: + return 1; + case Layer2: + return 2; + case Layer3: + return 3; + default: + return 0; + } +} + +int MPEGHeader::GetNumChannels() const +{ + switch(channel_mode) + { + case Stereo: + return 2; + case JointStereo: + return 2; + case DualChannel: + return 2; + case Mono: + return 1; + default: + return 0; + } +} |