From 2767136947208ade6afe3ea8783ac431b8d45a0c Mon Sep 17 00:00:00 2001 From: Hajime Hoshi Date: Sun, 18 Jun 2017 17:37:46 +0900 Subject: [PATCH] audio/mp3: Refactoring: readSideInfo (was readAudioL3) returns *mpeg1SideInfo --- audio/mp3/decode_notjs.go | 9 +--- audio/mp3/l3.go | 2 +- audio/mp3/maindata.go | 4 +- audio/mp3/read.go | 4 +- audio/mp3/sideinfo.go | 90 +++++++++++++++------------------------ audio/mp3/types.go | 32 +++++++++++++- 6 files changed, 72 insertions(+), 69 deletions(-) diff --git a/audio/mp3/decode_notjs.go b/audio/mp3/decode_notjs.go index 29cac5204..c399e4392 100644 --- a/audio/mp3/decode_notjs.go +++ b/audio/mp3/decode_notjs.go @@ -28,16 +28,9 @@ var ( readerEOF bool ) -func (f *frame) numberOfChannels() int { - if f.header.mode == mpeg1ModeSingleChannel { - return 1 - } - return 2 -} - func (f *frame) decodeL3() []uint8 { out := make([]uint8, 576*4*2) - nch := f.numberOfChannels() + nch := f.header.numberOfChannels() for gr := 0; gr < 2; gr++ { for ch := 0; ch < nch; ch++ { f.l3Requantize(gr, ch) diff --git a/audio/mp3/l3.go b/audio/mp3/l3.go index eab1813eb..626f59e3c 100644 --- a/audio/mp3/l3.go +++ b/audio/mp3/l3.go @@ -552,7 +552,7 @@ func (f *frame) l3SubbandSynthesis(gr int, ch int, out []uint8) { u_vec := make([]float32, 512) s_vec := make([]float32, 32) - nch := f.numberOfChannels() + nch := f.header.numberOfChannels() /* Setup the n_win windowing vector and the v_vec intermediate vector */ for ss := 0; ss < 18; ss++ { /* Loop through 18 samples in 32 subbands */ for i := 1023; i > 63; i-- { /* Shift up the V vector */ diff --git a/audio/mp3/maindata.go b/audio/mp3/maindata.go index 7e396cd2f..8f56a6a36 100644 --- a/audio/mp3/maindata.go +++ b/audio/mp3/maindata.go @@ -27,9 +27,9 @@ var mpeg1_scalefac_sizes = [16][2]int{ } func (f *frame) readMainL3() error { - nch := f.numberOfChannels() + nch := f.header.numberOfChannels() // Calculate header audio data size - framesize := f.size() + framesize := f.header.frameSize() if framesize > 2000 { return fmt.Errorf("mp3: framesize = %d", framesize) } diff --git a/audio/mp3/read.go b/audio/mp3/read.go index c36b90259..52f511d7b 100644 --- a/audio/mp3/read.go +++ b/audio/mp3/read.go @@ -63,9 +63,11 @@ func (f *frame) readNextFrame() (*frame, error) { return nil, fmt.Errorf("mp3: only layer3 (want %d; got %d) is supported!", mpeg1Layer3, nf.header.layer) } // Get side info - if err := nf.readAudioL3(); err != nil { + s, err := readSideInfo(&nf.header) + if err != nil { return nil, err } + nf.sideInfo = s // If there's not enough main data in the bit reservoir, // signal to calling function so that decoding isn't done! // Get main data(scalefactors and Huffman coded frequency data) diff --git a/audio/mp3/sideinfo.go b/audio/mp3/sideinfo.go index 2a497e764..6fb270246 100644 --- a/audio/mp3/sideinfo.go +++ b/audio/mp3/sideinfo.go @@ -21,35 +21,12 @@ import ( "io" ) -var mpeg1Bitrates = map[mpeg1Layer][15]int{ - mpeg1Layer1: { - 0, 32000, 64000, 96000, 128000, 160000, 192000, 224000, - 256000, 288000, 320000, 352000, 384000, 416000, 448000, - }, - mpeg1Layer2: { - 0, 32000, 48000, 56000, 64000, 80000, 96000, 112000, - 128000, 160000, 192000, 224000, 256000, 320000, 384000, - }, - mpeg1Layer3: { - 0, 32000, 40000, 48000, 56000, 64000, 80000, 96000, - 112000, 128000, 160000, 192000, 224000, 256000, 320000, - }, -} - -var samplingFrequency = [3]int{44100, 48000, 32000} - -func (f *frame) size() int { - return (144*mpeg1Bitrates[f.header.layer][f.header.bitrate_index])/ - samplingFrequency[f.header.sampling_frequency] + - int(f.header.padding_bit) -} - -func (f *frame) readAudioL3() error { - nch := f.numberOfChannels() +func readSideInfo(header *mpeg1FrameHeader) (*mpeg1SideInfo, error) { + nch := header.numberOfChannels() /* Calculate header audio data size */ - framesize := f.size() + framesize := header.frameSize() if framesize > 2000 { - return fmt.Errorf("mp3: framesize = %d\n", framesize) + return nil, fmt.Errorf("mp3: framesize = %d\n", framesize) } /* Sideinfo is 17 bytes for one channel and 32 bytes for two */ sideinfo_size := 32 @@ -59,67 +36,68 @@ func (f *frame) readAudioL3() error { /* Main data size is the rest of the frame,including ancillary data */ main_data_size := framesize - sideinfo_size - 4 /* sync+header */ /* CRC is 2 bytes */ - if f.header.protection_bit == 0 { + if header.protection_bit == 0 { main_data_size -= 2 } /* Read sideinfo from bitstream into buffer used by getSideBits() */ s, err := getSideinfo(sideinfo_size) if err != nil { - return err + return nil, err } /* Parse audio data */ /* Pointer to where we should start reading main data */ - f.sideInfo.main_data_begin = s.getSideBits(9) + si := &mpeg1SideInfo{} + si.main_data_begin = s.getSideBits(9) /* Get private bits. Not used for anything. */ - if f.header.mode == mpeg1ModeSingleChannel { - f.sideInfo.private_bits = s.getSideBits(5) + if header.mode == mpeg1ModeSingleChannel { + si.private_bits = s.getSideBits(5) } else { - f.sideInfo.private_bits = s.getSideBits(3) + si.private_bits = s.getSideBits(3) } /* Get scale factor selection information */ for ch := 0; ch < nch; ch++ { for scfsi_band := 0; scfsi_band < 4; scfsi_band++ { - f.sideInfo.scfsi[ch][scfsi_band] = s.getSideBits(1) + si.scfsi[ch][scfsi_band] = s.getSideBits(1) } } /* Get the rest of the side information */ for gr := 0; gr < 2; gr++ { for ch := 0; ch < nch; ch++ { - f.sideInfo.part2_3_length[gr][ch] = s.getSideBits(12) - f.sideInfo.big_values[gr][ch] = s.getSideBits(9) - f.sideInfo.global_gain[gr][ch] = s.getSideBits(8) - f.sideInfo.scalefac_compress[gr][ch] = s.getSideBits(4) - f.sideInfo.win_switch_flag[gr][ch] = s.getSideBits(1) - if f.sideInfo.win_switch_flag[gr][ch] == 1 { - f.sideInfo.block_type[gr][ch] = s.getSideBits(2) - f.sideInfo.mixed_block_flag[gr][ch] = s.getSideBits(1) + si.part2_3_length[gr][ch] = s.getSideBits(12) + si.big_values[gr][ch] = s.getSideBits(9) + si.global_gain[gr][ch] = s.getSideBits(8) + si.scalefac_compress[gr][ch] = s.getSideBits(4) + si.win_switch_flag[gr][ch] = s.getSideBits(1) + if si.win_switch_flag[gr][ch] == 1 { + si.block_type[gr][ch] = s.getSideBits(2) + si.mixed_block_flag[gr][ch] = s.getSideBits(1) for region := 0; region < 2; region++ { - f.sideInfo.table_select[gr][ch][region] = s.getSideBits(5) + si.table_select[gr][ch][region] = s.getSideBits(5) } for window := 0; window < 3; window++ { - f.sideInfo.subblock_gain[gr][ch][window] = s.getSideBits(3) + si.subblock_gain[gr][ch][window] = s.getSideBits(3) } - if (f.sideInfo.block_type[gr][ch] == 2) && (f.sideInfo.mixed_block_flag[gr][ch] == 0) { - f.sideInfo.region0_count[gr][ch] = 8 /* Implicit */ + if (si.block_type[gr][ch] == 2) && (si.mixed_block_flag[gr][ch] == 0) { + si.region0_count[gr][ch] = 8 /* Implicit */ } else { - f.sideInfo.region0_count[gr][ch] = 7 /* Implicit */ + si.region0_count[gr][ch] = 7 /* Implicit */ } /* The standard is wrong on this!!! */ /* Implicit */ - f.sideInfo.region1_count[gr][ch] = 20 - f.sideInfo.region0_count[gr][ch] + si.region1_count[gr][ch] = 20 - si.region0_count[gr][ch] } else { for region := 0; region < 3; region++ { - f.sideInfo.table_select[gr][ch][region] = s.getSideBits(5) + si.table_select[gr][ch][region] = s.getSideBits(5) } - f.sideInfo.region0_count[gr][ch] = s.getSideBits(4) - f.sideInfo.region1_count[gr][ch] = s.getSideBits(3) - f.sideInfo.block_type[gr][ch] = 0 /* Implicit */ + si.region0_count[gr][ch] = s.getSideBits(4) + si.region1_count[gr][ch] = s.getSideBits(3) + si.block_type[gr][ch] = 0 /* Implicit */ } - f.sideInfo.preflag[gr][ch] = s.getSideBits(1) - f.sideInfo.scalefac_scale[gr][ch] = s.getSideBits(1) - f.sideInfo.count1table_select[gr][ch] = s.getSideBits(1) + si.preflag[gr][ch] = s.getSideBits(1) + si.scalefac_scale[gr][ch] = s.getSideBits(1) + si.count1table_select[gr][ch] = s.getSideBits(1) } } - return nil + return si, nil } // A sideInfoBytes is a bit reservoir for side info diff --git a/audio/mp3/types.go b/audio/mp3/types.go index 5deaaff6e..322a26463 100644 --- a/audio/mp3/types.go +++ b/audio/mp3/types.go @@ -87,10 +87,40 @@ type frame struct { prev *frame header mpeg1FrameHeader - sideInfo mpeg1SideInfo + sideInfo *mpeg1SideInfo mainData mpeg1MainData mainDataBytes *mainDataBytes store [2][32][18]float32 v_vec [2][1024]float32 } + +var mpeg1Bitrates = map[mpeg1Layer][15]int{ + mpeg1Layer1: { + 0, 32000, 64000, 96000, 128000, 160000, 192000, 224000, + 256000, 288000, 320000, 352000, 384000, 416000, 448000, + }, + mpeg1Layer2: { + 0, 32000, 48000, 56000, 64000, 80000, 96000, 112000, + 128000, 160000, 192000, 224000, 256000, 320000, 384000, + }, + mpeg1Layer3: { + 0, 32000, 40000, 48000, 56000, 64000, 80000, 96000, + 112000, 128000, 160000, 192000, 224000, 256000, 320000, + }, +} + +var samplingFrequency = [3]int{44100, 48000, 32000} + +func (h *mpeg1FrameHeader) frameSize() int { + return (144*mpeg1Bitrates[h.layer][h.bitrate_index])/ + samplingFrequency[h.sampling_frequency] + + int(h.padding_bit) +} + +func (h *mpeg1FrameHeader) numberOfChannels() int { + if h.mode == mpeg1ModeSingleChannel { + return 1 + } + return 2 +}