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SubBand1.pas
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(*
* File: $RCSfile: SubBand1.pas,v $
* Revision: $Revision: 1.1.1.1 $
* Version : $Id: SubBand1.pas,v 1.1.1.1 2002/04/21 12:57:23 fobmagog Exp $
* Author: $Author: fobmagog $
* Homepage: http://delphimpeg.sourceforge.net/
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*)
unit SubBand1;
interface
uses
Windows, Shared, BitStream, Header, SynthFilter, SubBand, CRC;
type
// class for layer I subbands in single channel mode:
TSubBandLayer1 = class(TSubBand)
protected
FSubBandNumber: Cardinal;
FSampleNumber: Cardinal;
FAllocation: Cardinal;
FScaleFactor: Single;
FSampleLength: Cardinal;
FSample: Single;
FFactor, FOffset: Single;
public
constructor Create(SubBandNumber: Cardinal); virtual;
procedure ReadAllocation(Stream: TBitStream; Header: THeader; CRC: TCRC16); override;
procedure ReadScaleFactor(Stream: TBitStream; Header: THeader); override;
function ReadSampleData(Stream: TBitStream): Boolean; override;
function PutNextSample(Channels: TChannels; Filter1, Filter2: TSynthesisFilter): Boolean; override;
end;
// class for layer I subbands in joint stereo mode:
TSubBandLayer1IntensityStereo = class(TSubBandLayer1)
protected
FChannel2ScaleFactor: Single;
public
procedure ReadScaleFactor(Stream: TBitStream; Header: THeader); override;
function PutNextSample(Channels: TChannels; Filter1, Filter2: TSynthesisFilter): Boolean; override;
end;
// class for layer I subbands in stereo mode:
TSubBandLayer1Stereo = class(TSubBandLayer1)
protected
FChannel2Allocation: Cardinal;
FChannel2ScaleFactor: Single;
FChannel2SampleLength: Cardinal;
FChannel2Sample: Single;
FChannel2Factor: Single;
FChannel2Offset: Single;
public
procedure ReadAllocation(Stream: TBitStream; Header: THeader; CRC: TCRC16); override;
procedure ReadScaleFactor(Stream: TBitStream; Header: THeader); override;
function ReadSampleData(Stream: TBitStream): Boolean; override;
function PutNextSample(Channels: TChannels; Filter1, Filter2: TSynthesisFilter): Boolean; override;
end;
implementation
uses
ScaleFac;
const
// factors and offsets for sample requantization:
TableFactor: array[0..14] of Single = (
0.0, (1.0 / 2.0) * (4.0 / 3.0), (1.0 / 4.0) * (8.0 / 7.0), (1.0 / 8.0) * (16.0 / 15.0),
(1.0 / 16.0) * (32.0 / 31.0), (1.0 / 32.0) * (64.0/63.0), (1.0/64.0) * (128.0/127.0),
(1.0 / 128.0) * (256.0 / 255.0), (1.0 / 256.0) * (512.0 / 511.0),
(1.0 / 512.0) * (1024.0 / 1023.0), (1.0 / 1024.0) * (2048.0 / 2047.0),
(1.0 / 2048.0) * (4096.0 / 4095.0), (1.0 / 4096.0) * (8192.0 / 8191.0),
(1.0 / 8192.0) * (16384.0 / 16383.0), (1.0 / 16384.0) * (32768.0 / 32767.0));
TableOffset: array[0..14] of Single = (
0.0, ((1.0 / 2.0) - 1.0) * (4.0 / 3.0), ((1.0 / 4.0) - 1.0) * (8.0 / 7.0), ((1.0 / 8.0) - 1.0) * (16.0 / 15.0),
((1.0 / 16.0) - 1.0) * (32.0 / 31.0), ((1.0 / 32.0) - 1.0) * (64.0 / 63.0), ((1.0 / 64.0) - 1.0) * (128.0 / 127.0),
((1.0 / 128.0) - 1.0) * (256.0 / 255.0), ((1.0 / 256.0) - 1.0) * (512.0 / 511.0),
((1.0 / 512.0) - 1.0) * (1024.0 / 1023.0), ((1.0 / 1024.0) - 1.0) * (2048.0 / 2047.0),
((1.0 / 2048.0) - 1.0) * (4096.0 / 4095.0), ((1.0 / 4096.0) - 1.0) * (8192.0 / 8191.0),
((1.0 / 8192.0) - 1.0) * (16384.0 / 16383.0), ((1.0 / 16384.0) - 1.0) * (32768.0 / 32767.0));
{ TSubBandLayer1 }
constructor TSubBandLayer1.Create(SubBandNumber: Cardinal);
begin
FSubBandNumber := SubBandNumber;
FSampleNumber := 0;
end;
function TSubBandLayer1.PutNextSample(Channels: TChannels; Filter1,
Filter2: TSynthesisFilter): Boolean;
var ScaledSample: Single;
begin
if (FAllocation <> 0) and (Channels <> Right) then begin
ScaledSample := (FSample * FFactor + FOffset) * FScalefactor;
Filter1.InputSample(ScaledSample, FSubBandNumber);
end;
Result := True;
end;
procedure TSubBandLayer1.ReadAllocation(Stream: TBitStream;
Header: THeader; CRC: TCRC16);
begin
FAllocation := Stream.GetBits(4);
if (FAllocation = 15) then ;
// cerr << "WARNING: stream contains an illegal allocation!\n"; // MPEG-stream is corrupted!
if (CRC <> nil) then
CRC.AddBits(FAllocation, 4);
if (FAllocation <> 0) then begin
FSampleLength := FAllocation + 1;
FFactor := TableFactor[FAllocation];
FOffset := TableOffset[FAllocation];
end;
end;
function TSubBandLayer1.ReadSampleData(Stream: TBitStream): Boolean;
begin
if (FAllocation <> 0) then
FSample := Stream.GetBitsFloat(FSampleLength);
inc(FSampleNumber);
if (FSampleNumber = 12) then begin
FSampleNumber := 0;
Result := True;
end else
Result := False;
end;
procedure TSubBandLayer1.ReadScaleFactor(Stream: TBitStream;
Header: THeader);
begin
if (FAllocation <> 0) then
FScalefactor := ScaleFactors[Stream.GetBits(6)];
end;
{ TSubBandLayer1IntensityStereo }
function TSubBandLayer1IntensityStereo.PutNextSample(Channels: TChannels;
Filter1, Filter2: TSynthesisFilter): Boolean;
var Sample1, Sample2: Single;
begin
if (FAllocation <> 0) then begin
FSample := FSample * FFactor + FOffset; // requantization
if (Channels = Both) then begin
Sample1 := FSample * FScalefactor;
Sample2 := FSample * FChannel2ScaleFactor;
Filter1.InputSample(Sample1, FSubBandNumber);
Filter2.InputSample(Sample2, FSubBandNumber);
end else if (Channels = Left) then begin
Sample1 := FSample * FScaleFactor;
Filter1.InputSample(Sample1, FSubBandNumber);
end else begin
Sample2 := FSample * FChannel2ScaleFactor;
Filter2.InputSample(Sample2, FSubBandNumber);
end;
end;
Result := True;
end;
procedure TSubBandLayer1IntensityStereo.ReadScaleFactor(Stream: TBitStream;
Header: THeader);
begin
if (FAllocation <> 0) then begin
FScaleFactor := ScaleFactors[Stream.GetBits(6)];
FChannel2ScaleFactor := ScaleFactors[Stream.GetBits(6)];
end;
end;
{ TSubBandLayer1Stereo }
function TSubBandLayer1Stereo.PutNextSample(Channels: TChannels; Filter1,
Filter2: TSynthesisFilter): Boolean;
var Sample2: Single;
begin
inherited PutNextSample(Channels, Filter1, Filter2);
if (FChannel2Allocation <> 0) and (Channels <> Left) then begin
Sample2 := (FChannel2Sample * FChannel2Factor + FChannel2Offset) * FChannel2ScaleFactor;
if (Channels = Both) then
Filter2.InputSample(Sample2, FSubBandNumber)
else
Filter1.InputSample(Sample2, FSubBandNumber);
end;
Result := True;
end;
procedure TSubBandLayer1Stereo.ReadAllocation(Stream: TBitStream;
Header: THeader; CRC: TCRC16);
begin
FAllocation := Stream.GetBits(4);
FChannel2Allocation := Stream.GetBits(4);
if (CRC <> nil) then begin
CRC.AddBits(FAllocation, 4);
CRC.AddBits(FChannel2Allocation, 4);
end;
if (FAllocation <> 0) then begin
FSamplelength := FAllocation + 1;
FFactor := TableFactor[FAllocation];
FOffset := TableOffset[FAllocation];
end;
if (FChannel2Allocation <> 0) then begin
FChannel2SampleLength := FChannel2Allocation + 1;
FChannel2Factor := TableFactor[FChannel2Allocation];
FChannel2Offset := TableOffset[FChannel2Allocation];
end;
end;
function TSubBandLayer1Stereo.ReadSampleData(Stream: TBitStream): Boolean;
begin
Result := inherited ReadSampleData(Stream);
if (FChannel2Allocation <> 0) then
FChannel2Sample := Stream.GetBitsFloat(FChannel2SampleLength);
end;
procedure TSubBandLayer1Stereo.ReadScaleFactor(Stream: TBitStream;
Header: THeader);
begin
if (FAllocation <> 0) then
FScaleFactor := ScaleFactors[Stream.GetBits(6)];
if (FChannel2Allocation <> 0) then
FChannel2ScaleFactor := ScaleFactors[Stream.GetBits(6)];
end;
end.