120 lines
3.7 KiB
C++
120 lines
3.7 KiB
C++
/**********************************************************************
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Audacity: A Digital Audio Editor
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SampleFormat.h
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Dominic Mazzoni
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*******************************************************************//*!
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\file SampleFormat.cpp
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\brief Functions that work with Dither and initialise it.
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This file handles converting between all of the different
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sample formats that Audacity supports, such as 16-bit,
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24-bit (packed into a 32-bit int), and 32-bit float.
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Floating-point samples use the range -1.0...1.0, inclusive.
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Integer formats use the full signed range of their data type,
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for example 16-bit samples use the range -32768...32767.
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This means that reading in a wav file and writing it out again
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('round tripping'), via floats, is lossless; -32768 equates to -1.0f
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and 32767 equates to +1.0f - (a little bit).
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It also means (unfortunately) that writing out +1.0f leads to
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clipping by 1 LSB. This creates some distortion, but I (MJS) have
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not been able to measure it, it's so small. Zero is preserved.
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http://limpet.net/audacity/bugzilla/show_bug.cgi?id=200
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leads to some of the discussions that were held about this.
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Note: These things are now handled by the Dither class, which
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also replaces the CopySamples() method (msmeyer)
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*//*******************************************************************/
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#include "SampleFormat.h"
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#include <wx/intl.h>
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#include <math.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include "Prefs.h"
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#include "Internat.h"
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DitherType gLowQualityDither = DitherType::none;
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DitherType gHighQualityDither = DitherType::shaped;
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static Dither gDitherAlgorithm;
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void InitDitherers()
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{
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// Read dither preferences
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gLowQualityDither = Dither::FastDitherChoice();
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gHighQualityDither = Dither::BestDitherChoice();
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}
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TranslatableString GetSampleFormatStr(sampleFormat format)
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{
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switch(format) {
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case int16Sample:
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/* i18n-hint: Audio data bit depth (precision): 16-bit integers */
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return XO("16-bit PCM");
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case int24Sample:
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/* i18n-hint: Audio data bit depth (precision): 24-bit integers */
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return XO("24-bit PCM");
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case floatSample:
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/* i18n-hint: Audio data bit depth (precision): 32-bit floating point */
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return XO("32-bit float");
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}
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return XO("Unknown format"); // compiler food
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}
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// TODO: Risky? Assumes 0.0f is represented by 0x00000000;
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void ClearSamples(samplePtr dst, sampleFormat format,
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size_t start, size_t len)
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{
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auto size = SAMPLE_SIZE(format);
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memset(dst + start*size, 0, len*size);
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}
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void ReverseSamples(samplePtr dst, sampleFormat format,
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int start, int len)
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{
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auto size = SAMPLE_SIZE(format);
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samplePtr first = dst + start * size;
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samplePtr last = dst + (start + len - 1) * size;
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enum : size_t { fixedSize = SAMPLE_SIZE(floatSample) };
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wxASSERT(static_cast<size_t>(size) <= fixedSize);
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char temp[fixedSize];
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while (first < last) {
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memcpy(temp, first, size);
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memcpy(first, last, size);
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memcpy(last, temp, size);
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first += size;
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last -= size;
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}
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}
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void SamplesToFloats(constSamplePtr src, sampleFormat srcFormat,
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float *dst, size_t len, size_t srcStride, size_t dstStride)
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{
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CopySamples( src, srcFormat,
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reinterpret_cast<samplePtr>(dst), floatSample, len,
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DitherType::none,
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srcStride, dstStride);
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}
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void CopySamples(constSamplePtr src, sampleFormat srcFormat,
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samplePtr dst, sampleFormat dstFormat, size_t len,
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DitherType ditherType, /* = gHighQualityDither */
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unsigned int srcStride /* = 1 */,
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unsigned int dstStride /* = 1 */)
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{
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gDitherAlgorithm.Apply(
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ditherType,
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src, srcFormat, dst, dstFormat, len, srcStride, dstStride);
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}
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