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# main does not build: the two ADPCM encoders landed on top of each other #127

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Merged
Hawkynt merged 1 commit into from
Aug 29, 2026
Merged

# main does not build: the two ADPCM encoders landed on top of each other #127

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33 changes: 0 additions & 33 deletions Codecs/Codec.ImaAdpcm/ImaAdpcmCodec.Encode.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -6,8 +6,6 @@ public static partial class ImaAdpcmCodec {

private const int WaveHeaderBytesPerChannel = 4;
private const int WaveStereoGroupBytesPerChannel = 4;
private const int QuickTimePacketBytes = 34;
private const int QuickTimeSamplesPerPacket = 64;

/// <summary>
/// Encodes interleaved 16-bit PCM into Microsoft/IMA WAV ADPCM blocks.
Expand Down Expand Up @@ -132,35 +130,4 @@ private static void ValidateWaveLayout(ReadOnlySpan<short> interleaved, int chan

private static short GetSample(ReadOnlySpan<short> interleaved, int frames, int channels, int frame, int channel, short fallback)
=> frame < frames ? interleaved[frame * channels + channel] : fallback;

private static int StartIndexFor(int delta) {
var index = 0;
while (index < StepTable.Length - 1 && StepTable[index] < delta)
++index;
return index;
}

private static byte EncodeNibble(short sample, ref int predictor, ref int index) {
var step = StepTable[index];
var delta = (int)sample - predictor;
byte nibble = 0;
if (delta < 0) {
nibble = 8;
delta = -delta;
}

if (delta >= step) {
nibble |= 4;
delta -= step;
}
if (delta >= step >> 1) {
nibble |= 2;
delta -= step >> 1;
}
if (delta >= step >> 2)
nibble |= 1;

DecodeNibble(nibble, ref predictor, ref index);
return nibble;
}
}
17 changes: 8 additions & 9 deletions Codecs/Codec.MsAdpcm/MsAdpcmCodec.Encode.cs
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Expand Up @@ -68,18 +68,18 @@ public static byte[] Encode(ReadOnlySpan<short> interleaved, int channels, int b
for (var i = 0; i < dataBytes; ++i) {
var frame = baseFrame + 2 + i * 2;
var highSample = GetSample(interleaved, frames, channels, frame, 0, (short)sample1[0]);
var high = EncodeNibble(highSample, ref predictorIndex[0], ref delta[0], ref sample1[0], ref sample2[0]);
var high = SearchNibble(highSample, predictorIndex[0], ref delta[0], ref sample1[0], ref sample2[0]);
var lowSample = GetSample(interleaved, frames, channels, frame + 1, 0, (short)sample1[0]);
var low = EncodeNibble(lowSample, ref predictorIndex[0], ref delta[0], ref sample1[0], ref sample2[0]);
var low = SearchNibble(lowSample, predictorIndex[0], ref delta[0], ref sample1[0], ref sample2[0]);
output[p + i] = (byte)(high << 4 | low);
}
} else {
for (var i = 0; i < dataBytes; ++i) {
var frame = baseFrame + 2 + i;
var leftSample = GetSample(interleaved, frames, channels, frame, 0, (short)sample1[0]);
var left = EncodeNibble(leftSample, ref predictorIndex[0], ref delta[0], ref sample1[0], ref sample2[0]);
var left = SearchNibble(leftSample, predictorIndex[0], ref delta[0], ref sample1[0], ref sample2[0]);
var rightSample = GetSample(interleaved, frames, channels, frame, 1, (short)sample1[1]);
var right = EncodeNibble(rightSample, ref predictorIndex[1], ref delta[1], ref sample1[1], ref sample2[1]);
var right = SearchNibble(rightSample, predictorIndex[1], ref delta[1], ref sample1[1], ref sample2[1]);
output[p + i] = (byte)(left << 4 | right);
}
}
Expand Down Expand Up @@ -130,7 +130,7 @@ private static void SelectInitialState(

for (var sampleIndex = 2; sampleIndex < lookAhead; ++sampleIndex) {
var target = GetSample(interleaved, frames, channels, baseFrame + sampleIndex, channel, (short)s1);
EncodeNibble(target, ref statePredictor, ref stateDelta, ref s1, ref s2);
SearchNibble(target, statePredictor, ref stateDelta, ref s1, ref s2);
var difference = (long)target - s1;
error += difference * difference;
if (error >= bestError)
Expand All @@ -151,16 +151,15 @@ private static void SelectInitialState(
private static short GetSample(ReadOnlySpan<short> interleaved, int frames, int channels, int frame, int channel, short fallback)
=> frame < frames ? interleaved[frame * channels + channel] : fallback;

private static int EncodeNibble(short sample, ref int predictorIndex, ref int delta, ref int sample1, ref int sample2) {
private static int SearchNibble(short sample, int predictorIndex, ref int delta, ref int sample1, ref int sample2) {
var bestNibble = 0;
var bestError = int.MaxValue;

for (var nibble = 0; nibble < 16; ++nibble) {
var testPredictorIndex = predictorIndex;
var testDelta = delta;
var testSample1 = sample1;
var testSample2 = sample2;
var reconstructed = DecodeNibble(nibble, ref testPredictorIndex, ref testDelta, ref testSample1, ref testSample2);
var reconstructed = DecodeNibble((byte)nibble, predictorIndex, ref testDelta, ref testSample1, ref testSample2);
var error = Math.Abs((int)sample - reconstructed);
if (error >= bestError)
continue;
Expand All @@ -170,7 +169,7 @@ private static int EncodeNibble(short sample, ref int predictorIndex, ref int de
break;
}

DecodeNibble(bestNibble, ref predictorIndex, ref delta, ref sample1, ref sample2);
DecodeNibble((byte)bestNibble, predictorIndex, ref delta, ref sample1, ref sample2);
return bestNibble;
}
}