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refactor resampling code
This commit is contained in:
Eric Wasylishen
parent
d1fc2c314b
commit
d4ae16ee48
1 changed files with 105 additions and 90 deletions
195
Quake/snd_mem.c
195
Quake/snd_mem.c
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@ -46,6 +46,107 @@ static void putsample(byte *data, int outwidth, int i, int sample)
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((signed char *)data)[i] = sample >> 8;
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((signed char *)data)[i] = sample >> 8;
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}
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}
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/*
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================
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BoxFilter
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================
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*/
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void BoxFilter(int boxwidth, int numsamples, int width, void *data)
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{
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if (boxwidth <= 1)
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return;
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const int box_half_width = boxwidth / 2;
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boxwidth = (2 * box_half_width) + 1;
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int history[box_half_width];
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memset(history, 0, sizeof(history));
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int box_sum = 0;
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int i;
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for (i = 0; i < (numsamples + box_half_width); i++)
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{
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// calculate the new sample we will write
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const int sample_at_i = getsample(data, width, CLAMP(0, i, numsamples - 1));
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box_sum += sample_at_i;
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box_sum -= history[0];
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const int newsample = box_sum / boxwidth;
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// shift the entries in the history buffer left, discarding the entry
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// at history[0] and leaving a space at history[box_half_width-1]
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int j;
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for (j=0; j<(box_half_width-1); j++)
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{
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history[j] = history[j+1];
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}
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// save the sample we are going to overwrite at history[box_half_width-1]
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const int write_loc = i - box_half_width;
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history[box_half_width-1] = getsample(data, width, CLAMP(0, write_loc, numsamples - 1));
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// only write the new sample if it lies within the bounds of the output array
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if (write_loc >= 0 && write_loc < numsamples)
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{
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putsample(data, width, write_loc, newsample);
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}
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}
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}
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int ResamplerGetOutCount(int inrate, int incount, int outrate)
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{
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float stepscale = (float)inrate / outrate;
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int outcount = inrate / stepscale;
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return outcount;
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}
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#define USE_ID_RESAMPLER 0
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void ResamplerConvert(int inrate, int incount, int inwidth, void *indata,
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int outrate, int outcount, int outwidth, void *outdata)
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{
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float stepscale = (float)inrate / outrate;
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int i;
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float samplefrac;
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if (stepscale < 1 && !USE_ID_RESAMPLER)
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{
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// upsampling
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// linearly interpolate between the two closest source samples.
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// this alone sounds much better than id's method
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for (i = 0, samplefrac = 0; i < outcount; i++, samplefrac += stepscale)
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{
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int srcsample1 = CLAMP(0, floor(samplefrac), incount - 1);
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int srcsample2 = CLAMP(0, ceil(samplefrac), incount - 1);
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// how far between the samples. in [0, 1].
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float mu = samplefrac - floor(samplefrac);
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// FIXME: Get rid of getsamplefromfile; caller should ensure input data is host-endian
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int sample = ((1 - mu) * getsamplefromfile(indata, inwidth, srcsample1))
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+ (mu * getsamplefromfile(indata, inwidth, srcsample2));
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putsample(outdata, outwidth, i, sample);
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}
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// box filter to filter out garbage high frequencies produced by the upsampling
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// for 44100Hz output, a box width of 5 seems to sound the best
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const int boxwidth = CLAMP(0, (outrate / 11025) + 1, 4);
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BoxFilter(boxwidth, outcount, outwidth, outdata);
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}
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else
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{
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// general case / downsampling
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for (i = 0, samplefrac = 0; i < outcount; i++, samplefrac += stepscale)
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{
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int sample = getsamplefromfile(indata, inwidth, (int)samplefrac);
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putsample(outdata, outwidth, i, sample);
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}
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}
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}
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/*
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/*
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================
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================
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@ -55,16 +156,14 @@ ResampleSfx
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static void ResampleSfx (sfx_t *sfx, int inrate, int inwidth, byte *data)
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static void ResampleSfx (sfx_t *sfx, int inrate, int inwidth, byte *data)
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{
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{
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int incount, outcount;
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int incount, outcount;
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float stepscale, samplefrac;
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float stepscale;
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int i;
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int sample;
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sfxcache_t *sc;
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sfxcache_t *sc;
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sc = (sfxcache_t *) Cache_Check (&sfx->cache);
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sc = (sfxcache_t *) Cache_Check (&sfx->cache);
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if (!sc)
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if (!sc)
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return;
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return;
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stepscale = (float)inrate / shm->speed; // this is usually 0.5, 1, or 2
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stepscale = (float)inrate / shm->speed;
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incount = sc->length;
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incount = sc->length;
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outcount = sc->length / stepscale;
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outcount = sc->length / stepscale;
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@ -79,92 +178,8 @@ static void ResampleSfx (sfx_t *sfx, int inrate, int inwidth, byte *data)
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sc->width = 2;
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sc->width = 2;
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sc->stereo = 0;
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sc->stereo = 0;
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// resample / decimate to the current source rate
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ResamplerConvert(inrate, incount, inwidth, data,
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sc->speed, outcount, sc->width, sc->data);
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if (stepscale == 1 && inwidth == 1 && sc->width == 1)
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{
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// fast special case
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for (i = 0; i < outcount; i++)
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((signed char *)sc->data)[i] = (int)( (unsigned char)(data[i]) - 128);
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}
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else
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{
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if (stepscale < 1)
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{
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// upsampling
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// linearly interpolate between the two closest source samples.
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// this alone sounds much better than id's method, but still produces
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// high-frequency junk.
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for (i = 0, samplefrac = 0; i < outcount; i++, samplefrac += stepscale)
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{
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int srcsample1 = CLAMP(0, floor(samplefrac), incount - 1);
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int srcsample2 = CLAMP(0, ceil(samplefrac), incount - 1);
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// how far between the samples. in [0, 1].
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float mu = samplefrac - floor(samplefrac);
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float srcsample1weight = 1 - mu;
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float srcsample2weight = mu;
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sample = (srcsample1weight * getsamplefromfile(data, inwidth, srcsample1))
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+ (srcsample2weight * getsamplefromfile(data, inwidth, srcsample2));
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putsample(sc->data, sc->width, i, sample);
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}
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// box filter
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// box_half_width is the number of samples on each side of a given sample
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// that are averaged together.
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// for 44100Hz output, a box width of 5 (i.e. a box_half_width of 2) seems
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// to sound the best
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const int box_half_width = CLAMP(0, sc->speed / 22050, 4);
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if (box_half_width > 0)
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{
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const int box_width = (2 * box_half_width) + 1;
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int history[box_half_width];
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memset(history, 0, sizeof(history));
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int box_sum = 0;
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for (i = 0; i < (outcount + box_half_width); i++)
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{
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// calculate the new sample we will write
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const int sample_at_i = getsample(sc->data, sc->width, CLAMP(0, i, outcount - 1));
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box_sum += sample_at_i;
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box_sum -= history[0];
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const int newsample = box_sum / box_width;
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// shift the entries in the history buffer left, discarding the entry
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// at history[0] and leaving a space at history[box_half_width-1]
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int j;
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for (j=0; j<(box_half_width-1); j++)
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{
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history[j] = history[j+1];
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}
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// save the sample we are going to overwrite at history[box_half_width-1]
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const int write_loc = i - box_half_width;
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history[box_half_width-1] = getsample(sc->data, sc->width, CLAMP(0, write_loc, outcount - 1));
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// only write the new sample if it lies within the bounds of the output array
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if (write_loc >= 0 && write_loc < outcount)
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{
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putsample(sc->data, sc->width, write_loc, newsample);
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}
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}
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}
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}
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else
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{
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// general case / downsampling
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for (i = 0, samplefrac = 0; i < outcount; i++, samplefrac += stepscale)
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{
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sample = getsamplefromfile(data, inwidth, (int)samplefrac);
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putsample(sc->data, sc->width, i, sample);
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}
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}
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}
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}
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}
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//=============================================================================
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//=============================================================================
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