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/*
* Purpose: Application to local playback buffer resampling routine for vmix
*
* This file is almost the same than playmix.inc but uses simple
* linear interpolation algorithm for sample rate conversion.
*/
/*
*
* This file is part of Open Sound System.
*
* Copyright (C) 4Front Technologies 1996-2008.
*
* This this source file is released under GPL v2 license (no other versions).
* See the COPYING file included in the main directory of this source
* distribution for the license terms and conditions.
*
*/
/*
* Mixing function for virtual devices
*/
vmix_mixer_t *mixer = portc->mixer;
vmix_engine_t *eng = &mixer->play_engine;
dmap_t *dmap = audio_engines[portc->audio_dev]->dmap_out;
int frame_size;
int inptr, inmax;
int used_channels;
int i, ch, nch;
double vol, step;
double tmp;
/*
* Initial setup
*/
step = (double) portc->rate / (double) mixer->play_engine.rate;
#if 1
/*
* TODO:
* For some reason "trivial" conversion rations such as 4:1, 2:1, 1:2 and 1:4
* don't work properly. As a workaround we add a tiny error to break the
* evil ratio. Need to find out why the algorithm doesn't work with such ratios.
*/
if (step==4.0)step=4.0001;
if (step==2.0)step=2.0001;
if (step==0.5)step=0.5001;
if (step==0.25)step=0.25001;
#endif
frame_size = sizeof (*inp);
inmax = dmap->bytes_in_use / frame_size / portc->channels;
inptr = (int)(portc->play_dma_pointer_src / frame_size / portc->channels);
used_channels = portc->channels;
if (used_channels > eng->channels)
used_channels = eng->channels;
/* ignored_channels = portc->channels - used_channels; */
/*
* Handle mono playback by playing the mono stream twice (for left and right ch)
*/
nch=used_channels;
if (nch<2)nch=2;
/*
* Do the mixing
*/
for (ch = 0; ch < nch; ch++)
{
double ip = inptr + (ch%used_channels);
double vu = portc->vu[ch % 2];
float *chbuf = eng->chbufs[ch+portc->play_choffs];
inp = (BUFFER_TYPE) dmap->dmabuf;
inp += ch;
i = portc->volume[ch%2];
vol = vmix_db_table[i / 5];
vu = vu / 255.0;
for (i = 0; i < nsamples; i++)
{
double frag, tmp_next;
int ip_next;
#if 0 && defined(SINE_DEBUG)
if (ch > 1)
tmp = 0.0;
else
tmp = sine_table[sine_phase[ch]];
sine_phase[ch] = (sine_phase[ch] + 1) % SINE_SIZE;
#else
/*
* Convert the sample to right endianess.
*/
tmp = VMIX_BYTESWAP (inp[((int) ip) * portc->channels]);
/* perform linear interpolation */
ip_next = (((int) ip) + 1) % inmax;
tmp_next = VMIX_BYTESWAP (inp[ip_next * portc->channels]);
frag = ip - (int) ip; /* Pointer fraction */
tmp += (tmp_next - tmp) * frag;
tmp /= 2.0;
tmp = tmp * range;
#endif
tmp = tmp * vol;
*chbuf++ += tmp;
ip = ip + step;
if (ip > inmax)
ip -= inmax;
/* VU meter */
if (tmp < 0.0)
tmp = -tmp;
if (tmp > vu)
vu = tmp;
}
if (ch < 2)
{ /* Save left/right VU meters */
vu = vu * 255.0;
portc->vu[ch] = (int)vu;
}
}
/*
* Finally save the state variables
*/
tmp = (nsamples * frame_size * portc->channels);
tmp *= step;
portc->play_dma_pointer_src = portc->play_dma_pointer_src + tmp;
if (portc->play_dma_pointer_src > dmap->bytes_in_use)
portc->play_dma_pointer_src -= dmap->bytes_in_use;
portc->play_dma_pointer = (int)portc->play_dma_pointer_src;
frame_size *= portc->channels;
portc->play_dma_pointer = (portc->play_dma_pointer / frame_size) * frame_size;
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