mirror of
https://github.com/mpv-player/mpv
synced 2024-12-25 16:33:02 +00:00
223 lines
5.7 KiB
C
223 lines
5.7 KiB
C
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/* This audio filter changes the volume of the sound, and can be used
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when the mixer doesn't support the PCM channel. It can handel
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between 1 and 6 channels. The volume can be adjusted between -60dB
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to +10dB and is set on a per channels basis. The volume can be
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written ad read by AF_CONTROL_VOLUME_SET and AF_CONTROL_VOLUME_GET
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respectivly.
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The plugin has support for softclipping, it is enabled by
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AF_CONTROL_VOLUME_SOFTCLIPP. It has also a probing feature which
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can be used to measure the power in the audio stream, both an
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instantanious value and the maximum value can be probed. The
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probing is enable by AF_CONTROL_VOLUME_PROBE_ON_OFF and is done on a
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per channel basis. The result from the probing is obtained using
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AF_CONTROL_VOLUME_PROBE_GET and AF_CONTROL_VOLUME_PROBE_GET_MAX. The
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probed values are calculated in dB. The control of the volume can
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be turned off by the AF_CONTROL_VOLUME_ON_OFF switch.
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <inttypes.h>
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#include <math.h>
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#include "../config.h"
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#include "../mp_msg.h"
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#include "af.h"
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// Some limits
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#define MIN_S16 -32650
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#define MAX_S16 32650
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#define MAX_VOL +10.0
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#define MIN_VOL -60.0
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// Number of channels
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#define NCH 6
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#include "../libao2/afmt.h"
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// Data for specific instances of this filter
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typedef struct af_volume_s
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{
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double volume[NCH]; // Volume for each channel
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double power[NCH]; // Instantaneous power in each channel
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double maxpower[NCH]; // Maximum power in each channel
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double alpha; // Forgetting factor for power estimate
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int softclip; // Soft clippng on/off
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int probe; // Probing on/off
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int onoff; // Volume control on/off
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}af_volume_t;
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/* Convert to gain value from dB. Returns AF_OK if of and AF_ERROR if
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fail */
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inline int from_dB(double* in, double* out)
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{
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int i = 0;
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// Sanity check
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if(!in || !out)
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return AF_ERROR;
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for(i=0;i<NCH;i++)
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out[i]=pow(10.0,clamp(in[i],MIN_VOL,MAX_VOL)/10.0);
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return AF_OK;
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}
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/* Convert from gain value to dB. Returns AF_OK if of and AF_ERROR if
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fail */
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inline int to_dB(double* in, double* out)
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{
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int i = 0;
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// Sanity check
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if(!in || !out)
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return AF_ERROR;
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for(i=0;i<NCH;i++)
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out[i]=10.0*log10(clamp(in[i],MIN_VOL,MAX_VOL));
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return AF_OK;
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}
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// Initialization and runtime control
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static int control(struct af_instance_s* af, int cmd, void* arg)
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{
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af_volume_t* s = (af_volume_t*)af->setup;
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switch(cmd){
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case AF_CONTROL_REINIT:
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// Sanity check
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if(!arg) return AF_ERROR;
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af->data->rate = ((af_data_t*)arg)->rate;
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af->data->nch = ((af_data_t*)arg)->nch;
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af->data->format = AFMT_S16_LE;
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af->data->bps = 2;
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// Time constant set to 0.1s
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s->alpha = (1.0/0.2)/(2.0*M_PI*(double)((af_data_t*)arg)->rate);
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// Only AFMT_S16_LE is supported for now
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if(af->data->format != ((af_data_t*)arg)->format ||
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af->data->bps != ((af_data_t*)arg)->bps)
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return AF_FALSE;
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return AF_OK;
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case AF_CONTROL_VOLUME_SET:
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return from_dB((double*)arg,s->volume);
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case AF_CONTROL_VOLUME_GET:
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return to_dB(s->volume,(double*)arg);
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case AF_CONTROL_VOLUME_PROBE_GET:
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return to_dB(s->power,(double*)arg);
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case AF_CONTROL_VOLUME_PROBE_GET_MAX:
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return to_dB(s->maxpower,(double*)arg);
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case AF_CONTROL_VOLUME_SOFTCLIP:
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s->softclip = (int)arg;
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return AF_OK;
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case AF_CONTROL_VOLUME_PROBE_ON_OFF:
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s->probe = (int)arg;
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return AF_OK;
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case AF_CONTROL_VOLUME_ON_OFF:
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s->onoff = (int)arg;
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return AF_OK;
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}
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return AF_UNKNOWN;
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}
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// Deallocate memory
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static void uninit(struct af_instance_s* af)
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{
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if(af->data)
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free(af->data);
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if(af->setup)
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free(af->setup);
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}
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// Filter data through filter
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static af_data_t* play(struct af_instance_s* af, af_data_t* data)
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{
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af_data_t* c = data; // Current working data
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af_volume_t* s = (af_volume_t*)af->setup; // Setup for this instance
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int16_t* a = (int16_t*)c->audio; // Audio data
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int len = c->len/2; // Number of samples
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int ch = 0; // Channel counter
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register int nch = c->nch; // Number of channels
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register int i = 0;
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// Probe the data stream
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if(s->probe){
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for(ch = 0; ch < nch ; ch++){
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double alpha = s->alpha;
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double beta = 1 - alpha;
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double pow = s->power[ch];
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double maxpow = s->maxpower[ch];
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register double t = 0;
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for(i=ch;i<len;i+=nch){
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t = ((double)a[i])/32768.0;
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t *= t;
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// Check maximum power value
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if(t>maxpow)
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maxpow=t;
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// Power estimate made using first order AR model
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if(t>pow)
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pow=t;
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else
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pow = beta*pow+alpha*t;
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}
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s->power[ch] = pow;
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s->maxpower[ch] = maxpow;
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}
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}
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// Change the volume.
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if(s->onoff){
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register int sc = s->softclip;
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for(ch = 0; ch < nch ; ch++){
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register int vol = (int)(255.0 * s->volume[ch]);
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for(i=ch;i<len;i+=nch){
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register int x;
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x=(a[i] * vol) >> 8;
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if(sc){
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int64_t t=x*x;
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t=(t*x) >> 30;
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x = (3*x - (int)t) >> 1;
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}
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a[i]=clamp(x,MIN_S16,MAX_S16);
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}
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}
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}
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return c;
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}
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// Allocate memory and set function pointers
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static int open(af_instance_t* af){
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int i = 0;
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af->control=control;
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af->uninit=uninit;
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af->play=play;
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af->mul.n=1;
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af->mul.d=1;
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af->data=calloc(1,sizeof(af_data_t));
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af->setup=calloc(1,sizeof(af_volume_t));
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if(af->data == NULL || af->setup == NULL)
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return AF_ERROR;
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// Enable volume control and set initial volume to 0.1
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((af_volume_t*)af->setup)->onoff = 1;
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for(i=0;i<NCH;i++)
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((af_volume_t*)af->setup)->volume[i]=0.1;
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return AF_OK;
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}
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// Description of this filter
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af_info_t af_info_volume = {
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"Volume control audio filter",
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"volume",
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"Anders",
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"",
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AF_FLAGS_NOT_REENTRANT,
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open
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};
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