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/*
* null audio output driver
*
* This file is part of mpv.
*
* mpv is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* mpv is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with mpv. If not, see <http://www.gnu.org/licenses/>.
*/
/*
* Note: this does much more than just ignoring audio output. It simulates
* (to some degree) an ideal AO.
*/
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include "mpv_talloc.h"
#include "osdep/timer.h"
#include "options/m_option.h"
#include "common/common.h"
#include "common/msg.h"
#include "audio/format.h"
#include "ao.h"
#include "internal.h"
struct priv {
bool paused;
double last_time;
float buffered; // samples
int buffersize; // samples
bool playing;
bool untimed;
float bufferlen; // seconds
float speed; // multiplier
float latency_sec; // seconds
float latency; // samples
bool broken_eof;
bool broken_delay;
// Minimal unit of audio samples that can be written at once. If play() is
// called with sizes not aligned to this, a rounded size will be returned.
// (This is not needed by the AO API, but many AOs behave this way.)
int outburst; // samples
struct m_channels channel_layouts;
int format;
};
static void drain(struct ao *ao)
{
struct priv *priv = ao->priv;
if (ao->untimed) {
priv->buffered = 0;
return;
}
if (priv->paused)
return;
double now = mp_time_sec();
if (priv->buffered > 0) {
priv->buffered -= (now - priv->last_time) * ao->samplerate * priv->speed;
if (priv->buffered < 0)
priv->buffered = 0;
}
priv->last_time = now;
}
static int init(struct ao *ao)
{
struct priv *priv = ao->priv;
if (priv->format)
ao->format = priv->format;
ao->untimed = priv->untimed;
struct mp_chmap_sel sel = {.tmp = ao};
if (priv->channel_layouts.num_chmaps) {
for (int n = 0; n < priv->channel_layouts.num_chmaps; n++)
mp_chmap_sel_add_map(&sel, &priv->channel_layouts.chmaps[n]);
} else {
mp_chmap_sel_add_any(&sel);
}
if (!ao_chmap_sel_adjust(ao, &sel, &ao->channels))
mp_chmap_from_channels(&ao->channels, 2);
priv->latency = priv->latency_sec * ao->samplerate;
// A "buffer" for this many seconds of audio
int bursts = (int)(ao->samplerate * priv->bufferlen + 1) / priv->outburst;
ao->device_buffer = priv->outburst * bursts + priv->latency;
priv->last_time = mp_time_sec();
return 0;
}
// close audio device
static void uninit(struct ao *ao)
{
}
// stop playing and empty buffers (for seeking/pause)
static void reset(struct ao *ao)
{
struct priv *priv = ao->priv;
priv->buffered = 0;
priv->playing = false;
}
static void start(struct ao *ao)
{
struct priv *priv = ao->priv;
if (priv->paused)
MP_ERR(ao, "illegal state: start() while paused\n");
drain(ao);
priv->paused = false;
priv->last_time = mp_time_sec();
priv->playing = true;
}
static bool set_pause(struct ao *ao, bool paused)
{
struct priv *priv = ao->priv;
if (!priv->playing)
MP_ERR(ao, "illegal state: set_pause() while not playing\n");
if (priv->paused != paused) {
drain(ao);
priv->paused = paused;
if (!priv->paused)
priv->last_time = mp_time_sec();
}
return true;
}
static bool audio_write(struct ao *ao, void **data, int samples)
{
struct priv *priv = ao->priv;
if (priv->buffered <= 0)
priv->buffered = priv->latency; // emulate fixed latency
priv->buffered += samples;
return true;
}
static void get_state(struct ao *ao, struct mp_pcm_state *state)
{
struct priv *priv = ao->priv;
drain(ao);
state->free_samples = ao->device_buffer - priv->latency - priv->buffered;
state->free_samples = state->free_samples / priv->outburst * priv->outburst;
state->queued_samples = priv->buffered;
// Note how get_state returns the delay in audio device time (instead of
// adjusting for speed), since most AOs seem to also do that.
state->delay = priv->buffered;
// Drivers with broken EOF handling usually always report the same device-
// level delay that is additional to the buffer time.
if (priv->broken_eof && priv->buffered < priv->latency)
state->delay = priv->latency;
state->delay /= ao->samplerate;
if (priv->broken_delay) { // Report only multiples of outburst
double q = priv->outburst / (double)ao->samplerate;
if (state->delay > 0)
state->delay = (int)(state->delay / q) * q;
}
state->playing = priv->playing && priv->buffered > 0;
}
#define OPT_BASE_STRUCT struct priv
const struct ao_driver audio_out_null = {
.description = "Null audio output",
.name = "null",
.init = init,
.uninit = uninit,
.reset = reset,
.get_state = get_state,
.set_pause = set_pause,
.write = audio_write,
.start = start,
.priv_size = sizeof(struct priv),
.priv_defaults = &(const struct priv) {
.bufferlen = 0.2,
.outburst = 256,
.speed = 1,
},
.options = (const struct m_option[]) {
{"untimed", OPT_BOOL(untimed)},
{"buffer", OPT_FLOAT(bufferlen), M_RANGE(0, 100)},
{"outburst", OPT_INT(outburst), M_RANGE(1, 100000)},
{"speed", OPT_FLOAT(speed), M_RANGE(0, 10000)},
{"latency", OPT_FLOAT(latency_sec), M_RANGE(0, 100)},
{"broken-eof", OPT_BOOL(broken_eof)},
{"broken-delay", OPT_BOOL(broken_delay)},
{"channel-layouts", OPT_CHANNELS(channel_layouts)},
{"format", OPT_AUDIOFORMAT(format)},
{0}
},
.options_prefix = "ao-null",
};
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