mpv/audio/out/push.c

/*
 * This file is part of mpv.
 *
 * mpv is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with mpv.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <stddef.h>
#include <pthread.h>
#include <inttypes.h>
#include <unistd.h>
#include <errno.h>
#include <assert.h>

#include "osdep/io.h"

#include "ao.h"
#include "internal.h"
#include "audio/format.h"

#include "common/msg.h"
#include "common/common.h"

#include "input/input.h"

#include "osdep/threads.h"
#include "osdep/timer.h"
#include "compat/atomics.h"

#include "audio/audio.h"
#include "audio/audio_buffer.h"

struct ao_push_state {
    pthread_t thread;
    pthread_mutex_t lock;
    pthread_cond_t wakeup;
    pthread_cond_t wakeup_drain;

    // --- protected by lock

    struct mp_audio_buffer *buffer;

    bool terminate;
    bool drain;
    bool buffers_full;
    bool avoid_ao_wait;
    bool need_wakeup;
    bool requested_data;
    bool paused;

    // Whether the current buffer contains the complete audio.
    bool final_chunk;
    double expected_end_time;

    int wakeup_pipe[2];
};

// lock must be held
static void wakeup_playthread(struct ao *ao)
{
    struct ao_push_state *p = ao->api_priv;
    if (ao->driver->wakeup)
        ao->driver->wakeup(ao);
    p->need_wakeup = true;
    pthread_cond_signal(&p->wakeup);
}

static int control(struct ao *ao, enum aocontrol cmd, void *arg)
{
    int r = CONTROL_UNKNOWN;
    if (ao->driver->control) {
        struct ao_push_state *p = ao->api_priv;
        pthread_mutex_lock(&p->lock);
        r = ao->driver->control(ao, cmd, arg);
        pthread_mutex_unlock(&p->lock);
    }
    return r;
}

static float get_delay(struct ao *ao)
{
    struct ao_push_state *p = ao->api_priv;
    pthread_mutex_lock(&p->lock);
    double driver_delay = 0;
    if (ao->driver->get_delay)
        driver_delay = ao->driver->get_delay(ao);
    double delay = driver_delay + mp_audio_buffer_seconds(p->buffer);
    pthread_mutex_unlock(&p->lock);
    if (delay >= AO_EOF_DELAY && p->expected_end_time) {
        if (mp_time_sec() > p->expected_end_time) {
            MP_ERR(ao, "Audio device EOF reporting is broken!\n");
            MP_ERR(ao, "Please report this problem.\n");
            delay = 0;
        }
    }
    return delay;
}

static void reset(struct ao *ao)
{
    struct ao_push_state *p = ao->api_priv;
    pthread_mutex_lock(&p->lock);
    if (ao->driver->reset)
        ao->driver->reset(ao);
    mp_audio_buffer_clear(p->buffer);
    p->paused = false;
    wakeup_playthread(ao);
    pthread_mutex_unlock(&p->lock);
}

static void audio_pause(struct ao *ao)
{
    struct ao_push_state *p = ao->api_priv;
    pthread_mutex_lock(&p->lock);
    if (ao->driver->pause)
        ao->driver->pause(ao);
    p->paused = true;
    wakeup_playthread(ao);
    pthread_mutex_unlock(&p->lock);
}

static void resume(struct ao *ao)
{
    struct ao_push_state *p = ao->api_priv;
    pthread_mutex_lock(&p->lock);
    if (ao->driver->resume)
        ao->driver->resume(ao);
    p->paused = false;
    p->expected_end_time = 0;
    wakeup_playthread(ao);
    pthread_mutex_unlock(&p->lock);
}

static void drain(struct ao *ao)
{
    struct ao_push_state *p = ao->api_priv;

    pthread_mutex_lock(&p->lock);
    if (p->paused) {
        pthread_mutex_unlock(&p->lock);
        return;
    }
    p->final_chunk = true;
    p->drain = true;
    wakeup_playthread(ao);
    while (p->drain)
        pthread_cond_wait(&p->wakeup_drain, &p->lock);
    pthread_mutex_unlock(&p->lock);

    if (!ao->driver->drain)
        mp_sleep_us(get_delay(ao) * 1000000);
    reset(ao);
}

static int unlocked_get_space(struct ao *ao)
{
    struct ao_push_state *p = ao->api_priv;
    int space = mp_audio_buffer_get_write_available(p->buffer);
    if (ao->driver->get_space) {
        // The following code attempts to keep the total buffered audio to
        // MIN_BUFFER/2+device_buffer in order to improve latency.
        int device_space = ao->driver->get_space(ao);
        int device_buffered = ao->device_buffer - device_space;
        int soft_buffered = mp_audio_buffer_samples(p->buffer);
        int min_buffer = MIN_BUFFER / 2 * ao->samplerate + ao->device_buffer;
        int total_buffer = device_buffered + soft_buffered;
        int missing = min_buffer - total_buffer;
        space = MPMIN(space, missing);
        space = MPMAX(0, space);
    }
    return space;
}

static int get_space(struct ao *ao)
{
    struct ao_push_state *p = ao->api_priv;
    pthread_mutex_lock(&p->lock);
    int space = unlocked_get_space(ao);
    pthread_mutex_unlock(&p->lock);
    return space;
}

static int play(struct ao *ao, void **data, int samples, int flags)
{
    struct ao_push_state *p = ao->api_priv;

    pthread_mutex_lock(&p->lock);

    int write_samples = mp_audio_buffer_get_write_available(p->buffer);
    write_samples = MPMIN(write_samples, samples);

    if (write_samples < samples)
        flags = flags & ~AOPLAY_FINAL_CHUNK;
    bool is_final = flags & AOPLAY_FINAL_CHUNK;

    struct mp_audio audio;
    mp_audio_buffer_get_format(p->buffer, &audio);
    for (int n = 0; n < ao->num_planes; n++)
        audio.planes[n] = data[n];
    audio.samples = write_samples;
    mp_audio_buffer_append(p->buffer, &audio);

    bool got_data = write_samples > 0 || p->paused || p->final_chunk != is_final;

    p->expected_end_time = 0;
    p->final_chunk = is_final;
    p->paused = false;

    // If we don't have new data, the decoder thread basically promises it
    // will send new data as soon as it's available.
    if (got_data) {
        p->requested_data = false;
        wakeup_playthread(ao);
    }
    pthread_mutex_unlock(&p->lock);
    return write_samples;
}

// called locked
static void ao_play_data(struct ao *ao)
{
    struct ao_push_state *p = ao->api_priv;
    struct mp_audio data;
    mp_audio_buffer_peek(p->buffer, &data);
    int max = data.samples;
    int space = ao->driver->get_space(ao);
    space = MPMAX(space, 0);
    if (data.samples > space)
        data.samples = space;
    int flags = 0;
    if (p->final_chunk && data.samples == max)
        flags |= AOPLAY_FINAL_CHUNK;
    MP_STATS(ao, "start ao fill");
    int r = 0;
    if (data.samples)
        r = ao->driver->play(ao, data.planes, data.samples, flags);
    MP_STATS(ao, "end ao fill");
    if (r > data.samples) {
        MP_WARN(ao, "Audio device returned non-sense value.\n");
        r = data.samples;
    }
    r = MPMAX(r, 0);
    // Probably can't copy the rest of the buffer due to period alignment.
    bool stuck = r <= 0 && space >= max && data.samples > 0;
    if ((flags & AOPLAY_FINAL_CHUNK) && stuck) {
        MP_ERR(ao, "Audio output driver seems to ignore AOPLAY_FINAL_CHUNK.\n");
        r = max;
    }
    mp_audio_buffer_skip(p->buffer, r);
    if (p->final_chunk && mp_audio_buffer_samples(p->buffer) == 0) {
        p->expected_end_time = mp_time_sec() + AO_EOF_DELAY + 0.25; // + margin
        if (ao->driver->get_delay)
            p->expected_end_time += ao->driver->get_delay(ao);
    }
    // In both cases, we have to account for space!=0, but the AO not accepting
    // any new data (due to rounding to period boundaries).
    p->buffers_full = max >= space && r <= 0;
    p->avoid_ao_wait = (max == 0 && space > 0) || p->paused || stuck;
    MP_TRACE(ao, "in=%d, space=%d r=%d flags=%d aw=%d full=%d f=%d\n", max,
             space, r, flags, p->avoid_ao_wait, p->buffers_full, p->final_chunk);
}

// Estimate when the AO needs data again.
static double ao_estimate_timeout(struct ao *ao)
{
    struct ao_push_state *p = ao->api_priv;
    double timeout = 0;
    if (p->buffers_full && ao->driver->get_delay) {
        timeout = ao->driver->get_delay(ao) - 0.050;
        // Keep extra safety margin if the buffers are large
        if (timeout > 0.100)
            timeout = MPMAX(timeout - 0.200, 0.100);
    }
    return MPMAX(timeout, ao->device_buffer * 0.75 / ao->samplerate);
}

static void *playthread(void *arg)
{
    struct ao *ao = arg;
    struct ao_push_state *p = ao->api_priv;
    pthread_mutex_lock(&p->lock);
    while (!p->terminate) {
        if (!p->paused)
            ao_play_data(ao);

        // Request new data from decoder if buffer goes below "full".
        // Allow a small margin of missing data for AOs that use timeouts.
        double margin = ao->driver->wait ? 0 : ao->device_buffer / 8;
        if (!p->buffers_full && unlocked_get_space(ao) > margin) {
            if (!p->requested_data)
                mp_input_wakeup(ao->input_ctx);
            p->requested_data = true;
        }

        if (p->drain && (p->avoid_ao_wait || p->paused)) {
            if (ao->driver->drain)
                ao->driver->drain(ao);
            p->drain = false;
            pthread_cond_signal(&p->wakeup_drain);
        }

        if (!p->need_wakeup) {
            MP_STATS(ao, "start audio wait");
            if (p->avoid_ao_wait || p->paused) {
                // Avoid busy waiting, because the audio API will still report
                // that it needs new data, even if we're not ready yet, or if
                // get_space() decides that the amount of audio buffered in the
                // device is enough, and p->buffer can be empty.
                // The most important part is that the decoder is woken up, so
                // that the decoder will wake up us in turn.
                MP_TRACE(ao, "buffer inactive.\n");
                mp_input_wakeup(ao->input_ctx);
                pthread_cond_wait(&p->wakeup, &p->lock);
            } else {
                if (!ao->driver->wait || ao->driver->wait(ao, &p->lock) < 0) {
                    // Fallback to guessing.
                    double timeout = ao_estimate_timeout(ao);
                    mpthread_cond_timedwait_rel(&p->wakeup, &p->lock, timeout);
                }
            }
            MP_STATS(ao, "end audio wait");
        }
        p->need_wakeup = false;
    }
    pthread_mutex_unlock(&p->lock);
    return NULL;
}

static void uninit(struct ao *ao)
{
    struct ao_push_state *p = ao->api_priv;

    pthread_mutex_lock(&p->lock);
    p->terminate = true;
    wakeup_playthread(ao);
    pthread_mutex_unlock(&p->lock);

    pthread_join(p->thread, NULL);

    ao->driver->uninit(ao);

    for (int n = 0; n < 2; n++)
        close(p->wakeup_pipe[n]);

    pthread_cond_destroy(&p->wakeup);
    pthread_cond_destroy(&p->wakeup_drain);
    pthread_mutex_destroy(&p->lock);
}

static int init(struct ao *ao)
{
    struct ao_push_state *p = ao->api_priv;

    pthread_mutex_init(&p->lock, NULL);
    pthread_cond_init(&p->wakeup, NULL);
    pthread_cond_init(&p->wakeup_drain, NULL);
    mp_make_wakeup_pipe(p->wakeup_pipe);

    p->buffer = mp_audio_buffer_create(ao);
    mp_audio_buffer_reinit_fmt(p->buffer, ao->format,
                               &ao->channels, ao->samplerate);
    mp_audio_buffer_preallocate_min(p->buffer, ao->buffer);
    if (pthread_create(&p->thread, NULL, playthread, ao)) {
        ao->driver->uninit(ao);
        return -1;
    }
    return 0;
}

const struct ao_driver ao_api_push = {
    .init = init,
    .control = control,
    .uninit = uninit,
    .reset = reset,
    .get_space = get_space,
    .play = play,
    .get_delay = get_delay,
    .pause = audio_pause,
    .resume = resume,
    .drain = drain,
    .priv_size = sizeof(struct ao_push_state),
};

// Must be called locked.
int ao_play_silence(struct ao *ao, int samples)
{
    assert(ao->api == &ao_api_push);
    if (samples <= 0 || AF_FORMAT_IS_SPECIAL(ao->format) || !ao->driver->play)
        return 0;
    char *p = talloc_size(NULL, samples * ao->sstride);
    af_fill_silence(p, samples * ao->sstride, ao->format);
    void *tmp[MP_NUM_CHANNELS];
    for (int n = 0; n < MP_NUM_CHANNELS; n++)
        tmp[n] = p;
    int r = ao->driver->play(ao, tmp, samples, 0);
    talloc_free(p);
    return r;
}

#ifndef __MINGW32__

#include <poll.h>

#define MAX_POLL_FDS 20

// Call poll() for the given fds. This will extend the given fds with the
// wakeup pipe, so ao_wakeup_poll() will basically interrupt this function.
// Unlocks the lock temporarily.
// Returns <0 on error, 0 on success, 1 if the caller should return immediately.
int ao_wait_poll(struct ao *ao, struct pollfd *fds, int num_fds,
                 pthread_mutex_t *lock)
{
    struct ao_push_state *p = ao->api_priv;
    assert(ao->api == &ao_api_push);
    assert(&p->lock == lock);

    if (num_fds > MAX_POLL_FDS || p->wakeup_pipe[0] < 0)
        return -1;

    struct pollfd p_fds[MAX_POLL_FDS];
    memcpy(p_fds, fds, num_fds * sizeof(p_fds[0]));
    p_fds[num_fds] = (struct pollfd){
        .fd = p->wakeup_pipe[0],
        .events = POLLIN,
    };

    pthread_mutex_unlock(&p->lock);
    int r = poll(p_fds, num_fds + 1, -1);
    r = r < 0 ? -errno : 0;
    pthread_mutex_lock(&p->lock);

    memcpy(fds, p_fds, num_fds * sizeof(fds[0]));
    bool wakeup = false;
    if (p_fds[num_fds].revents & POLLIN) {
        wakeup = true;
        // flush the wakeup pipe contents - might "drown" some wakeups, but
        // that's ok for our use-case
        char buf[100];
        read(p->wakeup_pipe[0], buf, sizeof(buf));
    }
    return (r >= 0 || r == -EINTR) ? wakeup : -1;
}

void ao_wakeup_poll(struct ao *ao)
{
    assert(ao->api == &ao_api_push);
    struct ao_push_state *p = ao->api_priv;

    write(p->wakeup_pipe[1], &(char){0}, 1);
}

#endif