/*

 * 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/>.

 */

#include <stddef.h>

#include <stdbool.h>

#include <inttypes.h>

#include <math.h>

#include <assert.h>

#include "mpv_talloc.h"

#include "common/msg.h"

#include "options/options.h"

#include "options/m_config.h"

#include "options/m_option.h"

#include "common/common.h"

#include "common/encode.h"

#include "options/m_property.h"

#include "osdep/timer.h"

#include "audio/out/ao.h"

#include "audio/format.h"

#include "demux/demux.h"

#include "stream/stream.h"

#include "sub/osd.h"

#include "video/hwdec.h"

#include "filters/f_decoder_wrapper.h"

#include "video/out/vo.h"

#include "core.h"

#include "command.h"

#include "screenshot.h"

enum {

    // update_video() - code also uses: <0 error, 0 eof, >0 progress

    VD_ERROR = -1,

    VD_EOF = 0,         // end of file - no new output

    VD_PROGRESS = 1,    // progress, but no output; repeat call with no waiting

    VD_NEW_FRAME = 2,   // the call produced a new frame

    VD_WAIT = 3,        // no EOF, but no output; wait until wakeup

};

static const char av_desync_help_text[] =

"\n"

"Audio/Video desynchronisation detected! Possible reasons include too slow\n"

"hardware, temporary CPU spikes, broken drivers, and broken files. Audio\n"

"position will not match to the video (see A-V status field).\n"

"Consider trying `--profile=fast` and/or `--hwdec=auto` as they may help.\n"

"\n";

static bool recreate_video_filters(struct MPContext *mpctx)

{

    struct MPOpts *opts = mpctx->opts;

    struct vo_chain *vo_c = mpctx->vo_chain;

    mp_assert(vo_c);

    return mp_output_chain_update_filters(vo_c->filter, opts->vf_settings);

}

int reinit_video_filters(struct MPContext *mpctx)

{

    struct vo_chain *vo_c = mpctx->vo_chain;

    if (!vo_c)

        return 0;

    if (!recreate_video_filters(mpctx))

        return -1;

    mp_force_video_refresh(mpctx);

    mp_notify(mpctx, MPV_EVENT_VIDEO_RECONFIG, NULL);

    return 0;

}

static void vo_chain_reset_state(struct vo_chain *vo_c)

{

    vo_seek_reset(vo_c->vo);

    vo_c->underrun = false;

    vo_c->underrun_signaled = false;

}

void reset_video_state(struct MPContext *mpctx)

{

    if (mpctx->vo_chain) {

        vo_chain_reset_state(mpctx->vo_chain);

        struct track *t = mpctx->vo_chain->track;

        if (t && t->dec)

            mp_decoder_wrapper_set_play_dir(t->dec, mpctx->play_dir);

    }

    for (int n = 0; n < mpctx->num_next_frames; n++)

        mp_image_unrefp(&mpctx->next_frames[n]);

    mpctx->num_next_frames = 0;

    mp_image_unrefp(&mpctx->saved_frame);

    mpctx->delay = 0;

    mpctx->time_frame = 0;

    mpctx->video_pts = MP_NOPTS_VALUE;

    mpctx->last_frame_duration = 0;

    mpctx->num_past_frames = 0;

    mpctx->total_avsync_change = 0;

    mpctx->last_av_difference = 0;

    mpctx->mistimed_frames_total = 0;

    mpctx->drop_message_shown = 0;

    mpctx->display_sync_drift_dir = 0;

    mpctx->display_sync_error = 0;

    mpctx->display_sync_active = 0;

    mpctx->video_status = mpctx->vo_chain ? STATUS_SYNCING : STATUS_EOF;

}

void uninit_video_out(struct MPContext *mpctx)

{

    uninit_video_chain(mpctx);

    if (mpctx->video_out) {

        vo_destroy(mpctx->video_out);

        mpctx->video_out = NULL;

        mp_notify(mpctx, MPV_EVENT_VIDEO_RECONFIG, NULL);

    }

}

static void vo_chain_uninit(struct vo_chain *vo_c)

{

    struct track *track = vo_c->track;

    if (track) {

        mp_assert(track->vo_c == vo_c);

        track->vo_c = NULL;

        if (vo_c->dec_src)

            mp_assert(track->dec->f->pins[0] == vo_c->dec_src);

        talloc_free(track->dec->f);

        track->dec = NULL;

    }

    if (vo_c->filter_src)

        mp_pin_disconnect(vo_c->filter_src);

    talloc_free(vo_c->filter->f);

    talloc_free(vo_c);

    // this does not free the VO

}

void uninit_video_chain(struct MPContext *mpctx)

{

    if (mpctx->vo_chain) {

        reset_video_state(mpctx);

        vo_chain_uninit(mpctx->vo_chain);

        mpctx->vo_chain = NULL;

        mpctx->video_status = STATUS_EOF;

        mp_notify(mpctx, MPV_EVENT_VIDEO_RECONFIG, NULL);

    }

}

int init_video_decoder(struct MPContext *mpctx, struct track *track)

{

    mp_assert(!track->dec);

    if (!track->stream)

        goto err_out;

    struct mp_filter *parent = mpctx->filter_root;

    // If possible, set this as parent so the decoder gets the hwdec and DR

    // interfaces.

    // Note: We rely on being able to get rid of all references to the VO by

    //       destroying the VO chain. Thus, decoders not linked to vo_chain

    //       must not use the hwdec context.

    if (track->vo_c)

        parent = track->vo_c->filter->f;

    track->dec = mp_decoder_wrapper_create(parent, track->stream);

    if (!track->dec)

        goto err_out;

    if (!mp_decoder_wrapper_reinit(track->dec))

        goto err_out;

    return 1;

err_out:

    if (track->sink)

        mp_pin_disconnect(track->sink);

    track->sink = NULL;

    error_on_track(mpctx, track);

    return 0;

}

void reinit_video_chain(struct MPContext *mpctx)

{

    struct track *track = mpctx->current_track[0][STREAM_VIDEO];

    if (!track || !track->stream) {

        error_on_track(mpctx, track);

        return;

    }

    reinit_video_chain_src(mpctx, track);

}

static void filter_update_subtitles(void *ctx, double pts)

{

    struct MPContext *mpctx = ctx;

    if (osd_get_render_subs_in_filter(mpctx->osd))

        update_subtitles(mpctx, pts);

}

// (track=NULL creates a blank chain, used for lavfi-complex)

void reinit_video_chain_src(struct MPContext *mpctx, struct track *track)

{

    mp_assert(!mpctx->vo_chain);

    if (!mpctx->video_out) {

        struct vo_extra ex = {

            .input_ctx = mpctx->input,

            .osd = mpctx->osd,

            .encode_lavc_ctx = mpctx->encode_lavc_ctx,

            .wakeup_cb = mp_wakeup_core_cb,

            .wakeup_ctx = mpctx,

        };

        mpctx->video_out = init_best_video_out(mpctx->global, &ex);

        if (!mpctx->video_out) {

            MP_FATAL(mpctx, "Error opening/initializing "

                    "the selected video_out (--vo) device.\n");

            mpctx->error_playing = MPV_ERROR_VO_INIT_FAILED;

            goto err_out;

        }

        mpctx->mouse_cursor_visible = true;

    }

    update_window_title(mpctx, true);

    struct vo_chain *vo_c = talloc_zero(NULL, struct vo_chain);

    mpctx->vo_chain = vo_c;

    vo_c->log = mpctx->log;

    vo_c->vo = mpctx->video_out;

    vo_c->filter =

        mp_output_chain_create(mpctx->filter_root, MP_OUTPUT_CHAIN_VIDEO);

    mp_output_chain_set_vo(vo_c->filter, vo_c->vo);

    vo_c->filter->update_subtitles = filter_update_subtitles;

    vo_c->filter->update_subtitles_ctx = mpctx;

    if (track) {

        vo_c->track = track;

        track->vo_c = vo_c;

        if (!init_video_decoder(mpctx, track))

            goto err_out;

        vo_c->dec_src = track->dec->f->pins[0];

        vo_c->filter->container_fps =

            mp_decoder_wrapper_get_container_fps(track->dec);

        vo_c->is_coverart = !!track->attached_picture;

        vo_c->is_sparse = track->stream->still_image || vo_c->is_coverart;

        if (vo_c->is_coverart)

            mp_decoder_wrapper_set_coverart_flag(track->dec, true);

        track->vo_c = vo_c;

        vo_c->track = track;

        mp_pin_connect(vo_c->filter->f->pins[0], vo_c->dec_src);

    }

    if (!recreate_video_filters(mpctx))

        goto err_out;

    update_content_type(mpctx, track);

    update_screensaver_state(mpctx);

    vo_set_paused(vo_c->vo, get_internal_paused(mpctx));

    reset_video_state(mpctx);

    term_osd_clear_subs(mpctx);

    return;

err_out:

    uninit_video_chain(mpctx);

    error_on_track(mpctx, track);

    handle_force_window(mpctx, true);

}

// Try to refresh the video by doing a precise seek to the currently displayed

// frame. This can go wrong in all sorts of ways, so use sparingly.

void mp_force_video_refresh(struct MPContext *mpctx)

{

    struct MPOpts *opts = mpctx->opts;

    struct vo_chain *vo_c = mpctx->vo_chain;

    if (!vo_c)

        return;

    // If not paused, the next frame should come soon enough.

    if (opts->pause || mpctx->time_frame >= 0.5 ||

        mpctx->video_status == STATUS_EOF)

    {

        issue_refresh_seek(mpctx, MPSEEK_VERY_EXACT);

    }

}

static void check_framedrop(struct MPContext *mpctx, struct vo_chain *vo_c)

{

    struct MPOpts *opts = mpctx->opts;

    // check for frame-drop:

    if (mpctx->video_status == STATUS_PLAYING && !mpctx->paused &&

        mpctx->audio_status == STATUS_PLAYING && !ao_untimed(mpctx->ao) &&

        vo_c->track && vo_c->track->dec && (opts->frame_dropping & 2))

    {

        float fps = vo_c->filter->container_fps;

        // it's a crappy heuristic; avoid getting upset by incorrect fps

        if (fps <= 20 || fps >= 500)

            return;

        double frame_time =  1.0 / fps;

        // try to drop as many frames as we appear to be behind

        mp_decoder_wrapper_set_frame_drops(vo_c->track->dec,

            MPCLAMP((mpctx->last_av_difference - 0.010) / frame_time, 0, 100));

    }

}

/* Modify video timing to match the audio timeline. There are two main

 * reasons this is needed. First, video and audio can start from different

 * positions at beginning of file or after a seek (MPlayer starts both

 * immediately even if they have different pts). Second, the file can have

 * audio timestamps that are inconsistent with the duration of the audio

 * packets, for example two consecutive timestamp values differing by

 * one second but only a packet with enough samples for half a second

 * of playback between them.

 */

static void adjust_sync(struct MPContext *mpctx, double v_pts, double frame_time)

{

    struct MPOpts *opts = mpctx->opts;

    if (mpctx->audio_status != STATUS_PLAYING)

        return;

    double a_pts = written_audio_pts(mpctx) + opts->audio_delay - mpctx->delay;

    double av_delay = a_pts - v_pts;

    double change = av_delay * 0.1;

    double factor = fabs(av_delay) < 0.3 ? 0.1 : 0.4;

    double max_change = opts->default_max_pts_correction >= 0 ?

                        opts->default_max_pts_correction : frame_time * factor;

    if (change < -max_change)

        change = -max_change;

    else if (change > max_change)

        change = max_change;

    mpctx->delay += change;

    mpctx->total_avsync_change += change;

    if (mpctx->display_sync_active)

        mpctx->total_avsync_change = 0;

}

// Make the frame at position 0 "known" to the playback logic. This must happen

// only once for each frame, so this function has to be called carefully.

// Generally, if position 0 gets a new frame, this must be called.

static void handle_new_frame(struct MPContext *mpctx)

{

    mp_assert(mpctx->num_next_frames >= 1);

    double frame_time = 0;

    double pts = mpctx->next_frames[0]->pts;

    bool is_sparse = mpctx->vo_chain && mpctx->vo_chain->is_sparse;

    if (mpctx->video_pts != MP_NOPTS_VALUE) {

        frame_time = pts - mpctx->video_pts;

        double tolerance = mpctx->demuxer->ts_resets_possible &&

                           !is_sparse ? 5 : 1e4;

        if (frame_time <= 0 || frame_time >= tolerance) {

            // Assume a discontinuity.

            MP_WARN(mpctx, "Invalid video timestamp: %f -> %f\n",

                    mpctx->video_pts, pts);

            frame_time = 0;

        }

    }

    mpctx->time_frame += frame_time / mpctx->video_speed;

    if (mpctx->ao_chain && !mpctx->ao_chain->delaying_audio_start)

        mpctx->delay -= frame_time;

    if (mpctx->video_status >= STATUS_PLAYING)

        adjust_sync(mpctx, pts, frame_time);

    MP_TRACE(mpctx, "frametime=%5.3f\n", frame_time);

}

// Remove the first frame in mpctx->next_frames

static void shift_frames(struct MPContext *mpctx)

{

    if (mpctx->num_next_frames < 1)

        return;

    talloc_free(mpctx->next_frames[0]);

    for (int n = 0; n < mpctx->num_next_frames - 1; n++)

        mpctx->next_frames[n] = mpctx->next_frames[n + 1];

    mpctx->num_next_frames -= 1;

}

static bool use_video_lookahead(struct MPContext *mpctx)

{

    return mpctx->video_out &&

           !(mpctx->video_out->driver->caps & VO_CAP_NORETAIN) &&

           !(mpctx->opts->untimed || (mpctx->video_out->driver->caps & VO_CAP_UNTIMED)) &&

           !mpctx->opts->video_latency_hacks;

}

static int get_req_frames(struct MPContext *mpctx, bool eof)

{

    // On EOF, drain all frames.

    if (eof)

        return 1;

    if (!use_video_lookahead(mpctx))

        return 1;

    if (mpctx->vo_chain && mpctx->vo_chain->is_sparse)

        return 1;

    // Normally require at least 2 frames, so we can compute a frame duration.

    int min = 2;

    // On the first frame, output a new frame as quickly as possible.

    if (mpctx->video_pts == MP_NOPTS_VALUE)

        return min;

    int req = vo_get_num_req_frames(mpctx->video_out);

    return MPCLAMP(req, min, MP_ARRAY_SIZE(mpctx->next_frames) - 1);

}

// Whether it's fine to call add_new_frame() now.

static bool needs_new_frame(struct MPContext *mpctx)

{

    return mpctx->num_next_frames < get_req_frames(mpctx, false);

}

// Queue a frame to mpctx->next_frames[]. Call only if needs_new_frame() signals ok.

static void add_new_frame(struct MPContext *mpctx, struct mp_image *frame)

{

    mp_assert(mpctx->num_next_frames < MP_ARRAY_SIZE(mpctx->next_frames));

    mp_assert(frame);

    mpctx->next_frames[mpctx->num_next_frames++] = frame;

    if (mpctx->num_next_frames == 1)

        handle_new_frame(mpctx);

}

// Enough video filtered already to push one frame to the VO?

// Set eof to true if no new frames are to be expected.

static bool have_new_frame(struct MPContext *mpctx, bool eof)

{

    return mpctx->num_next_frames >= get_req_frames(mpctx, eof);

}

// Fill mpctx->next_frames[] with a newly filtered or decoded image.

// logical_eof: is set to true if there is EOF after currently queued frames

// returns VD_* code

static int video_output_image(struct MPContext *mpctx, bool *logical_eof)

{

    struct vo_chain *vo_c = mpctx->vo_chain;

    bool hrseek = false;

    double hrseek_pts = mpctx->hrseek_pts;

    double tolerance = mpctx->hrseek_backstep ? 0 : .005;

    if (mpctx->video_status == STATUS_SYNCING) {

        hrseek = mpctx->hrseek_active;

        // playback_pts is normally only set when audio and video have started

        // playing normally. If video is in syncing mode, then this must mean

        // video was just enabled via track switching - skip to current time.

        if (!hrseek && mpctx->playback_pts != MP_NOPTS_VALUE) {

            hrseek = true;

            hrseek_pts = mpctx->playback_pts;

        }

    }

    if (vo_c->is_coverart) {

        *logical_eof = true;

        if (vo_has_frame(mpctx->video_out))

            return VD_EOF;

        hrseek = false;

    }

    if (have_new_frame(mpctx, false))

        return VD_NEW_FRAME;

    // Get a new frame if we need one.

    int r = VD_PROGRESS;

    if (needs_new_frame(mpctx)) {

        // Filter a new frame.

        struct mp_image *img = NULL;

        struct mp_frame frame = mp_pin_out_read(vo_c->filter->f->pins[1]);

        if (frame.type == MP_FRAME_NONE) {

            r = vo_c->filter->got_output_eof ? VD_EOF : VD_WAIT;

        } else if (frame.type == MP_FRAME_EOF) {

            r = VD_EOF;

        } else if (frame.type == MP_FRAME_VIDEO) {

            img = frame.data;

        } else {

            MP_ERR(mpctx, "unexpected frame type %s\n",

                   mp_frame_type_str(frame.type));

            mp_frame_unref(&frame);

            return VD_ERROR;

        }

        if (img) {

            double endpts = get_play_end_pts(mpctx);

            if (endpts != MP_NOPTS_VALUE)

                endpts *= mpctx->play_dir;

            if ((endpts != MP_NOPTS_VALUE && img->pts >= endpts) ||

                mpctx->max_frames == 0)

            {

                mp_pin_out_unread(vo_c->filter->f->pins[1], frame);

                img = NULL;

                r = VD_EOF;

            } else if (hrseek && (img->pts < hrseek_pts - tolerance ||

                                  mpctx->hrseek_lastframe))

            {

                /* just skip - but save in case it was the last frame */

                mp_image_setrefp(&mpctx->saved_frame, img);

            } else {

                if (hrseek && mpctx->hrseek_backstep) {

                    if (mpctx->saved_frame) {

                        add_new_frame(mpctx, mpctx->saved_frame);

                        mpctx->saved_frame = NULL;

                    } else {

                        MP_WARN(mpctx, "Backstep failed.\n");

                    }

                    mpctx->hrseek_backstep = false;

                }

                mp_image_unrefp(&mpctx->saved_frame);

                add_new_frame(mpctx, img);

                img = NULL;

            }

            talloc_free(img);

        }

    }

    if (!hrseek)

        mp_image_unrefp(&mpctx->saved_frame);

    if (r == VD_EOF) {

        // If hr-seek went past EOF, use the last frame.

        if (mpctx->saved_frame)

            add_new_frame(mpctx, mpctx->saved_frame);

        mpctx->saved_frame = NULL;

        *logical_eof = true;

    }

    return have_new_frame(mpctx, r <= 0) ? VD_NEW_FRAME : r;

}

static bool check_for_hwdec_fallback(struct MPContext *mpctx)

{

    struct vo_chain *vo_c = mpctx->vo_chain;

    if (!vo_c->filter->failed_output_conversion || !vo_c->track || !vo_c->track->dec)

        return false;

    if (mp_decoder_wrapper_control(vo_c->track->dec,

                            VDCTRL_FORCE_HWDEC_FALLBACK, NULL) != CONTROL_OK)

        return false;

    mp_output_chain_reset_harder(vo_c->filter);

    return true;

}

static bool check_for_forced_eof(struct MPContext *mpctx)

{

    struct vo_chain *vo_c = mpctx->vo_chain;

    if (!vo_c->track || !vo_c->track->dec)

        return false;

    struct mp_decoder_wrapper *dec = vo_c->track->dec;

    bool forced_eof = false;

    mp_decoder_wrapper_control(dec, VDCTRL_CHECK_FORCED_EOF, &forced_eof);

    return forced_eof;

}

/* Update avsync before a new video frame is displayed. Actually, this can be

 * called arbitrarily often before the actual display.

 * This adjusts the time of the next video frame */

static void update_avsync_before_frame(struct MPContext *mpctx)

{

    struct MPOpts *opts = mpctx->opts;

    struct vo *vo = mpctx->video_out;

    if (mpctx->video_status < STATUS_READY) {

        mpctx->time_frame = 0;

    } else if (mpctx->display_sync_active || vo->opts->video_sync == VS_NONE) {

        // don't touch the timing

    } else if (mpctx->audio_status == STATUS_PLAYING &&

               mpctx->video_status == STATUS_PLAYING &&

               !ao_untimed(mpctx->ao))

    {

        double buffered_audio = ao_get_delay(mpctx->ao);

        double predicted = mpctx->delay / mpctx->video_speed +

                           mpctx->time_frame;

        double difference = buffered_audio - predicted;

        MP_STATS(mpctx, "value %f audio-diff", difference);

        if (opts->autosync) {

            /* Smooth reported playback position from AO by averaging

             * it with the value expected based on previous value and

             * time elapsed since then. May help smooth video timing

             * with audio output that have inaccurate position reporting.

             * This is badly implemented; the behavior of the smoothing

             * now undesirably depends on how often this code runs

             * (mainly depends on video frame rate). */

            buffered_audio = predicted + difference / opts->autosync;

        }

        mpctx->time_frame = buffered_audio - mpctx->delay / mpctx->video_speed;

    } else {

        /* If we're more than 200 ms behind the right playback

         * position, don't try to speed up display of following

         * frames to catch up; continue with default speed from

         * the current frame instead.

         * If untimed is set always output frames immediately

         * without sleeping.

         */

        if (mpctx->time_frame < -0.2 || opts->untimed ||

            (vo->driver->caps & VO_CAP_UNTIMED))

            mpctx->time_frame = 0;

    }

}

// Update the A/V sync difference when a new video frame is being shown.

static void update_av_diff(struct MPContext *mpctx, double offset)

{

    struct MPOpts *opts = mpctx->opts;

    mpctx->last_av_difference = 0;

    if (mpctx->audio_status != STATUS_PLAYING ||

        mpctx->video_status != STATUS_PLAYING)

        return;

    if (mpctx->vo_chain && mpctx->vo_chain->is_sparse)

        return;

    double a_pos = playing_audio_pts(mpctx);

    if (a_pos != MP_NOPTS_VALUE && mpctx->video_pts != MP_NOPTS_VALUE) {

        mpctx->last_av_difference = a_pos - mpctx->video_pts

                                  + opts->audio_delay + offset;

    }

    if (fabs(mpctx->last_av_difference) > 0.5 && !mpctx->drop_message_shown) {

        MP_WARN(mpctx, "%s", av_desync_help_text);

        mpctx->drop_message_shown = true;

    }

}

double calc_average_frame_duration(struct MPContext *mpctx)

{

    double total = 0;

    int num = 0;

    for (int n = 0; n < mpctx->num_past_frames; n++) {

        double dur = mpctx->past_frames[n].approx_duration;

        if (dur <= 0)

            continue;

        total += dur;

        num += 1;

    }

    return num > 0 ? total / num : 0;

}

// Find a speed factor such that the display FPS is an integer multiple of the

// effective video FPS. If this is not possible, try to do it for multiples,

// which still leads to an improved end result.

// Both parameters are durations in seconds.

static double calc_best_speed(double vsync, double frame,

                              double max_change, int max_factor)

{

    double ratio = frame / vsync;

    for (int factor = 1; factor <= max_factor; factor++) {

        double scale = ratio * factor / rint(ratio * factor);

        if (fabs(scale - 1) <= max_change)

            return scale;

    }

    return -1;

}

static double find_best_speed(struct MPContext *mpctx, double vsync)

{

    double total = 0;

    int num = 0;

    for (int n = 0; n < mpctx->num_past_frames; n++) {

        double dur = mpctx->past_frames[n].approx_duration;

        if (dur <= 0)

            continue;

        double best = calc_best_speed(vsync, dur / mpctx->opts->playback_speed,

                                 mpctx->opts->sync_max_video_change / 100,

                                 mpctx->opts->sync_max_factor);

        if (best <= 0)

            continue;

        total += best;

        num++;

    }

    // If it doesn't work, play at normal speed.

    return num > 0 ? total / num : 1;

}

static bool using_spdif_passthrough(struct MPContext *mpctx)

{

    if (mpctx->ao_chain && mpctx->ao_chain->ao) {

        int samplerate;

        int format;

        struct mp_chmap channels;

        ao_get_format(mpctx->ao_chain->ao, &samplerate, &format, &channels);

        return !af_fmt_is_pcm(format);

    }

    return false;

}

// Compute the relative audio speed difference by taking A/V dsync into account.

static double compute_audio_drift(struct MPContext *mpctx, double vsync)

{

    // Least-squares linear regression, using relative real time for x, and

    // audio desync for y. Assume speed didn't change for the frames we're

    // looking at for simplicity. This also should actually use the realtime

    // (minus paused time) for x, but use vsync scheduling points instead.

    if (mpctx->num_past_frames <= 10)

        return NAN;

    int num = mpctx->num_past_frames - 1;

    double sum_x = 0, sum_y = 0, sum_xy = 0, sum_xx = 0;

    double x = 0;

    for (int n = 0; n < num; n++) {

        struct frame_info *frame = &mpctx->past_frames[n + 1];

        if (frame->num_vsyncs < 0)

            return NAN;

        double y = frame->av_diff;

        sum_x += x;

        sum_y += y;

        sum_xy += x * y;

        sum_xx += x * x;

        x -= frame->num_vsyncs * vsync;

    }

    return (sum_x * sum_y - num * sum_xy) / (sum_x * sum_x - num * sum_xx);

}

static void adjust_audio_drift_compensation(struct MPContext *mpctx, double vsync)

{

    struct MPOpts *opts = mpctx->opts;

    int mode = mpctx->video_out->opts->video_sync;

    if ((mode != VS_DISP_RESAMPLE && mode != VS_DISP_TEMPO) ||

        mpctx->audio_status != STATUS_PLAYING)

    {

        mpctx->speed_factor_a = mpctx->speed_factor_v;

        return;

    }

    // Try to smooth out audio timing drifts. This can happen if either

    // video isn't playing at expected speed, or audio is not playing at

    // the requested speed. Both are unavoidable.

    // The audio desync is made up of 2 parts: 1. drift due to rounding

    // errors and imperfect information, and 2. an offset, due to

    // unaligned audio/video start, or disruptive events halting audio

    // or video for a small time.

    // Instead of trying to be clever, just apply an awfully dumb drift

    // compensation with a constant factor, which does what we want. In

    // theory we could calculate the exact drift compensation needed,

    // but it likely would be wrong anyway, and we'd run into the same

    // issues again, except with more complex code.

    // 1 means drifts to positive, -1 means drifts to negative

    double max_drift = vsync / 2;

    double av_diff = mpctx->last_av_difference;

    int new = mpctx->display_sync_drift_dir;

    if (av_diff * -mpctx->display_sync_drift_dir >= 0)

        new = 0;

    if (fabs(av_diff) > max_drift)

        new = av_diff >= 0 ? 1 : -1;

    bool change = mpctx->display_sync_drift_dir != new;

    if (new || change) {

        if (change)

            MP_VERBOSE(mpctx, "Change display sync audio drift: %d\n", new);

        mpctx->display_sync_drift_dir = new;

        double max_correct = opts->sync_max_audio_change / 100;

        double audio_factor = 1 + max_correct * -mpctx->display_sync_drift_dir;

        if (new == 0) {

            // If we're resetting, actually try to be clever and pick a speed

            // which compensates the general drift we're getting.

            double drift = compute_audio_drift(mpctx, vsync);

            if (isnormal(drift)) {

                // other = will be multiplied with audio_factor for final speed

                double other = mpctx->opts->playback_speed * mpctx->speed_factor_v;

                audio_factor = (mpctx->audio_speed - drift) / other;

                MP_VERBOSE(mpctx, "Compensation factor: %f\n", audio_factor);

            }

        }

        audio_factor = MPCLAMP(audio_factor, 1 - max_correct, 1 + max_correct);

        mpctx->speed_factor_a = audio_factor * mpctx->speed_factor_v;

    }

}

// Manipulate frame timing for display sync, or do nothing for normal timing.

static void handle_display_sync_frame(struct MPContext *mpctx,

                                      struct vo_frame *frame)

{

    struct MPOpts *opts = mpctx->opts;

    struct vo *vo = mpctx->video_out;

    int mode = vo->opts->video_sync;

    if (!mpctx->display_sync_active) {

        mpctx->display_sync_error = 0.0;

        mpctx->display_sync_drift_dir = 0;

    }

    mpctx->display_sync_active = false;

    if (!VS_IS_DISP(mode) || !vo_is_visible(vo))

        return;

    bool resample = mode == VS_DISP_RESAMPLE || mode == VS_DISP_RESAMPLE_VDROP ||

                    mode == VS_DISP_RESAMPLE_NONE;

    bool drop = mode == VS_DISP_VDROP || mode == VS_DISP_RESAMPLE ||

                mode == VS_DISP_ADROP || mode == VS_DISP_RESAMPLE_VDROP ||

                mode == VS_DISP_TEMPO;

    drop &= frame->can_drop;

    if (resample && using_spdif_passthrough(mpctx))

        return;

    double vsync = vo_get_vsync_interval(vo) / 1e9;

    if (vsync <= 0)

        return;

    double approx_duration = MPMAX(0, mpctx->past_frames[0].approx_duration);

    double adjusted_duration = approx_duration / opts->playback_speed;

    if (adjusted_duration > 0.5)

        return;

    mpctx->speed_factor_v = 1.0;

    if (mode != VS_DISP_VDROP)

        mpctx->speed_factor_v = find_best_speed(mpctx, vsync);

    // Determine for how many vsyncs a frame should be displayed. This can be

    // e.g. 2 for 30hz on a 60hz display. It can also be 0 if the video

    // framerate is higher than the display framerate.

    // We use the speed-adjusted (i.e. real) frame duration for this.

    double frame_duration = adjusted_duration / mpctx->speed_factor_v;

    double ratio = (frame_duration + mpctx->display_sync_error) / vsync;

    int num_vsyncs = MPMAX(lrint(ratio), 0);

    double prev_error = mpctx->display_sync_error;

    mpctx->display_sync_error += frame_duration - num_vsyncs * vsync;

    MP_TRACE(mpctx, "s=%f vsyncs=%d dur=%f ratio=%f err=%.20f (%f/%f)\n",

            mpctx->speed_factor_v, num_vsyncs, adjusted_duration, ratio,

            mpctx->display_sync_error, mpctx->display_sync_error / vsync,

            mpctx->display_sync_error / frame_duration);

    double av_diff = mpctx->last_av_difference;

    MP_STATS(mpctx, "value %f avdiff", av_diff);

    // Intended number of additional display frames to drop (<0) or repeat (>0)

    int drop_repeat = 0;

    // If we are too far ahead/behind, attempt to drop/repeat frames.

    // Tolerate some desync to avoid frame dropping due to jitter.

    if (drop && fabs(av_diff) >= 0.020 && fabs(av_diff) / vsync >= 1)

        drop_repeat = -av_diff / vsync; // round towards 0

    // We can only drop all frames at most. We can repeat much more frames,

    // but we still limit it to 10 times the original frames to avoid that

    // corner cases or exceptional situations cause too much havoc.

    drop_repeat = MPCLAMP(drop_repeat, -num_vsyncs, num_vsyncs * 10);

    num_vsyncs += drop_repeat;

    // Always show the first frame.

    if (mpctx->num_past_frames <= 1 && num_vsyncs < 1)

        num_vsyncs = 1;

    // Estimate the video position, so we can calculate a good A/V difference

    // value below. This is used to estimate A/V drift.

    double time_left = vo_get_delay(vo);

    // We also know that the timing is (necessarily) off, because we have to

    // align frame timings on the vsync boundaries. This is unavoidable, and

    // for the sake of the A/V sync calculations we pretend it's perfect.

    time_left += prev_error;

    // Likewise, we know sync is off, but is going to be compensated.

    time_left += drop_repeat * vsync;

    // If syncing took too long, disregard timing of the first frame.

    if (mpctx->num_past_frames == 2 && time_left < 0) {

        vo_discard_timing_info(vo);

        time_left = 0;

    }

    if (drop_repeat) {

        mpctx->mistimed_frames_total += 1;

        MP_STATS(mpctx, "mistimed");

    }

    mpctx->total_avsync_change = 0;

    update_av_diff(mpctx, time_left * opts->playback_speed);

    mpctx->past_frames[0].num_vsyncs = num_vsyncs;

    mpctx->past_frames[0].av_diff = mpctx->last_av_difference;

    if (resample || mode == VS_DISP_ADROP || mode == VS_DISP_TEMPO) {

        adjust_audio_drift_compensation(mpctx, vsync);

    } else {

        mpctx->speed_factor_a = 1.0;

    }

    // A bad guess, only needed when reverting to audio sync.

    mpctx->time_frame = time_left;

    frame->vsync_interval = vsync;

    frame->vsync_offset = -prev_error;

    frame->ideal_frame_duration = frame_duration;

    frame->ideal_frame_vsync = (-prev_error / frame_duration) * approx_duration;

    frame->ideal_frame_vsync_duration = (vsync / frame_duration) * approx_duration;

    frame->num_vsyncs = num_vsyncs;

    frame->display_synced = true;

    frame->approx_duration = approx_duration;

    // Adjust frame virtual vsyncs by the repeat count

    if (drop_repeat > 0)

        frame->ideal_frame_vsync_duration /= drop_repeat;

    mpctx->display_sync_active = true;

    // Try to avoid audio underruns that may occur if we update

    // the playback speed while in the STATUS_SYNCING state.

    if (mpctx->video_status != STATUS_SYNCING)

        update_playback_speed(mpctx);

    MP_STATS(mpctx, "value %f aspeed", mpctx->speed_factor_a - 1);

    MP_STATS(mpctx, "value %f vspeed", mpctx->speed_factor_v - 1);

}

static void schedule_frame(struct MPContext *mpctx, struct vo_frame *frame)

{

    handle_display_sync_frame(mpctx, frame);

    if (mpctx->num_past_frames > 1 &&

        ((mpctx->past_frames[1].num_vsyncs >= 0) != mpctx->display_sync_active))

    {

        MP_VERBOSE(mpctx, "Video sync mode %s.\n",

                   mpctx->display_sync_active ? "enabled" : "disabled");

    }

    if (!mpctx->display_sync_active) {

        if (mpctx->num_past_frames > 1 && mpctx->past_frames[1].num_vsyncs >= 0) {

            mpctx->speed_factor_a = 1.0;

            mpctx->speed_factor_v = 1.0;

            update_playback_speed(mpctx);

        }

        update_av_diff(mpctx, mpctx->time_frame > 0 ?

            mpctx->time_frame * mpctx->video_speed : 0);

    }