1
0
mirror of https://github.com/mpv-player/mpv synced 2024-12-29 10:32:15 +00:00
mpv/audio/out/ao_wasapi.h
sunpenghao 6863eefc3d ao_wasapi: address premature buffer fills in exclusive mode
Currently, running AO control wakes up the WASAPI renderer thread in the
`WASAPI_THREAD_FEED` state, where `thread_feed` will be called. However,
it seems that in recent Windows versions (tested on Windows 10 build
19044.3930 and Windows 11 build 22631.3007) we can't know if it is safe
to feed more audio data in event-driven exclusive mode:
- `IAudioClient_GetCurrentPadding` always returns `bufferFrameCount`,
  even if *NO* data has ever been written. This means we don't know how
  much free space we have that is available for writing. This is not the
  case in shared mode, where the return value correctly reflects the
  size of data waiting to be processed. As a sidenote, MS did not
  document the precise definition of the return value for an
  event-driven, exclusive stream [1].
- `IAudioRenderClient_GetBuffer` never fails. We can call it for 10
  times in a roll, each time requesting an entire buffer (the unit at
  which data is exchanged in exclusive mode using event-driven
  buffering; there are 2 such buffers) and get a successful return code
  everytime. In shared mode, we get `AUDCLNT_E_BUFFER_TOO_LARGE` if we
  request a buffer larger than that currently available.

As a result, `thread_feed` will always write `bufferFrameCount` frames
of audio in exclusive mode. There will therefore be glitches each time
`thread_control` is called due to the subsequent `thread_feed`
overwriting frames yet to be processed. Also, an irreversible error is
accumulated to `sample_count` as long as there is no AO reset, leading
to eventual, unbounded A/V desync.

As a fix to the issue, add a dedicated state for dispatch queue
processing so that `thread_feed` is only called when signaled by the OS.
The buffer checks in `thread_feed` that use `GetCurrentPadding` in
exclusive mode are kept in case there are older versions where the two
APIs behave differently.

Closes #12615.

[1] https://learn.microsoft.com/en-us/windows/win32/api/audioclient/nf-audioclient-iaudioclient-getcurrentpadding
2024-02-24 05:26:56 +00:00

118 lines
3.9 KiB
C

/*
* This file is part of mpv.
*
* Original author: Jonathan Yong <10walls@gmail.com>
*
* 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/>.
*/
#ifndef MP_AO_WASAPI_H_
#define MP_AO_WASAPI_H_
#include <stdatomic.h>
#include <stdlib.h>
#include <stdbool.h>
#include <windows.h>
#include <mmdeviceapi.h>
#include <audioclient.h>
#include <audiopolicy.h>
#include <endpointvolume.h>
#include "common/msg.h"
#include "osdep/windows_utils.h"
#include "internal.h"
#include "ao.h"
typedef struct change_notify {
IMMNotificationClient client; // this must be first in the structure!
IMMDeviceEnumerator *pEnumerator; // object where client is registered
LPWSTR monitored; // Monitored device
bool is_hotplug;
struct ao *ao;
} change_notify;
HRESULT wasapi_change_init(struct ao* ao, bool is_hotplug);
void wasapi_change_uninit(struct ao* ao);
enum wasapi_thread_state {
WASAPI_THREAD_FEED = 0,
WASAPI_THREAD_DISPATCH,
WASAPI_THREAD_RESUME,
WASAPI_THREAD_RESET,
WASAPI_THREAD_SHUTDOWN
};
typedef struct wasapi_state {
struct mp_log *log;
bool init_ok; // status of init phase
// Thread handles
HANDLE hInitDone; // set when init is complete in audio thread
HANDLE hAudioThread; // the audio thread itself
HANDLE hWake; // thread wakeup event
atomic_int thread_state; // enum wasapi_thread_state (what to do on wakeup)
struct mp_dispatch_queue *dispatch; // for volume/mute/session display
// for setting the audio thread priority
HANDLE hTask;
// ID of the device to use
LPWSTR deviceID;
// WASAPI object handles owned and used by audio thread
IMMDevice *pDevice;
IAudioClient *pAudioClient;
IAudioRenderClient *pRenderClient;
// WASAPI internal clock information, for estimating delay
IAudioClock *pAudioClock;
atomic_ullong sample_count; // samples per channel written by GetBuffer
UINT64 clock_frequency; // scale for position returned by GetPosition
LARGE_INTEGER qpc_frequency; // frequency of Windows' high resolution timer
// WASAPI control
IAudioSessionControl *pSessionControl; // setting the stream title
IAudioEndpointVolume *pEndpointVolume; // exclusive mode volume/mute
ISimpleAudioVolume *pAudioVolume; // shared mode volume/mute
DWORD vol_hw_support; // is hardware volume supported for exclusive-mode?
// ao options
int opt_exclusive;
// format info
WAVEFORMATEXTENSIBLE format;
AUDCLNT_SHAREMODE share_mode; // AUDCLNT_SHAREMODE_EXCLUSIVE / SHARED
UINT32 bufferFrameCount; // number of frames in buffer
struct ao_convert_fmt convert_format;
change_notify change;
} wasapi_state;
char *mp_PKEY_to_str_buf(char *buf, size_t buf_size, const PROPERTYKEY *pkey);
#define mp_PKEY_to_str(pkey) mp_PKEY_to_str_buf((char[42]){0}, 42, (pkey))
void wasapi_list_devs(struct ao *ao, struct ao_device_list *list);
bstr wasapi_get_specified_device_string(struct ao *ao);
LPWSTR wasapi_find_deviceID(struct ao *ao);
bool wasapi_thread_init(struct ao *ao);
void wasapi_thread_uninit(struct ao *ao);
#define EXIT_ON_ERROR(hres) \
do { if (FAILED(hres)) { goto exit_label; } } while(0)
#define SAFE_DESTROY(unk, release) \
do { if ((unk) != NULL) { release; (unk) = NULL; } } while(0)
#endif