wasapi: first stab of audio output using the Windows Audio Session API

This is _very_ incomplete and buggy:
 - no time synchronization,
 - no sample format, sample rate and channels mask negotiation,
 - no channels reordering,
 - no S/PDIF and HDMI pass-through,
 - no volume control,
 - no device selection,
 - no fail-over to another device when needed,
 - leaking COM thread data at exit (missing dedicated thread),
 - incomplete build system integration.

But it compiles (with mingw-w64) and outputs working audio.

modules/audio_output/Modules.am

@@ -45,6 +45,12 @@ if HAVE_PULSE
 libvlc_LTLIBRARIES += libpulse_plugin.la
 endif
 
+libwasapi_plugin_la_SOURCES = wasapi.c
+libwasapi_plugin_la_CFLAGS = $(AM_CFLAGS)
+libwasapi_plugin_la_LIBADD = $(AM_LIBADD) -lole32 -lksuser
+libwasapi_plugin_la_DEPENDENCIES =
+EXTRA_LTLIBRARIES += libwasapi_plugin.la
+
 libkai_plugin_la_SOURCES = kai.c packet.c
 libkai_plugin_la_CFLAGS = $(AM_CFLAGS)
 libkai_plugin_la_LIBADD = $(AM_LIBADD) $(KAI_LIBS)

modules/audio_output/wasapi.c

+/*****************************************************************************
+ * wasapi.c : Windows Audio Session API output plugin for VLC
+ *****************************************************************************
+ * Copyright (C) 2012 Rémi Denis-Courmont
+ *
+ * This program 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.
+ *
+ * This program 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 this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
+ *****************************************************************************/
+
+#ifdef HAVE_CONFIG_H
+# include "config.h"
+#endif
+
+#define INITGUID
+#define COBJMACROS
+
+#include <assert.h>
+#include <audioclient.h>
+#include <mmdeviceapi.h>
+
+#include <vlc_common.h>
+#include <vlc_plugin.h>
+#include <vlc_aout.h>
+
+static int Open(vlc_object_t *);
+static void Close(vlc_object_t *);
+
+vlc_module_begin()
+    set_shortname("WASAPI")
+    set_description(N_("Windows Audio Session output") )
+    set_capability("audio output", 150)
+    set_category(CAT_AUDIO)
+    set_subcategory(SUBCAT_AUDIO_AOUT)
+    add_shortcut("was", "audioclient")
+    set_callbacks(Open, Close)
+vlc_module_end()
+
+struct aout_sys_t
+{
+    IAudioClient *client;
+    IAudioRenderClient *render;
+    UINT32 frames;
+};
+
+static void Play(audio_output_t *aout, block_t *block)
+{
+    aout_sys_t *sys = aout->sys;
+    HRESULT hr;
+
+    while (block->i_nb_samples > 0)
+    {
+        UINT32 frames;
+        hr = IAudioClient_GetCurrentPadding(sys->client, &frames);
+        if (FAILED(hr))
+        {
+            msg_Err(aout, "cannot get current padding (error 0x%lx)", hr);
+            break;
+        }
+
+        assert(frames <= sys->frames);
+        frames = sys->frames - frames;
+        if (frames > block->i_nb_samples)
+            frames = block->i_nb_samples;
+
+        BYTE *dst;
+        hr = IAudioRenderClient_GetBuffer(sys->render, frames, &dst);
+        if (FAILED(hr))
+        {
+            msg_Err(aout, "cannot get buffer (error 0x%lx)", hr);
+            break;
+        }
+
+        const size_t copy = frames * (size_t)aout->format.i_bytes_per_frame;
+
+        memcpy(dst, block->p_buffer, copy);
+        hr = IAudioRenderClient_ReleaseBuffer(sys->render, frames, 0);
+        if (FAILED(hr))
+        {
+            msg_Err(aout, "cannot release buffer (error 0x%lx)", hr);
+            break;
+        }
+
+        block->p_buffer += copy;
+        block->i_buffer -= copy;
+        block->i_nb_samples -= frames;
+
+        /* FIXME: implement synchro */
+        IAudioClient_Start(sys->client);
+        Sleep(AOUT_MIN_PREPARE_TIME / 1000);
+    }
+
+    block_Release(block);
+}
+
+static void Pause(audio_output_t *aout, bool paused, mtime_t date)
+{
+    aout_sys_t *sys = aout->sys;
+    HRESULT hr;
+
+    if (!paused)
+        return;
+
+    hr = IAudioClient_Stop(sys->client);
+    if (FAILED(hr))
+        msg_Warn(aout, "cannot stop stream (error 0x%lx)", hr);
+    (void) date;
+}
+
+static void Flush(audio_output_t *aout, bool wait)
+{
+    aout_sys_t *sys = aout->sys;
+    HRESULT hr;
+
+    if (wait)
+        return;
+
+    hr = IAudioClient_Reset(sys->client);
+    if (FAILED(hr))
+        msg_Warn(aout, "cannot reset stream (error 0x%lx)", hr);
+}
+
+/*static int VolumeSet(audio_output_t *aout, float vol, bool mute)
+{
+    aout_sys_t *sys = aout->sys;
+
+    return 0;
+}*/
+
+static void vlc_ToWave(WAVEFORMATEXTENSIBLE *restrict wf,
+                       audio_sample_format_t *restrict audio)
+{
+    switch (audio->i_format)
+    {
+#if 0
+        case VLC_CODEC_FL32:
+        case VLC_CODEC_FL64:
+            wf->SubFormat = KSDATAFORMAT_SUBTYPE_IEEE_FLOAT;
+            break;
+
+        case VLC_CODEC_S8:
+        case VLC_CODEC_S16N:
+        case VLC_CODEC_S24N:
+        case VLC_CODEC_S32N:
+            wf->SubFormat = KSDATAFORMAT_SUBTYPE_PCM;
+            break;
+#endif
+        default:
+            audio->i_format = VLC_CODEC_FL32;
+            audio->i_rate = 48000;
+            wf->SubFormat = KSDATAFORMAT_SUBTYPE_IEEE_FLOAT;
+            break;
+     }
+     aout_FormatPrepare (audio);
+
+     wf->Format.wFormatTag = WAVE_FORMAT_EXTENSIBLE;
+     wf->Format.nChannels = audio->i_channels;
+     wf->Format.nSamplesPerSec = audio->i_rate;
+     wf->Format.nAvgBytesPerSec = audio->i_bytes_per_frame * audio->i_rate;
+     wf->Format.nBlockAlign = audio->i_bytes_per_frame;
+     wf->Format.wBitsPerSample = audio->i_bitspersample;
+     wf->Format.cbSize = sizeof (*wf) - sizeof (wf->Format);
+
+     wf->Samples.wValidBitsPerSample = audio->i_bitspersample;
+
+     wf->dwChannelMask = 0;
+     if (audio->i_physical_channels & AOUT_CHAN_LEFT)
+         wf->dwChannelMask |= SPEAKER_FRONT_LEFT;
+     if (audio->i_physical_channels & AOUT_CHAN_RIGHT)
+         wf->dwChannelMask |= SPEAKER_FRONT_RIGHT;
+     if (audio->i_physical_channels & AOUT_CHAN_CENTER)
+         wf->dwChannelMask |= SPEAKER_FRONT_CENTER;
+     if (audio->i_physical_channels & AOUT_CHAN_LFE)
+         wf->dwChannelMask |= SPEAKER_LOW_FREQUENCY;
+     // TODO: reorder
+     if (audio->i_physical_channels & AOUT_CHAN_REARLEFT)
+         wf->dwChannelMask |= SPEAKER_BACK_LEFT;
+     if (audio->i_physical_channels & AOUT_CHAN_REARRIGHT)
+         wf->dwChannelMask |= SPEAKER_BACK_RIGHT;
+     /* ... */
+     if (audio->i_physical_channels & AOUT_CHAN_REARCENTER)
+         wf->dwChannelMask |= SPEAKER_BACK_CENTER;
+     if (audio->i_physical_channels & AOUT_CHAN_MIDDLELEFT)
+         wf->dwChannelMask |= SPEAKER_SIDE_LEFT;
+     if (audio->i_physical_channels & AOUT_CHAN_MIDDLERIGHT)
+         wf->dwChannelMask |= SPEAKER_SIDE_RIGHT;
+     /* ... */
+}
+
+static int vlc_FromWave(const WAVEFORMATEX *restrict wf,
+                        audio_sample_format_t *restrict audio)
+{
+    /* FIXME? different sample format? possible? */
+    audio->i_rate = wf->nSamplesPerSec;
+    /* FIXME */
+    if (wf->nChannels != audio->i_channels)
+        return -1;
+
+    aout_FormatPrepare(audio);
+    return 0;
+}
+
+static int Open(vlc_object_t *obj)
+{
+    audio_output_t *aout = (audio_output_t *)obj;
+    HRESULT hr;
+
+    aout_sys_t *sys = malloc(sizeof (*sys));
+    if (unlikely(sys == NULL))
+        return VLC_ENOMEM;
+
+    aout->sys = sys;
+    sys->client = NULL;
+    sys->render = NULL;
+
+    hr = CoInitializeEx(NULL, COINIT_MULTITHREADED);
+    if (FAILED(hr))
+    {
+        free(sys);
+        return VLC_EGENERIC;
+    }
+
+    /* Select audio device */
+    IMMDeviceEnumerator *devs;
+    hr = CoCreateInstance(&CLSID_MMDeviceEnumerator, NULL, CLSCTX_ALL,
+                          &IID_IMMDeviceEnumerator, (void **)&devs);
+    if (FAILED(hr))
+    {
+        msg_Dbg(aout, "cannot create device enumerator (error 0x%lx)", hr);
+        goto error;
+    }
+
+    /* TODO: support selecting a device from config? */
+    IMMDevice *dev;
+    hr = IMMDeviceEnumerator_GetDefaultAudioEndpoint(devs, eRender,
+                                                     eConsole, &dev);
+    IMMDeviceEnumerator_Release(devs);
+    if (FAILED(hr))
+    {
+        msg_Err(aout, "cannot get audio endpoint (error 0x%lx)", hr);
+        goto error;
+    }
+
+    LPWSTR str;
+    hr = IMMDevice_GetId(dev, &str);
+    if (SUCCEEDED(hr))
+    {
+        msg_Dbg(aout, "using device %ls", str);
+        CoTaskMemFree(str);
+    }
+
+    hr = IMMDevice_Activate(dev, &IID_IAudioClient, CLSCTX_ALL, NULL,
+                            (void **)&sys->client);
+    IMMDevice_Release(dev);
+    if (FAILED(hr))
+    {
+        msg_Err(aout, "cannot activate audio client (error 0x%lx)", hr);
+        goto error;
+    }
+
+    /* Configure audio stream */
+    audio_sample_format_t format = aout->format;
+    WAVEFORMATEXTENSIBLE wf;
+    WAVEFORMATEX *pwf;
+
+    vlc_ToWave(&wf, &format);
+    hr = IAudioClient_IsFormatSupported(sys->client, AUDCLNT_SHAREMODE_SHARED,
+                                        &wf.Format, &pwf);
+    // TODO: deal with (hr == AUDCLNT_E_DEVICE_INVALIDATED) ?
+    if (FAILED(hr))
+    {
+        msg_Err(aout, "cannot negotiate audio format (error 0x%lx)", hr);
+        goto error;
+    }
+
+    if (hr == S_FALSE)
+    {
+        assert(pwf != NULL);
+        if (vlc_FromWave(pwf, &format))
+        {
+            CoTaskMemFree(pwf);
+            msg_Err(aout, "unsupported audio format");
+            goto error;
+        }
+        msg_Dbg(aout, "modified format");
+    }
+    else
+        assert(pwf == NULL);
+    hr = IAudioClient_Initialize(sys->client, AUDCLNT_SHAREMODE_SHARED, 0,
+                                 AOUT_MAX_PREPARE_TIME * 10, 0,
+                                 (hr == S_OK) ? &wf.Format : pwf, NULL);
+    CoTaskMemFree(pwf);
+    if (FAILED(hr))
+    {
+        msg_Err(aout, "cannot initialize audio client (error 0x%lx)", hr);
+        goto error;
+    }
+
+    hr = IAudioClient_GetBufferSize(sys->client, &sys->frames);
+    if (FAILED(hr))
+    {
+        msg_Err(aout, "cannot get buffer size (error 0x%lx)", hr);
+        goto error;
+    }
+
+    hr = IAudioClient_GetService(sys->client, &IID_IAudioRenderClient,
+                                 (void **)&sys->render);
+    if (FAILED(hr))
+    {
+        msg_Err(aout, "cannot get audio render service (error 0x%lx)", hr);
+        goto error;
+    }
+
+    aout->format = format;
+    aout->sys = sys;
+    aout->pf_play = Play;
+    aout->pf_pause = Pause;
+    aout->pf_flush = Flush;
+    aout_VolumeNoneInit (aout);
+    return VLC_SUCCESS;
+error:
+    Close(obj);
+    return VLC_EGENERIC;
+}
+
+static void Close (vlc_object_t *obj)
+{
+    audio_output_t *aout = (audio_output_t *)obj;
+    aout_sys_t *sys = aout->sys;
+
+    if (sys->render != NULL)
+        IAudioRenderClient_Release(sys->render);
+    if (sys->client != NULL)
+        IAudioClient_Release(sys->client);
+    /* FIXME: CoUninitialize(); */
+    free(sys);
+}