diff mbox series

[FFmpeg-devel,v3] lavdevice: Add AudioToolbox output device.

Message ID a13215f9-5360-a796-5505-05059a583692@mail.de
State Accepted
Headers show
Series [FFmpeg-devel,v3] lavdevice: Add AudioToolbox output device. | expand

Checks

Context Check Description
andriy/default pending
andriy/configure warning Failed to apply patch

Commit Message

Thilo Borgmann June 8, 2020, 7:45 p.m. UTC
$subject, v3.

-Thilo
From c9002ece648aa59b4334efe9fea83d265d64e258 Mon Sep 17 00:00:00 2001
From: Thilo Borgmann <thilo.borgmann@mail.de>
Date: Mon, 8 Jun 2020 21:42:27 +0200
Subject: [PATCH] lavdevice: Add AudioToolbox output device.

---
 Changelog                  |   1 +
 configure                  |   3 +
 doc/outdevs.texi           |  46 ++++++
 libavdevice/Makefile       |   1 +
 libavdevice/alldevices.c   |   1 +
 libavdevice/audiotoolbox.m | 309 +++++++++++++++++++++++++++++++++++++
 6 files changed, 361 insertions(+)
 create mode 100644 libavdevice/audiotoolbox.m

Comments

Thilo Borgmann June 12, 2020, 3:55 p.m. UTC | #1
Am 08.06.20 um 21:45 schrieb Thilo Borgmann:
> $subject, v3.

If there are no more comments I'll push this next week.

-Thilo
Thilo Borgmann June 15, 2020, 1:12 p.m. UTC | #2
Am 12.06.20 um 17:55 schrieb Thilo Borgmann:
> Am 08.06.20 um 21:45 schrieb Thilo Borgmann:
>> $subject, v3.
> 
> If there are no more comments I'll push this next week.

Pushed, thanks!

-Thilo
diff mbox series

Patch

diff --git a/Changelog b/Changelog
index e9781131a3..061be6f882 100644
--- a/Changelog
+++ b/Changelog
@@ -70,6 +70,7 @@  version <next>:
 - NotchLC decoder
 - gradients source video filter
 - MediaFoundation encoder wrapper
+- AudioToolbox output device
 
 
 version 4.2:
diff --git a/configure b/configure
index f97cad0298..1aab998d8e 100755
--- a/configure
+++ b/configure
@@ -3366,6 +3366,8 @@  alsa_outdev_deps="alsa"
 avfoundation_indev_deps="avfoundation corevideo coremedia pthreads"
 avfoundation_indev_suggest="coregraphics applicationservices"
 avfoundation_indev_extralibs="-framework Foundation"
+audiotoolbox_outdev_deps="audiotoolbox pthreads"
+audiotoolbox_outdev_extralibs="-framework AudioToolbox -framework CoreAudio"
 bktr_indev_deps_any="dev_bktr_ioctl_bt848_h machine_ioctl_bt848_h dev_video_bktr_ioctl_bt848_h dev_ic_bt8xx_h"
 caca_outdev_deps="libcaca"
 decklink_deps_any="libdl LoadLibrary"
@@ -6151,6 +6153,7 @@  enabled videotoolbox && check_apple_framework VideoToolbox
 check_apple_framework CoreFoundation
 check_apple_framework CoreMedia
 check_apple_framework CoreVideo
+check_apple_framework CoreAudio
 
 enabled avfoundation && {
     disable coregraphics applicationservices
diff --git a/doc/outdevs.texi b/doc/outdevs.texi
index 60606eb6e7..aaf247995c 100644
--- a/doc/outdevs.texi
+++ b/doc/outdevs.texi
@@ -38,6 +38,52 @@  ffmpeg -i INPUT -f alsa hw:1,7
 @end example
 @end itemize
 
+@section AudioToolbox
+
+AudioToolbox output device.
+
+Allows native output to CoreAudio devices on OSX.
+
+The output filename can be empty (or @code{-}) to refer to the default system output device or a number that refers to the device index as shown using: @code{-list_devices true}.
+
+Alternatively, the audio input device can be chosen by index using the
+@option{
+    -audio_device_index <INDEX>
+}
+, overriding any device name or index given in the input filename.
+
+All available devices can be enumerated by using @option{-list_devices true}, listing
+all device names, UIDs and corresponding indices.
+
+@subsection Options
+
+AudioToolbox supports the following options:
+
+@table @option
+
+@item -audio_device_index <INDEX>
+Specify the audio device by its index. Overrides anything given in the output filename.
+
+@end table
+
+@subsection Examples
+
+@itemize
+
+@item
+Print the list of supported devices and output a sine wave to the default device:
+@example
+$ ffmpeg -f lavfi -i sine=r=44100 -f audiotoolbox -list_devices true -
+@end example
+
+@item
+Output a sine wave to the device with the index 2, overriding any output filename:
+@example
+$ ffmpeg -f lavfi -i sine=r=44100 -f audiotoolbox -audio_device_index 2 -
+@end example
+
+@end itemize
+
 @section caca
 
 CACA output device.
diff --git a/libavdevice/Makefile b/libavdevice/Makefile
index 6ea62b914e..0dfe47a1f4 100644
--- a/libavdevice/Makefile
+++ b/libavdevice/Makefile
@@ -15,6 +15,7 @@  OBJS-$(CONFIG_SHARED)                    += reverse.o
 OBJS-$(CONFIG_ALSA_INDEV)                += alsa_dec.o alsa.o timefilter.o
 OBJS-$(CONFIG_ALSA_OUTDEV)               += alsa_enc.o alsa.o
 OBJS-$(CONFIG_ANDROID_CAMERA_INDEV)      += android_camera.o
+OBJS-$(CONFIG_AUDIOTOOLBOX_OUTDEV)       += audiotoolbox.o
 OBJS-$(CONFIG_AVFOUNDATION_INDEV)        += avfoundation.o
 OBJS-$(CONFIG_BKTR_INDEV)                += bktr.o
 OBJS-$(CONFIG_CACA_OUTDEV)               += caca.o
diff --git a/libavdevice/alldevices.c b/libavdevice/alldevices.c
index 8633433254..a6f68dd3bb 100644
--- a/libavdevice/alldevices.c
+++ b/libavdevice/alldevices.c
@@ -27,6 +27,7 @@ 
 extern AVInputFormat  ff_alsa_demuxer;
 extern AVOutputFormat ff_alsa_muxer;
 extern AVInputFormat  ff_android_camera_demuxer;
+extern AVOutputFormat ff_audiotoolbox_muxer;
 extern AVInputFormat  ff_avfoundation_demuxer;
 extern AVInputFormat  ff_bktr_demuxer;
 extern AVOutputFormat ff_caca_muxer;
diff --git a/libavdevice/audiotoolbox.m b/libavdevice/audiotoolbox.m
new file mode 100644
index 0000000000..c8ac729c2b
--- /dev/null
+++ b/libavdevice/audiotoolbox.m
@@ -0,0 +1,309 @@ 
+/*
+ * AudioToolbox output device
+ * Copyright (c) 2020 Thilo Borgmann <thilo.borgmann@mail.de>
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg 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.
+ *
+ * FFmpeg 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 FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * @file
+ * AudioToolbox output device
+ * @author Thilo Borgmann <thilo.borgmann@mail.de>
+ */
+
+#import <AudioToolbox/AudioToolbox.h>
+#include <pthread.h>
+
+#include "libavutil/opt.h"
+#include "libavformat/internal.h"
+#include "libavutil/internal.h"
+#include "avdevice.h"
+
+typedef struct
+{
+    AVClass             *class;
+
+    AudioQueueBufferRef buffer[2];
+    pthread_mutex_t     buffer_lock[2];
+    int                 cur_buf;
+    AudioQueueRef       queue;
+
+    int                 list_devices;
+    int                 audio_device_index;
+
+} ATContext;
+
+static int check_status(AVFormatContext *avctx, OSStatus *status, const char *msg)
+{
+    if (*status != noErr) {
+        av_log(avctx, AV_LOG_ERROR, "Error: %s (%i)\n", msg, *status);
+        return 1;
+    } else {
+        av_log(avctx, AV_LOG_DEBUG, " OK  : %s\n", msg);
+        return 0;
+    }
+}
+
+static void queue_callback(void* atctx, AudioQueueRef inAQ,
+                           AudioQueueBufferRef inBuffer)
+{
+    // unlock the buffer that has just been consumed
+    ATContext *ctx = (ATContext*)atctx;
+    for (int i = 0; i < 2; i++) {
+        if (inBuffer == ctx->buffer[i]) {
+            pthread_mutex_unlock(&ctx->buffer_lock[i]);
+        }
+    }
+}
+
+static av_cold int at_write_header(AVFormatContext *avctx)
+{
+    ATContext *ctx = (ATContext*)avctx->priv_data;
+    OSStatus err = noErr;
+    CFStringRef device_UID = NULL;
+    AudioDeviceID *devices;
+    int num_devices;
+
+
+    // get devices
+    UInt32 data_size = 0;
+    AudioObjectPropertyAddress prop;
+    prop.mSelector = kAudioHardwarePropertyDevices;
+    prop.mScope    = kAudioObjectPropertyScopeGlobal;
+    prop.mElement  = kAudioObjectPropertyElementMaster;
+    err = AudioObjectGetPropertyDataSize(kAudioObjectSystemObject, &prop, 0, NULL, &data_size);
+    if (check_status(avctx, &err, "AudioObjectGetPropertyDataSize devices"))
+        return AVERROR(EINVAL);
+
+    num_devices = data_size / sizeof(AudioDeviceID);
+
+    devices = (AudioDeviceID*)(av_malloc(data_size));
+    err = AudioObjectGetPropertyData(kAudioObjectSystemObject, &prop, 0, NULL, &data_size, devices);
+    if (check_status(avctx, &err, "AudioObjectGetPropertyData devices")) {
+        av_freep(&devices);
+        return AVERROR(EINVAL);
+    }
+
+    // list devices
+    if (ctx->list_devices) {
+        CFStringRef device_name = NULL;
+        prop.mScope = kAudioDevicePropertyScopeInput;
+
+        av_log(ctx, AV_LOG_INFO, "CoreAudio devices:\n");
+        for(UInt32 i = 0; i < num_devices; ++i) {
+            // UID
+            data_size = sizeof(device_UID);
+            prop.mSelector = kAudioDevicePropertyDeviceUID;
+            err = AudioObjectGetPropertyData(devices[i], &prop, 0, NULL, &data_size, &device_UID);
+            if (check_status(avctx, &err, "AudioObjectGetPropertyData UID"))
+                continue;
+
+            // name
+            data_size = sizeof(device_name);
+            prop.mSelector = kAudioDevicePropertyDeviceNameCFString;
+            err = AudioObjectGetPropertyData(devices[i], &prop, 0, NULL, &data_size, &device_name);
+            if (check_status(avctx, &err, "AudioObjecTGetPropertyData name"))
+                continue;
+
+            av_log(ctx, AV_LOG_INFO, "[%d] %30s, %s\n", i,
+                   CFStringGetCStringPtr(device_name, kCFStringEncodingMacRoman),
+                   CFStringGetCStringPtr(device_UID, kCFStringEncodingMacRoman));
+        }
+    }
+
+    // get user-defined device UID or use default device
+    // -audio_device_index overrides any URL given
+    const char *stream_name = avctx->url;
+    if (stream_name && ctx->audio_device_index == -1) {
+        sscanf(stream_name, "%d", &ctx->audio_device_index);
+    }
+
+    if (ctx->audio_device_index >= 0) {
+        // get UID of selected device
+        data_size = sizeof(device_UID);
+        prop.mSelector = kAudioDevicePropertyDeviceUID;
+        err = AudioObjectGetPropertyData(devices[ctx->audio_device_index], &prop, 0, NULL, &data_size, &device_UID);
+        if (check_status(avctx, &err, "AudioObjecTGetPropertyData UID")) {
+            av_freep(&devices);
+            return AVERROR(EINVAL);
+        }
+    } else {
+        // use default device
+        device_UID = NULL;
+    }
+
+    av_log(ctx, AV_LOG_DEBUG, "stream_name:        %s\n", stream_name);
+    av_log(ctx, AV_LOG_DEBUG, "audio_device_idnex: %i\n", ctx->audio_device_index);
+    av_log(ctx, AV_LOG_DEBUG, "UID:                %s\n", CFStringGetCStringPtr(device_UID, kCFStringEncodingMacRoman));
+
+    // check input stream
+    if (avctx->nb_streams != 1 || avctx->streams[0]->codecpar->codec_type != AVMEDIA_TYPE_AUDIO) {
+        av_log(ctx, AV_LOG_ERROR, "Only a single audio stream is supported.\n");
+        return AVERROR(EINVAL);
+    }
+
+    av_freep(&devices);
+    AVCodecParameters *codecpar = avctx->streams[0]->codecpar;
+
+    // audio format
+    AudioStreamBasicDescription device_format = {0};
+    device_format.mSampleRate        = codecpar->sample_rate;
+    device_format.mFormatID          = kAudioFormatLinearPCM;
+    device_format.mFormatFlags      |= (codecpar->format == AV_SAMPLE_FMT_FLT) ? kLinearPCMFormatFlagIsFloat : 0;
+    device_format.mFormatFlags      |= (codecpar->codec_id == AV_CODEC_ID_PCM_S8) ? kLinearPCMFormatFlagIsSignedInteger : 0;
+    device_format.mFormatFlags      |= (codecpar->codec_id == AV_NE(AV_CODEC_ID_PCM_S16BE, AV_CODEC_ID_PCM_S16LE)) ? kLinearPCMFormatFlagIsSignedInteger : 0;
+    device_format.mFormatFlags      |= (codecpar->codec_id == AV_NE(AV_CODEC_ID_PCM_S24BE, AV_CODEC_ID_PCM_S24LE)) ? kLinearPCMFormatFlagIsSignedInteger : 0;
+    device_format.mFormatFlags      |= (codecpar->codec_id == AV_NE(AV_CODEC_ID_PCM_S32BE, AV_CODEC_ID_PCM_S32LE)) ? kLinearPCMFormatFlagIsSignedInteger : 0;
+    device_format.mFormatFlags      |= (av_sample_fmt_is_planar(codecpar->format)) ? kAudioFormatFlagIsNonInterleaved : 0;
+    device_format.mFormatFlags      |= (codecpar->codec_id == AV_CODEC_ID_PCM_F32BE) ? kAudioFormatFlagIsBigEndian : 0;
+    device_format.mFormatFlags      |= (codecpar->codec_id == AV_CODEC_ID_PCM_S16BE) ? kAudioFormatFlagIsBigEndian : 0;
+    device_format.mFormatFlags      |= (codecpar->codec_id == AV_CODEC_ID_PCM_S24BE) ? kAudioFormatFlagIsBigEndian : 0;
+    device_format.mFormatFlags      |= (codecpar->codec_id == AV_CODEC_ID_PCM_S32BE) ? kAudioFormatFlagIsBigEndian : 0;
+    device_format.mChannelsPerFrame  = codecpar->channels;
+    device_format.mBitsPerChannel    = (codecpar->codec_id == AV_NE(AV_CODEC_ID_PCM_S24BE, AV_CODEC_ID_PCM_S24LE)) ? 24 : (av_get_bytes_per_sample(codecpar->format) << 3);
+    device_format.mBytesPerFrame     = (device_format.mBitsPerChannel >> 3) * device_format.mChannelsPerFrame;
+    device_format.mFramesPerPacket   = 1;
+    device_format.mBytesPerPacket    = device_format.mBytesPerFrame * device_format.mFramesPerPacket;
+    device_format.mReserved          = 0;
+
+    av_log(ctx, AV_LOG_DEBUG, "device_format.mSampleRate        = %i\n", codecpar->sample_rate);
+    av_log(ctx, AV_LOG_DEBUG, "device_format.mFormatID          = %s\n", "kAudioFormatLinearPCM");
+    av_log(ctx, AV_LOG_DEBUG, "device_format.mFormatFlags      |= %s\n", (codecpar->format == AV_SAMPLE_FMT_FLT) ? "kLinearPCMFormatFlagIsFloat" : "0");
+    av_log(ctx, AV_LOG_DEBUG, "device_format.mFormatFlags      |= %s\n", (codecpar->codec_id == AV_CODEC_ID_PCM_S8) ? "kLinearPCMFormatFlagIsSignedInteger" : "0");
+    av_log(ctx, AV_LOG_DEBUG, "device_format.mFormatFlags      |= %s\n", (codecpar->codec_id == AV_NE(AV_CODEC_ID_PCM_S32BE, AV_CODEC_ID_PCM_S32LE)) ? "kLinearPCMFormatFlagIsSignedInteger" : "0");
+    av_log(ctx, AV_LOG_DEBUG, "device_format.mFormatFlags      |= %s\n", (codecpar->codec_id == AV_NE(AV_CODEC_ID_PCM_S16BE, AV_CODEC_ID_PCM_S16LE)) ? "kLinearPCMFormatFlagIsSignedInteger" : "0");
+    av_log(ctx, AV_LOG_DEBUG, "device_format.mFormatFlags      |= %s\n", (codecpar->codec_id == AV_NE(AV_CODEC_ID_PCM_S24BE, AV_CODEC_ID_PCM_S24LE)) ? "kLinearPCMFormatFlagIsSignedInteger" : "0");
+    av_log(ctx, AV_LOG_DEBUG, "device_format.mFormatFlags      |= %s\n", (av_sample_fmt_is_planar(codecpar->format)) ? "kAudioFormatFlagIsNonInterleaved" : "0");
+    av_log(ctx, AV_LOG_DEBUG, "device_format.mFormatFlags      |= %s\n", (codecpar->codec_id == AV_CODEC_ID_PCM_F32BE) ? "kAudioFormatFlagIsBigEndian" : "0");
+    av_log(ctx, AV_LOG_DEBUG, "device_format.mFormatFlags      |= %s\n", (codecpar->codec_id == AV_CODEC_ID_PCM_S16BE) ? "kAudioFormatFlagIsBigEndian" : "0");
+    av_log(ctx, AV_LOG_DEBUG, "device_format.mFormatFlags      |= %s\n", (codecpar->codec_id == AV_CODEC_ID_PCM_S24BE) ? "kAudioFormatFlagIsBigEndian" : "0");
+    av_log(ctx, AV_LOG_DEBUG, "device_format.mFormatFlags      |= %s\n", (codecpar->codec_id == AV_CODEC_ID_PCM_S32BE) ? "kAudioFormatFlagIsBigEndian" : "0");
+    av_log(ctx, AV_LOG_DEBUG, "device_format.mFormatFlags      == %i\n", device_format.mFormatFlags);
+    av_log(ctx, AV_LOG_DEBUG, "device_format.mChannelsPerFrame  = %i\n", codecpar->channels);
+    av_log(ctx, AV_LOG_DEBUG, "device_format.mBitsPerChannel    = %i\n", av_get_bytes_per_sample(codecpar->format) << 3);
+    av_log(ctx, AV_LOG_DEBUG, "device_format.mBytesPerFrame     = %i\n", (device_format.mBitsPerChannel >> 3) * codecpar->channels);
+    av_log(ctx, AV_LOG_DEBUG, "device_format.mBytesPerPacket    = %i\n", device_format.mBytesPerFrame);
+    av_log(ctx, AV_LOG_DEBUG, "device_format.mFramesPerPacket   = %i\n", 1);
+    av_log(ctx, AV_LOG_DEBUG, "device_format.mReserved          = %i\n", 0);
+
+    // create new output queue for the device
+    err = AudioQueueNewOutput(&device_format, queue_callback, ctx,
+                              NULL, kCFRunLoopCommonModes,
+                              0, &ctx->queue);
+    if (check_status(avctx, &err, "AudioQueueNewOutput")) {
+        if (err == kAudioFormatUnsupportedDataFormatError)
+            av_log(ctx, AV_LOG_ERROR, "Unsupported output format.\n");
+        return AVERROR(EINVAL);
+    }
+
+    // set user-defined device or leave untouched for default
+    if (device_UID != NULL) {
+        err = AudioQueueSetProperty(ctx->queue, kAudioQueueProperty_CurrentDevice, &device_UID, sizeof(device_UID));
+        if (check_status(avctx, &err, "AudioQueueSetProperty output UID"))
+            return AVERROR(EINVAL);
+    }
+
+    // start the queue
+    err = AudioQueueStart(ctx->queue, NULL);
+    if (check_status(avctx, &err, "AudioQueueStart"))
+        return AVERROR(EINVAL);
+
+    // init the mutexes for double-buffering
+    pthread_mutex_init(&ctx->buffer_lock[0], NULL);
+    pthread_mutex_init(&ctx->buffer_lock[1], NULL);
+
+    return 0;
+}
+
+static int at_write_packet(AVFormatContext *avctx, AVPacket *pkt)
+{
+    ATContext *ctx = (ATContext*)avctx->priv_data;
+    OSStatus err = noErr;
+
+    // use the other buffer
+    ctx->cur_buf = !ctx->cur_buf;
+
+    // lock for writing or wait for the buffer to be available
+    // will be unlocked by queue callback
+    pthread_mutex_lock(&ctx->buffer_lock[ctx->cur_buf]);
+
+    // (re-)allocate the buffer if not existant or of different size
+    if (!ctx->buffer[ctx->cur_buf] || ctx->buffer[ctx->cur_buf]->mAudioDataBytesCapacity != pkt->size) {
+        err = AudioQueueAllocateBuffer(ctx->queue, pkt->size, &ctx->buffer[ctx->cur_buf]);
+        if (check_status(avctx, &err, "AudioQueueAllocateBuffer")) {
+            pthread_mutex_unlock(&ctx->buffer_lock[ctx->cur_buf]);
+            return AVERROR(ENOMEM);
+        }
+    }
+
+    AudioQueueBufferRef buf = ctx->buffer[ctx->cur_buf];
+
+    // copy audio data into buffer and enqueue the buffer
+    memcpy(buf->mAudioData, pkt->data, buf->mAudioDataBytesCapacity);
+    buf->mAudioDataByteSize = buf->mAudioDataBytesCapacity;
+    err = AudioQueueEnqueueBuffer(ctx->queue, buf, 0, NULL);
+    if (check_status(avctx, &err, "AudioQueueEnqueueBuffer")) {
+        pthread_mutex_unlock(&ctx->buffer_lock[ctx->cur_buf]);
+        return AVERROR(EINVAL);
+    }
+
+    return 0;
+}
+
+static av_cold int at_write_trailer(AVFormatContext *avctx)
+{
+    ATContext *ctx = (ATContext*)avctx->priv_data;
+    OSStatus err = noErr;
+
+    pthread_mutex_destroy(&ctx->buffer_lock[0]);
+    pthread_mutex_destroy(&ctx->buffer_lock[1]);
+
+    err = AudioQueueFlush(ctx->queue);
+    check_status(avctx, &err, "AudioQueueFlush");
+    err = AudioQueueDispose(ctx->queue, true);
+    check_status(avctx, &err, "AudioQueueDispose");
+
+    return 0;
+}
+
+static const AVOption options[] = {
+    { "list_devices", "list available audio devices", offsetof(ATContext, list_devices), AV_OPT_TYPE_BOOL, {.i64=0}, 0, 1, AV_OPT_FLAG_ENCODING_PARAM },
+    { "audio_device_index", "select audio device by index (starts at 0)", offsetof(ATContext, audio_device_index), AV_OPT_TYPE_INT, {.i64 = -1}, -1, INT_MAX, AV_OPT_FLAG_ENCODING_PARAM },
+    { NULL },
+};
+
+static const AVClass at_class = {
+    .class_name = "AudioToolbox",
+    .item_name  = av_default_item_name,
+    .option     = options,
+    .version    = LIBAVUTIL_VERSION_INT,
+    .category   = AV_CLASS_CATEGORY_DEVICE_AUDIO_OUTPUT,
+};
+
+AVOutputFormat ff_audiotoolbox_muxer = {
+    .name           = "audiotoolbox",
+    .long_name      = NULL_IF_CONFIG_SMALL("AudioToolbox output device"),
+    .priv_data_size = sizeof(ATContext),
+    .audio_codec    = AV_NE(AV_CODEC_ID_PCM_S16BE, AV_CODEC_ID_PCM_S16LE),
+    .video_codec    = AV_CODEC_ID_NONE,
+    .write_header   = at_write_header,
+    .write_packet   = at_write_packet,
+    .write_trailer  = at_write_trailer,
+    .flags          = AVFMT_NOFILE,
+    .priv_class     = &at_class,
+};
+