auhal.c

/*****************************************************************************
 * auhal.c: AUHAL and Coreaudio output plugin
 *****************************************************************************
 * Copyright (C) 2005 the VideoLAN team
 * $Id$
 *
 * Authors: Derk-Jan Hartman <hartman at videolan dot org>
 *
 * This program 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.
 *
 * 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 General Public License for more details.
 *
 * You should have received a copy of the GNU 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.
 *****************************************************************************/

/*****************************************************************************
 * Preamble
 *****************************************************************************/
#ifdef HAVE_CONFIG_H
# include "config.h"
#endif

#include <unistd.h>

#include <vlc/vlc.h>
#include <vlc_interface.h>
#include <vlc_aout.h>

#include <CoreAudio/CoreAudio.h>
#include <AudioUnit/AudioUnitProperties.h>
#include <AudioUnit/AudioUnitParameters.h>
#include <AudioUnit/AudioOutputUnit.h>
#include <AudioToolbox/AudioFormat.h>

#define STREAM_FORMAT_MSG( pre, sfm ) \
    pre "[%ld][%4.4s][%ld][%ld][%ld][%ld][%ld][%ld]", \
    (UInt32)sfm.mSampleRate, (char *)&sfm.mFormatID, \
    sfm.mFormatFlags, sfm.mBytesPerPacket, \
    sfm.mFramesPerPacket, sfm.mBytesPerFrame, \
    sfm.mChannelsPerFrame, sfm.mBitsPerChannel

#define STREAM_FORMAT_MSG_FULL( pre, sfm ) \
    pre ":\nsamplerate: [%ld]\nFormatID: [%4.4s]\nFormatFlags: [%ld]\nBypesPerPacket: [%ld]\nFramesPerPacket: [%ld]\nBytesPerFrame: [%ld]\nChannelsPerFrame: [%ld]\nBitsPerChannel[%ld]", \
    (UInt32)sfm.mSampleRate, (char *)&sfm.mFormatID, \
    sfm.mFormatFlags, sfm.mBytesPerPacket, \
    sfm.mFramesPerPacket, sfm.mBytesPerFrame, \
    sfm.mChannelsPerFrame, sfm.mBitsPerChannel

#define BUFSIZE 0xffffff
#define AOUT_VAR_SPDIF_FLAG 0xf00000

/*
 * TODO:
 * - clean up the debug info
 * - clean up C99'isms
 * - be better at changing stream setup or devices setup changes while playing.
 * - fix 6.1 and 7.1
 */

/*****************************************************************************
 * aout_sys_t: private audio output method descriptor
 *****************************************************************************
 * This structure is part of the audio output thread descriptor.
 * It describes the CoreAudio specific properties of an output thread.
 *****************************************************************************/
struct aout_sys_t
{
    AudioDeviceID               i_default_dev;  /* Keeps DeviceID of defaultOutputDevice */
    AudioDeviceID               i_selected_dev; /* Keeps DeviceID of the selected device */
    UInt32                      i_devices;      /* Number of CoreAudio Devices */
    bool                  b_supports_digital;/* Does the currently selected device support digital mode? */
    bool                  b_digital;      /* Are we running in digital mode? */
    mtime_t                     clock_diff;     /* Difference between VLC clock and Device clock */

    /* AUHAL specific */
    Component                   au_component;   /* The Audiocomponent we use */
    AudioUnit                   au_unit;        /* The AudioUnit we use */
    uint8_t                     p_remainder_buffer[BUFSIZE];
    uint32_t                    i_read_bytes;
    uint32_t                    i_total_bytes;

    /* CoreAudio SPDIF mode specific */
    pid_t                       i_hog_pid;      /* The keep the pid of our hog status */
    AudioStreamID               i_stream_id;    /* The StreamID that has a cac3 streamformat */
    int                         i_stream_index; /* The index of i_stream_id in an AudioBufferList */
    AudioStreamBasicDescription stream_format;  /* The format we changed the stream to */
    AudioStreamBasicDescription sfmt_revert;    /* The original format of the stream */
    bool                  b_revert;       /* Wether we need to revert the stream format */
    bool                  b_changed_mixing;/* Wether we need to set the mixing mode back */
};

/*****************************************************************************
 * Local prototypes.
 *****************************************************************************/
static int      Open                    ( vlc_object_t * );
static int      OpenAnalog              ( aout_instance_t * );
static int      OpenSPDIF               ( aout_instance_t * );
static void     Close                   ( vlc_object_t * );

static void     Play                    ( aout_instance_t * );
static void     Probe                   ( aout_instance_t * );

static int      AudioDeviceHasOutput    ( AudioDeviceID );
static int      AudioDeviceSupportsDigital( aout_instance_t *, AudioDeviceID );
static int      AudioStreamSupportsDigital( aout_instance_t *, AudioStreamID );
static int      AudioStreamChangeFormat ( aout_instance_t *, AudioStreamID, AudioStreamBasicDescription );

static OSStatus RenderCallbackAnalog    ( vlc_object_t *, AudioUnitRenderActionFlags *, const AudioTimeStamp *,
                                          unsigned int, unsigned int, AudioBufferList *);
static OSStatus RenderCallbackSPDIF     ( AudioDeviceID, const AudioTimeStamp *, const void *, const AudioTimeStamp *,
                                          AudioBufferList *, const AudioTimeStamp *, void * );
static OSStatus HardwareListener        ( AudioHardwarePropertyID, void *);
static OSStatus StreamListener          ( AudioStreamID, UInt32,
                                          AudioDevicePropertyID, void * );
static int      AudioDeviceCallback     ( vlc_object_t *, const char *,
                                          vlc_value_t, vlc_value_t, void * );


/*****************************************************************************
 * Module descriptor
 *****************************************************************************/
#define ADEV_TEXT N_("Audio Device")
#define ADEV_LONGTEXT N_("Choose a number corresponding to the number of an " \
    "audio device, as listed in your 'Audio Device' menu. This device will " \
    "then be used by default for audio playback.")

vlc_module_begin();
    set_shortname( "auhal" );
    set_description( _("HAL AudioUnit output") );
    set_capability( "audio output", 101 );
    set_category( CAT_AUDIO );
    set_subcategory( SUBCAT_AUDIO_AOUT );
    set_callbacks( Open, Close );
    add_integer( "macosx-audio-device", 0, NULL, ADEV_TEXT, ADEV_LONGTEXT, false );
vlc_module_end();

/*****************************************************************************
 * Open: open macosx audio output
 *****************************************************************************/
static int Open( vlc_object_t * p_this )
{
    OSStatus                err = noErr;
    UInt32                  i_param_size = 0;
    struct aout_sys_t       *p_sys = NULL;
    vlc_value_t             val;
    aout_instance_t         *p_aout = (aout_instance_t *)p_this;

    /* Use int here, to match kAudioDevicePropertyDeviceIsAlive
     * property size */
    int                     b_alive = false; 

    /* Allocate structure */
    p_aout->output.p_sys = malloc( sizeof( aout_sys_t ) );
    if( p_aout->output.p_sys == NULL )
    {
        msg_Err( p_aout, "out of memory" );
        return( VLC_ENOMEM );
    }

    p_sys = p_aout->output.p_sys;
    p_sys->i_default_dev = 0;
    p_sys->i_selected_dev = 0;
    p_sys->i_devices = 0;
    p_sys->b_supports_digital = false;
    p_sys->b_digital = false;
    p_sys->au_component = NULL;
    p_sys->au_unit = NULL;
    p_sys->clock_diff = (mtime_t) 0;
    p_sys->i_read_bytes = 0;
    p_sys->i_total_bytes = 0;
    p_sys->i_hog_pid = -1;
    p_sys->i_stream_id = 0;
    p_sys->i_stream_index = -1;
    p_sys->b_revert = false;
    p_sys->b_changed_mixing = false;
    memset( p_sys->p_remainder_buffer, 0, sizeof(uint8_t) * BUFSIZE );

    p_aout->output.pf_play = Play;
 
    aout_FormatPrint( p_aout, "VLC is looking for:", (audio_sample_format_t *)&p_aout->output.output );
 
    /* Persistent device variable */
    if( var_Type( p_aout->p_libvlc, "macosx-audio-device" ) == 0 )
    {
        var_Create( p_aout->p_libvlc, "macosx-audio-device", VLC_VAR_INTEGER | VLC_VAR_DOINHERIT );
    }

    /* Build a list of devices */
    if( var_Type( p_aout, "audio-device" ) == 0 )
    {
        Probe( p_aout );
    }

    /* What device do we want? */
    if( var_Get( p_aout, "audio-device", &val ) < 0 )
    {
        msg_Err( p_aout, "audio-device var does not exist. device probe failed." );
        goto error;
    }

    p_sys->i_selected_dev = val.i_int & ~AOUT_VAR_SPDIF_FLAG; /* remove SPDIF flag to get the true DeviceID */
    p_sys->b_supports_digital = ( val.i_int & AOUT_VAR_SPDIF_FLAG ) ? true : false;

    /* Check if the desired device is alive and usable */
    /* TODO: add a callback to the device to alert us if the device dies */
    i_param_size = sizeof( b_alive );
    err = AudioDeviceGetProperty( p_sys->i_selected_dev, 0, FALSE,
                                  kAudioDevicePropertyDeviceIsAlive,
                                  &i_param_size, &b_alive );

    if( err != noErr )
    {
        /* Be tolerant, only give a warning here */
        msg_Warn( p_aout, "could not check whether device [0x%x] is alive: %4.4s", (unsigned int)p_sys->i_selected_dev, (char *)&err );
        b_alive = false;
    }

    if( b_alive == false )
    {
        msg_Warn( p_aout, "selected audio device is not alive, switching to default device" );
        p_sys->i_selected_dev = p_sys->i_default_dev;
    }

    i_param_size = sizeof( p_sys->i_hog_pid );
    err = AudioDeviceGetProperty( p_sys->i_selected_dev, 0, FALSE,
                                  kAudioDevicePropertyHogMode,
                                  &i_param_size, &p_sys->i_hog_pid );

    if( err != noErr )
    {
        /* This is not a fatal error. Some drivers simply don't support this property */
        msg_Warn( p_aout, "could not check whether device is hogged: %4.4s",
                 (char *)&err );
        p_sys->i_hog_pid = -1;
    }

    if( p_sys->i_hog_pid != -1 && p_sys->i_hog_pid != getpid() )
    {
        msg_Err( p_aout, "Selected audio device is exclusively in use by another program." );
        intf_UserFatal( p_aout, false, _("Audio output failed"),
                        _("The selected audio output device is exclusively in "
                          "use by another program.") );
        goto error;
    }

    /* Check for Digital mode or Analog output mode */
    if( AOUT_FMT_NON_LINEAR( &p_aout->output.output ) && p_sys->b_supports_digital )
    {
        if( OpenSPDIF( p_aout ) )
            return VLC_SUCCESS;
    }
    else
    {
        if( OpenAnalog( p_aout ) )
            return VLC_SUCCESS;
    }

error:
    /* If we reach this, this aout has failed */
    var_Destroy( p_aout, "audio-device" );
    free( p_sys );
    return VLC_EGENERIC;
}

/*****************************************************************************
 * Open: open and setup a HAL AudioUnit to do analog (multichannel) audio output
 *****************************************************************************/
static int OpenAnalog( aout_instance_t *p_aout )
{
    struct aout_sys_t           *p_sys = p_aout->output.p_sys;
    OSStatus                    err = noErr;
    UInt32                      i_param_size = 0, i = 0;
    int                         i_original;
    ComponentDescription        desc;
    AudioStreamBasicDescription DeviceFormat;
    AudioChannelLayout          *layout;
    AudioChannelLayout          new_layout;
    AURenderCallbackStruct      input;

    /* Lets go find our Component */
    desc.componentType = kAudioUnitType_Output;
    desc.componentSubType = kAudioUnitSubType_HALOutput;
    desc.componentManufacturer = kAudioUnitManufacturer_Apple;
    desc.componentFlags = 0;
    desc.componentFlagsMask = 0;

    p_sys->au_component = FindNextComponent( NULL, &desc );
    if( p_sys->au_component == NULL )
    {
        msg_Warn( p_aout, "we cannot find our HAL component" );
        return false;
    }

    err = OpenAComponent( p_sys->au_component, &p_sys->au_unit );
    if( err != noErr )
    {
        msg_Warn( p_aout, "we cannot open our HAL component" );
        return false;
    }
 
    /* Set the device we will use for this output unit */
    err = AudioUnitSetProperty( p_sys->au_unit,
                         kAudioOutputUnitProperty_CurrentDevice,
                         kAudioUnitScope_Global,
                         0,
                         &p_sys->i_selected_dev,
                         sizeof( AudioDeviceID ));
 
    if( err != noErr )
    {
        msg_Warn( p_aout, "we cannot select the audio device" );
        return false;
    }
 
    /* Get the current format */
    i_param_size = sizeof(AudioStreamBasicDescription);

    err = AudioUnitGetProperty( p_sys->au_unit,
                                   kAudioUnitProperty_StreamFormat,
                                   kAudioUnitScope_Input,
                                   0,
                                   &DeviceFormat,
                                   &i_param_size );
 
    if( err != noErr ) return false;
    else msg_Dbg( p_aout, STREAM_FORMAT_MSG( "current format is: ", DeviceFormat ) );

    /* Get the channel layout of the device side of the unit (vlc -> unit -> device) */
    err = AudioUnitGetPropertyInfo( p_sys->au_unit,
                                   kAudioDevicePropertyPreferredChannelLayout,
                                   kAudioUnitScope_Output,
                                   0,
                                   &i_param_size,
                                   NULL );

    if( err == noErr )
    {
        layout = (AudioChannelLayout *)malloc( i_param_size);

        verify_noerr( AudioUnitGetProperty( p_sys->au_unit,
                                       kAudioDevicePropertyPreferredChannelLayout,
                                       kAudioUnitScope_Output,
                                       0,
                                       layout,
                                       &i_param_size ));
 
        /* We need to "fill out" the ChannelLayout, because there are multiple ways that it can be set */
        if( layout->mChannelLayoutTag == kAudioChannelLayoutTag_UseChannelBitmap)
        {
            /* bitmap defined channellayout */
            verify_noerr( AudioFormatGetProperty( kAudioFormatProperty_ChannelLayoutForBitmap,
                                    sizeof( UInt32), &layout->mChannelBitmap,
                                    &i_param_size,
                                    layout ));
        }
        else if( layout->mChannelLayoutTag != kAudioChannelLayoutTag_UseChannelDescriptions )
        {
            /* layouttags defined channellayout */
            verify_noerr( AudioFormatGetProperty( kAudioFormatProperty_ChannelLayoutForTag,
                                    sizeof( AudioChannelLayoutTag ), &layout->mChannelLayoutTag,
                                    &i_param_size,
                                    layout ));
        }

        msg_Dbg( p_aout, "layout of AUHAL has %d channels" , (int)layout->mNumberChannelDescriptions );
 
        /* Initialize the VLC core channel count */
        p_aout->output.output.i_physical_channels = 0;
        i_original = p_aout->output.output.i_original_channels & AOUT_CHAN_PHYSMASK;
 
        if( i_original == AOUT_CHAN_CENTER || layout->mNumberChannelDescriptions < 2 )
        {
            /* We only need Mono or cannot output more than 1 channel */
            p_aout->output.output.i_physical_channels = AOUT_CHAN_CENTER;
        }
        else if( i_original == (AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT) || layout->mNumberChannelDescriptions < 3 )
        {
            /* We only need Stereo or cannot output more than 2 channels */
            p_aout->output.output.i_physical_channels = AOUT_CHAN_RIGHT | AOUT_CHAN_LEFT;
        }
        else
        {
            /* We want more than stereo and we can do that */
            for( i = 0; i < layout->mNumberChannelDescriptions; i++ )
            {
                msg_Dbg( p_aout, "this is channel: %d", (int)layout->mChannelDescriptions[i].mChannelLabel );

                switch( layout->mChannelDescriptions[i].mChannelLabel )
                {
                    case kAudioChannelLabel_Left:
                        p_aout->output.output.i_physical_channels |= AOUT_CHAN_LEFT;
                        continue;
                    case kAudioChannelLabel_Right:
                        p_aout->output.output.i_physical_channels |= AOUT_CHAN_RIGHT;
                        continue;
                    case kAudioChannelLabel_Center:
                        p_aout->output.output.i_physical_channels |= AOUT_CHAN_CENTER;
                        continue;
                    case kAudioChannelLabel_LFEScreen:
                        p_aout->output.output.i_physical_channels |= AOUT_CHAN_LFE;
                        continue;
                    case kAudioChannelLabel_LeftSurround:
                        p_aout->output.output.i_physical_channels |= AOUT_CHAN_REARLEFT;
                        continue;
                    case kAudioChannelLabel_RightSurround:
                        p_aout->output.output.i_physical_channels |= AOUT_CHAN_REARRIGHT;
                        continue;
                    case kAudioChannelLabel_RearSurroundLeft:
                        p_aout->output.output.i_physical_channels |= AOUT_CHAN_MIDDLELEFT;
                        continue;
                    case kAudioChannelLabel_RearSurroundRight:
                        p_aout->output.output.i_physical_channels |= AOUT_CHAN_MIDDLERIGHT;
                        continue;
                    case kAudioChannelLabel_CenterSurround:
                        p_aout->output.output.i_physical_channels |= AOUT_CHAN_REARCENTER;
                        continue;
                    default:
                        msg_Warn( p_aout, "unrecognized channel form provided by driver: %d", (int)layout->mChannelDescriptions[i].mChannelLabel );
                }
            }
            if( p_aout->output.output.i_physical_channels == 0 )
            {
                p_aout->output.output.i_physical_channels = AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT;
                msg_Err( p_aout, "You should configure your speaker layout with Audio Midi Setup Utility in /Applications/Utilities. Now using Stereo mode." );
                intf_UserFatal( p_aout, false, _("Audio device is not configured"),
                                _("You should configure your speaker layout with "
                                  "the \"Audio Midi Setup\" utility in /Applications/"
                                  "Utilities. Stereo mode is being used now.") );
            }
        }
        free( layout );
    }
    else
    {
        msg_Warn( p_aout, "this driver does not support kAudioDevicePropertyPreferredChannelLayout. BAD DRIVER AUTHOR !!!" );
        p_aout->output.output.i_physical_channels = AOUT_CHAN_LEFT | AOUT_CHAN_RIGHT;
    }

    msg_Dbg( p_aout, "selected %d physical channels for device output", aout_FormatNbChannels( &p_aout->output.output ) );
    msg_Dbg( p_aout, "VLC will output: %s", aout_FormatPrintChannels( &p_aout->output.output ));

    memset (&new_layout, 0, sizeof(new_layout));
    switch( aout_FormatNbChannels( &p_aout->output.output ) )
    {
        case 1:
            new_layout.mChannelLayoutTag = kAudioChannelLayoutTag_Mono;
            break;
        case 2:
            new_layout.mChannelLayoutTag = kAudioChannelLayoutTag_Stereo;
            break;
        case 3:
            if( p_aout->output.output.i_physical_channels & AOUT_CHAN_CENTER )
            {
                new_layout.mChannelLayoutTag = kAudioChannelLayoutTag_DVD_7; // L R C
            }
            else if( p_aout->output.output.i_physical_channels & AOUT_CHAN_LFE )
            {
                new_layout.mChannelLayoutTag = kAudioChannelLayoutTag_DVD_4; // L R LFE
            }
            break;
        case 4:
            if( p_aout->output.output.i_physical_channels & ( AOUT_CHAN_CENTER | AOUT_CHAN_LFE ) )
            {
                new_layout.mChannelLayoutTag = kAudioChannelLayoutTag_DVD_10; // L R C LFE
            }
            else if( p_aout->output.output.i_physical_channels & ( AOUT_CHAN_REARLEFT | AOUT_CHAN_REARRIGHT ) )
            {
                new_layout.mChannelLayoutTag = kAudioChannelLayoutTag_DVD_3; // L R Ls Rs
            }
            else if( p_aout->output.output.i_physical_channels & ( AOUT_CHAN_CENTER | AOUT_CHAN_REARCENTER ) )
            {
                new_layout.mChannelLayoutTag = kAudioChannelLayoutTag_DVD_3; // L R C Cs
            }
            break;
        case 5:
            if( p_aout->output.output.i_physical_channels & ( AOUT_CHAN_CENTER ) )
            {
                new_layout.mChannelLayoutTag = kAudioChannelLayoutTag_DVD_19; // L R Ls Rs C
            }
            else if( p_aout->output.output.i_physical_channels & ( AOUT_CHAN_LFE ) )
            {
                new_layout.mChannelLayoutTag = kAudioChannelLayoutTag_DVD_18; // L R Ls Rs LFE
            }
            break;
        case 6:
            if( p_aout->output.output.i_physical_channels & ( AOUT_CHAN_LFE ) )
            {
                new_layout.mChannelLayoutTag = kAudioChannelLayoutTag_DVD_20; // L R Ls Rs C LFE
            }
            else
            {
                new_layout.mChannelLayoutTag = kAudioChannelLayoutTag_AudioUnit_6_0; // L R Ls Rs C Cs
            }
            break;
        case 7:
            /* FIXME: This is incorrect. VLC uses the internal ordering: L R Lm Rm Lr Rr C LFE but this is wrong */
            new_layout.mChannelLayoutTag = kAudioChannelLayoutTag_MPEG_6_1_A; // L R C LFE Ls Rs Cs
            break;
        case 8:
            /* FIXME: This is incorrect. VLC uses the internal ordering: L R Lm Rm Lr Rr C LFE but this is wrong */
            new_layout.mChannelLayoutTag = kAudioChannelLayoutTag_MPEG_7_1_A; // L R C LFE Ls Rs Lc Rc
            break;
    }

    /* Set up the format to be used */
    DeviceFormat.mSampleRate = p_aout->output.output.i_rate;
    DeviceFormat.mFormatID = kAudioFormatLinearPCM;

    /* We use float 32. It's the best supported format by both VLC and Coreaudio */
    p_aout->output.output.i_format = VLC_FOURCC( 'f','l','3','2');
    DeviceFormat.mFormatFlags = kAudioFormatFlagsNativeFloatPacked;
    DeviceFormat.mBitsPerChannel = 32;
    DeviceFormat.mChannelsPerFrame = aout_FormatNbChannels( &p_aout->output.output );
 
    /* Calculate framesizes and stuff */
    DeviceFormat.mFramesPerPacket = 1;
    DeviceFormat.mBytesPerFrame = DeviceFormat.mBitsPerChannel * DeviceFormat.mChannelsPerFrame / 8;
    DeviceFormat.mBytesPerPacket = DeviceFormat.mBytesPerFrame * DeviceFormat.mFramesPerPacket;
 
    /* Set the desired format */
    i_param_size = sizeof(AudioStreamBasicDescription);
    verify_noerr( AudioUnitSetProperty( p_sys->au_unit,
                                   kAudioUnitProperty_StreamFormat,
                                   kAudioUnitScope_Input,
                                   0,
                                   &DeviceFormat,
                                   i_param_size ));
 
    msg_Dbg( p_aout, STREAM_FORMAT_MSG( "we set the AU format: " , DeviceFormat ) );
 
    /* Retrieve actual format */
    verify_noerr( AudioUnitGetProperty( p_sys->au_unit,
                                   kAudioUnitProperty_StreamFormat,
                                   kAudioUnitScope_Input,
                                   0,
                                   &DeviceFormat,
                                   &i_param_size ));
 
    msg_Dbg( p_aout, STREAM_FORMAT_MSG( "the actual set AU format is " , DeviceFormat ) );

    /* Do the last VLC aout setups */
    aout_FormatPrepare( &p_aout->output.output );
    p_aout->output.i_nb_samples = 2048;
    aout_VolumeSoftInit( p_aout );

    /* set the IOproc callback */
    input.inputProc = (AURenderCallback) RenderCallbackAnalog;
    input.inputProcRefCon = p_aout;
 
    verify_noerr( AudioUnitSetProperty( p_sys->au_unit,
                            kAudioUnitProperty_SetRenderCallback,
                            kAudioUnitScope_Input,
                            0, &input, sizeof( input ) ) );

    input.inputProc = (AURenderCallback) RenderCallbackAnalog;
    input.inputProcRefCon = p_aout;
 
    /* Set the new_layout as the layout VLC will use to feed the AU unit */
    verify_noerr( AudioUnitSetProperty( p_sys->au_unit,
                            kAudioUnitProperty_AudioChannelLayout,
                            kAudioUnitScope_Input,
                            0, &new_layout, sizeof(new_layout) ) );
 
    if( new_layout.mNumberChannelDescriptions > 0 )
        free( new_layout.mChannelDescriptions );
 
    /* AU initiliaze */
    verify_noerr( AudioUnitInitialize(p_sys->au_unit) );

    /* Find the difference between device clock and mdate clock */
    p_sys->clock_diff = - (mtime_t)
        AudioConvertHostTimeToNanos( AudioGetCurrentHostTime() ) / 1000;
    p_sys->clock_diff += mdate();

    /* Start the AU */
    verify_noerr( AudioOutputUnitStart(p_sys->au_unit) );
 
    return true;
}

/*****************************************************************************
 * Setup a encoded digital stream (SPDIF)
 *****************************************************************************/
static int OpenSPDIF( aout_instance_t * p_aout )
{
    struct aout_sys_t       *p_sys = p_aout->output.p_sys;
    OSStatus                err = noErr;
    UInt32                  i_param_size = 0, b_mix = 0;
    Boolean                 b_writeable = false;
    AudioStreamID           *p_streams = NULL;
    int                     i = 0, i_streams = 0;

    /* Start doing the SPDIF setup proces */
    p_sys->b_digital = true;

    /* Hog the device */
    i_param_size = sizeof( p_sys->i_hog_pid );
    p_sys->i_hog_pid = getpid() ;
 
    err = AudioDeviceSetProperty( p_sys->i_selected_dev, 0, 0, FALSE,
                                  kAudioDevicePropertyHogMode, i_param_size, &p_sys->i_hog_pid );
 
    if( err != noErr )
    {
        msg_Err( p_aout, "failed to set hogmode: [%4.4s]", (char *)&err );
        return false;
    }

    /* Set mixable to false if we are allowed to */
    err = AudioDeviceGetPropertyInfo( p_sys->i_selected_dev, 0, FALSE, kAudioDevicePropertySupportsMixing,
                                    &i_param_size, &b_writeable );

    err = AudioDeviceGetProperty( p_sys->i_selected_dev, 0, FALSE, kAudioDevicePropertySupportsMixing,
                                    &i_param_size, &b_mix );
 
    if( !err && b_writeable )
    {
        b_mix = 0;
        err = AudioDeviceSetProperty( p_sys->i_selected_dev, 0, 0, FALSE,
                            kAudioDevicePropertySupportsMixing, i_param_size, &b_mix );
        p_sys->b_changed_mixing = true;
    }
 
    if( err != noErr )
    {
        msg_Err( p_aout, "failed to set mixmode: [%4.4s]", (char *)&err );
        return false;
    }

    /* Get a list of all the streams on this device */
    err = AudioDeviceGetPropertyInfo( p_sys->i_selected_dev, 0, FALSE,
                                      kAudioDevicePropertyStreams,
                                      &i_param_size, NULL );
    if( err != noErr )
    {
        msg_Err( p_aout, "could not get number of streams: [%4.4s]", (char *)&err );
        return false;
    }
 
    i_streams = i_param_size / sizeof( AudioStreamID );
    p_streams = (AudioStreamID *)malloc( i_param_size );
    if( p_streams == NULL )
    {
        msg_Err( p_aout, "out of memory" );
        return false;
    }
 
    err = AudioDeviceGetProperty( p_sys->i_selected_dev, 0, FALSE,
                                    kAudioDevicePropertyStreams,
                                    &i_param_size, p_streams );
 
    if( err != noErr )
    {
        msg_Err( p_aout, "could not get number of streams: [%4.4s]", (char *)&err );
        free( p_streams );
        return false;
    }

    for( i = 0; i < i_streams && p_sys->i_stream_index < 0 ; i++ )
    {
        /* Find a stream with a cac3 stream */
        AudioStreamBasicDescription *p_format_list = NULL;
        int                         i_formats = 0, j = 0;
        bool                  b_digital = false;
 
        /* Retrieve all the stream formats supported by each output stream */
        err = AudioStreamGetPropertyInfo( p_streams[i], 0,
                                          kAudioStreamPropertyPhysicalFormats,
                                          &i_param_size, NULL );
        if( err != noErr )
        {
            msg_Err( p_aout, "could not get number of streamformats: [%4.4s]", (char *)&err );
            continue;
        }
 
        i_formats = i_param_size / sizeof( AudioStreamBasicDescription );
        p_format_list = (AudioStreamBasicDescription *)malloc( i_param_size );
        if( p_format_list == NULL )
        {
            msg_Err( p_aout, "could not malloc the memory" );
            continue;
        }
 
        err = AudioStreamGetProperty( p_streams[i], 0,
                                          kAudioStreamPropertyPhysicalFormats,
                                          &i_param_size, p_format_list );
        if( err != noErr )
        {
            msg_Err( p_aout, "could not get the list of streamformats: [%4.4s]", (char *)&err );
            free( p_format_list );
            continue;
        }

        /* Check if one of the supported formats is a digital format */
        for( j = 0; j < i_formats; j++ )
        {
            if( p_format_list[j].mFormatID == 'IAC3' ||
                  p_format_list[j].mFormatID == kAudioFormat60958AC3 )
            {
                b_digital = true;
                break;
            }
        }
 
        if( b_digital )
        {
            /* if this stream supports a digital (cac3) format, then go set it. */
            int i_requested_rate_format = -1;
            int i_current_rate_format = -1;
            int i_backup_rate_format = -1;

            p_sys->i_stream_id = p_streams[i];
            p_sys->i_stream_index = i;

            if( p_sys->b_revert == false )
            {
                /* Retrieve the original format of this stream first if not done so already */
                i_param_size = sizeof( p_sys->sfmt_revert );
                err = AudioStreamGetProperty( p_sys->i_stream_id, 0,
                                              kAudioStreamPropertyPhysicalFormat,
                                              &i_param_size,
                                              &p_sys->sfmt_revert );
                if( err != noErr )
                {
                    msg_Err( p_aout, "could not retrieve the original streamformat: [%4.4s]", (char *)&err );
                    continue;
                }
                p_sys->b_revert = true;
            }

            for( j = 0; j < i_formats; j++ )
            {
                if( p_format_list[j].mFormatID == 'IAC3' ||
                      p_format_list[j].mFormatID == kAudioFormat60958AC3 )
                {
                    if( p_format_list[j].mSampleRate == p_aout->output.output.i_rate )
                    {
                        i_requested_rate_format = j;
                        break;
                    }
                    else if( p_format_list[j].mSampleRate == p_sys->sfmt_revert.mSampleRate )
                    {
                        i_current_rate_format = j;
                    }
                    else
                    {
                        if( i_backup_rate_format < 0 || p_format_list[j].mSampleRate > p_format_list[i_backup_rate_format].mSampleRate )
                            i_backup_rate_format = j;
                    }
                }
 
            }
 
            if( i_requested_rate_format >= 0 ) /* We prefer to output at the samplerate of the original audio */
                p_sys->stream_format = p_format_list[i_requested_rate_format];
            else if( i_current_rate_format >= 0 ) /* If not possible, we will try to use the current samplerate of the device */
                p_sys->stream_format = p_format_list[i_current_rate_format];
            else p_sys->stream_format = p_format_list[i_backup_rate_format]; /* And if we have to, any digital format will be just fine (highest rate possible) */
        }
        free( p_format_list );
    }
    free( p_streams );

    msg_Dbg( p_aout, STREAM_FORMAT_MSG( "original stream format: ", p_sys->sfmt_revert ) );

    if( !AudioStreamChangeFormat( p_aout, p_sys->i_stream_id, p_sys->stream_format ) )
        return false;

    /* Set the format flags */
    if( p_sys->stream_format.mFormatFlags & kAudioFormatFlagIsBigEndian )
        p_aout->output.output.i_format = VLC_FOURCC('s','p','d','b');
    else
        p_aout->output.output.i_format = VLC_FOURCC('s','p','d','i');
    p_aout->output.output.i_bytes_per_frame = AOUT_SPDIF_SIZE;
    p_aout->output.output.i_frame_length = A52_FRAME_NB;
    p_aout->output.i_nb_samples = p_aout->output.output.i_frame_length;
    p_aout->output.output.i_rate = (unsigned int)p_sys->stream_format.mSampleRate;
    aout_FormatPrepare( &p_aout->output.output );
    aout_VolumeNoneInit( p_aout );

    /* Add IOProc callback */
    err = AudioDeviceAddIOProc( p_sys->i_selected_dev,
                               (AudioDeviceIOProc)RenderCallbackSPDIF,
                               (void *)p_aout );

    if( err != noErr )
    {
        msg_Err( p_aout, "AudioDeviceAddIOProc failed: [%4.4s]", (char *)&err );
        return false;
    }

    /* Check for the difference between the Device clock and mdate */
    p_sys->clock_diff = - (mtime_t)
        AudioConvertHostTimeToNanos( AudioGetCurrentHostTime() ) / 1000;
    p_sys->clock_diff += mdate();
 
    /* Start device */
    err = AudioDeviceStart( p_sys->i_selected_dev, (AudioDeviceIOProc)RenderCallbackSPDIF );
    if( err != noErr )
    {
        msg_Err( p_aout, "AudioDeviceStart failed: [%4.4s]", (char *)&err );

        err = AudioDeviceRemoveIOProc( p_sys->i_selected_dev,
                                     (AudioDeviceIOProc)RenderCallbackSPDIF );
        if( err != noErr )
        {
            msg_Err( p_aout, "AudioDeviceRemoveIOProc failed: [%4.4s]", (char *)&err );
        }
        return false;
    }

    return true;
}


/*****************************************************************************
 * Close: Close HAL AudioUnit
 *****************************************************************************/
static void Close( vlc_object_t * p_this )
{
    aout_instance_t     *p_aout = (aout_instance_t *)p_this;
    struct aout_sys_t   *p_sys = p_aout->output.p_sys;
    OSStatus            err = noErr;
    UInt32              i_param_size = 0;
 
    if( p_sys->au_unit )
    {
        verify_noerr( AudioOutputUnitStop( p_sys->au_unit ) );
        verify_noerr( AudioUnitUninitialize( p_sys->au_unit ) );
        verify_noerr( CloseComponent( p_sys->au_unit ) );
    }
 
    if( p_sys->b_digital )
    {
        /* Stop device */
        err = AudioDeviceStop( p_sys->i_selected_dev,
                               (AudioDeviceIOProc)RenderCallbackSPDIF );
        if( err != noErr )
        {
            msg_Err( p_aout, "AudioDeviceStop failed: [%4.4s]", (char *)&err );
        }

        /* Remove IOProc callback */
        err = AudioDeviceRemoveIOProc( p_sys->i_selected_dev,
                                      (AudioDeviceIOProc)RenderCallbackSPDIF );
        if( err != noErr )
        {
            msg_Err( p_aout, "AudioDeviceRemoveIOProc failed: [%4.4s]", (char *)&err );
        }
 
        if( p_sys->b_revert )
        {
            AudioStreamChangeFormat( p_aout, p_sys->i_stream_id, p_sys->sfmt_revert );
        }

        if( p_sys->b_changed_mixing && p_sys->sfmt_revert.mFormatID != kAudioFormat60958AC3 )
        {
            int b_mix;
            Boolean b_writeable;
            /* Revert mixable to true if we are allowed to */
            err = AudioDeviceGetPropertyInfo( p_sys->i_selected_dev, 0, FALSE, kAudioDevicePropertySupportsMixing,
                                        &i_param_size, &b_writeable );

            err = AudioDeviceGetProperty( p_sys->i_selected_dev, 0, FALSE, kAudioDevicePropertySupportsMixing,
                                        &i_param_size, &b_mix );
 
            if( !err && b_writeable )
            {
                msg_Dbg( p_aout, "mixable is: %d", b_mix );
                b_mix = 1;
                err = AudioDeviceSetProperty( p_sys->i_selected_dev, 0, 0, FALSE,
                                    kAudioDevicePropertySupportsMixing, i_param_size, &b_mix );
            }

            if( err != noErr )
            {
                msg_Err( p_aout, "failed to set mixmode: [%4.4s]", (char *)&err );
            }
        }
    }

    err = AudioHardwareRemovePropertyListener( kAudioHardwarePropertyDevices,
                                               HardwareListener );
 
    if( err != noErr )
    {
        msg_Err( p_aout, "AudioHardwareRemovePropertyListener failed: [%4.4s]", (char *)&err );
    }
 
    if( p_sys->i_hog_pid == getpid() )
    {
        p_sys->i_hog_pid = -1;
        i_param_size = sizeof( p_sys->i_hog_pid );
        err = AudioDeviceSetProperty( p_sys->i_selected_dev, 0, 0, FALSE,
                                         kAudioDevicePropertyHogMode, i_param_size, &p_sys->i_hog_pid );
        if( err != noErr ) msg_Err( p_aout, "Could not release hogmode: [%4.4s]", (char *)&err );
    }
 
    free( p_sys );
}

/*****************************************************************************
 * Play: nothing to do
 *****************************************************************************/
static void Play( aout_instance_t * p_aout )
{
}


/*****************************************************************************
 * Probe: Check which devices the OS has, and add them to our audio-device menu
 *****************************************************************************/
static void Probe( aout_instance_t * p_aout )