usb-audio: support more than two channels of audio (3e44607e) · Commits · SUMMER2020 / students / proj-2021291

hw/usb/dev-audio.c

+366 −53

Original line number	Diff line number	Diff line
		@@ -37,11 +37,15 @@
		#include "desc.h"
		#include "audio/audio.h"

		static void usb_audio_reinit(USBDevice *dev, unsigned channels);

		#define USBAUDIO_VENDOR_NUM 0x46f4 /* CRC16() of "QEMU" */
		#define USBAUDIO_PRODUCT_NUM 0x0002

		#define DEV_CONFIG_VALUE 1 /* The one and only */

		#define USBAUDIO_MAX_CHANNELS(s) (s->multi ? 8 : 2)

		/* Descriptor subtypes for AC interfaces */
		#define DST_AC_HEADER 1
		#define DST_AC_INPUT_TERMINAL 2
		@@ -80,6 +84,27 @@ static const USBDescStrings usb_audio_stringtable = {
		[STRING_REAL_STREAM] = "Audio Output - 48 kHz Stereo",
		};

		/*
		* A USB audio device supports an arbitrary number of alternate
		* interface settings for each interface. Each corresponds to a block
		* diagram of parameterized blocks. This can thus refer to things like
		* number of channels, data rates, or in fact completely different
		* block diagrams. Alternative setting 0 is always the null block diagram,
		* which is used by a disabled device.
		*/
		enum usb_audio_altset {
		ALTSET_OFF = 0x00, /* No endpoint */
		ALTSET_STEREO = 0x01, /* Single endpoint */
		ALTSET_51 = 0x02,
		ALTSET_71 = 0x03,
		};

		static unsigned altset_channels[] = {
		[ALTSET_STEREO] = 2,
		[ALTSET_51] = 6,
		[ALTSET_71] = 8,
		};

		#define U16(x) ((x) & 0xff), (((x) >> 8) & 0xff)
		#define U24(x) U16(x), (((x) >> 16) & 0xff)
		#define U32(x) U24(x), (((x) >> 24) & 0xff)
		@@ -87,7 +112,8 @@ static const USBDescStrings usb_audio_stringtable = {
		/*
		* A Basic Audio Device uses these specific values
		*/
		#define USBAUDIO_PACKET_SIZE 192
		#define USBAUDIO_PACKET_SIZE_BASE 96
		#define USBAUDIO_PACKET_SIZE(channels) (USBAUDIO_PACKET_SIZE_BASE * channels)
		#define USBAUDIO_SAMPLE_RATE 48000
		#define USBAUDIO_PACKET_INTERVAL 1

		@@ -121,7 +147,7 @@ static const USBDescIface desc_iface[] = {
		0x01, /* u8 bTerminalID */
		U16(0x0101), /* u16 wTerminalType */
		0x00, /* u8 bAssocTerminal */
		0x02, /* u16 bNrChannels */
		0x02, /* u8 bNrChannels */
		U16(0x0003), /* u16 wChannelConfig */
		0x00, /* u8 iChannelNames */
		STRING_INPUT_TERMINAL, /* u8 iTerminal */
		@@ -156,14 +182,14 @@ static const USBDescIface desc_iface[] = {
		},
		},{
		.bInterfaceNumber = 1,
		.bAlternateSetting = 0,
		.bAlternateSetting = ALTSET_OFF,
		.bNumEndpoints = 0,
		.bInterfaceClass = USB_CLASS_AUDIO,
		.bInterfaceSubClass = USB_SUBCLASS_AUDIO_STREAMING,
		.iInterface = STRING_NULL_STREAM,
		},{
		.bInterfaceNumber = 1,
		.bAlternateSetting = 1,
		.bAlternateSetting = ALTSET_STEREO,
		.bNumEndpoints = 1,
		.bInterfaceClass = USB_CLASS_AUDIO,
		.bInterfaceSubClass = USB_SUBCLASS_AUDIO_STREAMING,
		@@ -199,7 +225,7 @@ static const USBDescIface desc_iface[] = {
		{
		.bEndpointAddress = USB_DIR_OUT \| 0x01,
		.bmAttributes = 0x0d,
		.wMaxPacketSize = USBAUDIO_PACKET_SIZE,
		.wMaxPacketSize = USBAUDIO_PACKET_SIZE(2),
		.bInterval = 1,
		.is_audio = 1,
		/* Stereo Headphone Class-specific
		@@ -247,17 +273,274 @@ static const USBDesc desc_audio = {
		.str = usb_audio_stringtable,
		};

		/*
		* A USB audio device supports an arbitrary number of alternate
		* interface settings for each interface. Each corresponds to a block
		* diagram of parameterized blocks. This can thus refer to things like
		* number of channels, data rates, or in fact completely different
		* block diagrams. Alternative setting 0 is always the null block diagram,
		* which is used by a disabled device.
		*/
		enum usb_audio_altset {
		ALTSET_OFF = 0x00, /* No endpoint */
		ALTSET_ON = 0x01, /* Single endpoint */
		/* multi channel compatible desc */

		static const USBDescIface desc_iface_multi[] = {
		{
		.bInterfaceNumber = 0,
		.bNumEndpoints = 0,
		.bInterfaceClass = USB_CLASS_AUDIO,
		.bInterfaceSubClass = USB_SUBCLASS_AUDIO_CONTROL,
		.bInterfaceProtocol = 0x04,
		.iInterface = STRING_USBAUDIO_CONTROL,
		.ndesc = 4,
		.descs = (USBDescOther[]) {
		{
		/* Headphone Class-Specific AC Interface Header Descriptor */
		.data = (uint8_t[]) {
		0x09, /* u8 bLength */
		USB_DT_CS_INTERFACE, /* u8 bDescriptorType */
		DST_AC_HEADER, /* u8 bDescriptorSubtype */
		U16(0x0100), /* u16 bcdADC */
		U16(0x38), /* u16 wTotalLength */
		0x01, /* u8 bInCollection */
		0x01, /* u8 baInterfaceNr */
		}
		},{
		/* Generic Stereo Input Terminal ID1 Descriptor */
		.data = (uint8_t[]) {
		0x0c, /* u8 bLength */
		USB_DT_CS_INTERFACE, /* u8 bDescriptorType */
		DST_AC_INPUT_TERMINAL, /* u8 bDescriptorSubtype */
		0x01, /* u8 bTerminalID */
		U16(0x0101), /* u16 wTerminalType */
		0x00, /* u8 bAssocTerminal */
		0x08, /* u8 bNrChannels */
		U16(0x063f), /* u16 wChannelConfig */
		0x00, /* u8 iChannelNames */
		STRING_INPUT_TERMINAL, /* u8 iTerminal */
		}
		},{
		/* Generic Stereo Feature Unit ID2 Descriptor */
		.data = (uint8_t[]) {
		0x19, /* u8 bLength */
		USB_DT_CS_INTERFACE, /* u8 bDescriptorType */
		DST_AC_FEATURE_UNIT, /* u8 bDescriptorSubtype */
		0x02, /* u8 bUnitID */
		0x01, /* u8 bSourceID */
		0x02, /* u8 bControlSize */
		U16(0x0001), /* u16 bmaControls(0) */
		U16(0x0002), /* u16 bmaControls(1) */
		U16(0x0002), /* u16 bmaControls(2) */
		U16(0x0002), /* u16 bmaControls(3) */
		U16(0x0002), /* u16 bmaControls(4) */
		U16(0x0002), /* u16 bmaControls(5) */
		U16(0x0002), /* u16 bmaControls(6) */
		U16(0x0002), /* u16 bmaControls(7) */
		U16(0x0002), /* u16 bmaControls(8) */
		STRING_FEATURE_UNIT, /* u8 iFeature */
		}
		},{
		/* Headphone Ouptut Terminal ID3 Descriptor */
		.data = (uint8_t[]) {
		0x09, /* u8 bLength */
		USB_DT_CS_INTERFACE, /* u8 bDescriptorType */
		DST_AC_OUTPUT_TERMINAL, /* u8 bDescriptorSubtype */
		0x03, /* u8 bUnitID */
		U16(0x0301), /* u16 wTerminalType (SPK) */
		0x00, /* u8 bAssocTerminal */
		0x02, /* u8 bSourceID */
		STRING_OUTPUT_TERMINAL, /* u8 iTerminal */
		}
		}
		},
		},{
		.bInterfaceNumber = 1,
		.bAlternateSetting = ALTSET_OFF,
		.bNumEndpoints = 0,
		.bInterfaceClass = USB_CLASS_AUDIO,
		.bInterfaceSubClass = USB_SUBCLASS_AUDIO_STREAMING,
		.iInterface = STRING_NULL_STREAM,
		},{
		.bInterfaceNumber = 1,
		.bAlternateSetting = ALTSET_STEREO,
		.bNumEndpoints = 1,
		.bInterfaceClass = USB_CLASS_AUDIO,
		.bInterfaceSubClass = USB_SUBCLASS_AUDIO_STREAMING,
		.iInterface = STRING_REAL_STREAM,
		.ndesc = 2,
		.descs = (USBDescOther[]) {
		{
		/* Headphone Class-specific AS General Interface Descriptor */
		.data = (uint8_t[]) {
		0x07, /* u8 bLength */
		USB_DT_CS_INTERFACE, /* u8 bDescriptorType */
		DST_AS_GENERAL, /* u8 bDescriptorSubtype */
		0x01, /* u8 bTerminalLink */
		0x00, /* u8 bDelay */
		0x01, 0x00, /* u16 wFormatTag */
		}
		},{
		/* Headphone Type I Format Type Descriptor */
		.data = (uint8_t[]) {
		0x0b, /* u8 bLength */
		USB_DT_CS_INTERFACE, /* u8 bDescriptorType */
		DST_AS_FORMAT_TYPE, /* u8 bDescriptorSubtype */
		0x01, /* u8 bFormatType */
		0x02, /* u8 bNrChannels */
		0x02, /* u8 bSubFrameSize */
		0x10, /* u8 bBitResolution */
		0x01, /* u8 bSamFreqType */
		U24(USBAUDIO_SAMPLE_RATE), /* u24 tSamFreq */
		}
		}
		},
		.eps = (USBDescEndpoint[]) {
		{
		.bEndpointAddress = USB_DIR_OUT \| 0x01,
		.bmAttributes = 0x0d,
		.wMaxPacketSize = USBAUDIO_PACKET_SIZE(2),
		.bInterval = 1,
		.is_audio = 1,
		/* Stereo Headphone Class-specific
		AS Audio Data Endpoint Descriptor */
		.extra = (uint8_t[]) {
		0x07, /* u8 bLength */
		USB_DT_CS_ENDPOINT, /* u8 bDescriptorType */
		DST_EP_GENERAL, /* u8 bDescriptorSubtype */
		0x00, /* u8 bmAttributes */
		0x00, /* u8 bLockDelayUnits */
		U16(0x0000), /* u16 wLockDelay */
		},
		},
		}
		},{
		.bInterfaceNumber = 1,
		.bAlternateSetting = ALTSET_51,
		.bNumEndpoints = 1,
		.bInterfaceClass = USB_CLASS_AUDIO,
		.bInterfaceSubClass = USB_SUBCLASS_AUDIO_STREAMING,
		.iInterface = STRING_REAL_STREAM,
		.ndesc = 2,
		.descs = (USBDescOther[]) {
		{
		/* Headphone Class-specific AS General Interface Descriptor */
		.data = (uint8_t[]) {
		0x07, /* u8 bLength */
		USB_DT_CS_INTERFACE, /* u8 bDescriptorType */
		DST_AS_GENERAL, /* u8 bDescriptorSubtype */
		0x01, /* u8 bTerminalLink */
		0x00, /* u8 bDelay */
		0x01, 0x00, /* u16 wFormatTag */
		}
		},{
		/* Headphone Type I Format Type Descriptor */
		.data = (uint8_t[]) {
		0x0b, /* u8 bLength */
		USB_DT_CS_INTERFACE, /* u8 bDescriptorType */
		DST_AS_FORMAT_TYPE, /* u8 bDescriptorSubtype */
		0x01, /* u8 bFormatType */
		0x06, /* u8 bNrChannels */
		0x02, /* u8 bSubFrameSize */
		0x10, /* u8 bBitResolution */
		0x01, /* u8 bSamFreqType */
		U24(USBAUDIO_SAMPLE_RATE), /* u24 tSamFreq */
		}
		}
		},
		.eps = (USBDescEndpoint[]) {
		{
		.bEndpointAddress = USB_DIR_OUT \| 0x01,
		.bmAttributes = 0x0d,
		.wMaxPacketSize = USBAUDIO_PACKET_SIZE(6),
		.bInterval = 1,
		.is_audio = 1,
		/* Stereo Headphone Class-specific
		AS Audio Data Endpoint Descriptor */
		.extra = (uint8_t[]) {
		0x07, /* u8 bLength */
		USB_DT_CS_ENDPOINT, /* u8 bDescriptorType */
		DST_EP_GENERAL, /* u8 bDescriptorSubtype */
		0x00, /* u8 bmAttributes */
		0x00, /* u8 bLockDelayUnits */
		U16(0x0000), /* u16 wLockDelay */
		},
		},
		}
		},{
		.bInterfaceNumber = 1,
		.bAlternateSetting = ALTSET_71,
		.bNumEndpoints = 1,
		.bInterfaceClass = USB_CLASS_AUDIO,
		.bInterfaceSubClass = USB_SUBCLASS_AUDIO_STREAMING,
		.iInterface = STRING_REAL_STREAM,
		.ndesc = 2,
		.descs = (USBDescOther[]) {
		{
		/* Headphone Class-specific AS General Interface Descriptor */
		.data = (uint8_t[]) {
		0x07, /* u8 bLength */
		USB_DT_CS_INTERFACE, /* u8 bDescriptorType */
		DST_AS_GENERAL, /* u8 bDescriptorSubtype */
		0x01, /* u8 bTerminalLink */
		0x00, /* u8 bDelay */
		0x01, 0x00, /* u16 wFormatTag */
		}
		},{
		/* Headphone Type I Format Type Descriptor */
		.data = (uint8_t[]) {
		0x0b, /* u8 bLength */
		USB_DT_CS_INTERFACE, /* u8 bDescriptorType */
		DST_AS_FORMAT_TYPE, /* u8 bDescriptorSubtype */
		0x01, /* u8 bFormatType */
		0x08, /* u8 bNrChannels */
		0x02, /* u8 bSubFrameSize */
		0x10, /* u8 bBitResolution */
		0x01, /* u8 bSamFreqType */
		U24(USBAUDIO_SAMPLE_RATE), /* u24 tSamFreq */
		}
		}
		},
		.eps = (USBDescEndpoint[]) {
		{
		.bEndpointAddress = USB_DIR_OUT \| 0x01,
		.bmAttributes = 0x0d,
		.wMaxPacketSize = USBAUDIO_PACKET_SIZE(8),
		.bInterval = 1,
		.is_audio = 1,
		/* Stereo Headphone Class-specific
		AS Audio Data Endpoint Descriptor */
		.extra = (uint8_t[]) {
		0x07, /* u8 bLength */
		USB_DT_CS_ENDPOINT, /* u8 bDescriptorType */
		DST_EP_GENERAL, /* u8 bDescriptorSubtype */
		0x00, /* u8 bmAttributes */
		0x00, /* u8 bLockDelayUnits */
		U16(0x0000), /* u16 wLockDelay */
		},
		},
		}
		}
		};

		static const USBDescDevice desc_device_multi = {
		.bcdUSB = 0x0100,
		.bMaxPacketSize0 = 64,
		.bNumConfigurations = 1,
		.confs = (USBDescConfig[]) {
		{
		.bNumInterfaces = 2,
		.bConfigurationValue = DEV_CONFIG_VALUE,
		.iConfiguration = STRING_CONFIG,
		.bmAttributes = USB_CFG_ATT_ONE \| USB_CFG_ATT_SELFPOWER,
		.bMaxPower = 0x32,
		.nif = ARRAY_SIZE(desc_iface_multi),
		.ifs = desc_iface_multi,
		}
		},
		};

		static const USBDesc desc_audio_multi = {
		.id = {
		.idVendor = USBAUDIO_VENDOR_NUM,
		.idProduct = USBAUDIO_PRODUCT_NUM,
		.bcdDevice = 0,
		.iManufacturer = STRING_MANUFACTURER,
		.iProduct = STRING_PRODUCT,
		.iSerialNumber = STRING_SERIALNUMBER,
		},
		.full = &desc_device_multi,
		.str = usb_audio_stringtable,
		};

		/*
		@@ -300,10 +583,11 @@ struct streambuf {
		uint32_t cons;
		};

		static void streambuf_init(struct streambuf *buf, uint32_t size)
		static void streambuf_init(struct streambuf *buf, uint32_t size,
		uint32_t channels)
		{
		g_free(buf->data);
		buf->size = size - (size % USBAUDIO_PACKET_SIZE);
		buf->size = size - (size % USBAUDIO_PACKET_SIZE(channels));
		buf->data = g_malloc(buf->size);
		buf->prod = 0;
		buf->cons = 0;
		@@ -315,21 +599,21 @@ static void streambuf_fini(struct streambuf *buf)
		buf->data = NULL;
		}

		static int streambuf_put(struct streambuf buf, USBPacket p)
		static int streambuf_put(struct streambuf buf, USBPacket p, uint32_t channels)
		{
		uint32_t free = buf->size - (buf->prod - buf->cons);

		if (free < USBAUDIO_PACKET_SIZE) {
		if (free < USBAUDIO_PACKET_SIZE(channels)) {
		return 0;
		}
		if (p->iov.size != USBAUDIO_PACKET_SIZE) {
		if (p->iov.size != USBAUDIO_PACKET_SIZE(channels)) {
		return 0;
		}

		usb_packet_copy(p, buf->data + (buf->prod % buf->size),
		USBAUDIO_PACKET_SIZE);
		buf->prod += USBAUDIO_PACKET_SIZE;
		return USBAUDIO_PACKET_SIZE;
		USBAUDIO_PACKET_SIZE(channels));
		buf->prod += USBAUDIO_PACKET_SIZE(channels);
		return USBAUDIO_PACKET_SIZE(channels);
		}

		static uint8_t streambuf_get(struct streambuf buf, size_t *len)
		@@ -357,14 +641,15 @@ typedef struct USBAudioState {
		enum usb_audio_altset altset;
		struct audsettings as;
		SWVoiceOut *voice;
		bool mute;
		uint8_t vol[2];
		Volume vol;
		struct streambuf buf;
		uint32_t channels;
		} out;

		/* properties */
		uint32_t debug;
		uint32_t buffer;
		uint32_t buffer_user, buffer;
		bool multi;
		} USBAudioState;

		#define TYPE_USB_AUDIO "usb-audio"
		@@ -397,10 +682,15 @@ static int usb_audio_set_output_altset(USBAudioState *s, int altset)
		{
		switch (altset) {
		case ALTSET_OFF:
		streambuf_init(&s->out.buf, s->buffer);
		AUD_set_active_out(s->out.voice, false);
		break;
		case ALTSET_ON:
		case ALTSET_STEREO:
		case ALTSET_51:
		case ALTSET_71:
		if (s->out.channels != altset_channels[altset]) {
		usb_audio_reinit(USB_DEVICE(s), altset_channels[altset]);
		}
		streambuf_init(&s->out.buf, s->buffer, s->out.channels);
		AUD_set_active_out(s->out.voice, true);
		break;
		default:
		@@ -431,33 +721,33 @@ static int usb_audio_get_control(USBAudioState *s, uint8_t attrib,

		switch (aid) {
		case ATTRIB_ID(MUTE_CONTROL, CR_GET_CUR, 0x0200):
		data[0] = s->out.mute;
		data[0] = s->out.vol.mute;
		ret = 1;
		break;
		case ATTRIB_ID(VOLUME_CONTROL, CR_GET_CUR, 0x0200):
		if (cn < 2) {
		uint16_t vol = (s->out.vol[cn] * 0x8800 + 127) / 255 + 0x8000;
		if (cn < USBAUDIO_MAX_CHANNELS(s)) {
		uint16_t vol = (s->out.vol.vol[cn] * 0x8800 + 127) / 255 + 0x8000;
		data[0] = vol;
		data[1] = vol >> 8;
		ret = 2;
		}
		break;
		case ATTRIB_ID(VOLUME_CONTROL, CR_GET_MIN, 0x0200):
		if (cn < 2) {
		if (cn < USBAUDIO_MAX_CHANNELS(s)) {
		data[0] = 0x01;
		data[1] = 0x80;
		ret = 2;
		}
		break;
		case ATTRIB_ID(VOLUME_CONTROL, CR_GET_MAX, 0x0200):
		if (cn < 2) {
		if (cn < USBAUDIO_MAX_CHANNELS(s)) {
		data[0] = 0x00;
		data[1] = 0x08;
		ret = 2;
		}
		break;
		case ATTRIB_ID(VOLUME_CONTROL, CR_GET_RES, 0x0200):
		if (cn < 2) {
		if (cn < USBAUDIO_MAX_CHANNELS(s)) {
		data[0] = 0x88;
		data[1] = 0x00;
		ret = 2;
		@@ -479,16 +769,17 @@ static int usb_audio_set_control(USBAudioState *s, uint8_t attrib,

		switch (aid) {
		case ATTRIB_ID(MUTE_CONTROL, CR_SET_CUR, 0x0200):
		s->out.mute = data[0] & 1;
		s->out.vol.mute = data[0] & 1;
		set_vol = true;
		ret = 0;
		break;
		case ATTRIB_ID(VOLUME_CONTROL, CR_SET_CUR, 0x0200):
		if (cn < 2) {
		if (cn < USBAUDIO_MAX_CHANNELS(s)) {
		uint16_t vol = data[0] + (data[1] << 8);

		if (s->debug) {
		fprintf(stderr, "usb-audio: vol %04x\n", (uint16_t)vol);
		fprintf(stderr, "usb-audio: cn %d vol %04x\n", cn,
		(uint16_t)vol);
		}

		vol -= 0x8000;
		@@ -497,7 +788,7 @@ static int usb_audio_set_control(USBAudioState *s, uint8_t attrib,
		vol = 255;
		}

		s->out.vol[cn] = vol;
		s->out.vol.vol[cn] = vol;
		set_vol = true;
		ret = 0;
		}
		@@ -506,11 +797,14 @@ static int usb_audio_set_control(USBAudioState *s, uint8_t attrib,

		if (set_vol) {
		if (s->debug) {
		fprintf(stderr, "usb-audio: mute %d, lvol %3d, rvol %3d\n",
		s->out.mute, s->out.vol[0], s->out.vol[1]);
		int i;
		fprintf(stderr, "usb-audio: mute %d", s->out.vol.mute);
		for (i = 0; i < USBAUDIO_MAX_CHANNELS(s); ++i) {
		fprintf(stderr, ", vol[%d] %3d", i, s->out.vol.vol[i]);
		}
		fprintf(stderr, "\n");
		}
		AUD_set_volume_out(s->out.voice, s->out.mute,
		s->out.vol[0], s->out.vol[1]);
		audio_set_volume_out(s->out.voice, &s->out.vol);
		}

		return ret;
		@@ -603,7 +897,7 @@ static void usb_audio_handle_dataout(USBAudioState s, USBPacket p)
		return;
		}

		streambuf_put(&s->out.buf, p);
		streambuf_put(&s->out.buf, p, s->out.channels);
		if (p->actual_length < p->iov.size && s->debug > 1) {
		fprintf(stderr, "usb-audio: output overrun (%zd bytes)\n",
		p->iov.size - p->actual_length);
		@@ -645,6 +939,9 @@ static void usb_audio_unrealize(USBDevice dev, Error *errp)
		static void usb_audio_realize(USBDevice dev, Error *errp)
		{
		USBAudioState *s = USB_AUDIO(dev);
		int i;

		dev->usb_desc = s->multi ? &desc_audio_multi : &desc_audio;

		usb_desc_create_serial(dev);
		usb_desc_init(dev);
		@@ -652,18 +949,35 @@ static void usb_audio_realize(USBDevice dev, Error *errp)
		AUD_register_card(TYPE_USB_AUDIO, &s->card);

		s->out.altset = ALTSET_OFF;
		s->out.mute = false;
		s->out.vol[0] = 240; /* 0 dB */
		s->out.vol[1] = 240; /* 0 dB */
		s->out.vol.mute = false;
		for (i = 0; i < USBAUDIO_MAX_CHANNELS(s); ++i) {
		s->out.vol.vol[i] = 240; /* 0 dB */
		}

		usb_audio_reinit(dev, 2);
		}

		static void usb_audio_reinit(USBDevice *dev, unsigned channels)
		{
		USBAudioState *s = USB_AUDIO(dev);

		s->out.channels = channels;
		if (!s->buffer_user) {
		s->buffer = 32 * USBAUDIO_PACKET_SIZE(s->out.channels);
		} else {
		s->buffer = s->buffer_user;
		}

		s->out.vol.channels = s->out.channels;
		s->out.as.freq = USBAUDIO_SAMPLE_RATE;
		s->out.as.nchannels = 2;
		s->out.as.nchannels = s->out.channels;
		s->out.as.fmt = AUDIO_FORMAT_S16;
		s->out.as.endianness = 0;
		streambuf_init(&s->out.buf, s->buffer);
		streambuf_init(&s->out.buf, s->buffer, s->out.channels);

		s->out.voice = AUD_open_out(&s->card, s->out.voice, TYPE_USB_AUDIO,
		s, output_callback, &s->out.as);
		AUD_set_volume_out(s->out.voice, s->out.mute, s->out.vol[0], s->out.vol[1]);
		audio_set_volume_out(s->out.voice, &s->out.vol);
		AUD_set_active_out(s->out.voice, 0);
		}

		@@ -675,8 +989,8 @@ static const VMStateDescription vmstate_usb_audio = {
		static Property usb_audio_properties[] = {
		DEFINE_AUDIO_PROPERTIES(USBAudioState, card),
		DEFINE_PROP_UINT32("debug", USBAudioState, debug, 0),
		DEFINE_PROP_UINT32("buffer", USBAudioState, buffer,
		32 * USBAUDIO_PACKET_SIZE),
		DEFINE_PROP_UINT32("buffer", USBAudioState, buffer_user, 0),
		DEFINE_PROP_BOOL("multi", USBAudioState, multi, false),
		DEFINE_PROP_END_OF_LIST(),
		};

		@@ -689,7 +1003,6 @@ static void usb_audio_class_init(ObjectClass klass, void data)
		dc->props = usb_audio_properties;
		set_bit(DEVICE_CATEGORY_SOUND, dc->categories);
		k->product_desc = "QEMU USB Audio Interface";
		k->usb_desc = &desc_audio;
		k->realize = usb_audio_realize;
		k->handle_reset = usb_audio_handle_reset;
		k->handle_control = usb_audio_handle_control;