darwin-x86_64/lib/emulator_controller.proto

// Copyright (C) 2018 The Android Open Source Project
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

// Note that if you add/remove methods in this file you must update
// the metrics sql as well ./android/scripts/gen-grpc-sql.py
//
// Please group deleted methods in a block including the date (MM/DD/YY)
// it was removed. This enables us to easily keep metrics around after removal
//
// List of deleted methods
// rpc iWasDeleted (03/12/12)
// ...
syntax = "proto3";

option java_multiple_files = true;
option java_package = "com.android.emulator.control";
option objc_class_prefix = "AEC";

package android.emulation.control;
import "google/protobuf/empty.proto";

// An EmulatorController service lets you control the emulator.
// Note that this is currently an experimental feature, and that the
// service definition might change without notice. Use at your own risk!
//
// We use the following rough conventions:
//
// streamXXX --> streams values XXX (usually for emulator lifetime). Values
//               are updated as soon as they become available.
// getXXX    --> gets a single value XXX
// setXXX    --> sets a single value XXX, does not returning state, these
//               usually have an observable lasting side effect.
// sendXXX   --> send a single event XXX, possibly returning state information.
//               android usually responds to these events.
service EmulatorController {
  // set/get/stream the sensor data
  rpc streamSensor(SensorValue) returns (stream SensorValue) {}
  rpc getSensor(SensorValue) returns (SensorValue) {}
  rpc setSensor(SensorValue) returns (google.protobuf.Empty) {}

  // set/get/stream the physical model, this is likely the one you are
  // looking for when you wish to modify the device state.
  rpc setPhysicalModel(PhysicalModelValue) returns (google.protobuf.Empty) {}
  rpc getPhysicalModel(PhysicalModelValue) returns (PhysicalModelValue) {}
  rpc streamPhysicalModel(PhysicalModelValue)
      returns (stream PhysicalModelValue) {}

  // Set/get the battery to the given state.
  rpc setBattery(BatteryState) returns (google.protobuf.Empty) {}
  rpc getBattery(google.protobuf.Empty) returns (BatteryState) {}

  // Set/get the state of the gps.
  rpc getGps(google.protobuf.Empty) returns (GpsState) {}
  rpc setGps(GpsState) returns (google.protobuf.Empty) {}

  // Simulate a touch event on the finger print sensor.
  rpc sendFingerprint(Fingerprint) returns (google.protobuf.Empty) {}

  // Send a keyboard event. Translating the event.
  rpc sendKey(KeyboardEvent) returns (google.protobuf.Empty) {}

  // Send touch/mouse events. Note that mouse events can be simulated
  // by touch events.
  rpc sendTouch(TouchEvent) returns (google.protobuf.Empty) {}
  rpc sendMouse(MouseEvent) returns (google.protobuf.Empty) {}

  // Make a phone call.
  rpc sendPhone(PhoneCall) returns (PhoneResponse) {}

  // Retrieve the status of the emulator. This will contain general
  // hardware information, and whether the device has booted or not.
  rpc getStatus(google.protobuf.Empty) returns (EmulatorStatus) {}

  // Gets an individual screenshot in the desired format.
  //
  // The image will be scaled to the desired ImageFormat, while maintaining
  // the aspect ratio. The returned image will never exceed the provided width
  // and height. Not setting the width or height (i.e. they are 0) will result
  // in using the device width and height.
  //
  // The resulting image will be properly oriented and can be displayed
  // directly without post processing. For example, if the device has a
  // 1080x1920 screen and is in landscape mode and called with no width or
  // height parameter, it will return an 1920x1080 image.
  //
  // This method will return an empty image if the display is not visible.
  rpc getScreenshot(ImageFormat) returns (Image) {}

  // Streams a series of screenshots in the desired format.
  // A new frame will be delivered whenever the device produces a new frame.
  // (Beware that this can produce a significant amount of data, and that
  // certain translations are (png transform) can be costly).
  //
  // If the requested display is not visible it will send a single empty image
  // and wait start producing images once the display becomes active, again
  // producing a single empty image when the display becomes inactive.
  rpc streamScreenshot(ImageFormat) returns (stream Image) {}

  // Streams a series of audio packets in the desired format.
  // A new frame will be delivered whenever the emulated device
  // produces a new audio frame.
  rpc streamAudio(AudioFormat) returns (stream AudioPacket) {}

  // Returns the last 128Kb of logcat output from the emulator
  // Note that parsed logcat messages are only available after L (Api >23).
  // it is possible that the logcat buffer gets overwritten, or falls behind.
  rpc getLogcat(LogMessage) returns (LogMessage) {}

  // Streams the logcat output from the emulator. The first call
  // can retrieve up to 128Kb. This call will not return.
  // Note that parsed logcat messages are only available after L (Api >23)
  // it is possible that the logcat buffer gets overwritten, or falls behind.
  rpc streamLogcat(LogMessage) returns (stream LogMessage) {}

  // Transition the virtual machine to the desired state. Note that
  // some states are only observable. For example you cannot transition
  // to the error state.
  rpc setVmState(VmRunState) returns (google.protobuf.Empty) {}

  // Gets the state of the virtual machine.
  rpc getVmState(google.protobuf.Empty) returns (VmRunState) {}
}

// A Run State that describes the state of the Virtual Machine.
message VmRunState {
  enum RunState {
    // The emulator is in an unknown state. You cannot transition to this state.
    UNKNOWN = 0;
    // Guest is actively running. You can transition to this state from the
    // paused state.
    RUNNING = 1;
    // Guest is paused to load a snapshot. You cannot transition to this state.
    RESTORE_VM = 2;
    // Guest has been paused. Transitioning to this state will pause the
    // emulator the guest will not be consuming any cpu cycles.
    PAUSED = 3;
    // Guest is paused to take or export a snapshot. You cannot
    // transition to this state.
    SAVE_VM = 4;
    // System shutdown, note that it is similar to power off. It tries to set
    // the system status and notify guest. The system is likely going to
    // disappear soon and do proper cleanup of resources, possibly taking
    // a snapshot. This is the same behavior as closing the emulator by clicking
    // the X (close) in the user interface.
    SHUTDOWN = 5;
    // Immediately terminate the emulator. No resource cleanup will take place.
    // There is a good change to corrupt the system.
    TERMINATE = 7;
    // Will cause the emulator to reset. This is not a state you can observe.
    RESET = 9;
    // Guest experienced some error state, you cannot transition to this state.
    INTERNAL_ERROR = 10;
  }

  RunState state = 1;
}

message ParameterValue { repeated float data = 1 [ packed = true ]; }

message PhysicalModelValue {
  enum State {
    OK = 0;
    NO_SERVICE = -3; // qemud service is not available/initiated.
    DISABLED = -2;   // Sensor is disabled.
    UNKNOWN = -1;    // Unknown sensor (should not happen)
  }

  // Details on the sensors documentation can be found here:
  // https://developer.android.com/reference/android/hardware/Sensor.html#TYPE_
  enum PhysicalType {
    POSITION = 0;

    // All values are angles in degrees.
    // values = [x,y,z]
    ROTATION = 1;

    MAGNETIC_FIELD = 2;

    // Temperature in °C
    TEMPERATURE = 3;

    // Proximity sensor distance measured in centimeters
    PROXIMITY = 4;

    // Ambient light level in SI lux units
    LIGHT = 5;

    // Atmospheric pressure in hPa (millibar)
    PRESSURE = 6;

    // Relative ambient air humidity in percent
    HUMIDITY = 7;

    VELOCITY = 8;
    AMBIENT_MOTION = 9;
  }
  PhysicalType target = 1;

  // [Output Only]
  State status = 2;

  // Value interpretation depends on sensor, will contain at most 3 values.
  ParameterValue value = 3;
}

// A single sensor value.
message SensorValue {
  enum State {
    OK = 0;
    NO_SERVICE = -3; // qemud service is not available/initiated.
    DISABLED = -2;   // Sensor is disabled.
    UNKNOWN = -1;    // Unknown sensor (should not happen)
  }

  // These are the various sensors that can be available in an emulated
  // devices.
  enum SensorType {
    // Measures the acceleration force in m/s2 that is applied to a device
    // on all three physical axes (x, y, and z), including the force of
    // gravity.
    ACCELERATION = 0;
    // Measures a device's rate of rotation in rad/s around each of the
    // three physical axes (x, y, and z).
    GYROSCOPE = 1;
    // Measures the ambient geomagnetic field for all three physical axes
    // (x, y, z) in μT.
    MAGNETIC_FIELD = 2;
    // Measures degrees of rotation that a device makes around all three
    // physical axes (x, y, z)
    ORIENTATION = 3;
    // Measures the temperature of the device in degrees Celsius (°C).
    TEMPERATURE = 4;
    // Measures the proximity of an object in cm relative to the view screen
    // of a device. This sensor is typically used to determine whether a
    // handset is being held up to a person's ear.
    PROXIMITY = 5;
    // Measures the ambient light level (illumination) in lx.
    LIGHT = 6;
    // Measures the ambient air pressure in hPa or mbar.
    PRESSURE = 7;
    // Measures the relative ambient humidity in percent (%).
    HUMIDITY = 8;
    MAGNETIC_FIELD_UNCALIBRATED = 9;
    GYROSCOPE_UNCALIBRATED = 10;
  }

  // Type of sensor
  SensorType target = 1;

  // [Output Only]
  State status = 2;

  // Value interpretation depends on sensor enum, will contain at most 3
  // values.
  ParameterValue value = 3;
}

message LogMessage {
  // [Output Only] The contents of the log output.
  string contents = 1;
  // The starting byte position of the output that was returned. This
  // should match the start parameter sent with the request. If the serial
  // console output exceeds the size of the buffer, older output will be
  // overwritten by newer content and the start values will be mismatched.
  int64 start = 2;
  //[Output Only] The position of the next byte of content from the serial
  // console output. Use this value in the next request as the start
  // parameter.
  int64 next = 3;

  // Set the sort of response you are interested it in.
  // It the type is "Parsed" the entries field will contain the parsed
  // results. otherwise the contents field will be set.
  LogType sort = 4;

  // [Output Only] The parsed logcat entries so far. Only set if sort is
  // set to Parsed
  repeated LogcatEntry entries = 5;

  enum LogType {
    Text = 0;
    Parsed = 1;
  }
}

// A parsed logcat entry.
message LogcatEntry {
  // The possible log levels.
  enum LogLevel {
    UNKNOWN = 0;
    DEFAULT = 1;
    VERBOSE = 2;
    DEBUG = 3;
    INFO = 4;
    WARN = 5;
    ERR = 6;
    FATAL = 7;
    SILENT = 8;
  };

  // A Unix timestamps in  milliseconds (The number of milliseconds that
  // have elapsed since January 1, 1970 (midnight UTC/GMT), not counting
  // leap seconds)
  uint64 timestamp = 1;

  // Process id.
  uint32 pid = 2;

  // Thread id.
  uint32 tid = 3;
  LogLevel level = 4;
  string tag = 5;
  string msg = 6;
}

// Information about the hypervisor that is currently in use.
message VmConfiguration {
  enum VmHypervisorType {
    // An unknown hypervisor
    UNKNOWN = 0;

    // No hypervisor is in use. This usually means that the guest is
    // running on a different CPU than the host, or you are using a
    // platform where no hypervisor is available.
    NONE = 1;

    // The Kernel based Virtual Machine
    // (https://www.linux-kvm.org/page/Main_Page)
    KVM = 2;

    // Intel® Hardware Accelerated Execution Manager (Intel® HAXM)
    // https://github.com/intel/haxm
    HAXM = 3;

    // Hypervisor Framework.
    // https://developer.apple.com/documentation/hypervisor
    HVF = 4;

    // Window Hypervisor Platform
    // https://docs.microsoft.com/en-us/virtualization/api/
    WHPX = 5;

    GVM = 6;
  };

  VmHypervisorType hypervisorType = 1;
  int32 numberOfCpuCores = 2;
  int64 ramSizeBytes = 3;
}

// The Touch interface represents a single contact point on a
// touch-sensitive device. The contact point is commonly a finger or stylus
// and the device may be a touchscreen or trackpad.
message Touch {
  // The horizontal coordinate. This is the physical location on the
  // screen For example 0 indicates the leftmost coordinate.
  int32 x = 1;

  // The vertical coordinate. This is the physical location on the screen
  // For example 0 indicates the top left coordinate.
  int32 y = 2;

  // The identifier is an arbitrary non-negative integer that is used to
  // identify and track each tool independently when multiple tools are
  // active. For example, when multiple fingers are touching the device,
  // each finger should be assigned a distinct tracking id that is used as
  // long as the finger remains in contact. Tracking ids may be reused
  // when their associated tools move out of range.
  //
  // The emulator currently supports up to 10 concurrent touch events. The
  // identifier should be a value from the set [0, 10]
  int32 identifier = 3;

  // Reports the physical pressure applied to the tip of the tool or the
  // signal strength of the touch contact.
  //
  // The values reported must be non-zero when the tool is touching the
  // device and zero otherwise to indicate that the touch event is
  // completed.
  //
  // Make sure to deliver a pressure of 0 for the given identifier when
  // the touch event is completed, otherwise the touch identifier will not
  // be unregistered!
  int32 pressure = 4;

  // Optionally reports the cross-sectional area of the touch contact, or
  // the length of the longer dimension of the touch contact.
  int32 touch_major = 5;

  // Optionally reports the length of the shorter dimension of the touch
  // contact. This axis will be ignored if touch_major is reporting an
  // area measurement greater than 0.
  int32 touch_minor = 6;
}

// A TouchEvent contains a list of Touch objects that are in contact with
// the touch surface.
//
// Touch events are delivered in sequence as specified in the touchList.
//
// TouchEvents are delivered to the emulated devices using ["Protocol
// B"](https://www.kernel.org/doc/Documentation/input/multi-touch-protocol.txt)
message TouchEvent {
  // The list of Touch objects, note that these do not need to be unique
  repeated Touch touches = 1;

  // The display device where the touch event occurred.
  // Omitting or using the value 0 indicates the main display.
  //
  // Touch events cannot be send to devices other than 0, due to
  // https://issuetracker.google.com/issues/150699691
  int32 device = 2;
}

// The MouseEvent interface represents events that occur due to the user
// interacting with a pointing device (such as a mouse).
message MouseEvent {
  // The horizontal coordinate. This is the physical location on the
  // screen For example 0 indicates the leftmost coordinate.
  int32 x = 1;

  // The vertical coordinate. This is the physical location on the screen
  // For example 0 indicates the top left coordinate.
  int32 y = 2;

  // Indicates which buttons are pressed.
  // 0: No button was pressed
  // 1: Primary button (left)
  // 2: Secondary button (right)
  int32 buttons = 3;

  // The display device where the mouse event occurred.
  // Omitting or using the value 0 indicates the main display.
  int32 device = 4;
}

// KeyboardEvent objects describe a user interaction with the keyboard; each
// event describes a single interaction between the user and a key (or
// combination of a key with modifier keys) on the keyboard.
// This follows the pattern as set by
// (javascript)[https://developer.mozilla.org/en-US/docs/Web/API/KeyboardEvent]
//
// Note: that only keyCode, key, or text can be set and that the semantics
// will slightly vary.
message KeyboardEvent {
  // Code types that the emulator can receive. Note that the emulator
  // will do its best to translate the code to an evdev value that
  // will be send to the emulator. This translation is based on
  // the chromium translation tables. See
  // (this)[https://android.googlesource.com/platform/external/qemu/+/refs/heads/emu-master-dev/android/android-grpc/android/emulation/control/keyboard/keycode_converter_data.inc]
  // for details on the translation.
  enum KeyCodeType {
    Usb = 0;
    Evdev = 1;
    XKB = 2;
    Win = 3;
    Mac = 4;
  };

  enum KeyEventType {
    // Indicates that this keyevent should be send to the emulator
    // as a key down event. Meaning that the key event will be
    // translated to an EvDev event type and bit 11 (0x400) will be
    // set before it is sent to the emulator.
    keydown = 0;

    // Indicates that the keyevent should be send to the emulator
    // as a key up event. Meaning that the key event will be
    // translated to an EvDev event type and
    // sent to the emulator.
    keyup = 1;

    // Indicates that the keyevent will be send to the emulator
    // as e key down event and immediately followed by a keyup event.
    keypress = 2;
  };

  // Type of keycode contained in the keyCode field.
  KeyCodeType codeType = 1;

  // The type of keyboard event that should be sent to the emulator
  KeyEventType eventType = 2;

  // This property represents a physical key on the keyboard (as opposed
  // to the character generated by pressing the key). In other words, this
  // property is a value which isn't altered by keyboard layout or the
  // state of the modifier keys. This value will be interpreted by the
  // emulator depending on the KeyCodeType. The incoming key code will be
  // translated to an evdev code type and send to the emulator.
  // The values in key and text will be ignored.
  int32 keyCode = 3;

  // The value of the key pressed by the user, taking into consideration
  // the state of modifier keys such as Shift as well as the keyboard
  // locale and layout. This follows the w3c standard used in browsers.
  // You can find an accurate description of valid values
  // [here](https://developer.mozilla.org/en-US/docs/Web/API/KeyboardEvent/key/Key_Values)
  //
  // Note that some keys can result in multiple evdev events that are
  // delivered to the emulator. for example the Key "A" will result in a
  // sequence:
  // ["Shift", "a"] -> [0x2a, 0x1e] whereas "a" results in ["a"] -> [0x1e].
  //
  // Not all documented keys are understood by android, and only printable
  // ASCII [32-127) characters are properly translated.
  //
  // Keep in mind that there are a set of key values that result in android
  // specific behavior
  // [see](https://developer.mozilla.org/en-US/docs/Web/API/KeyboardEvent/key/Key_Values#Phone_keys):
  //
  // - "AppSwitch": Behaves as the "Overview" button in android.
  // - "GoBack": The Back button.
  // - "GoHome": The Home button, which takes the user to the phone's main
  //             screen (usually an application launcher).
  // - "Power":  The Power button.
  string key = 4;

  // Series of utf8 encoded characters to send to the emulator. An attempt
  // will be made to translate every character will an EvDev event type and
  // send to the emulator as a keypress event. The values in keyCode,
  // eventType, codeType and key will be ignored.
  //
  // Note that most printable ASCII characters (range [32-127) can be send
  // individually with the "key" param. Do not expect arbitrary UTF symbols to
  // arrive in the emulator (most will be ignored).
  string text = 5;
}

message Fingerprint {
  // True when the fingprint is touched.
  bool isTouching = 1;

  // The identifier of the registered fingerprint.
  int32 touchId = 2;
}

message GpsState {
  bool passiveUpdate = 1;

  // The latitude, in degrees.
  double latitude = 2;

  // The longitude, in degrees.
  double longitude = 3;

  // The speed if it is available, in meters/second over ground
  double speed = 4;

  // gets the horizontal direction of travel of this device, and is not
  // related to the device orientation. It is guaranteed to be in the
  // range [0.0, 360.0] if the device has a bearing. 0=North, 90=East,
  // 180=South, etc..
  double bearing = 5;

  // The altitude if available, in meters above the WGS 84 reference
  // ellipsoid.
  double altitude = 6;

  // The number of satellites used to derive the fix
  int32 satellites = 7;
}

message BatteryState {
  enum BatteryStatus {
    UNKNOWN = 0;
    CHARGING = 1;
    DISCHARGING = 2;
    NOT_CHARGING = 3;
    FULL = 4;
  };
  enum BatteryCharger {
    NONE = 0;
    AC = 1;
    USB = 2;
    WIRELESS = 3;
  };

  enum BatteryHealth {
    GOOD = 0;
    FAILED = 1;
    DEAD = 2;
    OVERVOLTAGE = 3;
    OVERHEATED = 4;
  };
  bool hasBattery = 1;
  bool isPresent = 2;
  BatteryCharger charger = 3;
  int32 chargeLevel = 4;
  BatteryHealth health = 5;
  BatteryStatus status = 6;
}

message ImageFormat {
  enum ImgFormat {
    // Portable Network Graphics format
    // (https://en.wikipedia.org/wiki/Portable_Network_Graphics)
    PNG = 0;

    // Three-channel RGB color model supplemented with a fourth alpha
    // channel. https://en.wikipedia.org/wiki/RGBA_color_model
    // Each pixel consists of 4 bytes.
    RGBA8888 = 1;

    // Three-channel RGB color model, each pixel consists of 3 bytes
    RGB888 = 2;
  }

  // The (desired) format of the resulting bytes.
  ImgFormat format = 1;

  // [Output Only] The rotation of the image. The image will be rotated
  // based upon the coarse grained orientation of the device.
  Rotation rotation = 2;

  // The (desired) width of the image. When passed as input
  // the image will be scaled to match the given
  // width, while maintaining the aspect ratio of the device.
  // The returned image will never exceed the given width, but can be less.
  // Omitting this value (or passing in 0) will result in no scaling,
  // and the width of the actual device will be used.
  uint32 width = 3;

  // The (desired) height of the image.  When passed as input
  // the image will be scaled to match the given
  // height, while maintaining the aspect ratio of the device.
  // The returned image will never exceed the given height, but can be less.
  // Omitting this value (or passing in 0) will result in no scaling,
  // and the height of the actual device will be used.
  uint32 height = 4;

  // The (desired) display id of the device. Setting this to 0 (or omitting)
  // indicates the main display.
  uint32 display = 5;
}

message Image {
  ImageFormat format = 1;

  uint32 width = 2 [ deprecated = true ];  // width is contained in format.
  uint32 height = 3 [ deprecated = true ]; // height is contained in format.

  // The organization of the pixels in the image buffer is from left to
  // right and bottom up.
  bytes image = 4;

  // [Output Only] Monotonically increasing sequence number in a stream of
  // screenshots. The first screenshot will have a sequence of 0. A single
  // screenshot will always have a sequence number of 0. The sequence is not
  // necessarily contiguous, and can be used to detect how many frames were
  // dropped. An example sequence could be: [0, 3, 5, 7, 9, 11].
  uint32 seq = 5;
}

message Rotation {
  enum SkinRotation {
    PORTRAIT = 0;          // 0 degrees
    LANDSCAPE = 1;         // 90 degrees
    REVERSE_PORTRAIT = 2;  // -180 degrees
    REVERSE_LANDSCAPE = 3; // -90 degrees
  }
  SkinRotation rotation = 1; // Can be inferred from z-axis as well.

  // Specifies the angle of rotation, in degrees [-180, 180]
  double xAxis = 2;
  double yAxis = 3;
  double zAxis = 4;
}

message PhoneCall {
  enum Operation {
    InitCall = 0;
    AcceptCall = 1;
    RejectCallExplicit = 2;
    RejectCallBusy = 3;
    DisconnectCall = 4;
    PlaceCallOnHold = 5;
    TakeCallOffHold = 6;
  }
  Operation operation = 1;
  string number = 2;
}

message PhoneResponse {
  enum Response {
    OK = 0;
    BadOperation = 1;  // Enum out of range
    BadNumber = 2;     // Mal-formed telephone number
    InvalidAction = 3; // E.g., disconnect when no call is in progress
    ActionFailed = 4;  // Internal error
    RadioOff = 5;      // Radio power off
  }
  Response response = 1;
}

message Entry {
  string key = 1;
  string value = 2;
}

message EntryList { repeated Entry entry = 1; }

message EmulatorStatus {
  // The emulator version string.
  string version = 1;

  // The time the emulator has been active in .ms
  uint64 uptime = 2;

  // True if the device has completed booting.
  // For P and later this information will accurate,
  // for older images we rely on adb.
  bool booted = 3;

  // The current vm configuration
  VmConfiguration vmConfig = 4;

  // The hardware configuration of the running emulator as
  // key valure pairs.
  EntryList hardwareConfig = 5;
};

message AudioFormat {
  enum SampleFormat {
    AUD_FMT_U8 = 0;  // Unsigned 8 bit
    AUD_FMT_S16 = 1; // Signed 16 bit (little endian)
  };

  enum Channels {
    Mono = 0;
    Stereo = 1;
  };

  // Sampling rate to use, defaulting to 44100 if this is not set.
  // Note, that android devices typically will not use a sampling
  // rate higher than 48kHz. See https://developer.android.com/ndk/guides/audio.
  uint64 samplingRate = 1;
  Channels channels = 2;
  SampleFormat format = 3;
};

message AudioPacket {
  AudioFormat format = 1;

  // Unix epoch in us when this frame was captured.
  uint64 timestamp = 2;

  // Contains a sample in the given audio format.
  bytes audio = 3;
}