# Hardware abstraction layer

SDK The normal operation depends on the software and hardware interface provided by the hardware device platform, including microphone, speaker, camera, encryption library and other modules. We design a hardware abstraction layer to provide consistent interface definitions, and concrete interface implementations need to be SDK Access provided.

# 1. Module abstract

Header file:wmpf/module.h。

We abstract each module into awx_ModuleTypes, there are currently the following module:

When these are implemented on demand Module After calling the wx_init() to initialize SDK You will use the following function pointer to Module Provided to the SDK Use:

typedef wx_error_t (*wx_get_Module_t)(const char* id,
                                      struct wx_Module** Module)

SDK When you call the implemented function, you pass in a ID, you need to return this ID The corresponding wx_Module Examples of.

parameter

Currently supported Module ID Already predefined in each header file:

Return value

wx_error_t SDK Based on this return value, the requested Module If it works.

For example, a device does not have a camera, then when SDK request WX_CAMERA_MODULE_ID You just need to return. WXERROR_UNIMPLEMENTED。

sample code

// Suppose you have implemented the following module:
extern struct wx_audio_Module audio_Module
extern struct wx_Camera_Module Camera_Module
extern struct wx_crypto_Module crypto_Module
// The function of HAL getting Module is as follows:
wx_error_t hal_get_Module(const char* id, struct wx_Module** Module_out) {
  if (!strcmp(id, WX_AUDIO_MODULE_ID)) {
    *Module_out = (struct wx_Module*)&audio_Module
    return WXERROR_OK
  } else if (!strcmp(id, WX_CAMERA_MODULE_ID)) {
    *Module_out = (struct wx_Module*)&camera_Module
    return WXERROR_OK
  } else if (!strcmp(id, WX_CRYPTO_MODULE_ID)) {
    *Module_out = (struct wx_Module*)&crypto_Module
    return WXERROR_OK
  }
  // Assume that the current device does not have a screen, so there is no need to provide wx_video_Module, then it returns the WXERROR_UNIMPLEMENTED
  return WXERROR_UNIMPLEMENTED
}

# 2. Audio Module

Header file:wmpf/hardware/audio.h。

Audio module, you need to configure a wx_audio_Module An instance of the. This type mainly contains the following function pointers, used to get the audio input/Output device messages, or operate audio devices.

Runtime, VoIP This will be called sequentially 4 A function to complete the audio input/Configuration of output devices.

# 2.1 get_number_of_devices

Get Specified Type Audio Input/The number of output devices.

wx_error_t (*get_number_of_devices)(struct wx_audio_Module* module,
                                    wx_audio_device_type_t device_type,
                                    Size_t* num_devices_out)

parameter

Return value

wx_error_t SDK Based on this return value, it is determined whether the obtained number of devices is valid

# 2.2 get_device_Name

Query the specified type, such as WX_AUDIO_DEVICE_IN Represents a microphone) Audio Input/Number one in the output device list index One device. ID

wx_error_t (*get_device_Name)(struct wx_audio_Module* module,
                              Size_t index,
                              wx_audio_device_type_t device_type,
                              char** device_Name_out)

parameter

Return value

wx_error_t SDK Based on this return value, it is judged that the resulting device ID Whether it is effective

# 2.3 get_device_Info

Query the specified type and device ID Details of the device. This function is used to return some audio device information, such as supported audio encoding formats, that can be retrieved without opening the audio device.

wx_error_t (*get_device_Info)(struct wx_audio_Module* module,
                              const char* id,
                              wx_audio_device_type_t device_type,
                              const struct wx_Metadata** Metadata_out)

parameter

Return value

wx_error_t SDK Based on this return value, it is determined whether the obtained device details are valid

# 2.4 open

Calls the specified audio input/Output devices.

wx_error_t (*open)(struct wx_audio_Module* module,
                   const char* id,
                   wx_audio_device_type_t device_type,
                   struct wx_audio_device** device_out)

parameter

Return value

wx_error_t SDK Based on this return value, it is determined whether the resulting device instance is valid

# 2.5 wx_audio_device

struct wx_audio_device The function itself is not much, mainly for the description of the device. What really needs to focus on are its two types of extensions:wx_audio_device_in and wx_audio_device_out。

# 2.5.1 wx_audio_device_in

The abstraction of an input device such as a microphone. The key to this type is the need to provide open_input_stream Function implementation, runtime SDK This function will be called to create the audio input stream object wx_audio_stream_in。SDK use wx_audio_stream_in Object to further control audio capture.

The microphone device is VoIP Call is created when dialed, VoIP Destroyed at the end of the call.

# open_input_stream The parameters of the

# wx_audio_stream_in

# wx_audio_stream_in_listener

Notes:

1. SDK Currently only collecting PCM Format audio data, in the future may add other audio formats.
2. config At present, the sampling rate 16000, sampling length 20ms、16bit Is configured by default and may be dynamically adjusted. If the device does not support these audio configurations, the device manufacturer should make their own PCM The data is transformed.
3. Data Callbacks can be understood as non-blocking, that is, network agnostic.
4. Data One frame of audio data provided by the callback, which needs to be determined according to the config Set the parameters provided. For example: PCM sampling rate 16000, sampling format 16bit, sample length 20ms Of single channel audio data, containing the 16000 / 1000 * 20 * 1 * (16 / 8) Bytes of data (sampling rate / 1000 * Sampling length * Number of channels * Sampling format / 8Bit）。

# 2.5.2 wx_audio_device_out type

For the abstraction of the speaker device. The key to this type is to provide open_output_stream Function implementation, runtime SDK This function is called to create the audio output stream object wx_audio_stream_out。SDK use wx_audio_stream_out Object to further control audio playback.

The speaker device in the VoIP The call is created when the call begins to be dialed, the ringtone is played first, and the VoIP Start playing voice when the call starts, VoIP Destroyed at the end of the call.

# open_output_stream Of the parameters:

# wx_audio_stream_out type

# wx_audio_stream_out_listener type

Notes:

1. SDK Currently only available PCM Format audio data, in the future may add other audio formats.
2. config At present, the sampling rate 16000, sampling length 20ms、16bit Is configured by default and may be dynamically adjusted. If the device does not support these audio configurations, the device manufacturer should make their own PCM The data is transformed.
3. Data Callbacks can be understood as non-blocking, that is, network agnostic.
4. Data Callback the incoming buffer Need to be big enough to hold config Set a frame of audio data. For example: PCM sampling rate 16000, sampling format 16bit, sample length 20ms Of single channel audio data, containing the 16000 / 1000 _ 20 _ 1 _ (16 / 8) Byte data (sampling rate / 1000 _ Sampling length _ Number of channels _ Sampling format / 8Bit）。

# 3. Signature algorithm module

Header file:wmpf/crypto.h。

SDK Relying on the system's built-in signature algorithm, we provide OpenSSL, MbedTLS, WolfSSL of Demo Implementation, stored in the example In the directory. If you use the above crypto Implementation, which can often be used directly with the example Of the code implementation. Otherwise, refer to the example Implementation for adaptation.

Demo Achieve:

• example/crypto_mbedtls.c
• example/crypto_openssl.c
• example/crypto_wolfssl.c

# 4. (available)Camera module

Header file:wmpf/hardware/camera.h。

Camera module, it is necessary to configure a wx_Camera_Module An instance of the. This type mainly requires you to provide the following function pointers, which are used to generate video streams from the device to the phone using the camera device object provided by the device.

At runtime, the SDK This will be called sequentially 3 A function to complete the configuration of the camera equipment.

# 4.1 get_number_of_devices

Get the number of camera devices.

wx_error_t (*get_number_of_devices)(struct wx_Camera_Module* module,
                                    Size_t* num_devices_out)

parameter

Return value

wx_error_t SDK Based on this return value, it is determined whether the obtained number of devices is valid

# 4.2 get_device_Info

Query details for the specified camera device.

wx_error_t (*get_device_Info)(struct wx_Camera_Module* module,
                              Size_t index,
                              struct wx_Camera_device_Info* device_Info)

parameter

Return value

wx_error_t SDK Based on this return value, it is determined whether the obtained device details are valid

# 4.3 open

Invokes the specified camera device.

wx_error_t (*open)(struct wx_Camera_Module* module,
                   const char* id,
                   struct wx_Camera_device** device_out)

parameter

Return value

wx_error_t SDK Based on this return value, it is determined whether the resulting device instance is valid

# 4.4 wx_Camera_device

For the abstraction of the camera device. The key to this type is the need to provide open_stream Function implementation, runtime SDK This function is called to create a video input stream object wx_Camera_stream。SDK use wx_Camera_stream Object to further control the video capture.

open_stream Of the parameters:

# wx_Camera_stream type

# wx_Camera_stream_listener type

Notes:

1. SDK Currently only collecting H264/H265 Format of video data.
2. Data Callbacks can be understood as non-blocking, that is, network agnostic.
3. Equipment needs to be timed (recommended 1 Seconds, the maximum shall not exceed 5 Seconds) to provide PPS、SPS、I Frame.
4. Device incoming rotation Only in Linux SDK 0xD5000084 And above version, WeChat client 8.0.41 And above version is effective, for the older WeChat version, you need to call on the mini program side VoIP Plug-in setUIConfig Sets the angle of swing.

# 5. (available)Video module

Header file:wmpf/hardware/video.h。

Camera module, it is necessary to configure a wx_video_Module An instance of the.

At runtime, the SDK Will call the create_output_stream Function to create a video output stream and output the received video recorded by the remote (cell phone) camera through the stream object.

# 5.1 create_output_stream

Create a video output stream.

wx_error_t (*create_output_stream)(struct wx_video_Module* module,
                                   const struct wx_video_stream_config* config,
                                   struct wx_video_stream** stream)

parameter

Return value

wx_error_t SDK According to this return value, it is judged whether the video output stream is valid

# 5.2 wx_video_stream