Question

我正在尝试为嵌入式Android设备设置音频。该设备将连接到USB音频设备，该设备应该是主要设备和默认设备。

由于我是为Android 6开发的，因此音频文档here太新了，无法详细说明应该如何设置。

这是当前的audio_policy.conf：

# Global configuration section: lists input and output devices always present on the device
# as well as the output device selected by default.
# Devices are designated by a string that corresponds to the enum in audio.h

global_configuration {
  attached_output_devices AUDIO_DEVICE_OUT_AUX_DIGITAL
  default_output_device AUDIO_DEVICE_OUT_AUX_DIGITAL
  attached_input_devices AUDIO_DEVICE_IN_BUILTIN_MIC
}

# audio hardware module section: contains descriptors for all audio hw modules present on the
# device. Each hw module node is named after the corresponding hw module library base name.
# For instance, "primary" corresponds to audio.primary.<device>.so.
# The "primary" module is mandatory and must include at least one output with
# AUDIO_OUTPUT_FLAG_PRIMARY flag.
# Each module descriptor contains one or more output profile descriptors and zero or more
# input profile descriptors. Each profile lists all the parameters supported by a given output
# or input stream category.
# The "channel_masks", "formats", "devices" and "flags" are specified using strings corresponding
# to enums in audio.h and audio_policy.h. They are concatenated by use of "|" without space or "\n".

audio_hw_modules {
  primary {
    outputs {
      primary {
        sampling_rates 8000|11025|16000|22050|24000|32000|44100|48000
        channel_masks AUDIO_CHANNEL_OUT_STEREO
        formats AUDIO_FORMAT_PCM_16_BIT
        devices AUDIO_DEVICE_OUT_SPEAKER|AUDIO_DEVICE_OUT_WIRED_HEADSET|AUDIO_DEVICE_OUT_WIRED_HEADPHONE|AUDIO_DEVICE_OUT_AUX_DIGITAL
        flags AUDIO_OUTPUT_FLAG_PRIMARY
        }
    hdmi {
        sampling_rates dynamic
        channel_masks dynamic
        formats AUDIO_FORMAT_PCM_16_BIT
        devices AUDIO_DEVICE_OUT_AUX_DIGITAL
        flags AUDIO_OUTPUT_FLAG_DIRECT
        }
    }
    inputs {
      primary {
        sampling_rates 48000
        channel_masks AUDIO_CHANNEL_IN_STEREO
        formats AUDIO_FORMAT_PCM_16_BIT
        devices AUDIO_DEVICE_IN_BUILTIN_MIC|AUDIO_DEVICE_IN_WIRED_HEADSET
      }
    }
  }
}

首先，我不确定是否应该按如下方式更改全局配置：

global_configuration {
  attached_output_devices AUDIO_DEVICE_OUT_AUX_DIGITAL|AUDIO_DEVICE_OUT_USB_DEVICE
  default_output_device AUDIO_DEVICE_OUT_USB_DEVICE
  attached_input_devices AUDIO_DEVICE_IN_BUILTIN_MIC
}

另外，

我应该在主要输出下定义usb（例如当前是HDMI），还是应该像在一些在线示例中看到的那样在主要下创建单独的部分：

audio_hw_modules {
  primary {
    outputs {
      primary {
        sampling_rates 8000|11025|16000|22050|24000|32000|44100|48000
        channel_masks AUDIO_CHANNEL_OUT_STEREO
        formats AUDIO_FORMAT_PCM_16_BIT
        devices AUDIO_DEVICE_OUT_SPEAKER|AUDIO_DEVICE_OUT_WIRED_HEADSET|AUDIO_DEVICE_OUT_WIRED_HEADPHONE|AUDIO_DEVICE_OUT_AUX_DIGITAL
        flags AUDIO_OUTPUT_FLAG_PRIMARY
        }
    hdmi { # The HDMI Device is considered the same as AUX_DIGITAL
        sampling_rates dynamic
        channel_masks dynamic
        formats AUDIO_FORMAT_PCM_16_BIT
        devices AUDIO_DEVICE_OUT_AUX_DIGITAL
        flags AUDIO_OUTPUT_FLAG_DIRECT
        }
   }
    inputs {
      primary {
        sampling_rates 48000
        channel_masks AUDIO_CHANNEL_IN_STEREO
        formats AUDIO_FORMAT_PCM_16_BIT
        devices AUDIO_DEVICE_IN_BUILTIN_MIC|AUDIO_DEVICE_IN_WIRED_HEADSET
      }
    }
  }
  usb {
    outputs {
      usb_accessory {
        sampling_rates 44100
        channel_masks AUDIO_CHANNEL_OUT_STEREO
        formats AUDIO_FORMAT_PCM_16_BIT
        devices AUDIO_DEVICE_OUT_USB_ACCESSORY
      }
      usb_device {
        sampling_rates 44100
        channel_masks AUDIO_CHANNEL_OUT_STEREO
        formats AUDIO_FORMAT_PCM_16_BIT
        devices AUDIO_DEVICE_OUT_USB_DEVICE
      }
    }
  }
}

接下来，在libhardware/modules/audio下，我看到android提供的audio_hw.c。与当前文档（和我当前的/device/<company>/<device>/audio）不同，它不在audio_policy.conf下。这是否意味着要复制到设备目录中。

在/libhardware/modules/usbaudio下还有一个名为audio_hal.c的文件。我需要这个吗？

任何有助于了解android 6 HAL的帮助都将非常有帮助。提前感谢！

适用于USB音频的Android 6设置HAL

0 个答案: