Audio TV

Pengelola Framework Input TV (TIF) bekerja dengan API perutean audio untuk mendukung perubahan jalur. Ketika Sistem di Chip (SoC) mengimplementasikan TV hardware abstraction layer (HAL), masing-masing Input TV (HDMI IN, Tuner, dll.) menyediakan TvInputHardwareInfo yang menentukan informasi AudioPort untuk jenis dan alamat audio.

• Perangkat input/output audio fisik memiliki AudioPort yang sesuai.
• Output/input audio software direpresentasikan sebagai AudioMixPort (kelas turunan dari PortaAudio).

TIF kemudian menggunakan informasi AudioPort untuk API perutean audio.

Gambar 1. Framework Input TV (TIF)

Persyaratan

SoC harus mengimplementasikan HAL audio dengan dukungan API perutean audio berikut:

Perangkat audio TV

Android mendukung perangkat audio berikut untuk input/output audio TV.

system/media/audio/include/system/audio.h

Catatan: Di Android 5.1 dan yang lebih lama, jalur ke file ini adalah: system/core/include/system/audio.h

/* output devices */
AUDIO_DEVICE_OUT_AUX_DIGITAL  = 0x400,
AUDIO_DEVICE_OUT_HDMI   = AUDIO_DEVICE_OUT_AUX_DIGITAL,
/* HDMI Audio Return Channel */
AUDIO_DEVICE_OUT_HDMI_ARC   = 0x40000,
/* S/PDIF out */
AUDIO_DEVICE_OUT_SPDIF    = 0x80000,
/* input devices */
AUDIO_DEVICE_IN_AUX_DIGITAL   = AUDIO_DEVICE_BIT_IN | 0x20,
AUDIO_DEVICE_IN_HDMI      = AUDIO_DEVICE_IN_AUX_DIGITAL,
/* TV tuner input */
AUDIO_DEVICE_IN_TV_TUNER    = AUDIO_DEVICE_BIT_IN | 0x4000,
/* S/PDIF in */
AUDIO_DEVICE_IN_SPDIF   = AUDIO_DEVICE_BIT_IN | 0x10000,
AUDIO_DEVICE_IN_LOOPBACK    = AUDIO_DEVICE_BIT_IN | 0x40000,

Ekstensi HAL audio

Ekstensi Audio HAL untuk API pemilihan rute audio ditentukan sebagai berikut:

system/media/audio/include/system/audio.h

Catatan: Di Android 5.1 dan yang lebih lama, jalur ke file ini adalah: system/core/include/system/audio.h

/* audio port configuration structure used to specify a particular configuration of an audio port */
struct audio_port_config {
    audio_port_handle_t      id;           /* port unique ID */
    audio_port_role_t        role;         /* sink or source */
    audio_port_type_t        type;         /* device, mix ... */
    unsigned int             config_mask;  /* e.g. AUDIO_PORT_CONFIG_ALL */
    unsigned int             sample_rate;  /* sampling rate in Hz */
    audio_channel_mask_t     channel_mask; /* channel mask if applicable */
    audio_format_t           format;       /* format if applicable */
    struct audio_gain_config gain;         /* gain to apply if applicable */
    union {
        struct audio_port_config_device_ext  device;  /* device specific info */
        struct audio_port_config_mix_ext     mix;     /* mix specific info */
        struct audio_port_config_session_ext session; /* session specific info */
    } ext;
};
struct audio_port {
    audio_port_handle_t      id;                /* port unique ID */
    audio_port_role_t        role;              /* sink or source */
    audio_port_type_t        type;              /* device, mix ... */
    unsigned int             num_sample_rates;  /* number of sampling rates in following array */
    unsigned int             sample_rates[AUDIO_PORT_MAX_SAMPLING_RATES];
    unsigned int             num_channel_masks; /* number of channel masks in following array */
    audio_channel_mask_t     channel_masks[AUDIO_PORT_MAX_CHANNEL_MASKS];
    unsigned int             num_formats;       /* number of formats in following array */
    audio_format_t           formats[AUDIO_PORT_MAX_FORMATS];
    unsigned int             num_gains;         /* number of gains in following array */
    struct audio_gain        gains[AUDIO_PORT_MAX_GAINS];
    struct audio_port_config active_config;     /* current audio port configuration */
    union {
        struct audio_port_device_ext  device;
        struct audio_port_mix_ext     mix;
        struct audio_port_session_ext session;
    } ext;
};

hardware/libhardware/include/hardware/audio.h

struct audio_hw_device {
  :
    /**
     * Routing control
     */

    /* Creates an audio patch between several source and sink ports.
     * The handle is allocated by the HAL and should be unique for this
     * audio HAL module. */
    int (*create_audio_patch)(struct audio_hw_device *dev,
                               unsigned int num_sources,
                               const struct audio_port_config *sources,
                               unsigned int num_sinks,
                               const struct audio_port_config *sinks,
                               audio_patch_handle_t *handle);

    /* Release an audio patch */
    int (*release_audio_patch)(struct audio_hw_device *dev,
                               audio_patch_handle_t handle);

    /* Fills the list of supported attributes for a given audio port.
     * As input, "port" contains the information (type, role, address etc...)
     * needed by the HAL to identify the port.
     * As output, "port" contains possible attributes (sampling rates, formats,
     * channel masks, gain controllers...) for this port.
     */
    int (*get_audio_port)(struct audio_hw_device *dev,
                          struct audio_port *port);

    /* Set audio port configuration */
    int (*set_audio_port_config)(struct audio_hw_device *dev,
                         const struct audio_port_config *config);

Menguji DEVICE_IN_LOOPBACK

Untuk menguji DEVICE_IN_LOOPBACK untuk pemantauan TV, gunakan kode pengujian berikut. Setelah menjalankan audio, audio yang direkam akan disimpan ke /sdcard/record_loopback.raw, tempat Anda dapat mendengarkan menggunakan FFmpeg.

<uses-permission android:name="android.permission.MODIFY_AUDIO_ROUTING" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

   AudioRecord mRecorder;
   Handler mHandler = new Handler();
   int mMinBufferSize = AudioRecord.getMinBufferSize(RECORD_SAMPLING_RATE,
           AudioFormat.CHANNEL_IN_MONO,
           AudioFormat.ENCODING_PCM_16BIT);;
   static final int RECORD_SAMPLING_RATE = 48000;
   public void doCapture() {
       mRecorder = new AudioRecord(MediaRecorder.AudioSource.DEFAULT, RECORD_SAMPLING_RATE,
               AudioFormat.CHANNEL_IN_MONO, AudioFormat.ENCODING_PCM_16BIT, mMinBufferSize * 10);
       AudioManager am = (AudioManager) getSystemService(Context.AUDIO_SERVICE);
       ArrayList<AudioPort> audioPorts = new ArrayList<AudioPort>();
       am.listAudioPorts(audioPorts);
       AudioPortConfig srcPortConfig = null;
       AudioPortConfig sinkPortConfig = null;
       for (AudioPort audioPort : audioPorts) {
           if (srcPortConfig == null
                   && audioPort.role() == AudioPort.ROLE_SOURCE
                   && audioPort instanceof AudioDevicePort) {
               AudioDevicePort audioDevicePort = (AudioDevicePort) audioPort;
               if (audioDevicePort.type() == AudioManager.DEVICE_IN_LOOPBACK) {
                   srcPortConfig = audioPort.buildConfig(48000, AudioFormat.CHANNEL_IN_DEFAULT,
                           AudioFormat.ENCODING_DEFAULT, null);
                   Log.d(LOG_TAG, "Found loopback audio source port : " + audioPort);
               }
           }
           else if (sinkPortConfig == null
                   && audioPort.role() == AudioPort.ROLE_SINK
                   && audioPort instanceof AudioMixPort) {
               sinkPortConfig = audioPort.buildConfig(48000, AudioFormat.CHANNEL_OUT_DEFAULT,
                       AudioFormat.ENCODING_DEFAULT, null);
               Log.d(LOG_TAG, "Found recorder audio mix port : " + audioPort);
           }
       }
       if (srcPortConfig != null && sinkPortConfig != null) {
           AudioPatch[] patches = new AudioPatch[] { null };
           int status = am.createAudioPatch(
                   patches,
                   new AudioPortConfig[] { srcPortConfig },
                   new AudioPortConfig[] { sinkPortConfig });
           Log.d(LOG_TAG, "Result of createAudioPatch(): " + status);
       }
       mRecorder.startRecording();
       processAudioData();
       mRecorder.stop();
       mRecorder.release();
   }
   private void processAudioData() {
       OutputStream rawFileStream = null;
       byte data[] = new byte[mMinBufferSize];
       try {
           rawFileStream = new BufferedOutputStream(
                   new FileOutputStream(new File("/sdcard/record_loopback.raw")));
       } catch (FileNotFoundException e) {
           Log.d(LOG_TAG, "Can't open file.", e);
       }
       long startTimeMs = System.currentTimeMillis();
       while (System.currentTimeMillis() - startTimeMs < 5000) {
           int nbytes = mRecorder.read(data, 0, mMinBufferSize);
           if (nbytes <= 0) {
               continue;
           }
           try {
               rawFileStream.write(data);
           } catch (IOException e) {
               Log.e(LOG_TAG, "Error on writing raw file.", e);
           }
       }
       try {
           rawFileStream.close();
       } catch (IOException e) {
       }
       Log.d(LOG_TAG, "Exit audio recording.");
   }

Temukan file audio yang direkam di /sdcard/record_loopback.raw dan dengarkan menggunakan FFmpeg:

adb pull /sdcard/record_loopback.raw
ffmpeg -f s16le -ar 48k -ac 1 -i record_loopback.raw record_loopback.wav
ffplay record_loopback.wav

Kasus penggunaan

Bagian ini mencakup kasus penggunaan umum untuk audio TV.

TV tuner dengan output speaker

Saat TV tuner menjadi aktif, API perutean audio akan membuat patch audio di antara tuner dan output default (misalnya, speaker). Output tuner tidak memerlukan decoding, tetapi output audio digabungkan dengan software output_stream.

Gambar 2. Patch Audio untuk TV tuner dengan output speaker.

HDMI OUT selama TV live

Pengguna sedang menonton TV live, lalu beralih ke output audio HDMI (Intent.ACTION_HDMI_AUDIO_PLUG) kami. Perangkat {i>output<i} dari semua output_stream berubah ke porta HDMI_OUT, dan pengelola TIF berubah porta sink dari {i>patch<i} audio tuner yang ada ke porta HDMI_OUT.

Gambar 3. Patch Audio untuk HDMI OUT dari TV live.