TV 輸入框架 (TIF) 管理員與音訊路由 API 搭配使用,支援靈活的音訊路徑變更。當系統單晶片 (SoC) 實作電視硬體抽象層 (HAL) 時,每個電視輸入(HDMI IN、調諧器等)都會提供TvInputHardwareInfo
,用於指定音訊類型和位址的 AudioPort 資訊。
- 實體音訊輸入/輸出設備都有對應的AudioPort。
- 軟體音訊輸出/輸入流表示為 AudioMixPort(AudioPort 的子類別)。
然後,TIF 將 AudioPort 資訊用於音訊路由 API。
要求
SoC 必須實作具有以下音訊路由 API 支援的音訊 HAL:
音訊連接埠 |
|
---|---|
預設輸入 | AudioRecord(使用 DEFAULT 輸入來源建立)必須佔用虛擬空輸入來源,以便在 Android TV 上取得 AUDIO_DEVICE_IN_DEFAULT。 |
裝置環回 | 需要支援 AUDIO_DEVICE_IN_LOOPBACK 輸入,該輸入是所有電視輸出(11Khz、16 位元單聲道或 48Khz、16 位元單聲道)的所有音訊輸出的完整混合。僅用於音訊捕獲。 |
電視音訊設備
Android 支援以下音訊裝置用於電視音訊輸入/輸出。
system/media/audio/include/system/audio.h
注意:在Android 5.1及更早版本中,該檔案的路徑為: 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,
音訊 HAL 擴展
音訊路由 API 的音訊 HAL 擴充定義如下:
system/media/audio/include/system/audio.h
注意:在Android 5.1及更早版本中,該檔案的路徑為: 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);
測試DEVICE_IN_LOOPBACK
若要測試 TV 監控的 DEVICE_IN_LOOPBACK,請使用下列測試程式碼。運行測試後,捕獲的音訊保存到/sdcard/record_loopback.raw
,您可以在其中使用FFmpeg
收聽它。
<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."); }
在/sdcard/record_loopback.raw
中找到捕獲的音訊檔案並使用FFmpeg
收聽它:
adb pull /sdcard/record_loopback.raw
ffmpeg -f s16le -ar 48k -ac 1 -i record_loopback.raw record_loopback.wav
ffplay record_loopback.wav
用例
本節包括電視音訊的常見用例。
帶有揚聲器輸出的電視調諧器
當電視調諧器啟動時,音訊路由API 會在調諧器和預設輸出(例如揚聲器)之間建立音訊修補程式。調諧器輸出不需要解碼,但最終的音訊輸出與軟體output_stream混合。
直播電視期間 HDMI OUT
使用者正在觀看直播電視,然後切換到 HDMI 音訊輸出 (Intent.ACTION_HDMI_AUDIO_PLUG) 。所有output_streams的輸出設備變更為HDMI_OUT端口,並且TIF管理器將現有調諧器音訊修補程式的接收器端口變更為HDMI_OUT端口。