Using OHAudio for Audio Playback

OHAudio is a set of native APIs introduced in API version 10. These APIs are normalized in design and support both common and low-latency audio channels.

Prerequisites

To use the playback or recording capability of OHAudio, you must first import the corresponding header files.

Specifically, to use APIs for audio playback, import <native_audiostreambuilder.h> and <native_audiorenderer.h>.

Audio Stream Builder

OHAudio provides the OH_AudioStreamBuilder class, which complies with the builder design pattern and is used to build audio streams. You need to specify OH_AudioStream_Type based on your service scenarios.

OH_AudioStream_Type can be set to either of the following:

• AUDIOSTREAM_TYPE_RENDERER
• AUDIOSTREAM_TYPE_CAPTURER

The following code snippet shows how to use OH_AudioStreamBuilder_Create to create a builder:

OH_AudioStreamBuilder* builder;
OH_AudioStreamBuilder_Create(&builder, streamType);

After the audio service is complete, call OH_AudioStreamBuilder_Destroy to destroy the builder.

OH_AudioStreamBuilder_Destroy(builder);

How to Develop

Read OHAudio for the API reference.

The following walks you through how to implement simple playback:

1. Create an audio stream builder.

   OH_AudioStreamBuilder* builder;
   OH_AudioStreamBuilder_Create(&builder, AUDIOSTREAM_TYPE_RENDERER);
   

2. Set audio stream parameters.

   After creating the builder for audio playback, set the parameters required.

   OH_AudioStreamBuilder_SetSamplingRate(builder, rate);
   OH_AudioStreamBuilder_SetChannelCount(builder, channelCount);
   OH_AudioStreamBuilder_SetSampleFormat(builder, format);
   OH_AudioStreamBuilder_SetEncodingType(builder, encodingType);
   OH_AudioStreamBuilder_SetRendererInfo(builder, usage);
   

   Note that the audio data to play is written through callbacks. You must call OH_AudioStreamBuilder_SetRendererCallback to implement the callbacks. For details about the declaration of the callback functions, see OH_AudioRenderer_Callbacks.

3. Set the callback functions.

   OH_AudioStreamBuilder_SetRendererCallback(builder, callbacks, nullptr);
   

4. Create an audio renderer instance.

   OH_AudioRenderer* audioRenderer;
   OH_AudioStreamBuilder_GenerateRenderer(builder, &audioRenderer);
   

5. Use the audio renderer.

   You can use the APIs listed below to control the audio streams.

|API |Description | |————————————————————|————| |OH_AudioStream_Result OH_AudioRenderer_Start(OH_AudioRenderer* renderer)|Starts the audio renderer. | |OH_AudioStream_Result OH_AudioRenderer_Pause(OH_AudioRenderer* renderer)|Pauses the audio renderer. | |OH_AudioStream_Result OH_AudioRenderer_Stop(OH_AudioRenderer* renderer)|Stops the audio renderer. | |OH_AudioStream_Result OH_AudioRenderer_Flush(OH_AudioRenderer* renderer)|Flushes written audio data.| |OH_AudioStream_Result OH_AudioRenderer_Release(OH_AudioRenderer* renderer)|Releases the audio renderer instance.|

1. Destroy the audio stream builder.

   When the builder is no longer used, release related resources.

   OH_AudioStreamBuilder_Destroy(builder);
   

Setting the Low Latency Mode

If the device supports the low-latency channel, you can use the low-latency mode to create a player for a higher-quality audio experience.

The development process is similar to that in the common playback scenario. The only difference is that you need to set the low delay mode by calling OH_AudioStreamBuilder_SetLatencyMode() when creating an audio stream builder.

The code snippet is as follows:

OH_AudioStream_LatencyMode latencyMode = AUDIOSTREAM_LATENCY_MODE_FAST;
OH_AudioStreamBuilder_SetLatencyMode(builder, latencyMode);

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