Interface AudioMixer

  • @Deprecated
    public interface AudioMixer
    Deprecated. is deprecated. Please migrate to androidx.media3 (which contains the same ExoPlayer code). See the migration guide for more details, including a script to help with the migration.
    An audio component which combines audio data from multiple sources into a single output.

    The mixer supports an arbitrary number of concurrent sources and will ensure audio data from all sources are aligned and mixed before producing output. Any periods without sources will be filled with silence. The total duration of the mixed track is controlled with setEndTimeUs(long), or is unbounded if left unset.

    Updates: The mixer supports the following updates at any time without the need for a reset().

    Changes to the output audio format, buffer size, or mixer start time require the mixer to first be reset, discarding all buffered data.

    Operation: The mixer must be configured before any methods are called. Once configured, sources can queue audio data via queueInput(int, java.nio.ByteBuffer) and the mixer will consume input audio up to the configured buffer size and end time. Once all sources have produced data for a period then getOutput() will return the mixed result. The cycle repeats until the mixer isEnded().

    • Method Detail

      • create

        static AudioMixer create()
        Creates an unconfigured instance.
      • configure

        void configure​(AudioProcessor.AudioFormat outputAudioFormat,
                       int bufferSizeMs,
                       long startTimeUs)
                throws AudioProcessor.UnhandledAudioFormatException
        Configures the mixer.

        The mixer must be configured before use and can only be reconfigured after a call to reset().

        The mixing buffer size is set by bufferSizeMs and indicates how much audio can be queued before getOutput() is called.

        outputAudioFormat - The audio format of buffers returned from getOutput().
        bufferSizeMs - The mixing buffer size in milliseconds.
        startTimeUs - The start time of the mixer output in microseconds.
        AudioProcessor.UnhandledAudioFormatException - If the output audio format is not supported.
      • setEndTimeUs

        void setEndTimeUs​(long endTimeUs)
        Sets the end time of the output audio.

        The mixer will not accept input nor produce output past this point.

        endTimeUs - The end time in microseconds.
        IllegalArgumentException - If endTimeUs is before the configured start time.
      • supportsSourceAudioFormat

        boolean supportsSourceAudioFormat​(AudioProcessor.AudioFormat sourceFormat)
        Indicates whether the mixer supports mixing sources with the given audio format.
      • addSource

        int addSource​(AudioProcessor.AudioFormat sourceFormat,
                      long startTimeUs)
               throws AudioProcessor.UnhandledAudioFormatException
        Adds an audio source to mix starting at the given time.

        If the mixer has already output samples past the startTimeUs, audio from this source will be discarded up to the last output end timestamp.

        If the source start time is earlier than the configured mixer start time then audio from this source will be discarded up to the mixer start time.

        All audio sources start with a volume of 1.0 on all channels.

        sourceFormat - Audio format of source buffers.
        startTimeUs - Source start time in microseconds.
        Non-negative integer identifying the source (sourceId).
        AudioProcessor.UnhandledAudioFormatException - If the source format is not supported.
      • queueInput

        void queueInput​(int sourceId,
                        ByteBuffer sourceBuffer)
        Queues audio data between the position and limit of the sourceBuffer.

        After calling this method output may be available via getOutput() if all sources have queued data.

        sourceId - Source identifier from addSource(, long).
        sourceBuffer - The source buffer to mix. It must be a direct byte buffer with native byte order. Its contents are treated as read-only. Its position will be advanced by the number of bytes consumed (which may be zero). The caller retains ownership of the provided buffer.
      • getOutput

        ByteBuffer getOutput()
        Returns a buffer containing output audio data between its position and limit.

        The buffer will be no larger than the configured buffer size and will include no more than the frames that have been queued from all sources, up to the end time. Silence will be generated for any periods with no sources.

        The buffer will always be a direct byte buffer with native byte order. Calling this method invalidates any previously returned buffer. The buffer will be empty if no output is available.

        A buffer containing output data between its position and limit.
      • isEnded

        boolean isEnded()
        Returns whether the mixer can accept more input or produce more output, based on the end time.

        Note: If no end time is set this will always return false.

      • reset

        void reset()
        Resets the mixer to its unconfigured state, releasing any resources.