playbacknode.cc

Audacity是一款用於錄音和編輯聲音的、免費的開放源碼軟體。它可以執行於Mac OS X、Microsoft Windows、GNU/Linux和其它作業系統

void PaPlaybackNode::NodeRegistered()
{
    DBUG(("NodeRegistered() called.\n"));

    /* Start the BMediaEventLooper thread */
    SetPriority(B_REAL_TIME_PRIORITY);
    Run();

    /* set up as much information about our output as we can */
    mOutput.source.port = ControlPort();
    mOutput.source.id = 0;
    mOutput.node = Node();
    ::strcpy(mOutput.name, "PortAudio Playback");
}


void PaPlaybackNode::HandleEvent( const media_timed_event *event,
                                  bigtime_t lateness, bool realTimeEvent )
{
    // DBUG(("HandleEvent() called.\n"));
    status_t err;

    switch(event->type)
    {
    case BTimedEventQueue::B_START:
        DBUG(("   Handling a B_START event\n"));
        if( RunState() != B_STARTED )
        {
            mStartTime = event->event_time + EventLatency();
            mSamplesSent = 0;
            mAborted = false;
            mRunning = true;
            media_timed_event firstEvent( mStartTime,
                                          BTimedEventQueue::B_HANDLE_BUFFER );
            EventQueue()->AddEvent( firstEvent );
        }
        break;

    case BTimedEventQueue::B_STOP:
        DBUG(("   Handling a B_STOP event\n"));
        mRunning = false;
        EventQueue()->FlushEvents( 0, BTimedEventQueue::B_ALWAYS, true,
                                   BTimedEventQueue::B_HANDLE_BUFFER );
        break;

    case BTimedEventQueue::B_HANDLE_BUFFER:
        //DBUG(("   Handling a B_HANDLE_BUFFER event\n"));

        /* make sure we're started and connected */
        if( RunState() != BMediaEventLooper::B_STARTED ||
                mOutput.destination == media_destination::null )
            break;

        BBuffer *buffer = FillNextBuffer(event->event_time);

        /* make sure we weren't aborted while this routine was running.
         * this can happen in one of two ways: either the callback returned
         * nonzero (in which case mAborted is set in FillNextBuffer() ) or
         * the client called AbortStream */
        if( mAborted )
        {
            if( buffer )
                buffer->Recycle();
            Stop(0, true);
            break;
        }

        if( buffer )
        {
            err = SendBuffer(buffer, mOutput.destination);
            if( err != B_OK )
                buffer->Recycle();
        }

        mSamplesSent += mOutput.format.u.raw_audio.buffer_size / mOutputSampleWidth;

        /* Now schedule the next buffer event, so we can send another
         * buffer when this one runs out. We calculate when it should
         * happen by calculating when the data we just sent will finish
         * playing.
         *
         * NOTE, however, that the event will actually get generated
         * earlier than we specify, to account for the latency it will
         * take to produce the buffer. It uses the latency value we
         * specified in SetEventLatency() to determine just how early
         * to generate it. */

        /* totalPerformanceTime includes the time represented by the buffer
         * we just sent */
        bigtime_t totalPerformanceTime = (bigtime_t)((double)mSamplesSent /
                                         (double)mOutput.format.u.raw_audio.channel_count /
                                         (double)mOutput.format.u.raw_audio.frame_rate * 1000000.0);

        bigtime_t nextEventTime = mStartTime + totalPerformanceTime;

        media_timed_event nextBufferEvent(nextEventTime,
                                          BTimedEventQueue::B_HANDLE_BUFFER);
        EventQueue()->AddEvent(nextBufferEvent);

        break;

    }
}




/*************************
 *
 *  BBufferProducer methods
 *
 */

status_t PaPlaybackNode::FormatSuggestionRequested( media_type type,
        int32 /*quality*/, media_format* format )
{
    /* the caller wants to know this node's preferred format and provides
     * a suggestion, asking if we support it */
    DBUG(("FormatSuggestionRequested() called.\n"));

    if(!format)
        return B_BAD_VALUE;

    *format = mPreferredFormat;

    /* we only support raw audio (a wildcard is okay too) */
    if ( type == B_MEDIA_UNKNOWN_TYPE || type == B_MEDIA_RAW_AUDIO )
        return B_OK;
    else
        return B_MEDIA_BAD_FORMAT;
}


status_t PaPlaybackNode::FormatProposal( const media_source& output,
        media_format* format )
{
    /* This is similar to FormatSuggestionRequested(), but it is actually part
     * of the negotiation process. We're given the opportunity to specify any
     * properties that are wildcards (ie. properties that the other node doesn't
     * care one way or another about) */
    DBUG(("FormatProposal() called.\n"));

    /* Make sure this proposal really applies to our output */
    if( output != mOutput.source )
        return B_MEDIA_BAD_SOURCE;

    /* We return two things: whether we support the proposed format, and our own
     * preferred format */
    *format = mPreferredFormat;

    if( format->type == B_MEDIA_UNKNOWN_TYPE || format->type == B_MEDIA_RAW_AUDIO )
        return B_OK;
    else
        return B_MEDIA_BAD_FORMAT;
}


status_t PaPlaybackNode::FormatChangeRequested( const media_source& source,
        const media_destination& destination, media_format* io_format, int32* )
{
    /* we refuse to change formats, supporting only 1 */
    DBUG(("FormatChangeRequested() called.\n"));

    return B_ERROR;
}


status_t PaPlaybackNode::GetNextOutput( int32* cookie, media_output* out_output )
{
    /* this is where we allow other to enumerate our outputs -- the cookie is
     * an integer we can use to keep track of where we are in enumeration. */
    DBUG(("GetNextOutput() called.\n"));

    if( *cookie == 0 )
    {
        *out_output = mOutput;
        *cookie = 1;
        return B_OK;
    }

    return B_BAD_INDEX;
}


status_t PaPlaybackNode::DisposeOutputCookie( int32 cookie )
{
    DBUG(("DisposeOutputCookie() called.\n"));
    return B_OK;
}


void PaPlaybackNode::LateNoticeReceived( const media_source& what,
        bigtime_t how_much, bigtime_t performance_time )
{
    /* This function is called as notification that a buffer we sent wasn't
     * received by the time we stamped it with -- it got there late. Basically,
     * it means we underestimated our own latency, so we should increase it */
    DBUG(("LateNoticeReceived() called.\n"));

    if( what != mOutput.source )
        return;

    if( RunMode() == B_INCREASE_LATENCY )
    {
        mInternalLatency += how_much;
        SetEventLatency( mDownstreamLatency + mInternalLatency );
        DBUG(("Increasing latency to %Ld\n", mDownstreamLatency + mInternalLatency));
    }
    else
        DBUG(("I don't know what to do with this notice!"));
}


void PaPlaybackNode::EnableOutput( const media_source& what, bool enabled,
                                   int32* )
{
    DBUG(("EnableOutput() called.\n"));
    /* stub -- we don't support this yet */
}


status_t PaPlaybackNode::PrepareToConnect( const media_source& what,
        const media_destination& where, media_format* format,
        media_source* out_source, char* out_name )
{
    /* the final stage of format negotiations. here we _must_ make specific any
     * remaining wildcards */
    DBUG(("PrepareToConnect() called.\n"));

    /* make sure this really refers to our source */
    if( what != mOutput.source )
        return B_MEDIA_BAD_SOURCE;

    /* make sure we're not already connected */
    if( mOutput.destination != media_destination::null )
        return B_MEDIA_ALREADY_CONNECTED;

    if( format->type != B_MEDIA_RAW_AUDIO )
        return B_MEDIA_BAD_FORMAT;

    if( format->u.raw_audio.format != mPreferredFormat.u.raw_audio.format )
        return B_MEDIA_BAD_FORMAT;

    if( format->u.raw_audio.buffer_size ==
            media_raw_audio_format::wildcard.buffer_size )
    {
        DBUG(("We were left to decide buffer size: choosing 2048"));
        format->u.raw_audio.buffer_size = 2048;
    }
    else
        DBUG(("Using consumer specified buffer size of %lu.\n",
              format->u.raw_audio.buffer_size));

    /* Reserve the connection, return the information */
    mOutput.destination = where;
    mOutput.format      = *format;
    *out_source         = mOutput.source;
    strncpy( out_name, mOutput.name, B_MEDIA_NAME_LENGTH );

    return B_OK;
}


void PaPlaybackNode::Connect(status_t error, const media_source& source,
                             const media_destination& destination, const media_format& format, char* io_name)
{
    DBUG(("Connect() called.\n"));