ios - Audio Queue Interface可以处理40ms Audio Frame吗？

Question

我正在尝试以 40 毫秒的时间段录制音频。Audio Queue Interface可以处理40ms Audio Frame吗？如果“是”，那么我们如何才能实现呢？

谢谢。

Answer 1

是的，有可能，您需要相应地设置配置 AudioQueue，

基本上 AudioQueue 缓冲区大小，必须设置为 40 毫秒，所以它会在附近，

int AQRecorder::ComputeRecordBufferSize(const AudioStreamBasicDescription *format, float seconds)
{
    int packets, frames, bytes = 0;
    try {
        frames = (int)ceil(seconds * format->mSampleRate);

        if (format->mBytesPerFrame > 0)
            bytes = frames * format->mBytesPerFrame;
        else {
            UInt32 maxPacketSize;
            if (format->mBytesPerPacket > 0)
                maxPacketSize = format->mBytesPerPacket;    // constant packet size
            else {
                UInt32 propertySize = sizeof(maxPacketSize);
                XThrowIfError(AudioQueueGetProperty(mQueue, kAudioQueueProperty_MaximumOutputPacketSize, &maxPacketSize,
                                                    &propertySize), "couldn't get queue's maximum output packet size");
            }
            if (format->mFramesPerPacket > 0)
                packets = frames / format->mFramesPerPacket;
            else
                packets = frames;   // worst-case scenario: 1 frame in a packet
            if (packets == 0)       // sanity check
                packets = 1;
            bytes = packets * maxPacketSize;
        }
    } catch (CAXException e) {
        char buf[256];
        return 0;
    }   
    return bytes;
}

并设置格式，

void AQRecorder::SetupAudioFormat(UInt32 inFormatID)
{
    AudioStreamBasicDescription sRecordFormat;
    FillOutASBDForLPCM (sRecordFormat,
                        SAMPLING_RATE,
                        1,
                        8*BYTES_PER_PACKET,
                        8*BYTES_PER_PACKET,
                        false,
                        false
                        );
    memset(&mRecordFormat, 0, sizeof(mRecordFormat));

    mRecordFormat.SetFrom(sRecordFormat);
}

就我而言，这些宏的值是，

#define SAMPLING_RATE 16000
#define kNumberRecordBuffers    3
#define BYTES_PER_PACKET 2