SpeechSynthesizer的SpeakProgressEventArgs是否不准确？

Question

在.Net 3.5中使用System.Speech.Synthesis.SpeechSynthesizer类时，SpeakProgressEventArgs的AudioPosition属性似乎不准确。

下面的代码生成以下输出：

代码：

using System;
using System.Speech.Synthesis;
using System.Threading;

namespace SpeechTest
{
    class Program
    {
        static ManualResetEvent speechDoneEvent = new ManualResetEvent(false);

        static void Main(string[] args)
        {
            SpeechSynthesizer synthesizer = new SpeechSynthesizer();

            synthesizer.SpeakProgress += new EventHandler<SpeakProgressEventArgs>(synthesizer_SpeakProgress);

            synthesizer.SpeakCompleted += new EventHandler<SpeakCompletedEventArgs>(synthesizer_SpeakCompleted);

            synthesizer.SetOutputToWaveFile("Test.wav");

            synthesizer.SpeakAsync("This holiday season, support the music you love by shopping at Made in Washington, online and at one of five local stores. Made in Washington chocolates, bountiful gift baskets and ornaments are the perfect holiday gifts for family, friends and co-workers.");

            speechDoneEvent.WaitOne();
        }

        static void synthesizer_SpeakCompleted(object sender, SpeakCompletedEventArgs e)
        {
            speechDoneEvent.Set();
        }

        static void synthesizer_SpeakProgress(object sender, SpeakProgressEventArgs e)
        {
            Console.WriteLine("SpeakProgress: AudioPosition=" + e.AudioPosition + ",\tCharacterPosition=" + e.CharacterPosition + ",\tCharacterCount=" + e.CharacterCount + ",\tText=" + e.Text);
        }
    }
}

输出：

SpeakProgress: AudioPosition=00:00:00.0043750,  CharacterPosition=0,    CharacterCount=4,       Text=This
SpeakProgress: AudioPosition=00:00:00.2925625,  CharacterPosition=5,    CharacterCount=7,       Text=holiday
SpeakProgress: AudioPosition=00:00:00.9086250,  CharacterPosition=13,   CharacterCount=6,       Text=season
SpeakProgress: AudioPosition=00:00:01.9421250,  CharacterPosition=21,   CharacterCount=7,       Text=support
SpeakProgress: AudioPosition=00:00:02.5621250,  CharacterPosition=29,   CharacterCount=3,       Text=the
SpeakProgress: AudioPosition=00:00:02.6760625,  CharacterPosition=33,   CharacterCount=5,       Text=music
SpeakProgress: AudioPosition=00:00:03.2648125,  CharacterPosition=39,   CharacterCount=3,       Text=you
SpeakProgress: AudioPosition=00:00:03.5199375,  CharacterPosition=43,   CharacterCount=4,       Text=love
SpeakProgress: AudioPosition=00:00:03.8435625,  CharacterPosition=48,   CharacterCount=2,       Text=by
SpeakProgress: AudioPosition=00:00:04.0701875,  CharacterPosition=51,   CharacterCount=8,       Text=shopping
SpeakProgress: AudioPosition=00:00:04.6840625,  CharacterPosition=60,   CharacterCount=2,       Text=at
SpeakProgress: AudioPosition=00:00:04.8036250,  CharacterPosition=63,   CharacterCount=4,       Text=Made
SpeakProgress: AudioPosition=00:00:05.0698125,  CharacterPosition=68,   CharacterCount=2,       Text=in
SpeakProgress: AudioPosition=00:00:05.2521250,  CharacterPosition=71,   CharacterCount=10,      Text=Washington
SpeakProgress: AudioPosition=00:00:06.2961875,  CharacterPosition=83,   CharacterCount=6,       Text=online
SpeakProgress: AudioPosition=00:00:07.0540625,  CharacterPosition=90,   CharacterCount=3,       Text=and
SpeakProgress: AudioPosition=00:00:07.3331250,  CharacterPosition=94,   CharacterCount=2,       Text=at
SpeakProgress: AudioPosition=00:00:07.6818750,  CharacterPosition=97,   CharacterCount=3,       Text=one
SpeakProgress: AudioPosition=00:00:08.0598750,  CharacterPosition=101,  CharacterCount=2,       Text=of
SpeakProgress: AudioPosition=00:00:08.2163750,  CharacterPosition=104,  CharacterCount=4,       Text=five
SpeakProgress: AudioPosition=00:00:08.5971875,  CharacterPosition=109,  CharacterCount=5,       Text=local
SpeakProgress: AudioPosition=00:00:09.0243750,  CharacterPosition=115,  CharacterCount=6,       Text=stores
SpeakProgress: AudioPosition=00:00:10.5325625,  CharacterPosition=123,  CharacterCount=4,       Text=Made
SpeakProgress: AudioPosition=00:00:10.7700625,  CharacterPosition=128,  CharacterCount=2,       Text=in
SpeakProgress: AudioPosition=00:00:10.9377500,  CharacterPosition=131,  CharacterCount=10,      Text=Washington
SpeakProgress: AudioPosition=00:00:11.6708125,  CharacterPosition=142,  CharacterCount=10,      Text=chocolates
SpeakProgress: AudioPosition=00:00:12.9798750,  CharacterPosition=154,  CharacterCount=9,       Text=bountiful
SpeakProgress: AudioPosition=00:00:13.6303125,  CharacterPosition=164,  CharacterCount=4,       Text=gift
SpeakProgress: AudioPosition=00:00:14.0959375,  CharacterPosition=169,  CharacterCount=7,       Text=baskets
SpeakProgress: AudioPosition=00:00:14.7848125,  CharacterPosition=177,  CharacterCount=3,       Text=and
SpeakProgress: AudioPosition=00:00:15.0507500,  CharacterPosition=181,  CharacterCount=9,       Text=ornaments
SpeakProgress: AudioPosition=00:00:15.7195000,  CharacterPosition=191,  CharacterCount=3,       Text=are
SpeakProgress: AudioPosition=00:00:15.9872500,  CharacterPosition=195,  CharacterCount=3,       Text=the
SpeakProgress: AudioPosition=00:00:16.1488750,  CharacterPosition=199,  CharacterCount=7,       Text=perfect
SpeakProgress: AudioPosition=00:00:16.7275000,  CharacterPosition=207,  CharacterCount=7,       Text=holiday
SpeakProgress: AudioPosition=00:00:17.3336875,  CharacterPosition=215,  CharacterCount=5,       Text=gifts
SpeakProgress: AudioPosition=00:00:17.9813125,  CharacterPosition=221,  CharacterCount=3,       Text=for
SpeakProgress: AudioPosition=00:00:18.2216875,  CharacterPosition=225,  CharacterCount=6,       Text=family
SpeakProgress: AudioPosition=00:00:19.0973750,  CharacterPosition=233,  CharacterCount=7,       Text=friends
SpeakProgress: AudioPosition=00:00:19.7726250,  CharacterPosition=241,  CharacterCount=3,       Text=and
SpeakProgress: AudioPosition=00:00:19.9655625,  CharacterPosition=245,  CharacterCount=10,      Text=co-workers
SpeakProgress: AudioPosition=00:00:20.2518750,  CharacterPosition=245,  CharacterCount=10,      Text=co-workers

但是，生成的.wav文件的持续时间为15.69秒。如果输出到Stream或输出到null，也会发生相同的行为。

该属性的documentation表示该属性是“表示事件在音频输出流中的时间位置的TimeSpan对象”。

在输出文件中，它应该是指示单词开始或结束说话时间的准确时间，还是我误解了它？

Answer 1

audioPosition取决于语音合成器的所选声音。对于一些Microsoft voices，例如Anna，Zira，David，Hazel，正如我所经历的，支持的音频格式是16000 is。因此，下面的解决方案可以纠正auido位置：

var format = 
new System.Speech.AudioFormat.SpeechAudioFormatInfo(EncodingFormat.Pcm, 
                                                    16000, 16, 1, 32000, 2, null);
synthesizer.SetOutputToWaveFile("Test.wav", format);

如果您注意到，SetOutputToWaveFile的默认采样率为22050，正确时间(15.69)与AudipPosition显示的时间(20.25)的比率约为0.77。如果将此比率乘以22050，则得到大约16000，这是正确的采样率。