c# - 连接/加入两个或多个 WAV 文件时的咔嗒声

Question

我正在做一个音乐项目，我需要加入几个 WAV 文件。我的代码运行良好，但您可以清楚地听到两个连接的 WAV 文件之间的咔嗒声。这是一个巨大的问题。

我是一名音频工程师。当我工作时，例如DAW(数字音频工作站)中的连续样本，我想防止两个 WAV 样本之间出现这种咔哒声，然后我必须创建交叉淡入淡出(基本上这是第一个样本的淡出和下一个样本的淡入)。

因此我的问题是我是否可以在连接两个 WAV 文件时创建这样的交叉淡入淡出。我需要消除级联波形文件之间的咔嗒声。

我在如何连接 WAV 文件下方提供了我的 C# 代码。这适用于相同“格式”的 WAV 文件。我在 (How to join 2 or more .WAV files together programatically?) 上找到了这段代码。此外，我发现了这个 FadeIn/FadeOut possibility但我不知道如何在代码上应用它。此外，我不知道这是否会阻止咔嗒声。

感谢您的建议和解决方案。希望马克希思能读到这个:)。

最好的祝福，
亚历克斯

波形文件格式:

平均字节每秒:264600 |
BitsPerSample:24 |
block 对齐:6 |
channel :2 |
编码:PCM |
额外尺寸:0 |
采样率:44100 |

    public static void Concatenate(string outputFile, IEnumerable<string> sourceFiles)
{
    byte[] buffer = new byte[6]; //1024 was the original. but my wave file format has the blockAlign 6. So 1024 was not working for me. 6 does.
    WaveFileWriter waveFileWriter = null;

    try
    {
        foreach (string sourceFile in sourceFiles)
        {
            using (WaveFileReader reader = new WaveFileReader(sourceFile))
            {
                if (waveFileWriter == null)
                {
                    // first time in create new Writer
                    waveFileWriter = new WaveFileWriter(outputFile, reader.WaveFormat);
                }
                else
                {
                    if (!reader.WaveFormat.Equals(waveFileWriter.WaveFormat))
                    {
                        throw new InvalidOperationException("Can't concatenate WAV Files that don't share the same format");
                    }
                }

                int read;
                while ((read = reader.Read(buffer, 0, buffer.Length)) > 0)
                {
                    waveFileWriter.WriteData(buffer, 0, read);
                }
            }
        }
    }
    finally
    {
        if (waveFileWriter != null)
        {
            waveFileWriter.Dispose();
        }
    }
}

Answer 1

这听起来很有趣:)

这是我为此编写的示例。它接受输入文件名模式的列表(假设当前目录)和输出文件的名称。它将文件拼接在一起，在一个文件的末尾淡出约 1 秒，然后在下一个文件的约 1 秒内淡入，依此类推。注意:它不会混合约 1 秒的重叠。不想那样做:)

我用了ReadNextSampleFrame WaveFileReader 上的方法将数据读取为 IEEE 浮点样本(每个 channel 一个浮点数)。这使得单方面应用音量调整变得更加容易，而不必担心实际的输入 PCM 表示。在输出中，它使用 WriteSamples在作家写调整样本。

我第一次使用 NAudio FadeInFadeOutSampleProvider .但是当你有多个音频 channel 时，我发现了一个奇怪的错误。

因此，代码手动为每个样本读取应用一个体积，在每个文件的开头(第一个文件除外)将体积从 0.0 增加到 1.0。然后它直接复制文件的“中间”。然后在文件结束前大约 1 秒(实际上， ( WaveFormat.SampleRate * WaveFormat.Channels ) 在文件结束前采样)，它将音量从 1.0f 降低到 0.0f。

我测试了一下，使用sox生成一个5秒长的440Hz正弦波文件，采样率=96K，立体声，如下:

sox -n -c 2 -r 96000 -b 24 sine.wav synth 5 sine 440

测试调用如下:

FadeWeaver.FadeWeave("weaved.wav", "sine.wav", "sine.wav", "sine.wav");

这是代码:

public class FadeWeaver
{
    static
    public
    void
    FadeWeave( string _outfilename,
               params string [] _inpatterns )
    {
        WaveFileWriter output = null;
        WaveFormat waveformat = null;
        float [] sample = null;

        float volume = 1.0f;
        float volumemod = 0.0f;

        // Add .wav extension to the output if not specified.
        string extension = Path.GetExtension(_outfilename);
        if( string.Compare(extension, ".wav", true) != 0 ) _outfilename += ".wav";

        // Assume we're using the current directory.  Let's get the
        // list of filenames.
        List<string> filenames = new List<string>();
        foreach( string pattern in _inpatterns )
        {
            filenames.AddRange(Directory.GetFiles(Directory.GetCurrentDirectory(), pattern));
        }

        try
        {
            // Alrighty.  Let's march over them.  We'll index them (rather than
            // foreach'ing) so that we can monitor first/last file.
            for( int index = 0; index < filenames.Count; ++index )
            {
                // Grab the file and use an 'audiofilereader' to load it.
                string filename = filenames[index];
                using( WaveFileReader reader = new WaveFileReader(filename) )
                {
                    // Get our first/last flags.
                    bool firstfile = (index == 0 );
                    bool lastfile = (index == filenames.Count - 1);

                    // If it's the first...
                    if( firstfile )
                    {
                        // Initialize the writer.
                        waveformat = reader.WaveFormat;
                        output = new WaveFileWriter(_outfilename, waveformat);
                    }
                    else
                    {
                        // All files must have a matching format.
                        if( !reader.WaveFormat.Equals(waveformat) )
                        {
                            throw new InvalidOperationException("Different formats");
                        }
                    }


                    long fadeinsamples = 0;
                    if( !firstfile )
                    {
                        // Assume 1 second of fade in, but set it to total size
                        // if the file is less than one second.
                        fadeinsamples = waveformat.SampleRate;
                        if( fadeinsamples > reader.SampleCount ) fadeinsamples = reader.SampleCount;

                    }

                    // Initialize volume and read from the start of the file to
                    // the 'fadeinsamples' count (which may be 0, if it's the first
                    // file).
                    volume = 0.0f;
                    volumemod = 1.0f / (float)fadeinsamples;
                    int sampleix = 0;
                    while( sampleix < (long)fadeinsamples )
                    {
                        sample = reader.ReadNextSampleFrame();
                        for( int floatix = 0; floatix < waveformat.Channels; ++floatix )
                        {
                            sample[floatix] = sample[floatix] * volume;
                        }

                        // Add modifier to volume.  We'll make sure it isn't over
                        // 1.0!
                        if( (volume = (volume + volumemod)) > 1.0f ) volume = 1.0f;

                        // Write them to the output and bump the index.
                        output.WriteSamples(sample, 0, sample.Length);
                        ++sampleix;
                    }

                    // Now for the time between fade-in and fade-out.
                    // Determine when to start.
                    long fadeoutstartsample = reader.SampleCount;
                    //if( !lastfile )
                    {
                        // We fade out every file except the last.  Move the
                        // sample counter back by one second.
                        fadeoutstartsample -= waveformat.SampleRate;
                        if( fadeoutstartsample < sampleix ) 
                        {
                            // We've actually crossed over into our fade-in
                            // timeframe.  We'll have to adjust the actual
                            // fade-out time accordingly.
                            fadeoutstartsample = reader.SampleCount - sampleix;
                        }
                    }

                    // Ok, now copy everything between fade-in and fade-out.
                    // We don't mess with the volume here.
                    while( sampleix < (int)fadeoutstartsample )
                    {
                        sample = reader.ReadNextSampleFrame();
                        output.WriteSamples(sample, 0, sample.Length);
                        ++sampleix;
                    }

                    // Fade out is next.  Initialize the volume.  Note that
                    // we use a bit-shorter of a time frame just to make sure
                    // we hit 0.0f as our ending volume.
                    long samplesleft = reader.SampleCount - fadeoutstartsample;
                    volume = 1.0f;
                    volumemod = 1.0f / ((float)samplesleft * 0.95f);

                    // And loop over the reamaining samples
                    while( sampleix < (int)reader.SampleCount )
                    {
                        // Grab a sample (one float per channel) and adjust by
                        // volume.
                        sample = reader.ReadNextSampleFrame();
                        for( int floatix = 0; floatix < waveformat.Channels; ++floatix )
                        {
                            sample[floatix] = sample[floatix] * volume;
                        }

                        // Subtract modifier from volume.  We'll make sure it doesn't
                        // accidentally go below 0.
                        if( (volume = (volume - volumemod)) < 0.0f ) volume = 0.0f;

                        // Write them to the output and bump the index.
                        output.WriteSamples(sample, 0, sample.Length);
                        ++sampleix;
                    }
                }
            }
        }
        catch( Exception _ex )
        {
            Console.WriteLine("Exception: {0}", _ex.Message);
        }
        finally
        {
            if( output != null ) try{ output.Dispose(); } catch(Exception){}
        }
    }
}