Matlab 的 Encoding.ASCII.GetBytes 问题

Question

WriteWavHeader 函数实现了 WAV 标头。问题是当我尝试在 Matlab 中使用wavread 读取 WAV 文件时，我失败了。通过在wavread 中添加断点，我检查了尽管Matlab 可以很好地读取“WAVE”、“fmt”和“数据”标头（即ck.ID 等于'WAVE'、'fmt ' 和@ 987654327@ 分别在每次迭代中），它无法正确读取'end of file' 字符串。具体来说，ck.ID 等于一堆奇怪的 ASCII 字符。当我对ck.ID = 'end of file' 进行硬编码时，我设法读取了 wav 文件。有关如何解决此问题的任何想法？

static void WriteWavHeader(Stream stream, int dataLength)
    {
        using (var memStream = new MemoryStream(64))
        {
            int cbFormat = 18; //sizeof(WAVEFORMATEX)

            WAVEFORMATEX format = new WAVEFORMATEX()
            {
                wFormatTag = 1,
                nChannels = 1,
                nSamplesPerSec = 16000,
                nAvgBytesPerSec = 32000,
                nBlockAlign = 2,
                wBitsPerSample = 16,
                cbSize = 0
            };

            using (var binarywriter = new BinaryWriter(memStream))
            {
                //RIFF header
                WriteString(memStream, "RIFF");
                binarywriter.Write(dataLength + 8 + cbFormat + 8 + 4); //File size - 8

                WriteString(memStream, "WAVE");
                WriteString(memStream, "fmt ");
                binarywriter.Write(cbFormat);

                //WAVEFORMATEX
                binarywriter.Write(format.wFormatTag);
                binarywriter.Write(format.nChannels);
                binarywriter.Write(format.nSamplesPerSec);
                binarywriter.Write(format.nAvgBytesPerSec);
                binarywriter.Write(format.nBlockAlign);
                binarywriter.Write(format.wBitsPerSample);
                binarywriter.Write(format.cbSize);

                //data header
                WriteString(memStream, "data");
                binarywriter.Write(dataLength);

                memStream.WriteTo(stream);
                WriteString(memStream, "end of file");

            }
        }
    }

static void WriteString(Stream stream, string s)
    {
        byte[] bytes = Encoding.ASCII.GetBytes(s);
        stream.Write(bytes, 0, bytes.Length);

    }

Answer 1

你在看这段代码吗（edit wavread 大约在第 208 行）？

function [ck,msg] = read_ckinfo(fid)

msg     = '';
ck.fid  = fid;
ck.Data = [];
err_msg = getString(message('MATLAB:audiovideo:wavread:TruncatedChunkHeader'));

[s,cnt] = fread(fid,4,'char');

% Do not error-out if a few (<4) trailing chars are in file
% Just return quickly:
if (cnt~=4),
    if feof(fid),
        % End of the file (not an error)
        ck.ID = 'end of file';  % unambiguous chunk ID (>4 chars)
        ck.Size = 0;
    else
        msg = err_msg;
    end
    return
end
...

据我所知，没有称为“文件结尾”的有效 ID/块（它也不是四个字符长）。该函数只是将'end of file' 字符串作为标志返回给find_cktype 函数（参见第76 和99 行）。换句话说，您似乎正在将一串数据（您的“奇怪的 ASCII 字符”）写入您的 WAV 文件：

WriteString(memStream, "end of file");

在Matlab中检查文件结尾的方法是feof或检查fread返回的输出的长度。

如果您想读取 WAV，我认为您将编写一些与您的标头内容相匹配的实际 WAV 数据。