第一次分析wav

最新推荐文章于 2023-10-30 21:09:30 发布

原创最新推荐文章于 2023-10-30 21:09:30 发布 · 1.2k 阅读

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#parameters #rest #header #windows #file

博客介绍了WAV格式文件的结构，包括RIFF头、“fmt ”子块和“data”子块的详细信息。作者尝试读取不同的WAV文件，发现多数Subchunk2Size与实际大小不符，Windows录音机录制的文件问题更严重，作者表示难以理解，怀疑自己理解有误。

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以下是从网上搜到的wav格式：

The canonical WAVE format starts with the RIFF header:

0         4   ChunkID          Contains the letters "RIFF" in ASCII form
                               (0x52494646 big-endian form).
4         4   ChunkSize        36 + SubChunk2Size, or more precisely:
                               4 + (8 + SubChunk1Size) + (8 + SubChunk2Size)
                               This is the size of the rest of the chunk
                               following this number. This is the size of the
                               entire file in bytes minus 8 bytes for the
                               two fields not included in this count:
                               ChunkID and ChunkSize.
8         4   Format           Contains the letters "WAVE"
                               (0x57415645 big-endian form).

The "WAVE" format consists of two subchunks: "fmt " and "data":
The "fmt " subchunk describes the sound data's format:

12        4   Subchunk1ID      Contains the letters "fmt "
                               (0x666d7420 big-endian form).
16        4   Subchunk1Size    16 for PCM. This is the size of the
                               rest of the Subchunk which follows this number.
20        2   AudioFormat      PCM = 1 (i.e. Linear quantization)
                               Values other than 1 indicate some
                               form of compression.
22        2   NumChannels      Mono = 1, Stereo = 2, etc.
24        4   SampleRate       8000, 44100, etc.
28        4   ByteRate         == SampleRate * NumChannels * BitsPerSample/8
32        2   BlockAlign       == NumChannels * BitsPerSample/8
                               The number of bytes for one sample including
                               all channels. I wonder what happens when
                               this number isn't an integer?
34        2   BitsPerSample    8 bits = 8, 16 bits = 16, etc.
          2   ExtraParamSize   if PCM, then doesn't exist
          X   ExtraParams      space for extra parameters

The "data" subchunk contains the size of the data and the actual sound:

36        4   Subchunk2ID      Contains the letters "data"
                               (0x64617461 big-endian form).
40        4   Subchunk2Size    == NumSamples * NumChannels * BitsPerSample/8
                               This is the number of bytes in the data.
                               You can also think of this as the size
                               of the read of the subchunk following this
                               number.
44        *   Data             The actual sound data.
尝试读取了不同的wav文件，但是很多都不对劲。
大多数Subchunk2Size都和实际大小不同，用windows录音机录出来的文件更离谱，subchunk2中的有些内容都不符。
好难理解啊。总觉得自己什么地方理解错了，但就是找不到，郁闷ing