Can we directly set the bitrate in a WAV file?

You can use Microsoft Media Foundation and MF_MT_AUDIO_AVG_BYTES_PER_SECOND

or with WinRT, interfaces like AudioEncodingProperties

I did this test with MMF and help from ChatGPT to convert a .wav to 256 kbps :

int TranscodeWav(const wchar_t* pwsInputPath, const wchar_t* pwsOutputPath)
{
	MFStartup(MF_VERSION);

	IMFSourceReader* pReader = nullptr;
	MFCreateSourceReaderFromURL(pwsInputPath, NULL, &pReader);

	IMFMediaType* pMediaTypeOut = nullptr;
	MFCreateMediaType(&pMediaTypeOut);
	pMediaTypeOut->SetGUID(MF_MT_MAJOR_TYPE, MFMediaType_Audio);
	pMediaTypeOut->SetGUID(MF_MT_SUBTYPE, MFAudioFormat_PCM);
	
	// From ChatGPT
	pMediaTypeOut->SetUINT32(MF_MT_AUDIO_SAMPLES_PER_SECOND, 16000); // 16 kHz
	pMediaTypeOut->SetUINT32(MF_MT_AUDIO_BITS_PER_SAMPLE, 16);      // 16‑bit depth
	pMediaTypeOut->SetUINT32(MF_MT_AUDIO_NUM_CHANNELS, 1);          // Mono
	// Average bytes per second = samplerate × channels × bits/sample ÷ 8
	// Byte rate = 16000 * 1 * 16 / 8 = 32,000 bytes/s
	// 256 kbps = 256000 bps (divide by 8 for bytes/sec)
	pMediaTypeOut->SetUINT32(MF_MT_AUDIO_AVG_BYTES_PER_SECOND, 16000 * 1 * 16 / 8);

	// Set the media type on the source reader's output
	pReader->SetCurrentMediaType(MF_SOURCE_READER_FIRST_AUDIO_STREAM, NULL, pMediaTypeOut);

	IMFSinkWriter* pWriter = nullptr;
	DWORD nStreamIndex = 0;
	MFCreateSinkWriterFromURL(pwsOutputPath, NULL, NULL, &pWriter);
	pWriter->AddStream(pMediaTypeOut, &nStreamIndex);
	pWriter->BeginWriting();

	// Transcode loop: read samples, optionally convert timestamps, write to output
	DWORD nFlags = 0;
	LONGLONG timestamp = 0;
	while (true)
	{
		IMFSample* pSample = nullptr;
		pReader->ReadSample(MF_SOURCE_READER_FIRST_AUDIO_STREAM, 0, nullptr, &nFlags, &timestamp, &pSample);
		if (nFlags & MF_SOURCE_READERF_ENDOFSTREAM) break;
		if (pSample)
		{
			pWriter->WriteSample(nStreamIndex, pSample);
			pSample->Release();
		}
	}

	pWriter->Finalize();

	pWriter->Release();
	pMediaTypeOut->Release();
	pReader->Release();
	MFShutdown();
	return 0;
}

with :

#include <mfapi.h>
#include <mfidl.h>
#include <mferror.h>
#include <mfreadwrite.h>

#pragma comment(lib, "Mfplat")
#pragma comment(lib, "mfreadwrite")
#pragma comment(lib, "mfuuid")

Thank you for sharing the details.

WAV files (especially PCM format) do not have an explicit "bitrate" field in their header. Instead, the bitrate is implicitly calculated based on:

Sample rate (e.g., 44100 Hz)

Bit depth (e.g., 16-bit)

Number of channels (e.g., 2 for stereo)

So, you cannot directly set a bitrate like 128 kbps or 256 kbps in the header. Instead, you control the bitrate by adjusting those three parameters.

Bitrate = Sample Rate × Bit Depth × Channels

For example:

44100 Hz × 16 bits × 2 channels = 1,411,200 bits/sec ≈ 1411 kbps

This is much higher than compressed formats like MP3, which is why WAV files are larger.

Let me know if the issue persists after following these steps. I’ll be happy to assist further if needed.

If the issue has been resolved, kindly mark the response as answered.