Change default bit-rate for lameDS-3.99.5 DirectShow filter

Question

I have an application that needs to encode some audio files in MP3 format, 320 kbps bitrate. I'm using DirectShow to accomplish this task and lameDS-3.99.5 DirectShow filter.

The problem is that even if I set lameDS-3.99.5 DirectShow filter in GraphEdit to use Constant Birate - 320 kbps, the encoding is made all the time at 128 kbps.

What I need is an way to set the bitrate of the lameDS-3.99.5 DirectShow filter grammatically.

I have investigated all the web but I didn't found an example of doing this.

Some advice that I have found is to use IAMStreamConfig Interface on the output pin of the filter, but I didn't found any code examples in achieves this.

Thank you for helping me.

@Roman

Thank you very much for your reply.

Please find my function:

HRESULT CDShowGraph::AddLAMEMP3EncoderFilter( CComPtr<IBaseFilter>& spCodec )
{
   HRESULT hr = spCodec.CoCreateInstance( IID_LAMEAudioEncoder_Filter );
   if (FAILED(hr) )
    {
      return hr;
    }

   IEnumPins *pEnum = NULL;
   IPin *pPin = NULL;
   hr = spCodec->EnumPins(&pEnum);
   if (FAILED(hr))
   {
   }
   while (S_OK == pEnum->Next(1, &pPin, NULL))
   {
        PIN_DIRECTION pinDir;
        PIN_DIRECTION dir = PINDIR_OUTPUT;
        hr = pPin->QueryDirection(&pinDir);
        if (SUCCEEDED(hr))
        {
            if(pinDir == dir)
            {
                 IAMStreamConfig * pamconfig = 0;   
                 hr = pPin->QueryInterface(IID_IAMStreamConfig, (void **)&pamconfig);   
                 if(FAILED(hr)) {}   
                 else 
                 {
                     AM_MEDIA_TYPE *pmt={0};   
                     hr = pamconfig->GetFormat(&pmt);
                     if(FAILED(hr)) {}   
                     else 
                     { 
                        //audio_set_capformat(pmt);
                        WAVEFORMATEX *format = (WAVEFORMATEX *) pmt->pbFormat;
                        format->nAvgBytesPerSec = 320*1024;
                        hr = pamconfig->SetFormat(pmt);               
                        DeleteMediaType(pmt);
                     }
                 }
                 pamconfig->Release();   
            }
        }
   }

   hr = m_ptrGraph->m_pGraphBuilder->AddFilter( spCodec, NULL );
   return hr;
}

It goes till here:

AM_MEDIA_TYPE *pmt={0};   
hr = pamconfig->GetFormat(&pmt);

For pmt I get 0x00000000 Bad Ptr and after it execute the next code with success:

AM_MEDIA_TYPE *pmt={0};   
hr = pamconfig->GetFormat(&pmt);

for the all fields in the format I get:

wFormatTag CXX0030: Error: expression cannot be evaluated

nChannels CXX0030: Error: expression cannot be evaluated

nSamplesPerSec CXX0030: Error: expression cannot be evaluated

nAvgBytesPerSec CXX0030: Error: expression cannot be evaluated

nBlockAlign CXX0030: Error: expression cannot be evaluated

wBitsPerSample CXX0030: Error: expression cannot be evaluated

cbSize CXX0030: Error: expression cannot be evaluated

score 0 · Answer 1 · edited May 23 '17 at 12:23

Using IAMStreamConfig::SetFormat - Sample rate and bit rate of a wave file created by DirectShow
There are multiple code snippets for IAMStreamConfig on StackOverflow for setting video media type, audio format is set the same way, another example of this is here
This question (and information here for older version) says that there is no support for IAMStreamConfig with LAME encoder, but there is another way to specify output details Configure LAME MP3 encoder in DirectShow application using IAudioEncoderProperties

Change default bit-rate for lameDS-3.99.5 DirectShow filter

1 Answers1