[Speex-dev] Re: High pitched whine with Speex

[Kevin Jenkins]

In order to save bandwidth, is it possible to detect that there is no 
data waiting, or only background noise, and not send if that is the 
case?  Does Speex have this built-in or should I just check to see if 
all input values are near 0?

Kevin Jenkins wrote:
> Changing from using floats to shorts did fix the high pitched tone 
> problem.  I'm having other problems but I'll look into it more first.
> 
> SteveK wrote:
>>
>> On May 21, 2006, at 6:33 PM, Kevin Jenkins wrote:
>>
>>> When I just copy the microphone input buffer to the output buffer the 
>>> sound plays OK.  But if I encode and decode the buffer through Speex 
>>> I get a high pitched constant tone in the background.  I actually do 
>>> hear my voice speaking when I talk, but it's faint and much quieter 
>>> than the tone.
>>>
>>> Here's what my data looks like:
>>> Input is the first 5 floats of each input buffer.
>>> Output is after Speex runs on it.
>>>
>>> Input: 0.000 0.000 0.000 0.000 -0.000
>>> Out: -0.029 -0.008 0.020 0.018 -0.001
>>> Input: 0.000 0.000 0.000 0.000 0.000
>>> Out: -0.029 -0.008 0.020 0.018 -0.001
>>> Input: -0.000 0.000 0.000 0.000 -0.000
>>> Out: -0.029 -0.008 0.020 0.018 -0.001
>>> Input: -0.000 -0.000 -0.000 -0.000 0.000
>>> Out: -0.029 -0.008 0.020 0.018 -0.001
>>>
>>> My samples are 4 byte floats.
>>>
>>> My sample rate is 8000
>>>
>>> Here's pretty much all my speex code:
>>> ENCODING INIT:
>>> channel->enc_state=speex_encoder_init(&speex_nb_mode);
>>> speex_encoder_ctl(channel->enc_state, SPEEX_GET_FRAME_SIZE, 
>>> &channel->speexOutgoingFrameSampleCount);
>>>
>>> DECODING INIT:
>>> channel->dec_state=speex_decoder_init(&speex_nb_mode);
>>> speex_decoder_ctl(channel->dec_state, SPEEX_GET_FRAME_SIZE, 
>>> &channel->speexIncomingFrameSampleCount);
>>>
>>> ENCODING:
>>> speex_encode(channel->enc_state, (float *) inputBuffer, &speexBits);
>>> bytesWritten = speex_bits_write(&speexBits, tempOutput+1, 2048-1);
>>>
>>> DECODING:
>>> speex_bits_read_from(&speexBits, (char*)(packet->data+1), 
>>> packet->length-1);
>>> speex_decode(channel->dec_state, &speexBits, (float*)tempOutput);
>>>
>>> That's pretty much the extent of the Speex code.  For the output, I 
>>> write all 0.0 to the buffer first, then add the equivalent inputs 
>>> from speex.
>>>
>>> When I copy bytes of input data, I use that 
>>> speexOutgoingFrameSampleCount * sizeof(float) to determine how many 
>>> bytes to consider read and written.
>>
>>>
>>> Any idea?
>>
>> It seems like your samples may all be in the range -1.0 .. 1.0.  For 
>> speex, they should be +-32767 or so.
>>
>> -SteveK
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