[Speex-dev] Is Speex 1.0 and >=1.1 compatible?

[Tobias]

On Saturday 10 April 2010 21.51.55 Jean-Marc Valin wrote:
> All version after 1.0 are compatible with each other and with 1.0.

Hi Jean-Marc and thanks for the quick reply.

I have now looked at this further and got the idea to hard code the number of 
frames in the decoder temporarily as a test and voilà, it works! The problem 
seem to be some incompatibility in the termination handling. After processing 
exactly four frames the number of remaining bits can be anything from zero to 
seven which I guess is normal. However, if I use the while loop below, 
speex_decode will get called one more time (a total of five times) and that 
seem to mess up the decoder state. The decoded audio get sort of "bubbly".

while ((speex_decode(dec_state,&bits, samples) == 0) &&
          (speex_bits_remaining(&bits) >=  0)) {}

As far as I can see, the termination handling is not compatible when encoding 
with, in this case, Speex ver 1.2rc1 and decoding with ver 1.0.5. Do you agree 
or have I done something wrong in my code?  The full code can be found here:

http://svxlink.svn.sf.net/viewvc/svxlink/trunk/src/async/audio/AsyncAudioDecoderSpeex.cpp?view=markup
http://svxlink.svn.sf.net/viewvc/svxlink/trunk/src/async/audio/AsyncAudioEncoderSpeex.cpp?view=markup

I guess I could solve this problem by transmitting the frame count out-of-band 
but if Speex can handle it, it's better.

Regards,
Tobias


> 
> 	Jean-Marc
> 
> On 2010-04-10 15:44, Tobias wrote:
> > Hi list,
> > 
> > I'm trying to figure out how to do the most compatible implementation
> > that will work with as many versions of Speex as possible. I am
> > streaming multi frame Speex blocks over a TCP connection which works
> > fine as long as the version of Speex is the same on both sides. When
> > using a newer Speex (1.1.?) to encode and an older version to decode
> > (1.0.5), it does not work.
> > 
> > The encoder code look like this:
> > 
> > int AudioEncoderSpeex::writeSamples(const float *samples, int count)
> > {
> > 
> >    for (int i=0; i<count; ++i)
> >    {
> >    
> >      sample_buf[buf_len++] = samples[i] * 32767.0;
> >      
> >      if (buf_len == frame_size)
> >      {
> >      
> >        speex_encode(enc_state, sample_buf,&bits);
> >        buf_len = 0;
> >        
> >        if (++frame_cnt == 4) // Four frames per packet
> >        {
> >        
> >          speex_bits_insert_terminator(&bits);
> >          int nbytes = speex_bits_nbytes(&bits);
> >          char output_buf[nbytes];
> >          nbytes = speex_bits_write(&bits, output_buf, nbytes);
> >          writeEncodedSamples(output_buf, nbytes);
> >          speex_bits_reset(&bits);
> >          frame_cnt = 0;
> >        
> >        }
> >      
> >      }
> >    
> >    }
> >    
> >    return count;
> > 
> > } /* AudioEncoderSpeex::writeSamples */
> > 
> > 
> > 
> > The decoder have looked like this for quite a while:
> > 
> > void AudioDecoderSpeex::writeEncodedSamples(void *buf, int size)
> > {
> > 
> >    char *ptr = (char *)buf;
> >    
> >    speex_bits_read_from(&bits, ptr, size);
> >    float samples[frame_size];
> > 
> > #if SPEEX_MAJOR>  1 || (SPEEX_MAJOR == 1&&  SPEEX_MINOR>= 1)
> > 
> >    while (speex_decode(dec_state,&bits, samples) == 0)
> > 
> > #else
> > 
> >    while ((speex_decode(dec_state,&bits, samples) == 0)&&
> >    
> >           (speex_bits_remaining(&bits)>  0))
> > 
> > #endif
> > 
> >    {
> >    
> >      for (int i=0; i<frame_size; ++i)
> >      {
> >      
> >        samples[i] = samples [i] / 32767.0;
> >      
> >      }
> >      sinkWriteSamples(samples, frame_size);
> >    
> >    }
> > 
> > } /* AudioDecoderSpeex::writeEncodedSamples */
> > 
> > 
> > This have worked well when using the same version of Speex on both sides.
> > When using 1.1 on the encoder and 1.0 on the decoder, the number of
> > frames decoded varies between three and four even though four frames are
> > always sent. The use of speex_bits_remaining is one I have found by
> > Googling. I started to wonder if it's wrong now though. If I change the
> > comparison to read
> > "speex_bits_remaining(&bits)>= 0" I always get four frames decoded.
> > However, it still does not sound correctly. The change from ">" to">="
> > makes sense though. It should be OK for speex_decode to consume all bits
> > so zero bits remaining should be OK (or?).
> > 
> > The original question was if versions 1.0 and>= 1.1 is compatible. Can I
> > make the code work in all cases or am I on a "mission impossible"?
> > 
> > Regards,
> > Tobias