[Speex-dev] bug fix for speex_resampler_reset_mem?

victor victor at speech.sri.com
Wed Nov 10 13:23:51 PST 2010

I'm using resample.c from speex in my project, and was testing it by 
processing the same waveform twice, with a reset() call in the middle, 
as follows:

short *input_data = read_waveform_as_linear(infileName, &rate, 
&num_samples, &num_channels);
SpeexResamplerState *state = speex_resampler_init_frac(num_channels, 
in_rate, out_rate, in_rate, out_rate, quality, &error);
speex_resampler_process_int(state, 0, input_data, ...)
speex_resampler_process_int(state, 0, input_data, ...)

When I run it this way, my two output waveforms are not identical on a 
binary basis.

Changing speex_resampler_reset_mem() as follows seems to fix the problem:

EXPORT int speex_resampler_reset_mem(SpeexResamplerState *st)
   spx_uint32_t i;
   for (i=0;i<st->nb_channels*(st->filt_len-1);i++)
      st->mem[i] = 0;
   // added bugfix below:
   st->started = 0;
   for (i=0;i<st->nb_channels;i++)
       st->last_sample[i] = 0;
       st->magic_samples[i] = 0;
       st->samp_frac_num[i] = 0;

Note that I have to call speex_resampler_skip_zeros() again after each 
reset call, whether or not I zero st->last_sample[i] or not.
Also, I'm not 100% sure whether resetting st->started = 0 is strictly 
necessary or not.

Thanks for a great addition to open source software,

Victor Abrash

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