Yes I think you're right Jereon! Well done - that's a subtle one and I
had to drink 2 cups of coffee and mess about with pencil and paper to
see the issue :-)
I've updated codec2.c and the C<->Octave unit tests with your fix.
Thanks,
David
On 16/01/17 00:07, Jeroen Vreeken wrote:
>
>
> On 01/15/2017 09:48 AM, David Rowe wrote:
>>
>> We need to call analyse_one_frame() every 10ms as that's the internal
>> frame rate of the core sinusoidal modeling inside Codec 2. Note the ptr
>> into the input speech vector is offset by 80 samples (10ms) each time.
>> We need the input speech sample driver to supply us with a 320 sample
>> (40ms) input vector. Various states need to be updated even though we
>> toss the output model parameters away for 3/4 of the frames in 700C.
>>
>> Just transmitting the model parameters 1 in every 4 frames is like
>> "decimation in time" of any sampled sequence. At the decoder, to
>> reconstruct the missing frames (say 2,3,4) we interpolate between need
>> frames 1 and 5.
>>
>> So we could send a sequence of frames 1,5,9 or 2,6,10 ... either way you
>> get a 40ms latency.
>
> The 40ms I get, but to me the current code looks like it is introducing
> yet another 30ms latency by not taking the updated model into account
> untill the next call to the function. I can even see it in the energy
> output of the different frames, it is almost a whole frame delayed
> compared to the other modes.
> Wouldn't the following change remove the 30ms without changing the reset
> of the interpolation?
>
> --- src/codec2.c (revision 2964)
> +++ src/codec2.c (working copy)
> @@ -1797,8 +1797,11 @@
>
> memset(bits, '\0', ((codec2_bits_per_frame(c2) + 7) / 8));
>
> - analyse_one_frame(c2, &model, speech);
> + for(i=0; i<M; i++) {
> + analyse_one_frame(c2, &model, &speech[i*N_SAMP]);
> + }
>
> +
> int K = 20;
> float rate_K_vec[K], mean;
> float rate_K_vec_no_mean[K], rate_K_vec_no_mean_[K];
> @@ -1812,10 +1815,6 @@
> rate_K_vec_no_mean,
> rate_K_vec_no_mean_);
>
> - for(i=1; i<M; i++) {
> - analyse_one_frame(c2, &model, &speech[i*N_SAMP]);
> - }
> -
> pack_natural_or_gray(bits, &nbit, indexes[0], 9, 0);
> pack_natural_or_gray(bits, &nbit, indexes[1], 9, 0);
> pack_natural_or_gray(bits, &nbit, indexes[2], 4, 0);
>
>
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