[FFmpeg-devel] Channel mapping integration in af pan

[Nicolas George]

Le nonidi 29 nivôse, an CCXX, Clément Bœsch a écrit :
> +    // gains are pures, init the channel mapping array
> +    if (pan->pure_gains) {
> +        for (i = 0; i < pan->nb_output_channels; i++) {
> +            int ch_id = -1;
> +            for (j = 0; j < pan->nb_input_channels; j++) {
> +                if (pan->gain.d[i][j]) {
> 
> If I replace this with "if (pan->gain.i[i][j]) {", it doesn't work as expected:
> since the int are 32 bits and the gains are stored in double (64),
> pan->gain.i[0][3] will evaluate the first gain (low 32 bits of the second
> double) instead of the 3rd. That's how I understand the issue.

Oh, yes, I see. At that point, the coefficients are still stored as double,
so you _must_ use them as such. Unions are not, in general, an automatic
conversion system.

Imagine it was written that way:

	gain_d = malloc(n * n * sizeof(double));
	/* before */

	gain_i = malloc(n * n * sizeof(int));
	for (i, j)
	    gain_i[i][j] = 256 * gain_d[i][j];
	free(gain_d);

	/* after */

In the "before" code, you can and must only use gain_d, and in the "after"
code, you can and must only use gain_i.

> Playing with the spacing doesn't seem to help.

Then I will try to search what is wrong when I have time.

Regards,

-- 
  Nicolas George
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