[SoX-users] Channels effect reduces output file length

[William M. <wm...@ke...>]

I am using libsox to process voice files that are usually mono but occasionally are in 2 channel stereo format. I am creating a chain and, if the input signal has 2 channels, I am adding the "channels" effect with the option of "1".

// ensure number of channels is 1
		if (in->signal.channels != 1) {

			signalinfo.length = in->signal.length / in->signal.channels;

			fprintf(stderr, "Input file has %d Channels. Must only have 1!\n", (int) in->signal.channels);
			args[0] = "1";
			fprintf (stderr, "Change Channels to %s\n", args[0]);

			e = sox_create_effect(sox_find_effect("channels"));
			assert(sox_effect_options(e, 1, args) == SOX_SUCCESS);
			assert(sox_add_effect(chain, e, &in->signal, &signalinfo) == SOX_SUCCESS);

		}

Signal info is identical to in->signal except for length and number of channels.

When the input signal has 1 channel, of course this effect is not added, so all is well. However, if it is 2 channels, the resulting output file is 1/2 the length.

What am I missing here?


William C. Mortimore
Keystone Insights, LLC
S76W13054 Cambridge Ct. W.
Muskego, WI 53150
414-841-6067
Fax:414-425-9155
www.keystoneinsights.com