Drive desktop call clock from rendered PCM and capture timing

src/call/call_audio.c

@@ -492,7 +492,9 @@ int call_audio_pull_pcm(uint64_t call_id, int16_t* out, int max_samples) {
         }
         if (call_tones_ended_pending(tones))
             n = call_tones_render(tones, out, max_samples);
-        call_jitter_silence(j, (unsigned)n);
+        memset(out + n, 0, (size_t)(max_samples - n) * sizeof(*out));
+        call_jitter_silence(j, (unsigned)max_samples);
+        n = max_samples;
     } else {
         n = call_jitter_pull(j, out, max_samples);
         int previous_gap = g_gap_samples;