avcodec/ac3enc_template: use the initial_padding field

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/ac3enc_template.c

@@ -443,7 +443,7 @@ int AC3_NAME(encode_frame)(AVCodecContext *avctx, AVPacket *avpkt,
     ff_ac3_output_frame(s, avpkt->data);
 
     if (frame->pts != AV_NOPTS_VALUE)
-        avpkt->pts = frame->pts - ff_samples_to_time_base(avctx, avctx->delay);
+        avpkt->pts = frame->pts - ff_samples_to_time_base(avctx, avctx->initial_padding);
 
     *got_packet_ptr = 1;
     return 0;