diff --git a/daemon/codec.c b/daemon/codec.c
index f6496be3a..1707b5e6b 100644
--- a/daemon/codec.c
+++ b/daemon/codec.c
@@ -4381,6 +4381,7 @@ static void async_chain_finish(AVPacket *pkt, void *async_cb_obj) {
 }
 
 static bool __ssrc_handler_decode_common(struct codec_ssrc_handler *ch, struct codec_handler *h,
+		const format_t *dec_format,
 		const format_t *enc_format)
 {
 	if (h->pcm_dtmf_detect) {
@@ -4393,7 +4394,7 @@ static bool __ssrc_handler_decode_common(struct codec_ssrc_handler *ch, struct c
 			dtmf_rx_set_realtime_callback(ch->dtmf_dsp, __dtmf_dsp_callback, ch);
 	}
 
-	ch->decoder = decoder_new_fmtp(h->source_pt.codec_def, h->source_pt.clock_rate, h->source_pt.channels,
+	ch->decoder = decoder_new_fmtp(h->source_pt.codec_def, dec_format,
 			h->source_pt.ptime,
 			enc_format, &h->source_pt.format,
 			&h->source_pt.format_parameters, &h->source_pt.codec_opts);
@@ -4480,7 +4481,7 @@ static struct ssrc_entry *__ssrc_handler_transcode_new(void *p) {
 				&h->dest_pt.codec_opts))
 		goto err;
 
-	if (!__ssrc_handler_decode_common(ch, h, &ch->encoder_format))
+	if (!__ssrc_handler_decode_common(ch, h, &dec_format, &ch->encoder_format))
 		goto err;
 
 	ch->bytes_per_packet = (ch->encoder->samples_per_packet ?: ch->encoder->samples_per_frame)
@@ -4515,7 +4516,13 @@ static struct ssrc_entry *__ssrc_handler_decode_new(void *p) {
 		.format = AV_SAMPLE_FMT_S16,
 	};
 
-	if (!__ssrc_handler_decode_common(ch, h, &dest_format))
+	format_t dec_format = {
+		.clockrate = h->source_pt.clock_rate,
+		.channels = h->source_pt.channels,
+		.format = -1,
+	};
+
+	if (!__ssrc_handler_decode_common(ch, h, &dec_format, &dest_format))
 		goto err;
 
 	return &ch->h;
diff --git a/lib/codeclib.c b/lib/codeclib.c
index 21d25d0d0..6c7481bc9 100644
--- a/lib/codeclib.c
+++ b/lib/codeclib.c
@@ -75,7 +75,12 @@ codec_def_t *codec_get_pcm16(void) {
 decoder_t *decoder_new_fmt(codec_def_t *def, int clockrate, int channels, int ptime,
 		const format_t *resample_fmt)
 {
-	return decoder_new_fmtp(def, clockrate, channels, ptime, resample_fmt, NULL, NULL, NULL);
+	return decoder_new_fmtp(def,
+			&(format_t) {
+				.clockrate = clockrate,
+				.channels = channels,
+			},
+			ptime, resample_fmt, NULL, NULL, NULL);
 }
 
 bool codec_parse_fmtp(codec_def_t *def, struct rtp_codec_format *fmtp, const str *fmtp_string,
@@ -110,7 +115,7 @@ bool codec_parse_fmtp(codec_def_t *def, struct rtp_codec_format *fmtp, const str
 	return ret;
 }
 
-decoder_t *decoder_new_fmtp(codec_def_t *def, int clockrate, int channels, int ptime,
+decoder_t *decoder_new_fmtp(codec_def_t *def, const format_t *src_fmt, int ptime,
 		const format_t *resample_fmt,
 		struct rtp_codec_format *fmtp, const str *fmtp_string,
 		const str *extra_opts)
@@ -126,9 +131,9 @@ decoder_t *decoder_new_fmtp(codec_def_t *def, int clockrate, int channels, int p
 
 	ret->def = def;
 	ret->clockrate_fact = def->default_clockrate_fact;
-	format_init(&ret->in_format);
-	ret->in_format.channels = channels;
-	ret->in_format.clockrate = clockrate;
+
+	ret->in_format = *src_fmt;
+	ret->in_format.format = -1;
 
 	// output defaults to same as input
 	ret->dest_format = ret->in_format;
diff --git a/lib/codeclib.h b/lib/codeclib.h
index 2b1977e6c..66f753ec9 100644
--- a/lib/codeclib.h
+++ b/lib/codeclib.h
@@ -413,7 +413,7 @@ bool codec_parse_fmtp(codec_def_t *def, struct rtp_codec_format *fmtp, const str
 
 decoder_t *decoder_new_fmt(codec_def_t *def, int clockrate, int channels, int ptime,
 		const format_t *resample_fmt);
-decoder_t *decoder_new_fmtp(codec_def_t *def, int clockrate, int channels, int ptime,
+decoder_t *decoder_new_fmtp(codec_def_t *def, const format_t *src_fmt, int ptime,
 		const format_t *resample_fmt,
 		struct rtp_codec_format *fmtp, const str *fmtp_string, const str *codec_opts);
 void decoder_close(decoder_t *dec);
diff --git a/perf-tester/main.c b/perf-tester/main.c
index 1d64be1b7..b68e7bbe1 100644
--- a/perf-tester/main.c
+++ b/perf-tester/main.c
@@ -523,7 +523,7 @@ static void new_stream_params(
 				NULL, NULL, NULL);
 		assert(res == 0); // TODO: handle failures gracefully
 
-		s->decoder = decoder_new_fmtp(in_def, dec_format.clockrate, dec_format.channels, 20,
+		s->decoder = decoder_new_fmtp(in_def, &dec_format, 20,
 				&actual_enc_format, NULL, NULL, NULL); // TODO: support different options (fmtp etc)
 		assert(s->decoder != NULL); // TODO: handle failures gracefully
 	}
diff --git a/recording-daemon/decoder.c b/recording-daemon/decoder.c
index 54447f0ac..509caae34 100644
--- a/recording-daemon/decoder.c
+++ b/recording-daemon/decoder.c
@@ -66,10 +66,15 @@ decode_t *decoder_new(const char *payload_str, const char *format, int ptime) {
 		.channels = channels,
 		.format = AV_SAMPLE_FMT_S16,
 	};
+	format_t dec_format = (format_t) {
+		.clockrate = rtp_clockrate,
+		.channels = channels,
+		.format = -1,
+	};
 
 	str fmtp = STR(format);
 
-	decoder_t *dec = decoder_new_fmtp(def, rtp_clockrate, channels, ptime, &out_format, NULL, &fmtp, NULL);
+	decoder_t *dec = decoder_new_fmtp(def, &dec_format, ptime, &out_format, NULL, &fmtp, NULL);
 	if (!dec)
 		return NULL;
 	decode_t *deco = g_new0(decode_t, 1);
diff --git a/t/test-amr-decode.c b/t/test-amr-decode.c
index 6a2a7fbbb..aea904c39 100644
--- a/t/test-amr-decode.c
+++ b/t/test-amr-decode.c
@@ -64,7 +64,7 @@ static void do_test_amr_xx(const char *file, int line,
 	str fmtp = STR_NULL;
 	if (fmtp_s)
 		fmtp = STR(fmtp_s);
-	decoder_t *d = decoder_new_fmtp(def, clockrate, 1, 0, &fmt, NULL, NULL, &fmtp);
+	decoder_t *d = decoder_new_fmtp(def, &fmt, 0, &fmt, NULL, NULL, &fmtp);
 	assert(d);
 	const str data = STR_LEN(data_s, data_len);
 	int ret = decoder_input_data(d, &data, 1, false, frame_cb, &args, NULL);