trx-bridge: write back to input before reading

trx-bridge/bridge.c

@@ -310,6 +310,22 @@ int main(int argc, char *argv[]) {
 		// Read from output first to know how many samples should be read
 		output_read_count = output_trx_state.trx_read_func2(&output_trx_state, &output_rx_ts, (void **) output_channels, TRX_BUFFER_SIZE, 0, &read_md);
 
+		// Expected behavior: TX (i.e. write) timestamp is set once based on RX (i.e. read)
+		// timestamp and incremented after every write.
+		// The buffer size in TRX SDR is four times the samples rate, so this
+		// value is used here as an offset between the two timestamps.
+		if(output_tx_ts == 0) output_tx_ts = output_rx_ts + 4 * SAMPLE_RATE_KHZ;
+		output_tx_ts += output_read_count;
+
+		// Real behavior: sometimes, the TX timestamp deviates, so it should be matched again.
+		if(output_tx_ts != output_rx_ts + 4 * SAMPLE_RATE_KHZ) {
+			printf("trx-bridge: output timestamp deviated %lu != %lu\n", output_tx_ts, output_rx_ts + 4 * SAMPLE_RATE_KHZ);
+			output_tx_ts = output_rx_ts + 4 * SAMPLE_RATE_KHZ;
+		}
+
+		// Write back samples read from output
+		if(output_read_count > 0) input_trx_state.trx_write_func2(&input_trx_state, input_tx_ts, (const void **) output_channels, output_read_count, 0, &write_md);
+
 		// As much samples should be read from input than from output.
 		// However, sometimes, the input driver won't return enough samples,
 		// so we need to loop for samples.
@@ -326,25 +342,10 @@ int main(int argc, char *argv[]) {
 			input_read_count += input_read_count_extra;
 		}
 
-		// Expected behavior: TX (i.e. write) timestamp is set once based on RX (i.e. read)
-		// timestamp and incremented after every write.
-		// The buffer size in TRX SDR is four times the samples rate, so this
-		// value is used here as tn offset between the two timestamps.
-		if(output_tx_ts == 0) output_tx_ts = output_rx_ts + 4 * SAMPLE_RATE_KHZ;
 		if(input_tx_ts == 0) input_tx_ts = input_rx_ts + 4 * SAMPLE_RATE_KHZ;
-
-		output_tx_ts += output_read_count;
 		input_tx_ts += input_read_count;
 
-		// Write back samples read from input and output
 		if(input_read_count > 0) output_trx_state.trx_write_func2(&output_trx_state, output_tx_ts, (const void **) input_channels, input_read_count, 0, &write_md);
-		if(output_read_count > 0) input_trx_state.trx_write_func2(&input_trx_state, input_tx_ts, (const void **) output_channels, output_read_count, 0, &write_md);
-
-		// Real behavior: sometimes, the TX timestamp deviates, so it should be matched again.
-		if(output_tx_ts != output_rx_ts + 4 * SAMPLE_RATE_KHZ) {
-			printf("trx-bridge: output timestamp deviated %lu != %lu\n", output_tx_ts, output_rx_ts + 4 * SAMPLE_RATE_KHZ);
-			output_tx_ts = output_rx_ts + 4 * SAMPLE_RATE_KHZ;
-		}
 
 		if(input_tx_ts != input_rx_ts + 4 * SAMPLE_RATE_KHZ) {
 			printf("trx-bridge: input timestamp deviated %lu != %lu\n", input_tx_ts, input_rx_ts + 4 * SAMPLE_RATE_KHZ);