decoder/ffmpeg: simplify ffmpeg_send_packet()

src/decoder/plugins/FfmpegDecoderPlugin.cxx

@@ -379,11 +379,15 @@ ffmpeg_send_packet(Decoder &decoder, InputStream &is,
 			break;
 		}
 
+		packet.data += len;
+		packet.size -= len;
+
+		if (!got_frame)
+			continue;
+
 		uint8_t *output_buffer = nullptr;
-		int audio_size = 0;
-		if (got_frame) {
-			audio_size = copy_interleave_frame(codec_context,
-							   *frame,
+		int audio_size =
+			copy_interleave_frame(codec_context, *frame,
 					      &output_buffer,
 					      buffer);
 		if (audio_size < 0) {
@@ -392,10 +396,6 @@ ffmpeg_send_packet(Decoder &decoder, InputStream &is,
 			LogFfmpegError(audio_size);
 			return DecoderCommand::STOP;
 		}
-		}
-
-		packet.data += len;
-		packet.size -= len;
 
 		if (audio_size <= 0)
 			continue;