Make stream push packets to sinks

Now that decoder and recorder implement the packet sink trait, make
stream push packets to the sinks without depending on the concrete sink
types.

app/src/decoder.c

@@ -41,8 +41,14 @@ decoder_close(struct decoder *decoder) {
     avcodec_free_context(&decoder->codec_ctx);
 }
 
-bool
+static bool
 decoder_push(struct decoder *decoder, const AVPacket *packet) {
+    bool is_config = packet->pts == AV_NOPTS_VALUE;
+    if (is_config) {
+        // nothing to do
+        return true;
+    }
+
     int ret;
     if ((ret = avcodec_send_packet(decoder->codec_ctx, packet)) < 0) {
         LOGE("Could not send video packet: %d", ret);