recorder: ignore packet queue in mux_packets()

I've looked and studied the flow in the recorder, and to my
understanding, the packet queue is moot after the initial sync, maybe
even then - but that's beyond me right now.
With the previous choice to mux trailing packets whatever the case, this
doesn't result in any new ill effects (and some missing packets at the
end is no big deal).
Notably, since we don't have to hold onto the packets after we get
muxing, we'll never run into any issues with veeery long GOPs filling up
our queue (resulting in dropped packets and much user chagrin).

common/recorder.c

@@ -223,30 +223,19 @@ static void mux_packet(struct mp_recorder_sink *rst,
         MP_ERR(priv, "Failed writing packet.\n");
 }
 
-// Write all packets that currently can be written.
-static void mux_packets(struct mp_recorder_sink *rst, bool force)
+// Write all packets available in the stream queue
+static void mux_packets(struct mp_recorder_sink *rst)
 {
     struct mp_recorder *priv = rst->owner;
     if (!priv->muxing || !rst->num_packets)
         return;
 
-    int safe_count = 0;
     for (int n = 0; n < rst->num_packets; n++) {
-        if (rst->packets[n]->keyframe)
-            safe_count = n;
-    }
-    if (force)
-        safe_count = rst->num_packets;
-
-    for (int n = 0; n < safe_count; n++) {
         mux_packet(rst, rst->packets[n]);
         talloc_free(rst->packets[n]);
     }
 
-    // Remove packets[0..safe_count]
-    memmove(&rst->packets[0], &rst->packets[safe_count],
-            (rst->num_packets - safe_count) * sizeof(rst->packets[0]));
-    rst->num_packets -= safe_count;
+    rst->num_packets = 0;
 }
 
 // If there was a discontinuity, check whether we can resume muxing (and from
@@ -297,7 +286,7 @@ void mp_recorder_destroy(struct mp_recorder *priv)
     if (priv->opened) {
         for (int n = 0; n < priv->num_streams; n++) {
             struct mp_recorder_sink *rst = priv->streams[n];
-            mux_packets(rst, true);
+            mux_packets(rst);
         }
 
         if (av_write_trailer(priv->mux) < 0)
@@ -321,7 +310,7 @@ void mp_recorder_mark_discontinuity(struct mp_recorder *priv)
 
     for (int n = 0; n < priv->num_streams; n++) {
         struct mp_recorder_sink *rst = priv->streams[n];
-        mux_packets(rst, true);
+        mux_packets(rst);
         rst->discont = true;
         rst->proper_eof = false;
     }
@@ -356,7 +345,7 @@ void mp_recorder_feed_packet(struct mp_recorder_sink *rst,
     if (!pkt) {
         rst->proper_eof = true;
         check_restart(priv);
-        mux_packets(rst, false);
+        mux_packets(rst);
         return;
     }
 
@@ -365,7 +354,7 @@ void mp_recorder_feed_packet(struct mp_recorder_sink *rst,
         // No, FFmpeg doesn't tell us which formats need DTS at all.
         // No, we can not shut up the FFmpeg warning, which will follow.
         MP_WARN(priv, "Source stream misses DTS on at least some packets!\n"
-                      "If the target file format requires DTS, the written\n"
+                      "If the target file format requires DTS, the written "
                       "file will be invalid.\n");
         priv->dts_warning = true;
     }
@@ -386,5 +375,5 @@ void mp_recorder_feed_packet(struct mp_recorder_sink *rst,
     MP_TARRAY_APPEND(rst, rst->packets, rst->num_packets, pkt);
 
     check_restart(priv);
-    mux_packets(rst, false);
+    mux_packets(rst);
 }