avformat/mux: Don't use stack packet when writing interleaved packets

Currently the interleave_packet functions use a packet for
a new packet to be interleaved (may be NULL if there is none) and
a packet for output; said packet is always a stack packet in
interleaved_write_packet(). But all the interleave_packet functions
in use first move the packet to the packet list and then check whether
a packet can be returned, i.e. the effective lifetime of the new packet
ends before the packet for output is touched.

So one can use one packet both for input and output by adding a new
parameter that indicates whether there is a packet to add to the packet
list; there is just one complication: In case the muxer is flushed,
there is no packet available. This can be solved by reusing one of
the packets from AVFormatInternal. They are currently unused when
flushing in av_interleaved_write_frame().

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

1 files changed, 19 insertions, 25 deletions

diff --git a/libavformat/mux.c b/libavformat/mux.c
index d7b2bdb4b3..d924bb08fc 100644
--- a/libavformat/mux.c
+++ b/libavformat/mux.c
@@ -903,8 +903,8 @@ static int interleave_compare_dts(AVFormatContext *s, const AVPacket *next,
     return comp > 0;
 }
 
-int ff_interleave_packet_per_dts(AVFormatContext *s, AVPacket *out,
-                                 AVPacket *pkt, int flush)
+int ff_interleave_packet_per_dts(AVFormatContext *s, AVPacket *pkt,
+                                 int flush, int has_packet)
 {
     FFFormatContext *const si = ffformatcontext(s);
     int stream_count = 0;
@@ -912,7 +912,7 @@ int ff_interleave_packet_per_dts(AVFormatContext *s, AVPacket *out,
     int ret;
     int eof = flush;
 
-    if (pkt) {
+    if (has_packet) {
         if ((ret = ff_interleave_add_packet(s, pkt, interleave_compare_dts)) < 0)
             return ret;
     }
@@ -1009,7 +1009,7 @@ int ff_interleave_packet_per_dts(AVFormatContext *s, AVPacket *out,
         AVStream *const st = s->streams[pktl->pkt.stream_index];
         FFStream *const sti = ffstream(st);
 
-        *out = pktl->pkt;
+        *pkt = pktl->pkt;
 
         si->packet_buffer = pktl->next;
         if (!si->packet_buffer)
@@ -1055,20 +1055,16 @@ const AVPacket *ff_interleaved_peek(AVFormatContext *s, int stream)
 }
 
 /**
- * Interleave an AVPacket correctly so it can be muxed.
- * @param out the interleaved packet will be output here
- * @param in the input packet; will always be blank on return if not NULL
- * @param flush 1 if no further packets are available as input and all
- *              remaining packets should be output
- * @return 1 if a packet was output, 0 if no packet could be output,
- *         < 0 if an error occurred
+ * A wrapper around AVOutputFormat.interleave_packet.
+ * See its documentation for details.
  */
-static int interleave_packet(AVFormatContext *s, AVPacket *out, AVPacket *in, int flush)
+static int interleave_packet(AVFormatContext *s, AVPacket *pkt,
+                             int flush, int has_packet)
 {
     if (s->oformat->interleave_packet) {
-        return s->oformat->interleave_packet(s, out, in, flush);
+        return s->oformat->interleave_packet(s, pkt, flush, has_packet);
     } else
-        return ff_interleave_packet_per_dts(s, out, in, flush);
+        return ff_interleave_packet_per_dts(s, pkt, flush, has_packet);
 }
 
 static int check_bitstream(AVFormatContext *s, FFStream *sti, AVPacket *pkt)
@@ -1090,20 +1086,18 @@ static int check_bitstream(AVFormatContext *s, FFStream *sti, AVPacket *pkt)
     return 1;
 }
 
-static int interleaved_write_packet(AVFormatContext *s, AVPacket *pkt, int flush)
+static int interleaved_write_packet(AVFormatContext *s, AVPacket *pkt,
+                                    int flush, int has_packet)
 {
     for (;; ) {
-        AVPacket opkt;
-        int ret = interleave_packet(s, &opkt, pkt, flush);
+        int ret = interleave_packet(s, pkt, flush, has_packet);
         if (ret <= 0)
             return ret;
 
-        pkt = NULL;
-
-        ret = write_packet(s, &opkt);
-
-        av_packet_unref(&opkt);
+        has_packet = 0;
 
+        ret = write_packet(s, pkt);
+        av_packet_unref(pkt);
         if (ret < 0)
             return ret;
     }
@@ -1127,7 +1121,7 @@ static int write_packet_common(AVFormatContext *s, AVStream *st, AVPacket *pkt,
     if (interleaved) {
         if (pkt->dts == AV_NOPTS_VALUE && !(s->oformat->flags & AVFMT_NOTIMESTAMPS))
             return AVERROR(EINVAL);
-        return interleaved_write_packet(s, pkt, 0);
+        return interleaved_write_packet(s, pkt, 0, 1);
     } else {
         return write_packet(s, pkt);
     }
@@ -1251,7 +1245,7 @@ int av_interleaved_write_frame(AVFormatContext *s, AVPacket *pkt)
         return ret;
     } else {
         av_log(s, AV_LOG_TRACE, "av_interleaved_write_frame FLUSH\n");
-        return interleaved_write_packet(s, NULL, 1/*flush*/);
+        return interleaved_write_packet(s, ffformatcontext(s)->parse_pkt, 1/*flush*/, 0);
     }
 }
 
@@ -1271,7 +1265,7 @@ int av_write_trailer(AVFormatContext *s)
                 ret = ret1;
         }
     }
-    ret1 = interleaved_write_packet(s, NULL, 1);
+    ret1 = interleaved_write_packet(s, pkt, 1, 0);
     if (ret >= 0)
         ret = ret1;