mpegtsenc: fix handling of large audio packets

(sorry i have no sample, just a user report)
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/mpegtsenc.c

@@ -24,6 +24,7 @@
 #include "libavutil/dict.h"
 #include "libavutil/mathematics.h"
 #include "libavutil/opt.h"
+#include "libavutil/avassert.h"
 #include "libavcodec/mpegvideo.h"
 #include "avformat.h"
 #include "internal.h"
@@ -1022,20 +1023,21 @@ static int mpegts_write_packet(AVFormatContext *s, AVPacket *pkt)
         }
     }
 
-    if (st->codec->codec_type != AVMEDIA_TYPE_AUDIO) {
-        // for video and subtitle, write a single pes packet
-        mpegts_write_pes(s, st, buf, size, pts, dts, pkt->flags & AV_PKT_FLAG_KEY);
-        av_free(data);
-        return 0;
-    }
-
-    if (ts_st->payload_index + size > DEFAULT_PES_PAYLOAD_SIZE) {
+    if (ts_st->payload_index && ts_st->payload_index + size > DEFAULT_PES_PAYLOAD_SIZE) {
         mpegts_write_pes(s, st, ts_st->payload, ts_st->payload_index,
                          ts_st->payload_pts, ts_st->payload_dts,
                          ts_st->payload_flags & AV_PKT_FLAG_KEY);
         ts_st->payload_index = 0;
     }
 
+    if (st->codec->codec_type != AVMEDIA_TYPE_AUDIO || size > DEFAULT_PES_PAYLOAD_SIZE) {
+        av_assert0(!ts_st->payload_index);
+        // for video and subtitle, write a single pes packet
+        mpegts_write_pes(s, st, buf, size, pts, dts, pkt->flags & AV_PKT_FLAG_KEY);
+        av_free(data);
+        return 0;
+    }
+
     if (!ts_st->payload_index) {
         ts_st->payload_pts = pts;
         ts_st->payload_dts = dts;