core: add common function to initialize AVPacket

Audio and video had their own (very similar) functions to initialize an
AVPacket (ffmpeg's packet struct) from a demux_packet (mplayer's packet
struct). Add a common function for these.

Also use this function for sd_lavc_conv. This is actually a functional
change, as some libavfilter subtitle demuxers add weird out-of-band
stuff as side-data.

audio/decode/ad_lavc.c

@@ -402,13 +402,10 @@ static int decode_new_packet(struct sh_audio *sh)
     }
 
     AVPacket pkt;
-    av_init_packet(&pkt);
+    mp_set_av_packet(&pkt, mpkt);
     pkt.data = start;
     pkt.size = insize;
-    if (mpkt && mpkt->avpacket) {
-        pkt.side_data = mpkt->avpacket->side_data;
-        pkt.side_data_elems = mpkt->avpacket->side_data_elems;
-    }
+
     if (pts != MP_NOPTS_VALUE && !packet_already_used) {
         sh->pts = pts;
         sh->pts_bytes = 0;

core/av_common.c

@@ -18,8 +18,10 @@
 #include <assert.h>
 
 #include <libavutil/common.h>
+#include <libavcodec/avcodec.h>
 
 #include "core/mp_talloc.h"
+#include "demux/demux_packet.h"
 #include "av_common.h"
 #include "codecs.h"
 
@@ -58,6 +60,24 @@ void mp_copy_lav_codec_headers(AVCodecContext *avctx, AVCodecContext *st)
     avctx->bits_per_coded_sample    = st->bits_per_coded_sample;
 }
 
+// Set dst from mpkt. Note that dst is not refcountable.
+// mpkt can be NULL to generate empty packets (used to flush delayed data).
+// Does not set pts or duration fields.
+void mp_set_av_packet(AVPacket *dst, struct demux_packet *mpkt)
+{
+    av_init_packet(dst);
+    dst->data = mpkt ? mpkt->buffer : NULL;
+    dst->size = mpkt ? mpkt->len : 0;
+    /* Some codecs (ZeroCodec, some cases of PNG) may want keyframe info
+     * from demuxer. */
+    if (mpkt && mpkt->keyframe)
+        dst->flags |= AV_PKT_FLAG_KEY;
+    if (mpkt && mpkt->avpacket) {
+        dst->side_data = mpkt->avpacket->side_data;
+        dst->side_data_elems = mpkt->avpacket->side_data_elems;
+    }
+}
+
 void mp_add_lavc_decoders(struct mp_decoder_list *list, enum AVMediaType type)
 {
     AVCodec *cur = NULL;

core/av_common.h

@@ -22,8 +22,10 @@
 #include <libavcodec/avcodec.h>
 
 struct mp_decoder_list;
+struct demux_packet;
 
 void mp_copy_lav_codec_headers(AVCodecContext *avctx, AVCodecContext *st);
+void mp_set_av_packet(AVPacket *dst, struct demux_packet *mpkt);
 void mp_add_lavc_decoders(struct mp_decoder_list *list, enum AVMediaType type);
 int mp_codec_to_av_codec_id(const char *codec);
 const char *mp_codec_from_av_codec_id(int codec_id);

sub/sd_lavc_conv.c

@@ -114,9 +114,7 @@ static void decode(struct sd *sd, struct demux_packet *packet)
     AVPacket pkt;
     int ret, got_sub;
 
-    av_init_packet(&pkt);
-    pkt.data = packet->buffer;
-    pkt.size = packet->len;
+    mp_set_av_packet(&pkt, packet);
     pkt.pts = packet->pts == MP_NOPTS_VALUE ? AV_NOPTS_VALUE : packet->pts * ts;
     pkt.duration = packet->duration * ts;
 
@@ -136,7 +134,6 @@ static void decode(struct sd *sd, struct demux_packet *packet)
         }
     }
 
-    av_free_packet(&pkt);
     avsubtitle_free(&sub);
 }
 

video/decode/vd_lavc.c

@@ -673,17 +673,8 @@ static int decode(struct sh_video *sh, struct demux_packet *packet,
     else
         avctx->skip_frame = ctx->skip_frame;
 
-    av_init_packet(&pkt);
-    pkt.data = packet ? packet->buffer : NULL;
-    pkt.size = packet ? packet->len : 0;
-    /* Some codecs (ZeroCodec, some cases of PNG) may want keyframe info
-     * from demuxer. */
-    if (packet && packet->keyframe)
-        pkt.flags |= AV_PKT_FLAG_KEY;
-    if (packet && packet->avpacket) {
-        pkt.side_data = packet->avpacket->side_data;
-        pkt.side_data_elems = packet->avpacket->side_data_elems;
-    }
+    mp_set_av_packet(&pkt, packet);
+
     // The avcodec opaque field stupidly supports only int64_t type
     union pts { int64_t i; double d; };
     avctx->reordered_opaque = (union pts){.d = *reordered_pts}.i;