avformat/utils: Remove unnecessary initializations

Up until now, read_frame_internal always initialized the packet it
received. But since the recent changes to ff_read_packet, this is no
longer needed: If the parsing queue is initially empty upon entering
read_frame_internal, the packet will now either contain content upon
success or be blank upon failure of ff_read_packet. If the parsing
queue is initially not empty, the packet will be overwritten with the
oldest one from the parsing queue.

Similarly, it is unnecessary to initialize ret in read_frame_internal.

In parse_packet, it is easily possible to only initialize the packet
used as temporary storage for the output if said packet is used at all;
furthermore, this packet doesn't need to be zero-initialized, because
av_init_packet will initialize every field except size and data and
those fields will be set by av_parser_parse2.

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

libavformat/utils.c

@@ -1447,15 +1447,15 @@ void ff_packet_list_free(AVPacketList **pkt_buf, AVPacketList **pkt_buf_end)
 static int parse_packet(AVFormatContext *s, AVPacket *pkt,
                         int stream_index, int flush)
 {
-    AVPacket out_pkt = { 0 };
+    AVPacket out_pkt;
     AVStream *st = s->streams[stream_index];
     uint8_t *data = pkt->data;
     int size      = pkt->size;
     int ret = 0, got_output = flush;
 
-    av_init_packet(&out_pkt);
-
-    if (!size && !flush && st->parser->flags & PARSER_FLAG_COMPLETE_FRAMES) {
+    if (size || flush) {
+        av_init_packet(&out_pkt);
+    } else if (st->parser->flags & PARSER_FLAG_COMPLETE_FRAMES) {
         // preserve 0-size sync packets
         compute_pkt_fields(s, st, st->parser, pkt, AV_NOPTS_VALUE, AV_NOPTS_VALUE);
     }
@@ -1576,11 +1576,9 @@ static int64_t ts_to_samples(AVStream *st, int64_t ts)
 
 static int read_frame_internal(AVFormatContext *s, AVPacket *pkt)
 {
-    int ret = 0, i, got_packet = 0;
+    int ret, i, got_packet = 0;
     AVDictionary *metadata = NULL;
 
-    av_init_packet(pkt);
-
     while (!got_packet && !s->internal->parse_queue) {
         AVStream *st;