avformat/demux: use a stream specific temporary packet for the parser

This will be useful for the next commit.

Signed-off-by: James Almer <jamrial@gmail.com>

libavformat/avformat.c

@@ -59,6 +59,8 @@ void ff_free_stream(AVStream **pst)
     av_freep(&sti->index_entries);
     av_freep(&sti->probe_data.buf);
 
+    av_packet_free(&sti->parse_pkt);
+
     av_bsf_free(&sti->extract_extradata.bsf);
 
     if (sti->info) {

libavformat/demux.c

@@ -1175,9 +1175,9 @@ static int parse_packet(AVFormatContext *s, AVPacket *pkt,
 {
     FormatContextInternal *const fci = ff_fc_internal(s);
     FFFormatContext *const si = &fci->fc;
-    AVPacket *out_pkt = si->parse_pkt;
     AVStream *st = s->streams[stream_index];
     FFStream *const sti = ffstream(st);
+    AVPacket *out_pkt = sti->parse_pkt;
     const AVPacketSideData *sd = NULL;
     const uint8_t *data = pkt->data;
     uint8_t *extradata = sti->avctx->extradata;

libavformat/internal.h

@@ -314,6 +314,21 @@ typedef struct FFStream {
     enum AVStreamParseType need_parsing;
     struct AVCodecParserContext *parser;
 
+    /**
+     * The generic code uses this as a temporary packet
+     * to parse packets or for muxing, especially flushing.
+     * For demuxers, it may also be used for other means
+     * for short periods that are guaranteed not to overlap
+     * with calls to av_read_frame() (or ff_read_packet())
+     * or with each other.
+     * It may be used by demuxers as a replacement for
+     * stack packets (unless they call one of the aforementioned
+     * functions with their own AVFormatContext).
+     * Every user has to ensure that this packet is blank
+     * after using it.
+     */
+    AVPacket *parse_pkt;
+
     /**
      * Number of frames that have been demuxed during avformat_find_stream_info()
      */

libavformat/options.c

@@ -270,6 +270,10 @@ AVStream *avformat_new_stream(AVFormatContext *s, const AVCodec *c)
 
     sti->fmtctx = s;
 
+    sti->parse_pkt = av_packet_alloc();
+    if (!sti->parse_pkt)
+        goto fail;
+
     if (s->iformat) {
         sti->avctx = avcodec_alloc_context3(NULL);
         if (!sti->avctx)