libavformat: Add option to queue packets during stream analysis.

queue_analysis.diff

commit cdc0833efaa19b695bea16b69a49d2e9adb90d0e
Author: Josh Allmann <joshua.allmann@gmail.com>
Date:   Sat Jul 21 23:32:16 2012 -0700

    libavformat: Add option to queue packets during stream analysis.
    
    Useful in cases where a significant analyzeduration is
    still needed, while minimizing buffering before output.
    
    Useful for eg, processing low-latency streams where all
    media types won't necessarily come in if the analysis
    phase is brief.

diff --git a/libavformat/avformat.h b/libavformat/avformat.h
index e292206..bd323dc 100644
--- a/libavformat/avformat.h
+++ b/libavformat/avformat.h
@@ -985,6 +985,11 @@ typedef struct AVFormatContext {
      * Flags to enable debugging.
      */
     int debug;
+
+    /**
+     * Flag to to queue packets read during stream analysis
+     */
+    int queue_analysis;
 #define FF_FDEBUG_TS        0x0001
     /*****************************************************************
      * All fields below this line are not part of the public API. They
diff --git a/libavformat/options_table.h b/libavformat/options_table.h
index 58f3dcf..9790e6b 100644
--- a/libavformat/options_table.h
+++ b/libavformat/options_table.h
@@ -41,6 +41,7 @@ static const AVOption options[]={
 {"igndts", "ignore dts", 0, AV_OPT_TYPE_CONST, {.dbl = AVFMT_FLAG_IGNDTS }, INT_MIN, INT_MAX, D, "fflags"},
 {"discardcorrupt", "discard corrupted frames", 0, AV_OPT_TYPE_CONST, {.dbl = AVFMT_FLAG_DISCARD_CORRUPT }, INT_MIN, INT_MAX, D, "fflags"},
 {"analyzeduration", "how many microseconds are analyzed to estimate duration", OFFSET(max_analyze_duration), AV_OPT_TYPE_INT, {.dbl = 5*AV_TIME_BASE }, 0, INT_MAX, D},
+{"queueanalysis", "queue packets read during stream analysis", OFFSET(queue_analysis), AV_OPT_TYPE_INT, {.dbl = 1}, 0, INT_MAX, E|D},
 {"cryptokey", "decryption key", OFFSET(key), AV_OPT_TYPE_BINARY, {.dbl = 0}, 0, 0, D},
 {"indexmem", "max memory used for timestamp index (per stream)", OFFSET(max_index_size), AV_OPT_TYPE_INT, {.dbl = 1<<20 }, 0, INT_MAX, D},
 {"rtbufsize", "max memory used for buffering real-time frames", OFFSET(max_picture_buffer), AV_OPT_TYPE_INT, {.dbl = 3041280 }, 0, INT_MAX, D}, /* defaults to 1s of 15fps 352x288 YUYV422 video */
diff --git a/libavformat/utils.c b/libavformat/utils.c
index 156c527..99fbb2f 100644
--- a/libavformat/utils.c
+++ b/libavformat/utils.c
@@ -2382,9 +2382,12 @@ int avformat_find_stream_info(AVFormatContext *ic, AVDictionary **options)
             break;
         }
 
+        if (ic->queue_analysis) {
         pkt= add_to_pktbuf(&ic->packet_buffer, &pkt1, &ic->packet_buffer_end);
         if ((ret = av_dup_packet(pkt)) < 0)
             goto find_stream_info_err;
+        } else
+            pkt = &pkt1;
 
         read_size += pkt->size;