avformat: add skip_estimate_duration_from_pts

For seekable mpegts streams, duration is calculated from
pts by seeking to the end of the file for a pts and subtracting
the initial pts to compute a duration.

This can be expensive in terms of added latency during
probe, especially when streaming over a network. This new
option lets you skip the duration calculation, which is useful
when you don't care about the value and want to save some overhead.

This patch is particularly useful when dealing with live mpegts
streams. Normally such streams are not seekable, so durations
are not calculated. However in my case I am dealing with a seekable
live mpegts stream (networked access to a .ts file which is still
being appended to).

Signed-off-by: Aman Gupta <aman@tmm1.net>

diff --git a/libavformat/avformat.h b/libavformat/avformat.h
index a2fe7c6bb2cafe8f9c16ab541d3d70079f26ba2a..669ddb423ee199ae3cf93b81926cadff1f9977fe 100644 (file)
--- a/libavformat/avformat.h
+++ b/libavformat/avformat.h
@@ -1926,6 +1926,13 @@ typedef struct AVFormatContext {
      * - decoding: set by user
      */
     int max_streams;
+
+    /**
+     * Skip duration calcuation in estimate_timings_from_pts.
+     * - encoding: unused
+     * - decoding: set by user
+     */
+    int skip_estimate_duration_from_pts;
 } AVFormatContext;
 
 #if FF_API_FORMAT_GET_SET

diff --git a/libavformat/options_table.h b/libavformat/options_table.h
index 7c4d84798e1af44fd87d154c97213a4b0c0cb1e0..b7a5b3c054b6bc93e1e42bb12449d065247f3f25 100644 (file)
--- a/libavformat/options_table.h
+++ b/libavformat/options_table.h
@@ -108,6 +108,7 @@ static const AVOption avformat_options[] = {
 {"protocol_whitelist", "List of protocols that are allowed to be used", OFFSET(protocol_whitelist), AV_OPT_TYPE_STRING, { .str = NULL },  CHAR_MIN, CHAR_MAX, D },
 {"protocol_blacklist", "List of protocols that are not allowed to be used", OFFSET(protocol_blacklist), AV_OPT_TYPE_STRING, { .str = NULL },  CHAR_MIN, CHAR_MAX, D },
 {"max_streams", "maximum number of streams", OFFSET(max_streams), AV_OPT_TYPE_INT, { .i64 = 1000 }, 0, INT_MAX, D },
+{"skip_estimate_duration_from_pts", "skip duration calculation in estimate_timings_from_pts", OFFSET(skip_estimate_duration_from_pts), AV_OPT_TYPE_BOOL, {.i64 = 0}, 0, 1, D},
 {NULL},
 };
 

diff --git a/libavformat/utils.c b/libavformat/utils.c
index c25eab4d49c5246831b98887f2cbe7bb7d562d29..636fae37798405e8e38b7221fef88b404c2a57a7 100644 (file)
--- a/libavformat/utils.c
+++ b/libavformat/utils.c
@@ -2812,6 +2812,11 @@ static void estimate_timings_from_pts(AVFormatContext *ic, int64_t old_offset)
         }
     }
 
+    if (ic->skip_estimate_duration_from_pts) {
+        av_log(ic, AV_LOG_INFO, "Skipping duration calculation in estimate_timings_from_pts\n");
+        goto skip_duration_calc;
+    }
+
     av_opt_set(ic, "skip_changes", "1", AV_OPT_SEARCH_CHILDREN);
     /* estimate the end time (duration) */
     /* XXX: may need to support wrapping */
@@ -2896,6 +2901,7 @@ static void estimate_timings_from_pts(AVFormatContext *ic, int64_t old_offset)
             }
         }
     }
+skip_duration_calc:
     fill_all_stream_timings(ic);
 
     avio_seek(ic->pb, old_offset, SEEK_SET);