avformat: add AVFMT_FLAG_FASTSEEK, use it for mp3

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

doc/APIchanges

@@ -15,6 +15,10 @@ libavutil:     2014-08-09
 
 API changes, most recent first:
 
+2015-xx-xx - xxxxxxx - lavf 56.xx.xxx - avformat.h
+  Add AVFMT_FLAG_FAST_SEEK flag. Some formats (initially mp3) use it to enable
+  fast, but inaccurate seeking.
+
 2015-xx-xx - xxxxxxx - lavu 54.12.0
   Add AV_LOG_TRACE for extremely verbose debugging.
 

doc/formats.texi

@@ -37,6 +37,8 @@ Possible values:
 @table @samp
 @item ignidx
 Ignore index.
+@item fastseek
+Enable fast, but inaccurate seeks for some formats.
 @item genpts
 Generate PTS.
 @item nofillin

libavformat/avformat.h

@@ -1391,6 +1391,7 @@ typedef struct AVFormatContext {
 #define AVFMT_FLAG_SORT_DTS    0x10000 ///< try to interleave outputted packets by dts (using this flag can slow demuxing down)
 #define AVFMT_FLAG_PRIV_OPT    0x20000 ///< Enable use of private options by delaying codec open (this could be made default once all code is converted)
 #define AVFMT_FLAG_KEEP_SIDE_DATA 0x40000 ///< Don't merge side data but keep it separate.
+#define AVFMT_FLAG_FAST_SEEK   0x80000 ///< Enable fast, but inaccurate seeks for some formats
 
     /**
      * @deprecated deprecated in favor of probesize2

libavformat/mp3dec.c

@@ -337,7 +337,7 @@ static int mp3_read_header(AVFormatContext *s)
     int i;
 
     if (mp3->usetoc < 0)
-        mp3->usetoc = 2;
+        mp3->usetoc = (s->flags & AVFMT_FLAG_FAST_SEEK) ? 0 : 2;
 
     st = avformat_new_stream(s, NULL);
     if (!st)

libavformat/options_table.h

@@ -49,6 +49,7 @@ static const AVOption avformat_options[] = {
 {"discardcorrupt", "discard corrupted frames", 0, AV_OPT_TYPE_CONST, {.i64 = AVFMT_FLAG_DISCARD_CORRUPT }, INT_MIN, INT_MAX, D, "fflags"},
 {"sortdts", "try to interleave outputted packets by dts", 0, AV_OPT_TYPE_CONST, {.i64 = AVFMT_FLAG_SORT_DTS }, INT_MIN, INT_MAX, D, "fflags"},
 {"keepside", "don't merge side data", 0, AV_OPT_TYPE_CONST, {.i64 = AVFMT_FLAG_KEEP_SIDE_DATA }, INT_MIN, INT_MAX, D, "fflags"},
+{"fastseek", "fast but inaccurate seeks", 0, AV_OPT_TYPE_CONST, {.i64 = AVFMT_FLAG_FAST_SEEK }, INT_MIN, INT_MAX, D, "fflags"},
 {"latm", "enable RTP MP4A-LATM payload", 0, AV_OPT_TYPE_CONST, {.i64 = AVFMT_FLAG_MP4A_LATM }, INT_MIN, INT_MAX, E, "fflags"},
 {"nobuffer", "reduce the latency introduced by optional buffering", 0, AV_OPT_TYPE_CONST, {.i64 = AVFMT_FLAG_NOBUFFER }, 0, INT_MAX, D, "fflags"},
 {"seek2any", "allow seeking to non-keyframes on demuxer level when supported", OFFSET(seek2any), AV_OPT_TYPE_INT, {.i64 = 0 }, 0, 1, D},

libavformat/version.h

@@ -30,7 +30,7 @@
 #include "libavutil/version.h"
 
 #define LIBAVFORMAT_VERSION_MAJOR 56
-#define LIBAVFORMAT_VERSION_MINOR  30
+#define LIBAVFORMAT_VERSION_MINOR  31
 #define LIBAVFORMAT_VERSION_MICRO 100
 
 #define LIBAVFORMAT_VERSION_INT AV_VERSION_INT(LIBAVFORMAT_VERSION_MAJOR, \