[FFmpeg-devel] [PATCH] avformat: add AVFMT_FLAG_FASTSEEK, use it for mp3

[wm4]

---
Proposal. Is not mp3-specific, and can be reused for other formats.
---
 doc/APIchanges              | 4 ++++
 doc/formats.texi            | 2 ++
 libavformat/avformat.h      | 1 +
 libavformat/mp3dec.c        | 4 ++--
 libavformat/options_table.h | 1 +
 5 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/doc/APIchanges b/doc/APIchanges
index b422e29..b65fd62 100644
--- a/doc/APIchanges
+++ b/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.
 
diff --git a/doc/formats.texi b/doc/formats.texi
index cbbdc10..aa39d4b 100644
--- a/doc/formats.texi
+++ b/doc/formats.texi
@@ -37,6 +37,8 @@ Possible values:
 @table @samp
 @item ignidx
 Ignore index.
+ at item fastseek
+Enable fast, but inaccurate seeks for some formats.
 @item genpts
 Generate PTS.
 @item nofillin
diff --git a/libavformat/avformat.h b/libavformat/avformat.h
index 93cfb20..85b5a1a 100644
--- a/libavformat/avformat.h
+++ b/libavformat/avformat.h
@@ -1390,6 +1390,7 @@ 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   0x8000 ///< Enable fast, but inaccurate seeks for some formats
 
     /**
      * @deprecated deprecated in favor of probesize2
diff --git a/libavformat/mp3dec.c b/libavformat/mp3dec.c
index 2227428..8c17776 100644
--- a/libavformat/mp3dec.c
+++ b/libavformat/mp3dec.c
@@ -337,7 +337,7 @@ static int mp3_read_header(AVFormatContext *s)
     int i;
 
     if (mp3->usetoc < 0)
-        mp3->usetoc = 0;
+        mp3->usetoc = (s->flags & AVFMT_FLAG_FAST_SEEK) ? 0 : 2;
 
     st = avformat_new_stream(s, NULL);
     if (!st)
@@ -504,7 +504,7 @@ static int mp3_seek(AVFormatContext *s, int stream_index, int64_t timestamp,
 }
 
 static const AVOption options[] = {
-    { "usetoc", "use table of contents", offsetof(MP3DecContext, usetoc), AV_OPT_TYPE_INT, {.i64 = 2}, -1, 2, AV_OPT_FLAG_DECODING_PARAM},
+    { "usetoc", "use table of contents", offsetof(MP3DecContext, usetoc), AV_OPT_TYPE_INT, {.i64 = -1}, -1, 2, AV_OPT_FLAG_DECODING_PARAM},
     { NULL },
 };
 
diff --git a/libavformat/options_table.h b/libavformat/options_table.h
index 40f1e0a..58670b0 100644
--- a/libavformat/options_table.h
+++ b/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},
-- 
2.1.4