From 50d1f4437be88a4b7e412e90d71153cae68017cc Mon Sep 17 00:00:00 2001
From: Anton Khirnov <anton@khirnov.net>
Date: Sun, 2 Sep 2012 15:36:18 +0200
Subject: mp3dec: read Xing frame TOC index

---
 libavformat/mp3dec.c | 58 +++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 57 insertions(+), 1 deletion(-)

(limited to 'libavformat/mp3dec.c')

diff --git a/libavformat/mp3dec.c b/libavformat/mp3dec.c
index ffc1c35a60..7d0c2fb6ed 100644
--- a/libavformat/mp3dec.c
+++ b/libavformat/mp3dec.c
@@ -31,6 +31,9 @@
 
 #define XING_FLAG_FRAMES 0x01
 #define XING_FLAG_SIZE   0x02
+#define XING_FLAG_TOC    0x04
+
+#define XING_TOC_COUNT 100
 
 /* mp3 read */
 
@@ -94,6 +97,26 @@ static int mp3_read_probe(AVProbeData *p)
 //mpegps_mp3_unrecognized_format.mpg has max_frames=3
 }
 
+static void read_xing_toc(AVFormatContext *s, int64_t filesize, int64_t duration)
+{
+    int i;
+
+    if (!filesize &&
+        !(filesize = avio_size(s->pb))) {
+        av_log(s, AV_LOG_WARNING, "Cannot determine file size, skipping TOC table.\n");
+        return;
+    }
+
+    for (i = 0; i < XING_TOC_COUNT; i++) {
+        uint8_t b = avio_r8(s->pb);
+
+        av_add_index_entry(s->streams[0],
+                           av_rescale(b, filesize, 256),
+                           av_rescale(i, duration, XING_TOC_COUNT),
+                           0, 0, AVINDEX_KEYFRAME);
+    }
+}
+
 /**
  * Try to find Xing/Info/VBRI tags and compute duration from info therein
  */
@@ -115,6 +138,8 @@ static int mp3_parse_vbr_tags(AVFormatContext *s, AVStream *st, int64_t base)
     if(c.layer != 3)
         return -1;
 
+    spf = c.lsf ? 576 : 1152; /* Samples per frame, layer 3 */
+
     /* Check for Xing / Info tag */
     avio_skip(s->pb, xing_offtbl[c.lsf == 1][c.nb_channels == 1]);
     v = avio_rb32(s->pb);
@@ -124,6 +149,9 @@ static int mp3_parse_vbr_tags(AVFormatContext *s, AVStream *st, int64_t base)
             frames = avio_rb32(s->pb);
         if(v & XING_FLAG_SIZE)
             size = avio_rb32(s->pb);
+        if (v & XING_FLAG_TOC && frames)
+            read_xing_toc(s, size, av_rescale_q(frames, (AVRational){spf, c.sample_rate},
+                                    st->time_base));
     }
 
     /* Check for VBRI tag (always 32 bytes after end of mpegaudio header) */
@@ -145,7 +173,6 @@ static int mp3_parse_vbr_tags(AVFormatContext *s, AVStream *st, int64_t base)
     /* Skip the vbr tag frame */
     avio_seek(s->pb, base + vbrtag_size, SEEK_SET);
 
-    spf = c.lsf ? 576 : 1152; /* Samples per frame, layer 3 */
     if(frames)
         st->duration = av_rescale_q(frames, (AVRational){spf, c.sample_rate},
                                     st->time_base);
@@ -206,12 +233,41 @@ static int mp3_read_packet(AVFormatContext *s, AVPacket *pkt)
     return ret;
 }
 
+static int mp3_seek(AVFormatContext *s, int stream_index, int64_t timestamp,
+                    int flags)
+{
+    AVIndexEntry *ie;
+    AVStream *st = s->streams[0];
+    int64_t ret  = av_index_search_timestamp(st, timestamp, flags);
+    uint32_t header = 0;
+
+    if (ret < 0)
+        return ret;
+
+    ie = &st->index_entries[ret];
+    ret = avio_seek(s->pb, ie->pos, SEEK_SET);
+    if (ret < 0)
+        return ret;
+
+    while (!s->pb->eof_reached) {
+        header = (header << 8) + avio_r8(s->pb);
+        if (ff_mpa_check_header(header) >= 0) {
+            ff_update_cur_dts(s, st, ie->timestamp);
+            ret = avio_seek(s->pb, -4, SEEK_CUR);
+            return (ret >= 0) ? 0 : ret;
+        }
+    }
+
+    return AVERROR_EOF;
+}
+
 AVInputFormat ff_mp3_demuxer = {
     .name           = "mp3",
     .long_name      = NULL_IF_CONFIG_SMALL("MP2/3 (MPEG audio layer 2/3)"),
     .read_probe     = mp3_read_probe,
     .read_header    = mp3_read_header,
     .read_packet    = mp3_read_packet,
+    .read_seek      = mp3_seek,
     .flags          = AVFMT_GENERIC_INDEX,
     .extensions     = "mp2,mp3,m2a", /* XXX: use probe */
 };
-- 
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