From 29d8cd265a536063420afe78375b2176a9e1abc5 Mon Sep 17 00:00:00 2001
From: Alexander Kojevnikov <alexander@kojevnikov.com>
Date: Tue, 26 Feb 2013 21:47:11 -0800
Subject: [PATCH] mp3dec: Fix VBR bit rate parsing

When parsing the Xing/Info tag, don't set the bit rate if it's an Info tag.

When parsing the stream, don't override the bit rate if it's already set,
otherwise calculate the mean bit rate from parsed frames. This way, the bit
rate will be set correctly both for CBR and VBR streams.

Signed-off-by: Alexander Kojevnikov <alexander@kojevnikov.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
---
 libavcodec/mpegaudio_parser.c | 10 +++++++---
 libavformat/mp3dec.c          |  6 ++++--
 tests/ref/lavf-fate/mp3       |  4 ++--
 3 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/libavcodec/mpegaudio_parser.c b/libavcodec/mpegaudio_parser.c
index 5f97d711c6..bb4d75c066 100644
--- a/libavcodec/mpegaudio_parser.c
+++ b/libavcodec/mpegaudio_parser.c
@@ -30,6 +30,7 @@ typedef struct MpegAudioParseContext {
     int frame_size;
     uint32_t header;
     int header_count;
+    int no_bitrate;
 } MpegAudioParseContext;
 
 #define MPA_HEADER_SIZE 4
@@ -74,15 +75,18 @@ static int mpegaudio_parse(AVCodecParserContext *s1,
                     if((state&SAME_HEADER_MASK) != (s->header&SAME_HEADER_MASK) && s->header)
                         s->header_count= -3;
                     s->header= state;
-                    s->header_count++;
                     s->frame_size = ret-4;
 
-                    if (s->header_count > 1) {
+                    if (s->header_count > 0) {
                         avctx->sample_rate= sr;
                         avctx->channels   = channels;
                         s1->duration      = frame_size;
-                        avctx->bit_rate   = bit_rate;
+                        if (s->no_bitrate || !avctx->bit_rate) {
+                            s->no_bitrate = 1;
+                            avctx->bit_rate += (bit_rate - avctx->bit_rate) / s->header_count;
+                        }
                     }
+                    s->header_count++;
                     break;
                 }
             }
diff --git a/libavformat/mp3dec.c b/libavformat/mp3dec.c
index c6d6987eaa..57e4ba33b1 100644
--- a/libavformat/mp3dec.c
+++ b/libavformat/mp3dec.c
@@ -120,6 +120,7 @@ static int mp3_parse_vbr_tags(AVFormatContext *s, AVStream *st, int64_t base)
     const int64_t xing_offtbl[2][2] = {{32, 17}, {17,9}};
     MPADecodeHeader c;
     int vbrtag_size = 0;
+    int is_cbr;
 
     v = avio_rb32(s->pb);
     if(ff_mpa_check_header(v) < 0)
@@ -135,7 +136,8 @@ static int mp3_parse_vbr_tags(AVFormatContext *s, AVStream *st, int64_t base)
     /* Check for Xing / Info tag */
     avio_skip(s->pb, xing_offtbl[c.lsf == 1][c.nb_channels == 1]);
     v = avio_rb32(s->pb);
-    if(v == MKBETAG('X', 'i', 'n', 'g') || v == MKBETAG('I', 'n', 'f', 'o')) {
+    is_cbr = v == MKBETAG('I', 'n', 'f', 'o');
+    if (v == MKBETAG('X', 'i', 'n', 'g') || is_cbr) {
         v = avio_rb32(s->pb);
         if(v & XING_FLAG_FRAMES)
             frames = avio_rb32(s->pb);
@@ -180,7 +182,7 @@ static int mp3_parse_vbr_tags(AVFormatContext *s, AVStream *st, int64_t base)
     if(frames)
         st->duration = av_rescale_q(frames, (AVRational){spf, c.sample_rate},
                                     st->time_base);
-    if(size && frames)
+    if (size && frames && !is_cbr)
         st->codec->bit_rate = av_rescale(size, 8 * c.sample_rate, frames * (int64_t)spf);
 
     return 0;
diff --git a/tests/ref/lavf-fate/mp3 b/tests/ref/lavf-fate/mp3
index 91e2b48c03..361314b2ca 100644
--- a/tests/ref/lavf-fate/mp3
+++ b/tests/ref/lavf-fate/mp3
@@ -1,3 +1,3 @@
-40a4e41ae74ec8dacdf02402831a6a58 *./tests/data/lavf-fate/lavf.mp3
-97230 ./tests/data/lavf-fate/lavf.mp3
+7fcf80c2059b5c058a6cdd2e2f798b6c *./tests/data/lavf-fate/lavf.mp3
+96366 ./tests/data/lavf-fate/lavf.mp3
 ./tests/data/lavf-fate/lavf.mp3 CRC=0x6c9850fe