[FFmpeg-devel] [PATCH 3/3] lavf/mp3dec: read encoder delay/padding from Info tag

[Jon Toohill]

Muxers can check AVCodecParameters.initial_padding for the
encoder+decoder delay, and read the AV_PKT_DATA_SKIP_SAMPLES
side data from the last packet for the encoder padding.

This change also fixes the first_discard_sample calculation
which erroneously included the decoder delay. Decoder delay
is already accounted for in st->skip_samples. The affected
FATE tests have been updated accordingly.
---
 libavformat/mp3dec.c                 |  3 ++-
 tests/ref/fate/audiomatch-square-mp3 |  2 +-
 tests/ref/fate/gapless-mp3           | 10 +++++-----
 3 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/libavformat/mp3dec.c b/libavformat/mp3dec.c
index 56c7f8c..e8b2428 100644
--- a/libavformat/mp3dec.c
+++ b/libavformat/mp3dec.c
@@ -239,9 +239,10 @@ static void mp3_parse_info_tag(AVFormatContext *s, AVStream *st,
 
         mp3->start_pad = v>>12;
         mp3->  end_pad = v&4095;
+        st->codecpar->initial_padding = mp3->start_pad + 528 + 1;
         st->start_skip_samples = mp3->start_pad + 528 + 1;
         if (mp3->frames) {
-            st->first_discard_sample = -mp3->end_pad + 528 + 1 + mp3->frames * (int64_t)spf;
+            st->first_discard_sample = -mp3->end_pad + mp3->frames * (int64_t)spf;
             st->last_discard_sample = mp3->frames * (int64_t)spf;
         }
         if (!st->start_time)
diff --git a/tests/ref/fate/audiomatch-square-mp3 b/tests/ref/fate/audiomatch-square-mp3
index 8de55c2..05176a0 100644
--- a/tests/ref/fate/audiomatch-square-mp3
+++ b/tests/ref/fate/audiomatch-square-mp3
@@ -1 +1 @@
-presig: 0 postsig:0 c: 0.9447 lenerr:0
+presig: 0 postsig:-529 c: 0.9334 lenerr:-529
diff --git a/tests/ref/fate/gapless-mp3 b/tests/ref/fate/gapless-mp3
index ebe7bfa..8b80bfc 100644
--- a/tests/ref/fate/gapless-mp3
+++ b/tests/ref/fate/gapless-mp3
@@ -1,5 +1,5 @@
-37534a3bcc3ef306e8c5ebfcfedfc41c *tests/data/fate/gapless-mp3.out-1
-c96c3ae7bd3300fd2f4debac222de5b7
-0cd1cdbcfd5cdbf6270cd98219bf31cd *tests/data/fate/gapless-mp3.out-2
-c96c3ae7bd3300fd2f4debac222de5b7
-9d3d8ba8a61b534f2d02ee648d6a8229 *tests/data/fate/gapless-mp3.out-3
+81695be427d45e8be4d527a6b2af2a85 *tests/data/fate/gapless-mp3.out-1
+c7879a827ab017364774069268d9a267
+62d074296f8c84a5f86a6afdd7bab459 *tests/data/fate/gapless-mp3.out-2
+c7879a827ab017364774069268d9a267
+e931f3fe1ba25e0d5eece4977c4061a9 *tests/data/fate/gapless-mp3.out-3
-- 
2.8.0.rc3.226.g39d4020