Reasonable enough
Spotify comments
----------------
Wrong duration due to not distracting padding samples.
Reported upstream: https://trac.ffmpeg.org/ticket/10163 (has patch) was
also sent as a patch to the dev mailing with subject “[FFmpeg-devel]
[PATCH v3] avformat/mp3dec: Subtract known padding from duration”
/Tomas
From 29d8147ed42ca52698ee594e42b3e7c496c3e402 Mon Sep 17 00:00:00 2001
From: Ulrik Mikaelsson <ulrik.mikaels...@gmail.com>
Date: Tue, 22 Aug 2023 13:55:14 +0200
Subject: [PATCH 14/15] avformat/mp3dec: Subtract known padding from duration
When an Info-tag is present, marking initial and trailing samples as
padding, those samples should not be included in the calculation of track
duration.
This solves a surprising user experience where converting a WAV->MP3->WAV,
ffprobe will show the duration of the mp3 as slightly longer than both the
input and the output.
As a result, the estimated duration and imprecise seek-results of some
FATE-tests have been updated.
---
libavformat/mp3dec.c | 20 ++++++++++++++------
tests/ref/fate/gapless-mp3-side-data | 4 ++--
tests/ref/seek/extra-mp3 | 8 ++++----
3 files changed, 20 insertions(+), 12 deletions(-)
diff --git a/libavformat/mp3dec.c b/libavformat/mp3dec.c
index dac91205d9..31eeb68ebb 100644
--- a/libavformat/mp3dec.c
+++ b/libavformat/mp3dec.c
@@ -52,6 +52,7 @@ typedef struct {
int usetoc;
unsigned frames; /* Total number of frames in file */
unsigned header_filesize; /* Total number of bytes in the stream */
+ unsigned frame_duration; /* Frame duration in st->time_base */
int is_cbr;
} MP3DecContext;
@@ -341,6 +342,7 @@ static int mp3_parse_vbr_tags(AVFormatContext *s, AVStream *st, int64_t base)
mp3->frames = 0;
mp3->header_filesize = 0;
+ mp3->frame_duration = av_rescale_q(spf, (AVRational){1, c.sample_rate}, st->time_base);
mp3_parse_info_tag(s, st, &c, spf);
mp3_parse_vbri_tag(s, st, base);
@@ -351,11 +353,18 @@ 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);
- if (mp3->frames)
- st->duration = av_rescale_q(mp3->frames, (AVRational){spf, c.sample_rate},
+ if (mp3->frames) {
+ int64_t full_duration_samples;
+
+ full_duration_samples = mp3->frames * (int64_t)spf;
+ st->duration = av_rescale_q(full_duration_samples - mp3->start_pad - mp3->end_pad,
+ (AVRational){1, c.sample_rate},
st->time_base);
- if (mp3->header_filesize && mp3->frames && !mp3->is_cbr)
- st->codecpar->bit_rate = av_rescale(mp3->header_filesize, 8 * c.sample_rate, mp3->frames * (int64_t)spf);
+
+ if (mp3->header_filesize && !mp3->is_cbr)
+ st->codecpar->bit_rate = av_rescale(mp3->header_filesize, 8 * c.sample_rate,
+ full_duration_samples);
+ }
return 0;
}
@@ -586,8 +595,7 @@ static int mp3_seek(AVFormatContext *s, int stream_index, int64_t timestamp,
return best_pos;
if (mp3->is_cbr && ie == &ie1 && mp3->frames && mp3->header_filesize > 0) {
- int frame_duration = av_rescale(st->duration, 1, mp3->frames);
- ie1.timestamp = frame_duration * av_rescale(best_pos - si->data_offset, mp3->frames, mp3->header_filesize);
+ ie1.timestamp = mp3->frame_duration * av_rescale(best_pos - si->data_offset, mp3->frames, mp3->header_filesize);
}
avpriv_update_cur_dts(s, st, ie->timestamp);
diff --git a/tests/ref/fate/gapless-mp3-side-data b/tests/ref/fate/gapless-mp3-side-data
index 49ebc32dc8..878425f092 100644
--- a/tests/ref/fate/gapless-mp3-side-data
+++ b/tests/ref/fate/gapless-mp3-side-data
@@ -593,5 +593,5 @@ packet|codec_type=audio|stream_index=0|pts=217866240|pts_time=15.438367|dts=2178
packet|codec_type=audio|stream_index=0|pts=218234880|pts_time=15.464490|dts=218234880|dts_time=15.464490|duration=368640|duration_time=0.026122|size=418|pos=248882|flags=K__|data_hash=CRC32:fbc83c3c
packet|codec_type=audio|stream_index=0|pts=218603520|pts_time=15.490612|dts=218603520|dts_time=15.490612|duration=368640|duration_time=0.026122|size=418|pos=249300|flags=K__|data_hash=CRC32:d5fb5f9c|side_datum/skip_samples:side_data_type=Skip Samples|side_datum/skip_samples:skip_samples=0|side_datum/skip_samples:discard_padding=303|side_datum/skip_samples:skip_reason=0|side_datum/skip_samples:discard_reason=0
packet|codec_type=audio|stream_index=0|pts=218972160|pts_time=15.516735|dts=218972160|dts_time=15.516735|duration=368640|duration_time=0.026122|size=418|pos=249718|flags=K__|data_hash=CRC32:3789f3cf|side_datum/skip_samples:side_data_type=Skip Samples|side_datum/skip_samples:skip_samples=0|side_datum/skip_samples:discard_padding=1152|side_datum/skip_samples:skip_reason=0|side_datum/skip_samples:discard_reason=0
-stream|index=0|codec_name=mp3|profile=unknown|codec_type=audio|codec_tag_string=[0][0][0][0]|codec_tag=0x0000|sample_fmt=fltp|sample_rate=44100|channels=2|channel_layout=stereo|bits_per_sample=0|initial_padding=0|id=N/A|r_frame_rate=0/0|avg_frame_rate=0/0|time_base=1/14112000|start_pts=353600|start_time=0.025057|duration_ts=219340800|duration=15.542857|bit_rate=128000|max_bit_rate=N/A|bits_per_raw_sample=N/A|nb_frames=N/A|nb_read_frames=N/A|nb_read_packets=595|disposition:default=0|disposition:dub=0|disposition:original=0|disposition:comment=0|disposition:lyrics=0|disposition:karaoke=0|disposition:forced=0|disposition:hearing_impaired=0|disposition:visual_impaired=0|disposition:clean_effects=0|disposition:attached_pic=0|disposition:timed_thumbnails=0|disposition:non_diegetic=0|disposition:captions=0|disposition:descriptions=0|disposition:metadata=0|disposition:dependent=0|disposition:still_image=0|disposition:multilayer=0|tag:encoder=LAME3.93
-format|filename=gapless.mp3|nb_streams=1|nb_programs=0|nb_stream_groups=0|format_name=mp3|start_time=0.025057|duration=15.542857|size=250264|bit_rate=128812|probe_score=51|tag:title=test
+stream|index=0|codec_name=mp3|profile=unknown|codec_type=audio|codec_tag_string=[0][0][0][0]|codec_tag=0x0000|sample_fmt=fltp|sample_rate=44100|channels=2|channel_layout=stereo|bits_per_sample=0|initial_padding=0|id=N/A|r_frame_rate=0/0|avg_frame_rate=0/0|time_base=1/14112000|start_pts=353600|start_time=0.025057|duration_ts=218521600|duration=15.484807|bit_rate=128000|max_bit_rate=N/A|bits_per_raw_sample=N/A|nb_frames=N/A|nb_read_frames=N/A|nb_read_packets=595|disposition:default=0|disposition:dub=0|disposition:original=0|disposition:comment=0|disposition:lyrics=0|disposition:karaoke=0|disposition:forced=0|disposition:hearing_impaired=0|disposition:visual_impaired=0|disposition:clean_effects=0|disposition:attached_pic=0|disposition:timed_thumbnails=0|disposition:non_diegetic=0|disposition:captions=0|disposition:descriptions=0|disposition:metadata=0|disposition:dependent=0|disposition:still_image=0|disposition:multilayer=0|tag:encoder=LAME3.93
+format|filename=gapless.mp3|nb_streams=1|nb_programs=0|nb_stream_groups=0|format_name=mp3|start_time=0.025057|duration=15.484807|size=250264|bit_rate=129295|probe_score=51|tag:title=test
diff --git a/tests/ref/seek/extra-mp3 b/tests/ref/seek/extra-mp3
index fdfb1a7c66..ec5947a9d5 100644
--- a/tests/ref/seek/extra-mp3
+++ b/tests/ref/seek/extra-mp3
@@ -8,11 +8,11 @@ ret: 0 st: 0 flags:1 dts: 0.809796 pts: 0.809796 pos: 14407 size: 418
ret: 0 st: 0 flags:1 ts:-0.317499
ret: 0 st: 0 flags:1 dts: 0.000000 pts: 0.000000 pos: 1451 size: 417
ret: 0 st:-1 flags:0 ts: 2.576668
-ret: 0 st: 0 flags:1 dts: 2.586122 pts: 2.586122 pos: 42828 size: 418
+ret: 0 st: 0 flags:1 dts: 2.612245 pts: 2.612245 pos: 43246 size: 418
ret: 0 st:-1 flags:1 ts: 1.470835
ret: 0 st: 0 flags:1 dts: 1.462857 pts: 1.462857 pos: 24856 size: 418
ret: 0 st: 0 flags:0 ts: 0.365002
-ret: 0 st: 0 flags:1 dts: 0.365714 pts: 0.365714 pos: 7302 size: 418
+ret: 0 st: 0 flags:1 dts: 0.391837 pts: 0.391837 pos: 7720 size: 418
ret: 0 st: 0 flags:1 ts:-0.740831
ret: 0 st: 0 flags:1 dts: 0.000000 pts: 0.000000 pos: 1451 size: 417
ret: 0 st:-1 flags:0 ts: 2.153336
@@ -22,11 +22,11 @@ ret: 0 st: 0 flags:1 dts: 1.044898 pts: 1.044898 pos: 18169 size: 418
ret: 0 st: 0 flags:0 ts:-0.058330
ret: 0 st: 0 flags:1 dts: 0.000000 pts: 0.000000 pos: 1451 size: 417
ret: 0 st: 0 flags:1 ts: 2.835837
-ret: 0 st: 0 flags:1 dts: 2.821224 pts: 2.821224 pos: 46590 size: 418
+ret: 0 st: 0 flags:1 dts: 2.847347 pts: 2.847347 pos: 47008 size: 418
ret: 0 st:-1 flags:0 ts: 1.730004
ret: 0 st: 0 flags:1 dts: 1.750204 pts: 1.750204 pos: 29454 size: 418
ret: 0 st:-1 flags:1 ts: 0.624171
-ret: 0 st: 0 flags:1 dts: 0.600816 pts: 0.600816 pos: 11064 size: 418
+ret: 0 st: 0 flags:1 dts: 0.626939 pts: 0.626939 pos: 11482 size: 418
ret: 0 st: 0 flags:0 ts:-0.481662
ret: 0 st: 0 flags:1 dts: 0.000000 pts: 0.000000 pos: 1451 size: 417
ret: 0 st: 0 flags:1 ts: 2.412505
--
2.39.2
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