From 15aeb1f5cc5bf5c4925897d5ae54d2b350822790 Mon Sep 17 00:00:00 2001
From: Andre Noll <maan@tuebingen.mpg.de>
Date: Wed, 11 Aug 2021 15:41:37 +0200
Subject: [PATCH] mp4: Introduce mp4ff_get_duration().

This allows us to get rid of an ugly hack in aac_afh.c where we peeked
at the audio-specific config structure to get the scaling factor which
was needed to compute the duration.
---
 aac_afh.c | 18 ++++++++----------
 mp4.c     | 19 ++++++++++++++++++-
 mp4.h     |  1 +
 3 files changed, 27 insertions(+), 11 deletions(-)

diff --git a/aac_afh.c b/aac_afh.c
index dd9247d7..15e338e5 100644
--- a/aac_afh.c
+++ b/aac_afh.c
@@ -24,7 +24,6 @@ struct aac_afh_context {
 	size_t fpos;
 	int32_t track;
 	struct mp4ff *mp4ff;
-	mp4AudioSpecificConfig masc;
 	struct mp4ff_callback cb;
 };
 
@@ -50,7 +49,7 @@ static uint32_t aac_afh_seek_cb(void *user_data, uint64_t pos)
 	return 0;
 }
 
-static int32_t aac_afh_get_track(struct mp4ff *mp4ff, mp4AudioSpecificConfig *masc)
+static int32_t aac_afh_get_track(struct mp4ff *mp4ff)
 {
 	int32_t i, rc, num_tracks = mp4ff_total_tracks(mp4ff);
 
@@ -61,7 +60,8 @@ static int32_t aac_afh_get_track(struct mp4ff *mp4ff, mp4AudioSpecificConfig *ma
 
 		mp4ff_get_decoder_config(mp4ff, i, &buf, &buf_size);
 		if (buf) {
-			rc = NeAACDecAudioSpecificConfig(buf, buf_size, masc);
+			mp4AudioSpecificConfig masc;
+			rc = NeAACDecAudioSpecificConfig(buf, buf_size, &masc);
 			free(buf);
 			if (rc < 0)
 				continue;
@@ -87,7 +87,7 @@ static int aac_afh_open(const void *map, size_t mapsize, void **afh_context)
 	c->mp4ff = mp4ff_open_read(&c->cb);
 	if (!c->mp4ff)
 		goto free_ctx;
-	c->track = aac_afh_get_track(c->mp4ff, &c->masc);
+	c->track = aac_afh_get_track(c->mp4ff);
 	ret = -E_MP4FF_TRACK;
 	if (c->track < 0)
 		goto close_mp4ff;
@@ -145,7 +145,7 @@ static int aac_get_file_info(char *map, size_t numbytes, __a_unused int fd,
 	int ret;
 	int32_t rv;
 	struct aac_afh_context *c;
-	int64_t tmp;
+	uint64_t milliseconds;
 	const char *buf;
 	uint32_t n, len;
 
@@ -176,11 +176,9 @@ static int aac_get_file_info(char *map, size_t numbytes, __a_unused int fd,
 			break;
 		afhi->max_chunk_size = PARA_MAX(afhi->max_chunk_size, len);
 	}
-
-	tmp = c->masc.sbr_present_flag == 1? 2048 : 1024;
-	afhi->seconds_total = tmp * afhi->chunks_total / afhi->frequency;
-	ms2tv(1000 * tmp / afhi->frequency, &afhi->chunk_tv);
-
+	milliseconds = mp4ff_get_duration(c->mp4ff, c->track);
+	afhi->seconds_total = milliseconds / 1000;
+	ms2tv(milliseconds / afhi->chunks_total, &afhi->chunk_tv);
 	if (aac_afh_get_chunk(0, c, &buf, &len) >= 0)
 		numbytes -= buf - map;
 	afhi->bitrate = 8 * numbytes / afhi->seconds_total / 1000;
diff --git a/mp4.c b/mp4.c
index 548f78ec..46aec2db 100644
--- a/mp4.c
+++ b/mp4.c
@@ -765,7 +765,6 @@ static int32_t tag_add_field(struct mp4ff_metadata *tags, const char *item,
 {
 	if (!item || (item && !*item) || !value)
 		return 0;
-
 	tags->tags = para_realloc(tags->tags,
 		(tags->count + 1) * sizeof(struct mp4ff_tag));
 	tags->tags[tags->count].item = para_strdup(item);
@@ -1408,6 +1407,24 @@ static int32_t sample_to_offset(const struct mp4ff *f, int32_t track,
 	return chunk_offset2;
 }
 
+/**
+ * Return the number of milliseconds of the given track.
+ *
+ * \param f As returned by \ref mp4ff_open_read(), must not be NULL.
+ * \param track Between zero and the value returned by \ref mp4ff_total_tracks().
+ *
+ * The function returns zero if the audio file is of zero length or contains a
+ * corrupt track header.
+ */
+uint64_t mp4ff_get_duration(const struct mp4ff *f, int32_t track)
+{
+	const struct mp4ff_track *t = f->track[track];
+
+	if (t->timeScale == 0)
+		return 0;
+	return t->duration * 1000 / t->timeScale;
+}
+
 void mp4ff_set_sample_position(struct mp4ff *f, int32_t track, int32_t sample)
 {
 	int32_t offset = sample_to_offset(f, track, sample);
diff --git a/mp4.h b/mp4.h
index 8cd08ccf..ecab89b3 100644
--- a/mp4.h
+++ b/mp4.h
@@ -30,6 +30,7 @@ int32_t mp4ff_get_sample_size(const struct mp4ff *f, int track, int sample);
 uint32_t mp4ff_get_sample_rate(const struct mp4ff *f, int32_t track);
 uint32_t mp4ff_get_channel_count(const struct mp4ff * f, int32_t track);
 int32_t mp4ff_num_samples(const struct mp4ff *f, int track);
+uint64_t mp4ff_get_duration(const struct mp4ff *f, int32_t track);
 struct mp4ff *mp4ff_open_read_metaonly(struct mp4ff_callback *f);
 
 int mp4ff_meta_get_by_index(const struct mp4ff *f, unsigned int index,
-- 
2.39.5