From: Andre Noll <maan@tuebingen.mpg.de>
Date: Wed, 18 Aug 2021 21:15:07 +0000 (+0200)
Subject: mp4: Simplify chunk_of_sample().
X-Git-Tag: v0.7.1~7^2~50
X-Git-Url: http://git.tue.mpg.de/?a=commitdiff_plain;h=623699153a7718e29d6571a9fea1b96244813ef9;p=paraslash.git

mp4: Simplify chunk_of_sample().

This function was unnecessarily complex. The equivalent replacement
code is much shorter and easier to read. Besides reducing the number
of local variables, we drop the chunk_sample parameter and return
this number via the return value of the function.
---

diff --git a/mp4.c b/mp4.c
index 1c20d89f..71858305 100644
--- a/mp4.c
+++ b/mp4.c
@@ -981,46 +981,24 @@ void mp4_close(struct mp4 *f)
 }
 
 static int32_t chunk_of_sample(const struct mp4 *f, int32_t track,
-		int32_t sample, int32_t *chunk_sample, int32_t *chunk)
+		int32_t sample, int32_t *chunk)
 {
-	int32_t total_entries = 0;
-	int32_t chunk2entry;
-	int32_t chunk1, chunk2, chunk1samples, range_samples, total = 0;
-
-	*chunk_sample = 0;
-	*chunk = 1;
-
-	total_entries = f->track[track]->stsc_entry_count;
-
-	chunk1 = 1;
-	chunk1samples = 0;
-	chunk2entry = 0;
-
-	do {
-		chunk2 = f->track[track]->stsc_first_chunk[chunk2entry];
-		*chunk = chunk2 - chunk1;
-		range_samples = *chunk * chunk1samples;
+	const struct mp4_track *t = f->track[track];
+	uint32_t *fc = t->stsc_first_chunk, *spc = t->stsc_samples_per_chunk;
+	int32_t chunk1, chunk1samples, n, total, i;
 
-		if (sample < total + range_samples)
+	for (i = 1, total = 0; i < t->stsc_entry_count; i++, total += n) {
+		n = (fc[i] - fc[i - 1]) * spc[i - 1]; /* number of samples */
+		if (sample < total + n)
 			break;
-
-		chunk1samples = f->track[track]->stsc_samples_per_chunk[chunk2entry];
-		chunk1 = chunk2;
-
-		if (chunk2entry < total_entries) {
-			chunk2entry++;
-			total += range_samples;
-		}
-	} while (chunk2entry < total_entries);
-
-	if (chunk1samples)
+	}
+	chunk1 = fc[i - 1];
+	chunk1samples = spc[i - 1];
+	if (chunk1samples != 0)
 		*chunk = (sample - total) / chunk1samples + chunk1;
 	else
 		*chunk = 1;
-
-	*chunk_sample = total + (*chunk - chunk1) * chunk1samples;
-
-	return 0;
+	return total + (*chunk - chunk1) * chunk1samples;
 }
 
 /**
@@ -1068,7 +1046,7 @@ int mp4_set_sample_position(struct mp4 *f, uint32_t track, int32_t sample)
 
 	if (sample >= t->stsz_sample_count || track >= f->total_tracks)
 		return -ERRNO_TO_PARA_ERROR(EINVAL);
-	chunk_of_sample(f, track, sample, &chunk_sample, &chunk);
+	chunk_sample = chunk_of_sample(f, track, sample, &chunk);
 	if (t->stsz_sample_size > 0)
 		srs = (sample - chunk_sample) * t->stsz_sample_size;
 	else {