From 8f9ed667cdc9cc31a31d53d35cf24cc45acb892a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?St=C3=A9phane=20Cerveau?= <scerveau@igalia.com>
Date: Wed, 9 Oct 2024 13:46:17 -0400
Subject: [PATCH] h264parse: use of ceil_log2 instead of bit_storage
According to the specification:
The length of the slice_group_id[ i ] syntax element is Ceil( Log2(
num_slice_groups_minus1 + 1 ) ) bits
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/7429>
---
.../gst-libs/gst/codecparsers/gsth264parser.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/subprojects/gst-plugins-bad/gst-libs/gst/codecparsers/gsth264parser.c b/subprojects/gst-plugins-bad/gst-libs/gst/codecparsers/gsth264parser.c
index 58514b5a29..c379061a14 100644
--- a/subprojects/gst-plugins-bad/gst-libs/gst/codecparsers/gsth264parser.c
+++ b/subprojects/gst-plugins-bad/gst-libs/gst/codecparsers/gsth264parser.c
@@ -2320,7 +2320,8 @@ gst_h264_parse_pps (GstH264NalParser * nalparser, GstH264NalUnit * nalu,
gint i;
READ_UE (&nr, pps->pic_size_in_map_units_minus1);
- bits = g_bit_storage (pps->num_slice_groups_minus1);
+ /* 7.4.2.2 7-23 slice_group_id */
+ bits = gst_util_ceil_log2 (pps->num_slice_groups_minus1 + 1);
pps->slice_group_id =
g_new (guint8, pps->pic_size_in_map_units_minus1 + 1);
@@ -2600,11 +2601,12 @@ gst_h264_parser_parse_slice_hdr (GstH264NalParser * nalparser,
if (pps->num_slice_groups_minus1 > 0 &&
pps->slice_group_map_type >= 3 && pps->slice_group_map_type <= 5) {
- /* Ceil(Log2(PicSizeInMapUnits / SliceGroupChangeRate + 1)) [7-33] */
+
guint32 PicWidthInMbs = sps->pic_width_in_mbs_minus1 + 1;
guint32 PicHeightInMapUnits = sps->pic_height_in_map_units_minus1 + 1;
guint32 PicSizeInMapUnits = PicWidthInMbs * PicHeightInMapUnits;
guint32 SliceGroupChangeRate = pps->slice_group_change_rate_minus1 + 1;
+ /* Ceil(Log2(PicSizeInMapUnits / SliceGroupChangeRate + 1)) [7-35] */
const guint n =
gst_util_ceil_log2 (PicSizeInMapUnits / SliceGroupChangeRate + 1);
READ_UINT16 (&nr, slice->slice_group_change_cycle, n);