1 files changed, 91 insertions, 0 deletions
diff --git a/media/libstagefright/avc_utils.cpp b/media/libstagefright/avc_utils.cpp
new file mode 100644
index 0000000..511ae12
--- /dev/null
+++ b/media/libstagefright/avc_utils.cpp
@@ -0,0 +1,91 @@
+/*
+ * Copyright (C) 2010 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "include/avc_utils.h"
+
+#include <media/stagefright/foundation/ABitReader.h>
+#include <media/stagefright/foundation/ADebug.h>
+
+namespace android {
+
+static unsigned parseUE(ABitReader *br) {
+    unsigned numZeroes = 0;
+    while (br->getBits(1) == 0) {
+        ++numZeroes;
+    }
+
+    unsigned x = br->getBits(numZeroes);
+
+    return x + (1u << numZeroes) - 1;
+}
+
+// Determine video dimensions from the sequence parameterset.
+void FindAVCDimensions(
+        const sp<ABuffer> &seqParamSet, int32_t *width, int32_t *height) {
+    ABitReader br(seqParamSet->data() + 1, seqParamSet->size() - 1);
+
+    unsigned profile_idc = br.getBits(8);
+    br.skipBits(16);
+    parseUE(&br);  // seq_parameter_set_id
+
+    if (profile_idc == 100 || profile_idc == 110
+            || profile_idc == 122 || profile_idc == 244
+            || profile_idc == 44 || profile_idc == 83 || profile_idc == 86) {
+        unsigned chroma_format_idc = parseUE(&br);
+        if (chroma_format_idc == 3) {
+            br.skipBits(1);  // residual_colour_transform_flag
+        }
+        parseUE(&br);  // bit_depth_luma_minus8
+        parseUE(&br);  // bit_depth_chroma_minus8
+        br.skipBits(1);  // qpprime_y_zero_transform_bypass_flag
+        CHECK_EQ(br.getBits(1), 0u);  // seq_scaling_matrix_present_flag
+    }
+
+    parseUE(&br);  // log2_max_frame_num_minus4
+    unsigned pic_order_cnt_type = parseUE(&br);
+
+    if (pic_order_cnt_type == 0) {
+        parseUE(&br);  // log2_max_pic_order_cnt_lsb_minus4
+    } else if (pic_order_cnt_type == 1) {
+        // offset_for_non_ref_pic, offset_for_top_to_bottom_field and
+        // offset_for_ref_frame are technically se(v), but since we are
+        // just skipping over them the midpoint does not matter.
+
+        br.getBits(1);  // delta_pic_order_always_zero_flag
+        parseUE(&br);  // offset_for_non_ref_pic
+        parseUE(&br);  // offset_for_top_to_bottom_field
+
+        unsigned num_ref_frames_in_pic_order_cnt_cycle = parseUE(&br);
+        for (unsigned i = 0; i < num_ref_frames_in_pic_order_cnt_cycle; ++i) {
+            parseUE(&br);  // offset_for_ref_frame
+        }
+    }
+
+    parseUE(&br);  // num_ref_frames
+    br.getBits(1);  // gaps_in_frame_num_value_allowed_flag
+
+    unsigned pic_width_in_mbs_minus1 = parseUE(&br);
+    unsigned pic_height_in_map_units_minus1 = parseUE(&br);
+    unsigned frame_mbs_only_flag = br.getBits(1);
+
+    *width = pic_width_in_mbs_minus1 * 16 + 16;
+
+    *height = (2 - frame_mbs_only_flag)
+        * (pic_height_in_map_units_minus1 * 16 + 16);
+}
+
+}  // namespace android
+