h264: factor out calculating the POC count into a separate file

This will allow decoupling the parser from the decoder.

1 files changed, 80 insertions, 0 deletions

diff --git a/libavcodec/h264_parse.c b/libavcodec/h264_parse.c
index bd1a50e..4ab0fde 100644
--- a/libavcodec/h264_parse.c
+++ b/libavcodec/h264_parse.c
@@ -225,3 +225,83 @@ fail:
     ref_count[1] = 0;
     return AVERROR_INVALIDDATA;
 }
+
+int ff_h264_init_poc(int pic_field_poc[2], int *pic_poc,
+                     const SPS *sps, H264POCContext *pc,
+                     int picture_structure, int nal_ref_idc)
+{
+    const int max_frame_num = 1 << sps->log2_max_frame_num;
+    int field_poc[2];
+
+    pc->frame_num_offset = pc->prev_frame_num_offset;
+    if (pc->frame_num < pc->prev_frame_num)
+        pc->frame_num_offset += max_frame_num;
+
+    if (sps->poc_type == 0) {
+        const int max_poc_lsb = 1 << sps->log2_max_poc_lsb;
+
+        if (pc->poc_lsb < pc->prev_poc_lsb &&
+            pc->prev_poc_lsb - pc->poc_lsb >= max_poc_lsb / 2)
+            pc->poc_msb = pc->prev_poc_msb + max_poc_lsb;
+        else if (pc->poc_lsb > pc->prev_poc_lsb &&
+                 pc->prev_poc_lsb - pc->poc_lsb < -max_poc_lsb / 2)
+            pc->poc_msb = pc->prev_poc_msb - max_poc_lsb;
+        else
+            pc->poc_msb = pc->prev_poc_msb;
+        field_poc[0] =
+        field_poc[1] = pc->poc_msb + pc->poc_lsb;
+        if (picture_structure == PICT_FRAME)
+            field_poc[1] += pc->delta_poc_bottom;
+    } else if (sps->poc_type == 1) {
+        int abs_frame_num, expected_delta_per_poc_cycle, expectedpoc;
+        int i;
+
+        if (sps->poc_cycle_length != 0)
+            abs_frame_num = pc->frame_num_offset + pc->frame_num;
+        else
+            abs_frame_num = 0;
+
+        if (nal_ref_idc == 0 && abs_frame_num > 0)
+            abs_frame_num--;
+
+        expected_delta_per_poc_cycle = 0;
+        for (i = 0; i < sps->poc_cycle_length; i++)
+            // FIXME integrate during sps parse
+            expected_delta_per_poc_cycle += sps->offset_for_ref_frame[i];
+
+        if (abs_frame_num > 0) {
+            int poc_cycle_cnt          = (abs_frame_num - 1) / sps->poc_cycle_length;
+            int frame_num_in_poc_cycle = (abs_frame_num - 1) % sps->poc_cycle_length;
+
+            expectedpoc = poc_cycle_cnt * expected_delta_per_poc_cycle;
+            for (i = 0; i <= frame_num_in_poc_cycle; i++)
+                expectedpoc = expectedpoc + sps->offset_for_ref_frame[i];
+        } else
+            expectedpoc = 0;
+
+        if (nal_ref_idc == 0)
+            expectedpoc = expectedpoc + sps->offset_for_non_ref_pic;
+
+        field_poc[0] = expectedpoc + pc->delta_poc[0];
+        field_poc[1] = field_poc[0] + sps->offset_for_top_to_bottom_field;
+
+        if (picture_structure == PICT_FRAME)
+            field_poc[1] += pc->delta_poc[1];
+    } else {
+        int poc = 2 * (pc->frame_num_offset + pc->frame_num);
+
+        if (!nal_ref_idc)
+            poc--;
+
+        field_poc[0] = poc;
+        field_poc[1] = poc;
+    }
+
+    if (picture_structure != PICT_BOTTOM_FIELD)
+        pic_field_poc[0] = field_poc[0];
+    if (picture_structure != PICT_TOP_FIELD)
+        pic_field_poc[1] = field_poc[1];
+    *pic_poc = FFMIN(pic_field_poc[0], pic_field_poc[1]);
+
+    return 0;
+}