Fixed encode of trailing B frames
In case a P frame was marked as the last frame to encode, the B frames
previous to it in the same gop were not getting encoded. This is fixed now.
Change-Id: I871f2a1d52b8db9ee75426b00287b58203586f23
diff --git a/encoder/ih264e_utils.c b/encoder/ih264e_utils.c
index b339143..2e5b812 100644
--- a/encoder/ih264e_utils.c
+++ b/encoder/ih264e_utils.c
@@ -347,6 +347,86 @@
ps_enc_buff->pv_pic_info = ps_inp_buf->pv_pic_info;
ps_enc_buff->u4_pic_info_type = ps_inp_buf->u4_pic_info_type;
+ /* Special case for encoding trailing B frames
+ *
+ * In encoding streams with B frames it may happen that we have a B frame
+ * at the end without a P/I frame after it. Hence when we are dequeing from
+ * the RC, it will return the P frame [next in display order but before in
+ * encoding order] first. Since the dequeue happens for an invalid frame we
+ * will get a frame with null buff and set u4_is_last. Hence lib with return
+ * last frame flag at this point and will stop encoding.
+ *
+ * Since for the last B frame, we does not have the forward ref frame
+ * it makes sense to force it into P.
+ *
+ * To solve this, in case the current frame is P and if the last frame flag
+ * is set, we need to see if there is and pending B frames. If there are any,
+ * we should just encode that picture as the current P frame and set
+ * that B frame as the last frame. Hence the encoder will terminate naturally
+ * once that B-frame is encoded after all the in between frames.
+ *
+ * Since we cannot touch RC stack directly, the option of actually swapping
+ * frames in RC is ruled out. We have to modify the as_inp_list to simulate
+ * such a behavior by RC. We can do that by
+ * 1) Search through as_inp_list to locate the largest u4_timestamp_low less
+ * than current u4_timestamp_low. This will give us the last B frame before
+ * the current P frame. Note that this will handle pre encode skip too since
+ * queue happens after pre enc skip.
+ * 2) Swap the position in as_inp_list. Hence now the last B frame is
+ * encoded as P frame. And the new last B frame will have u4_is_last
+ * set so that encoder will end naturally once we reached that B frame
+ * or any subsequent frame. Also the current GOP will have 1 less B frame
+ * Since we are swapping, the poc will also be in-order.
+ * 3) In case we have an IPP stream, the result of our search will be an
+ * I/P frame which is already encoded. Thus swap and encode will result
+ * in encoding of duplicate frames. Hence to avoid this we will only
+ * have this work around in case of u4_num_bframes > 0.
+ *
+ * In case we have forced an I/IDR frame In between this P frame and
+ * the last B frame -> This cannot happen as the current P frame is
+ * supposed to have u4_is_last set. Thus forcing an I/ IDR after this
+ * is illogical.
+ *
+ * In cae if we have forced an I such that the frame just before last frame
+ * in is I/P -> This case will never arise. Since we have a closed GOP now,
+ * once we force an I, the gop gets reset, hence there will be a B between
+ * I/P and I/P.
+ */
+ if (ps_enc_buff->u4_is_last && (ps_codec->pic_type == PIC_P)
+ && ps_codec->s_cfg.u4_num_bframes && (ps_codec->i4_poc > 1))
+ {
+ UWORD32 u4_cntr, u4_lst_bframe;
+ inp_buf_t *ps_swap_buff, *ps_inp_list, *ps_cur_pic;
+
+ u4_cntr = (u4_pic_id + 1) % MAX_NUM_BFRAMES;
+ u4_lst_bframe = u4_pic_id ? ((u4_pic_id - 1) % MAX_NUM_BFRAMES) : (MAX_NUM_BFRAMES - 1);
+
+ ps_inp_list = &ps_codec->as_inp_list[0];
+ ps_cur_pic = &ps_inp_list[u4_pic_id % MAX_NUM_BFRAMES];
+
+ /* Now search the pic in most recent past to current frame */
+ for(; u4_cntr != (u4_pic_id % MAX_NUM_BFRAMES);
+ u4_cntr = ((u4_cntr + 1) % MAX_NUM_BFRAMES))
+ {
+ if ( (ps_inp_list[u4_cntr].u4_timestamp_low <= ps_cur_pic->u4_timestamp_low) &&
+ (ps_inp_list[u4_cntr].u4_timestamp_high <= ps_cur_pic->u4_timestamp_high) &&
+ (ps_inp_list[u4_cntr].u4_timestamp_low >= ps_inp_list[u4_lst_bframe].u4_timestamp_low) &&
+ (ps_inp_list[u4_cntr].u4_timestamp_high >= ps_inp_list[u4_lst_bframe].u4_timestamp_high))
+ {
+ u4_lst_bframe = u4_cntr;
+ }
+ }
+
+ ps_swap_buff = &(ps_codec->as_inp_list[u4_lst_bframe]);
+
+ /* copy the last B buffer to output */
+ *ps_enc_buff = *ps_swap_buff;
+
+ /* Store the current buf into the queue in place of last B buf */
+ *ps_swap_buff = *ps_inp_buf;
+
+ }
+
if (ps_enc_buff->u4_is_last)
{
ps_codec->pic_type = PIC_NA;
