avcodec/hevc: Track long and short term RPS size for VDPAU

Today, we track the short term RPS size for DXVA, but only if the
SliceHeader RPS is being used. Otherwise it's left uninitialized.

NVIDIA's VDPAU implementation requires that the size be accurately
tracked even if an SPS RPS is being used. In this case, it's really
counting the size of the RPS idx information, but you end up with
mangled output if the value is not accurate.

VDPAU also needs the size of the long term RPS.
Signed-off-by: Philip Langdale <philipl@overt.org>

libavcodec/hevc.c

@@ -502,7 +502,7 @@ static int hls_slice_header(HEVCContext *s)
             sh->colour_plane_id = get_bits(gb, 2);
 
         if (!IS_IDR(s)) {
-            int poc;
+            int poc, pos;
 
             sh->pic_order_cnt_lsb = get_bits(gb, s->sps->log2_max_poc_lsb);
             poc = ff_hevc_compute_poc(s, sh->pic_order_cnt_lsb);
@@ -516,13 +516,12 @@ static int hls_slice_header(HEVCContext *s)
             s->poc = poc;
 
             sh->short_term_ref_pic_set_sps_flag = get_bits1(gb);
+            pos = get_bits_left(gb);
             if (!sh->short_term_ref_pic_set_sps_flag) {
-                int pos = get_bits_left(gb);
                 ret = ff_hevc_decode_short_term_rps(s, &sh->slice_rps, s->sps, 1);
                 if (ret < 0)
                     return ret;
 
-                sh->short_term_ref_pic_set_size = pos - get_bits_left(gb);
                 sh->short_term_rps = &sh->slice_rps;
             } else {
                 int numbits, rps_idx;
@@ -536,13 +535,16 @@ static int hls_slice_header(HEVCContext *s)
                 rps_idx = numbits > 0 ? get_bits(gb, numbits) : 0;
                 sh->short_term_rps = &s->sps->st_rps[rps_idx];
             }
+            sh->short_term_ref_pic_set_size = pos - get_bits_left(gb);
 
+            pos = get_bits_left(gb);
             ret = decode_lt_rps(s, &sh->long_term_rps, gb);
             if (ret < 0) {
                 av_log(s->avctx, AV_LOG_WARNING, "Invalid long term RPS.\n");
                 if (s->avctx->err_recognition & AV_EF_EXPLODE)
                     return AVERROR_INVALIDDATA;
             }
+            sh->long_term_ref_pic_set_size = pos - get_bits_left(gb);
 
             if (s->sps->sps_temporal_mvp_enabled_flag)
                 sh->slice_temporal_mvp_enabled_flag = get_bits1(gb);

libavcodec/hevc.h

@@ -579,6 +579,7 @@ typedef struct SliceHeader {
     int short_term_ref_pic_set_size;
     ShortTermRPS slice_rps;
     const ShortTermRPS *short_term_rps;
+    int long_term_ref_pic_set_size;
     LongTermRPS long_term_rps;
     unsigned int list_entry_lx[2][32];