hevc_ps: split the code for parsing the SPS and exporting it into the context

This will be useful in the later commits, where we want to parse an SPS
without having a whole decoding context.

libavcodec/hevc.c

@@ -594,7 +594,7 @@ static int hls_slice_header(HEVCContext *s)
             sh->short_term_ref_pic_set_sps_flag = get_bits1(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);
+                ret = ff_hevc_decode_short_term_rps(gb, s->avctx, &sh->slice_rps, s->sps, 1);
                 if (ret < 0)
                     return ret;
 

libavcodec/hevc.h

@@ -863,8 +863,21 @@ typedef struct HEVCContext {
     int sei_hflip, sei_vflip;
 } HEVCContext;
 
-int ff_hevc_decode_short_term_rps(HEVCContext *s, ShortTermRPS *rps,
-                                  const HEVCSPS *sps, int is_slice_header);
+int ff_hevc_decode_short_term_rps(GetBitContext *gb, AVCodecContext *avctx,
+                                  ShortTermRPS *rps, const HEVCSPS *sps, int is_slice_header);
+
+/**
+ * Parse the SPS from the bitstream into the provided HEVCSPS struct.
+ *
+ * @param sps_id the SPS id will be written here
+ * @param apply_defdispwin if set 1, the default display window from the VUI
+ *                         will be applied to the video dimensions
+ * @param vps_list if non-NULL, this function will validate that the SPS refers
+ *                 to an existing VPS
+ */
+int ff_hevc_parse_sps(HEVCSPS *sps, GetBitContext *gb, unsigned int *sps_id,
+                      int apply_defdispwin, AVBufferRef **vps_list, AVCodecContext *avctx);
+
 int ff_hevc_decode_nal_vps(HEVCContext *s);
 int ff_hevc_decode_nal_sps(HEVCContext *s);
 int ff_hevc_decode_nal_pps(HEVCContext *s);