libavcodec/mpegvideo.c:2208: error: Null Dereference
  pointer `desc` last assigned on line 2207 could be null and is dereferenced at line 2208, column 18.

libavcodec/mpegvideo.c:2202:1: start of procedure ff_draw_horiz_band()
2200.  * @param h is the normal height, this will be reduced automatically if needed for the last row
2201.  */
2202. void ff_draw_horiz_band(AVCodecContext *avctx, DSPContext *dsp, Picture *cur,
      ^
2203.                         Picture *last, int y, int h, int picture_structure,
2204.                         int first_field, int draw_edges, int low_delay,

libavcodec/mpegvideo.c:2207:5: 
2205.                         int v_edge_pos, int h_edge_pos)
2206. {
2207.     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(avctx->pix_fmt);
          ^
2208.     int hshift = desc->log2_chroma_w;
2209.     int vshift = desc->log2_chroma_h;

libavutil/pixdesc.c:1504:1: start of procedure av_pix_fmt_desc_get()
  1502. }
  1503. 
  1504. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
        ^
  1505. {
  1506.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)

libavutil/pixdesc.c:1506:9: Taking false branch
  1504. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
  1505. {
  1506.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
                ^
  1507.         return NULL;
  1508.     return &av_pix_fmt_descriptors[pix_fmt];

libavutil/pixdesc.c:1506:24: Taking true branch
  1504. const AVPixFmtDescriptor *av_pix_fmt_desc_get(enum AVPixelFormat pix_fmt)
  1505. {
  1506.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
                               ^
  1507.         return NULL;
  1508.     return &av_pix_fmt_descriptors[pix_fmt];

libavutil/pixdesc.c:1507:9: 
  1505. {
  1506.     if (pix_fmt < 0 || pix_fmt >= AV_PIX_FMT_NB)
  1507.         return NULL;
                ^
  1508.     return &av_pix_fmt_descriptors[pix_fmt];
  1509. }

libavutil/pixdesc.c:1509:1: return from a call to av_pix_fmt_desc_get
  1507.         return NULL;
  1508.     return &av_pix_fmt_descriptors[pix_fmt];
  1509. }
        ^
  1510. 
  1511. const AVPixFmtDescriptor *av_pix_fmt_desc_next(const AVPixFmtDescriptor *prev)

libavcodec/mpegvideo.c:2208:5: 
2206. {
2207.     const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(avctx->pix_fmt);
2208.     int hshift = desc->log2_chroma_w;
          ^
2209.     int vshift = desc->log2_chroma_h;
2210.     const int field_pic = picture_structure != PICT_FRAME;
