avcodec/mpeg12dec: fix time_base and framerate

They are not just inverses of each other.
This should restore behavior to before the introduction of framerate

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/mpeg12dec.c

@@ -1316,7 +1316,7 @@ static int mpeg_decode_postinit(AVCodecContext *avctx)
             // MPEG-2 fps
             av_reduce(&s->avctx->framerate.num,
                       &s->avctx->framerate.den,
-                      ff_mpeg12_frame_rate_tab[s->frame_rate_index].num * s1->frame_rate_ext.num * 2,
+                      ff_mpeg12_frame_rate_tab[s->frame_rate_index].num * s1->frame_rate_ext.num,
                       ff_mpeg12_frame_rate_tab[s->frame_rate_index].den * s1->frame_rate_ext.den,
                       1 << 30);
             avctx->ticks_per_frame = 2;

libavcodec/mpegvideo_parser.c

@@ -73,6 +73,7 @@ static void mpegvideo_extract_headers(AVCodecParserContext *s,
                 pc->frame_rate = avctx->framerate = ff_mpeg12_frame_rate_tab[frame_rate_index];
                 bit_rate = (buf[4]<<10) | (buf[5]<<2) | (buf[6]>>6);
                 avctx->codec_id = AV_CODEC_ID_MPEG1VIDEO;
+                avctx->ticks_per_frame = 1;
             }
             break;
         case EXT_START_CODE:
@@ -94,9 +95,10 @@ static void mpegvideo_extract_headers(AVCodecParserContext *s,
                         bit_rate = (bit_rate&0x3FFFF) | (bit_rate_ext << 18);
                         if(did_set_size)
                             ff_set_dimensions(avctx, pc->width, pc->height);
-                        avctx->framerate.num = pc->frame_rate.num * (frame_rate_ext_n + 1) * 2;
+                        avctx->framerate.num = pc->frame_rate.num * (frame_rate_ext_n + 1);
                         avctx->framerate.den = pc->frame_rate.den * (frame_rate_ext_d + 1);
                         avctx->codec_id = AV_CODEC_ID_MPEG2VIDEO;
+                        avctx->ticks_per_frame = 2;
                     }
                     break;
                 case 0x8: /* picture coding extension */
@@ -151,7 +153,7 @@ static void mpegvideo_extract_headers(AVCodecParserContext *s,
     }
 #if FF_API_AVCTX_TIMEBASE
     if (avctx->framerate.num)
-        avctx->time_base = av_inv_q(avctx->framerate);
+        avctx->time_base = av_inv_q(av_mul_q(avctx->framerate, (AVRational){avctx->ticks_per_frame, 1}));
 #endif
 }
 
@@ -181,7 +183,7 @@ static int mpegvideo_parse(AVCodecParserContext *s,
        function should be negligible for uncorrupted streams */
     mpegvideo_extract_headers(s, avctx, buf, buf_size);
     av_dlog(NULL, "pict_type=%d frame_rate=%0.3f repeat_pict=%d\n",
-            s->pict_type, (double)avctx->time_base.den / avctx->time_base.num, s->repeat_pict);
+            s->pict_type, av_q2d(avctx->framerate), s->repeat_pict);
 
     *poutbuf = buf;
     *poutbuf_size = buf_size;