avcodec/h264: 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/h264.c

@@ -688,10 +688,10 @@ av_cold int ff_h264_decode_init(AVCodecContext *avctx)
     ff_h264_reset_sei(h);
     if (avctx->codec_id == AV_CODEC_ID_H264) {
         if (avctx->ticks_per_frame == 1) {
-            if(h->avctx->framerate.num < INT_MAX/2) {
-                h->avctx->framerate.num *= 2;
+            if(h->avctx->time_base.den < INT_MAX/2) {
+                h->avctx->time_base.den *= 2;
             } else
-                h->avctx->framerate.den /= 2;
+                h->avctx->time_base.num /= 2;
         }
         avctx->ticks_per_frame = 2;
     }

libavcodec/h264_parser.c

@@ -490,6 +490,8 @@ static int h264_parse(AVCodecParserContext *s,
 
     parse_nal_units(s, avctx, buf, buf_size);
 
+    if (avctx->framerate.num)
+        avctx->time_base = av_inv_q(av_mul_q(avctx->framerate, (AVRational){avctx->ticks_per_frame, 1}));
     if (h->sei_cpb_removal_delay >= 0) {
         s->dts_sync_point    = h->sei_buffering_period_present;
         s->dts_ref_dts_delta = h->sei_cpb_removal_delay;

libavcodec/h264_slice.c

@@ -1171,7 +1171,7 @@ static int h264_slice_header_init(H264Context *h, int reinit)
         if (h->x264_build < 44U)
             den *= 2;
         av_reduce(&h->avctx->framerate.den, &h->avctx->framerate.num,
-                  h->sps.num_units_in_tick, den, 1 << 30);
+                  h->sps.num_units_in_tick * h->avctx->ticks_per_frame, den, 1 << 30);
     }
 
     if (reinit)