lavc/libopenh264enc: use framerate if available

Respecting the framerate in the libopenh264enc codec context.

Both the libx264 and libx265 encoders already contain similar logic
to first check the framerate before falling back to the timebase.

Reviewed-by: Martin Storsjö <martin@martin.st>
Signed-off-by: Jun Zhao <barryjzhao@tencent.com>

libavcodec/libopenh264enc.c

@@ -156,7 +156,16 @@ static av_cold int svc_encode_init(AVCodecContext *avctx)
 
     (*s->encoder)->GetDefaultParams(s->encoder, &param);
 
-    param.fMaxFrameRate              = 1/av_q2d(avctx->time_base);
+    if (avctx->framerate.num > 0 && avctx->framerate.den > 0) {
+        param.fMaxFrameRate = av_q2d(avctx->framerate);
+    } else {
+        if (avctx->ticks_per_frame > INT_MAX / avctx->time_base.num) {
+            av_log(avctx, AV_LOG_ERROR,
+                   "Could not set framerate for libopenh264enc: integer overflow\n");
+            return AVERROR(EINVAL);
+        }
+        param.fMaxFrameRate = 1.0 / av_q2d(avctx->time_base) / FFMAX(avctx->ticks_per_frame, 1);
+    }
     param.iPicWidth                  = avctx->width;
     param.iPicHeight                 = avctx->height;
     param.iTargetBitrate             = avctx->bit_rate > 0 ? avctx->bit_rate : TARGET_BITRATE_DEFAULT;