lavc/qsvenc: Add workaround for VP9 keyframe

The runtime doesn't set the frame type to MFX_FRAMETYPE_IDR on the
returned mfx bitstream for a keyframe, it set the frame type to
MFX_FRAMETYPE_I only. This patch added workaround for VP9 keyframe to
make the coded stream seekable.

Signed-off-by: Haihao Xiang <haihao.xiang@intel.com>

libavcodec/qsvenc.c

@@ -2578,9 +2578,11 @@ int ff_qsv_encode(AVCodecContext *avctx, QSVEncContext *q,
         if (qpkt.bs->FrameType & MFX_FRAMETYPE_IDR || qpkt.bs->FrameType & MFX_FRAMETYPE_xIDR) {
             qpkt.pkt.flags |= AV_PKT_FLAG_KEY;
             pict_type = AV_PICTURE_TYPE_I;
-        } else if (qpkt.bs->FrameType & MFX_FRAMETYPE_I || qpkt.bs->FrameType & MFX_FRAMETYPE_xI)
+        } else if (qpkt.bs->FrameType & MFX_FRAMETYPE_I || qpkt.bs->FrameType & MFX_FRAMETYPE_xI) {
+            if (avctx->codec_id == AV_CODEC_ID_VP9)
+                qpkt.pkt.flags |= AV_PKT_FLAG_KEY;
             pict_type = AV_PICTURE_TYPE_I;
-        else if (qpkt.bs->FrameType & MFX_FRAMETYPE_P || qpkt.bs->FrameType & MFX_FRAMETYPE_xP)
+        } else if (qpkt.bs->FrameType & MFX_FRAMETYPE_P || qpkt.bs->FrameType & MFX_FRAMETYPE_xP)
             pict_type = AV_PICTURE_TYPE_P;
         else if (qpkt.bs->FrameType & MFX_FRAMETYPE_B || qpkt.bs->FrameType & MFX_FRAMETYPE_xB)
             pict_type = AV_PICTURE_TYPE_B;