diff --git a/libavcodec/qsvenc.c b/libavcodec/qsvenc.c
--- a/libavcodec/qsvenc.c
+++ b/libavcodec/qsvenc.c
@@ -1419,6 +1419,18 @@
     return 0;
 }
 
+static int qsv_update_packet_size(QSVEncContext *q, const mfxInfoMFX *mfx)
+{
+    // Intel documents a larger buffer for complex CQP frames.
+    // https://github.com/Intel-Media-SDK/MediaSDK/blob/master/doc/mediasdk_release_notes.md
+    int64_t packet_size = (int64_t)mfx->BufferSizeInKB * mfx->BRCParamMultiplier * 1000 * 4;
+
+    if (packet_size > INT_MAX - AV_INPUT_BUFFER_PADDING_SIZE)
+        return AVERROR(ENOMEM);
+    q->packet_size = FFMAX(q->packet_size, packet_size);
+    return 0;
+}
+
 static int qsv_retrieve_enc_params(AVCodecContext *avctx, QSVEncContext *q)
 {
     AVCPBProperties *cpb_props;
@@ -1508,7 +1520,13 @@
         return ff_qsv_print_error(avctx, ret,
                                   "Error calling GetVideoParam");
 
-    q->packet_size = q->param.mfx.BufferSizeInKB * q->param.mfx.BRCParamMultiplier * 1000;
+    if (avctx->codec_id == AV_CODEC_ID_H264 || avctx->codec_id == AV_CODEC_ID_HEVC) {
+        ret = qsv_update_packet_size(q, &q->param.mfx);
+        if (ret < 0)
+            return ret;
+    } else {
+        q->packet_size = q->param.mfx.BufferSizeInKB * q->param.mfx.BRCParamMultiplier * 1000;
+    }
 
     if (!extradata.SPSBufSize || (need_pps && !extradata.PPSBufSize)
         || (q->hevc_vps && !extradata_vps.VPSBufSize)
@@ -2650,6 +2668,17 @@
     if (ret < 0)
         return ff_qsv_print_error(avctx, ret, "Error during resetting");
 
+    if (avctx->codec_id == AV_CODEC_ID_H264 || avctx->codec_id == AV_CODEC_ID_HEVC) {
+        mfxVideoParam param = { 0 };
+
+        ret = MFXVideoENCODE_GetVideoParam(q->session, &param);
+        if (ret < 0)
+            return ff_qsv_print_error(avctx, ret, "Error querying parameters after reset");
+        ret = qsv_update_packet_size(q, &param.mfx);
+        if (ret < 0)
+            return ret;
+    }
+
     return 0;
 }
 
@@ -2688,6 +2717,8 @@
             if (ret == MFX_WRN_IN_EXECUTION)
                 av_usleep(1000);
         } while (ret == MFX_WRN_IN_EXECUTION);
+        if (ret < 0)
+            return ff_qsv_print_error(avctx, ret, "Error synchronizing encoded frame");
         av_fifo_drain2(q->async_fifo, 1);
 
         qpkt.pkt.dts  = av_rescale_q(qpkt.bs->DecodeTimeStamp, (AVRational){1, 90000}, avctx->time_base);