libavcodec/qsvenc: Enable fixed QP configure in qsv CQP runtime

Enable dynamic QP configuration in runtime on qsv encoder. Through
AVFrame->metadata, we can set key "qsv_config_qp" to change QP
configuration when we encode video in CQP mode.

Signed-off-by: Yue Heng <yue.heng@intel.com>
Signed-off-by: Wenbin Chen <wenbin.chen@intel.com>
Signed-off-by: Haihao Xiang <haihao.xiang@intel.com>

doc/encoders.texi

@@ -3333,6 +3333,16 @@ Forcing I frames as IDR frames.
 For encoders set this flag to ON to reduce power consumption and GPU usage.
 @end table
 
+@subsection Runtime Options
+Following options can be used durning qsv encoding.
+
+@table @option
+@item @var{qsv_config_qp}
+Supported in h264_qsv and hevc_qsv.
+This option can be set in per-frame metadata. QP parameter can be dynamically
+changed when encoding in CQP mode.
+@end table
+
 @subsection H264 options
 These options are used by h264_qsv
 

libavcodec/qsvenc.c

@@ -146,6 +146,14 @@ static const struct {
     { MFX_RATECONTROL_QVBR,    "QVBR" },
 };
 
+#define UPDATE_PARAM(a, b)  \
+do {                        \
+    if ((a) != (b)) {       \
+        a = b;              \
+        updated = 1;        \
+    }                       \
+} while (0)                 \
+
 static const char *print_ratecontrol(mfxU16 rc_mode)
 {
     int i;
@@ -1613,6 +1621,83 @@ static int set_roi_encode_ctrl(AVCodecContext *avctx, const AVFrame *frame,
     return 0;
 }
 
+static int update_qp(AVCodecContext *avctx, QSVEncContext *q,
+                     const AVFrame *frame)
+{
+    int updated = 0, qp = 0, new_qp;
+    char *tail;
+    AVDictionaryEntry *entry = NULL;
+
+    if (avctx->codec_id != AV_CODEC_ID_H264 && avctx->codec_id != AV_CODEC_ID_HEVC)
+        return 0;
+
+    entry = av_dict_get(frame->metadata, "qsv_config_qp", NULL, 0);
+    if (entry && q->param.mfx.RateControlMethod == MFX_RATECONTROL_CQP) {
+        qp = strtol(entry->value, &tail, 10);
+        if (*tail) {
+            av_log(avctx, AV_LOG_WARNING, "Invalid qsv_config_qp string. Ignore this metadata\n");
+            return 0;
+        }
+        if (qp < 0 || qp > 51) {
+            av_log(avctx, AV_LOG_WARNING, "Invalid qp, clip to 0 ~ 51\n");
+            qp = av_clip(qp, 0, 51);
+        }
+        av_log(avctx, AV_LOG_DEBUG, "Configure qp: %d\n",qp);
+        UPDATE_PARAM(q->param.mfx.QPP, qp);
+        new_qp = av_clip(qp * fabs(avctx->i_quant_factor) +
+                            avctx->i_quant_offset, 0, 51);
+        UPDATE_PARAM(q->param.mfx.QPI, new_qp);
+        new_qp = av_clip(qp * fabs(avctx->b_quant_factor) +
+                            avctx->b_quant_offset, 0, 51);
+        UPDATE_PARAM(q->param.mfx.QPB, new_qp);
+        av_log(avctx, AV_LOG_DEBUG,
+                "using fixed qp = %d/%d/%d for idr/p/b frames\n",
+                q->param.mfx.QPI, q->param.mfx.QPP, q->param.mfx.QPB);
+    }
+    return updated;
+}
+
+static int update_parameters(AVCodecContext *avctx, QSVEncContext *q,
+                             const AVFrame *frame)
+{
+    int needReset = 0, ret = 0;
+
+    if (!frame)
+        return 0;
+
+    needReset = update_qp(avctx, q, frame);
+    if (!needReset)
+        return 0;
+
+    if (avctx->hwaccel_context) {
+        AVQSVContext *qsv = avctx->hwaccel_context;
+        int i, j;
+        q->param.ExtParam = q->extparam;
+        for (i = 0; i < qsv->nb_ext_buffers; i++)
+            q->param.ExtParam[i] = qsv->ext_buffers[i];
+        q->param.NumExtParam = qsv->nb_ext_buffers;
+
+        for (i = 0; i < q->nb_extparam_internal; i++) {
+            for (j = 0; j < qsv->nb_ext_buffers; j++) {
+                if (qsv->ext_buffers[j]->BufferId == q->extparam_internal[i]->BufferId)
+                    break;
+            }
+            if (j < qsv->nb_ext_buffers)
+                continue;
+            q->param.ExtParam[q->param.NumExtParam++] = q->extparam_internal[i];
+        }
+    } else {
+        q->param.ExtParam    = q->extparam_internal;
+        q->param.NumExtParam = q->nb_extparam_internal;
+    }
+    av_log(avctx, AV_LOG_DEBUG, "Parameter change, call msdk reset.\n");
+    ret = MFXVideoENCODE_Reset(q->session, &q->param);
+    if (ret < 0)
+        return ff_qsv_print_error(avctx, ret, "Error during resetting");
+
+    return 0;
+}
+
 static int encode_frame(AVCodecContext *avctx, QSVEncContext *q,
                         const AVFrame *frame)
 {
@@ -1731,6 +1816,10 @@ int ff_qsv_encode(AVCodecContext *avctx, QSVEncContext *q,
 {
     int ret;
 
+    ret = update_parameters(avctx, q, frame);
+    if (ret < 0)
+        return ret;
+
     ret = encode_frame(avctx, q, frame);
     if (ret < 0)
         return ret;