lavc/qsvenc: add VDENC support for H264

Add VDENC(lowpower mode) support for QSV H264

It's an experimental function(like lowpower in vaapi) with
some limitations:
- CBR/VBR require HuC which should be explicitly loaded via i915
module parameter(i915.enable_guc=2 for linux kernel version >= 4.16)

Use option "-low_power 1" to enable VDENC.
Add in dump_video_param() to show the status of VDENC in runtime log.
Signed-off-by: Linjie Fu <linjie.fu@intel.com>
Signed-off-by: Zhong Li <zhong.li@intel.com>

libavcodec/qsvenc.c

@@ -226,6 +226,10 @@ static void dump_video_param(AVCodecContext *avctx, QSVEncContext *q,
     av_log(avctx, AV_LOG_VERBOSE, "\n");
 #endif
 
+#if QSV_HAVE_VDENC
+    av_log(avctx, AV_LOG_VERBOSE, "VDENC: %s\n", print_threestate(info->LowPower));
+#endif
+
 #if QSV_VERSION_ATLEAST(1, 8)
     av_log(avctx, AV_LOG_VERBOSE,
            "RepeatPPS: %s; NumMbPerSlice: %"PRIu16"; LookAheadDS: ",
@@ -475,6 +479,9 @@ static int init_video_param(AVCodecContext *avctx, QSVEncContext *q)
         }
     }
 
+#if QSV_HAVE_VDENC
+    q->param.mfx.LowPower           = q->low_power ? MFX_CODINGOPTION_ON : MFX_CODINGOPTION_OFF;
+#endif
     q->param.mfx.CodecProfile       = q->profile;
     q->param.mfx.TargetUsage        = avctx->compression_level;
     q->param.mfx.GopPicSize         = FFMAX(0, avctx->gop_size);

libavcodec/qsvenc.h

@@ -44,6 +44,7 @@
 #define QSV_HAVE_LA     QSV_VERSION_ATLEAST(1, 7)
 #define QSV_HAVE_LA_DS  QSV_VERSION_ATLEAST(1, 8)
 #define QSV_HAVE_LA_HRD QSV_VERSION_ATLEAST(1, 11)
+#define QSV_HAVE_VDENC  QSV_VERSION_ATLEAST(1, 15)
 
 #if defined(_WIN32) || defined(__CYGWIN__)
 #define QSV_HAVE_AVBR   QSV_VERSION_ATLEAST(1, 3)
@@ -163,6 +164,7 @@ typedef struct QSVEncContext {
     int recovery_point_sei;
 
     int repeat_pps;
+    int low_power;
 
     int a53_cc;
 

libavcodec/qsvenc_h264.c

@@ -154,6 +154,10 @@ static const AVOption options[] = {
     { "auto"   , NULL, 0, AV_OPT_TYPE_CONST, { .i64 = MFX_MF_AUTO     }, INT_MIN, INT_MAX,     VE, "mfmode" },
 #endif
 
+#if QSV_HAVE_VDENC
+    { "low_power", "enable low power mode(experimental: many limitations by mfx version, BRC modes, etc.)", OFFSET(qsv.low_power), AV_OPT_TYPE_BOOL, { .i64 =  0 }, 0, 1, VE},
+#endif
+
     { "repeat_pps", "repeat pps for every frame", OFFSET(qsv.repeat_pps), AV_OPT_TYPE_BOOL, { .i64 = 0 }, 0, 1, VE },
 
     { NULL },