Re: [FFmpeg-devel] [PATCH] libavcodec/qsvenc: enable LowDelayBRC and MaxFrameSizeI/MaxFrameSizeP for more accurate bitrate control

["He, Fan F" <fan.f.he-at-intel.com@ffmpeg.org>]

> -----Original Message-----
> From: ffmpeg-devel <ffmpeg-devel-bounces@ffmpeg.org> On Behalf Of "zhilizhao(???)"
> Sent: Monday, March 21, 2022 1:18 PM
> To: FFmpeg development discussions and patches <ffmpeg-devel@ffmpeg.org>
> Subject: Re: [FFmpeg-devel] [PATCH] libavcodec/qsvenc: enable
> LowDelayBRC and MaxFrameSizeI/MaxFrameSizeP for more accurate bitrate control
> 
> 
> 
> > On Mar 10, 2022, at 6:11 PM, He, Fan F <fan.f.he-at-intel.com@ffmpeg.org> wrote:
> >
> > Feature introduction of LowDelayBRC, MaxFrameSizeI and MaxFrameSizeP could be found here:
> > https://github.com/Intel-Media-SDK/MediaSDK/blob/master/doc/mediasdk-man.md
> >
> > Signed-off-by: Dmitry Ermilov <dmitry.ermilov@intel.com>
> > Signed-off-by: Fan F He <fan.f.he@intel.com>
> > ---
> > doc/encoders.texi   | 26 ++++++++++++++++++++++++++
> > libavcodec/qsvenc.c | 17 +++++++++++++++++ libavcodec/qsvenc.h |  6
> > ++++++
> > 3 files changed, 49 insertions(+)
> >
> > diff --git a/doc/encoders.texi b/doc/encoders.texi index
> > 1bd38671ca..47c8577e09 100644
> > --- a/doc/encoders.texi
> > +++ b/doc/encoders.texi
> > @@ -3264,6 +3264,14 @@ Enable rate distortion optimization.
> > @item @var{max_frame_size}
> > Maximum encoded frame size in bytes.
> >
> > +@item @var{max_frame_size_i}
> > +Maximum encoded frame size for I frames in bytes. If this value is
> > +set as larger than zero, then for I frames the value set by max_frame_size is ignored.
> > +
> > +@item @var{max_frame_size_p}
> > +Maximum encoded frame size for P frames in bytes. If this value is
> > +set as larger than zero, then for P frames the value set by max_frame_size is ignored.
> > +
> > @item @var{max_slice_size}
> > Maximum encoded slice size in bytes.
> >
> > @@ -3280,6 +3288,11 @@ Setting this flag enables macroblock level
> > bitrate control that generally improves subjective visual quality.
> > Enabling this flag may have negative impact on performance and objective visual quality metric.
> >
> > +@item @var{low_delay_brc}
> > +Setting this flag turns on or off LowDelayBRC feautre in qsv plugin,
> > +which provides more accurate bitrate control to minimize the variance
> > +of bitstream size frame by frame. Value: -1-default 0-off 1-on
> > +
> > @item @var{adaptive_i}
> > This flag controls insertion of I frames by the QSV encoder. Turn ON
> > this flag to allow changing of frame type from P and B to I.
> > @@ -3392,6 +3405,14 @@ Enable rate distortion optimization.
> > @item @var{max_frame_size}
> > Maximum encoded frame size in bytes.
> >
> > +@item @var{max_frame_size_i}
> > +Maximum encoded frame size for I frames in bytes. If this value is
> > +set as larger than zero, then for I frames the value set by max_frame_size is ignored.
> > +
> > +@item @var{max_frame_size_p}
> > +Maximum encoded frame size for P frames in bytes. If this value is
> > +set as larger than zero, then for P frames the value set by max_frame_size is ignored.
> > +
> > @item @var{max_slice_size}
> > Maximum encoded slice size in bytes.
> >
> > @@ -3400,6 +3421,11 @@ Setting this flag enables macroblock level
> > bitrate control that generally improves subjective visual quality.
> > Enabling this flag may have negative impact on performance and objective visual quality metric.
> >
> > +@item @var{low_delay_brc}
> > +Setting this flag turns on or off LowDelayBRC feautre in qsv plugin,
> > +which provides more accurate bitrate control to minimize the variance
> > +of bitstream size frame by frame. Value: -1-default 0-off 1-on
> > +
> > @item @var{p_strategy}
> > Enable P-pyramid: 0-default 1-simple 2-pyramid(bf need to be set to 0).
> >
> > diff --git a/libavcodec/qsvenc.c b/libavcodec/qsvenc.c index
> > 9b71487666..d5e2c5fb32 100644
> > --- a/libavcodec/qsvenc.c
> > +++ b/libavcodec/qsvenc.c
> > @@ -374,6 +374,13 @@ static void dump_video_param(AVCodecContext
> > *avctx, QSVEncContext *q, #if QSV_VERSION_ATLEAST(1, 16)
> >     av_log(avctx, AV_LOG_VERBOSE, "IntRefCycleDist: %"PRId16"\n",
> > co3->IntRefCycleDist); #endif
> > +#if QSV_VERSION_ATLEAST(1, 23)
> > +    av_log(avctx, AV_LOG_VERBOSE, "LowDelayBRC: %s\n",
> > +print_threestate(co3->LowDelayBRC));
> > +#endif
> > +#if QSV_VERSION_ATLEAST(1, 19)
> > +    av_log(avctx, AV_LOG_VERBOSE, "MaxFrameSizeI: %d; ", co3-
> >MaxFrameSizeI);
> > +    av_log(avctx, AV_LOG_VERBOSE, "MaxFrameSizeP: %d\n",
> > +co3->MaxFrameSizeP); #endif
> > }
> >
> > static void dump_video_vp9_param(AVCodecContext *avctx, QSVEncContext
> > *q, @@ -988,6 +995,16 @@ static int init_video_param(AVCodecContext
> > *avctx, QSVEncContext *q) #if QSV_VERSION_ATLEAST(1, 16)
> >             if (q->int_ref_cycle_dist >= 0)
> >                 q->extco3.IntRefCycleDist = q->int_ref_cycle_dist;
> > +#endif
> > +#if QSV_VERSION_ATLEAST(1, 23)
> > +            if (q->low_delay_brc >= 0)
> > +                q->extco3.LowDelayBRC = q->low_delay_brc ?
> > +MFX_CODINGOPTION_ON : MFX_CODINGOPTION_OFF; #endif #if
> > +QSV_VERSION_ATLEAST(1, 19)
> > +            if (q->max_frame_size_p >= 0)
> > +                q->extco3.MaxFrameSizeI = q->max_frame_size_i;
> > +            if (q->max_frame_size_p >= 0)
> > +                q->extco3.MaxFrameSizeP = q->max_frame_size_p;
> > #endif
> >         }
> >
> > diff --git a/libavcodec/qsvenc.h b/libavcodec/qsvenc.h index
> > 2bda858427..5e07580289 100644
> > --- a/libavcodec/qsvenc.h
> > +++ b/libavcodec/qsvenc.h
> > @@ -91,6 +91,8 @@
> > { "veryslow",    NULL, 0, AV_OPT_TYPE_CONST, { .i64 =
> MFX_TARGETUSAGE_BEST_QUALITY  }, INT_MIN, INT_MAX, VE, "preset" }, \
> > { "rdo",            "Enable rate distortion optimization",    OFFSET(qsv.rdo), AV_OPT_TYPE_INT, { .i64 = -1 }, -1,          1, VE },                         \
> > { "max_frame_size", "Maximum encoded frame size in bytes", OFFSET(qsv.max_frame_size), AV_OPT_TYPE_INT, { .i64 = -1 }, -1, UINT16_MAX, VE },                         \
> > +{ "max_frame_size_i", "Maximum encoded I frame size in bytes",OFFSET(qsv.max_frame_size_i), AV_OPT_TYPE_INT, { .i64 = -1 }, -1, UINT16_MAX, VE },                       \
> > +{ "max_frame_size_p", "Maximum encoded P frame size in bytes",OFFSET(qsv.max_frame_size_p), AV_OPT_TYPE_INT, { .i64 = -1 }, -1, UINT16_MAX, VE },                       \
> 
> I can't find the threshold from 'mediasdk-man.md’.
> Does `UINT16_MAX` comes from mediasdk, or just a reasonable limitation
> set by this wrapper?
> 
Thanks for pointing it out. It should be INT32_MAX. Will refine the patch and send it again.

> > { "max_slice_size", "Maximum encoded slice size in bytes", OFFSET(qsv.max_slice_size), AV_OPT_TYPE_INT, { .i64 = -1 }, -1, UINT16_MAX, VE },                         \
> > { "bitrate_limit",  "Toggle bitrate limitations", OFFSET(qsv.bitrate_limit),  AV_OPT_TYPE_INT, { .i64 = -1 }, -1,          1, VE }, \
> > { "mbbrc",          "MB level bitrate control",               OFFSET(qsv.mbbrc), AV_OPT_TYPE_INT, { .i64 = -1 }, -1,          1, VE },                         \
> > @@ -102,6 +104,7 @@
> > { "forced_idr",     "Forcing I frames as IDR frames", OFFSET(qsv.forced_idr),     AV_OPT_TYPE_BOOL,{ .i64 = 0  },  0,          1, VE }, \
> > { "low_power", "enable low power mode(experimental: many limitations by mfx version, BRC modes, etc.)", OFFSET(qsv.low_power), AV_OPT_TYPE_BOOL, { .i64 = -1}, -1, 1, VE},\
> > { "dblk_idc", "This option disable deblocking. It has value in range 0~2.", OFFSET(qsv.dblk_idc),   AV_OPT_TYPE_INT,    { .i64 = 0 },   0,  2,  VE},    \
> > +{ "low_delay_brc",   "Allow to strictly obey avg frame size", OFFSET(qsv.low_delay_brc),  AV_OPT_TYPE_BOOL,{ .i64 = -1 }, -1,          1, VE },                         \
> >
> > extern const AVCodecHWConfigInternal *const ff_qsv_enc_hw_configs[];
> >
> > @@ -173,6 +176,8 @@ typedef struct QSVEncContext {
> >     int vcm;
> >     int rdo;
> >     int max_frame_size;
> > +    int max_frame_size_i;
> > +    int max_frame_size_p;
> >     int max_slice_size;
> >     int dblk_idc;
> >
> > @@ -212,6 +217,7 @@ typedef struct QSVEncContext {
> >     char *load_plugins;
> >     SetEncodeCtrlCB *set_encode_ctrl_cb;
> >     int forced_idr;
> > +    int low_delay_brc;
> > } QSVEncContext;
> >
> > int ff_qsv_enc_init(AVCodecContext *avctx, QSVEncContext *q);
> > --
> > 2.25.1
> >
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