[FFmpeg-devel] [PATCH 1/5] lavc/qsvenc: add forced_idr opiton

[Rogozhkin, Dmitry V]

On Tue, 2018-10-30 at 09:49 +0000, Li, Zhong wrote:
> > From: ffmpeg-devel [mailto:ffmpeg-devel-bounces at ffmpeg.org] On
> > Behalf
> > Of Mark Thompson
> > Sent: Tuesday, October 30, 2018 5:06 AM
> > To: ffmpeg-devel at ffmpeg.org
> > Subject: Re: [FFmpeg-devel] [PATCH 1/5] lavc/qsvenc: add forced_idr
> > opiton
> > 
> > On 25/10/18 13:36, Zhong Li wrote:
> > > This option can be used to repect original input I/IDR frame
> > > type.
> > > 
> > > Signed-off-by: Zhong Li <zhong.li at intel.com>
> > > ---
> > >  libavcodec/qsvenc.c | 7 +++++++
> > >  libavcodec/qsvenc.h | 2 ++
> > >  2 files changed, 9 insertions(+)
> > > 
> > > diff --git a/libavcodec/qsvenc.c b/libavcodec/qsvenc.c index
> > > 948751d..e534dcf 100644
> > > --- a/libavcodec/qsvenc.c
> > > +++ b/libavcodec/qsvenc.c
> > > @@ -1192,6 +1192,13 @@ static int encode_frame(AVCodecContext
> > 
> > *avctx, QSVEncContext *q,
> > >      if (qsv_frame) {
> > >          surf = &qsv_frame->surface;
> > >          enc_ctrl = &qsv_frame->enc_ctrl;
> > > +
> > > +        if (q->forced_idr >= 0 && frame->pict_type ==
> > 
> > AV_PICTURE_TYPE_I) {
> > > +            enc_ctrl->FrameType = MFX_FRAMETYPE_I |
> > 
> > MFX_FRAMETYPE_REF;
> > > +            if (q->forced_idr || frame->key_frame)
> > > +                enc_ctrl->FrameType |= MFX_FRAMETYPE_IDR;
> > > +        } else
> > > +            enc_ctrl->FrameType = MFX_FRAMETYPE_UNKNOWN;
> > >      }
> > > 
> > >      ret = av_new_packet(&new_pkt, q->packet_size); diff --git
> > > a/libavcodec/qsvenc.h b/libavcodec/qsvenc.h index
> > > 055b4a6..1f97f77
> > > 100644
> > > --- a/libavcodec/qsvenc.h
> > > +++ b/libavcodec/qsvenc.h
> > > @@ -87,6 +87,7 @@
> > >  { "adaptive_i",     "Adaptive I-frame placement",
> > 
> > OFFSET(qsv.adaptive_i),     AV_OPT_TYPE_INT, { .i64 = -1 }, -1,
> > 1, VE },                         \
> > >  { "adaptive_b",     "Adaptive B-frame placement",
> > 
> > OFFSET(qsv.adaptive_b),     AV_OPT_TYPE_INT, { .i64 = -1 }, -1,
> > 1, VE },                         \
> > >  { "b_strategy",     "Strategy to choose between I/P/B-frames",
> > 
> > OFFSET(qsv.b_strategy),    AV_OPT_TYPE_INT, { .i64 = -1 }, -1,
> > 1, VE },                         \
> > > +{ "forced_idr",     "Forcing I frames as IDR frames",
> > 
> > OFFSET(qsv.forced_idr),     AV_OPT_TYPE_INT, { .i64 = -1 }, -1,
> > 1, VE },                         \
> > > 
> > >  typedef int SetEncodeCtrlCB (AVCodecContext *avctx,
> > >                               const AVFrame *frame,
> > 
> > mfxEncodeCtrl*
> > > enc_ctrl); @@ -168,6 +169,7 @@ typedef struct QSVEncContext
> > > {  #endif
> > >      char *load_plugins;
> > >      SetEncodeCtrlCB *set_encode_ctrl_cb;
> > > +    int forced_idr;
> > >  } QSVEncContext;
> > > 
> > >  int ff_qsv_enc_init(AVCodecContext *avctx, QSVEncContext *q);
> > > 
> > 
> > This seems confusing, because it doesn't match what forced_idr does
> > in any
> > other encoder.
> > 
> > Checking of pict_type for AV_PICTURE_TYPE_I in order to get a key
> > frame
> > (of whatever kind) is always enabled if supported (many
> > encoders).  The
> > "forced_idr" option to H.26[45] encoders (libx264, libx265) then
> > forces that
> > to be an IDR frame, not just an I frame.
> > 
> > - Mark
> 
> Yup, I know it doesn’t match other encoders such as
> libx264/libx265/nvenc. 
> However, it is my intentional behavior. I believe current implement
> in libx264/libx265 is not complete.
> One case is ignored: user just want to keep the gop structure as
> input, not to force all I frames as IDR frames.
> So I have an idea:
> Default value = -1, ignore the input gop structure. 

I see the idea now, but I very much would like to see this at least
somehow reflected in ffmpeg option documentation. To me your
interpretation of -1, 0, 1 is quite non-intuitive. As you can see from
my other comments I did not guess your intent from the patch. End-users 
will have even more problems with this option since a little of them
will take care to look into the sources themselves.

Besides, I am still feeling that you try to mix 2 different options
together: one which will permit to follow (or not) input stream gop
structure and another which forces IDR frames for each I frame.

> 0: respect input gop structure but don't force I frame as IDR frame. 
> 1: force all I frame as IDR frame.
> 
> Since this is a qsv encoder private option, I just changed qsv
> implementation.
> But I believe it should be a good to make other encoders follow such
> a way with separated patches.
> 
> 
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