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

[Li, Zhong]

> 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. 
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.