> From: ffmpeg-devel [mailto:ffmpeg-devel-boun...@ffmpeg.org] On Behalf > Of Mark Thompson > Sent: Tuesday, March 6, 2018 8:32 AM > To: ffmpeg-devel@ffmpeg.org > Subject: Re: [FFmpeg-devel] [PATCH] lavc/qsvenc: disable h264 look_ahead > by default > > On 01/03/18 05:20, Zhong Li wrote: > > Look_ahead can provide quality improvements, but would better disable it > by default due to some reasons: > > 1. It is only available for some codecs (e.g. HEVC is not supported) on > > Intel > > Haswell and plus platforms. Thus means it will be failed on some > platforms. > > 2. It significantly increases encoding latency and memory consumption. > > 3. It may overwrite some other options such as CBR and CAVLC. > > > > Signed-off-by: Zhong Li <zhong...@intel.com> > > --- > > libavcodec/qsvenc_h264.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/libavcodec/qsvenc_h264.c b/libavcodec/qsvenc_h264.c index > > 09e4c0e..e01a2a3 100644 > > --- a/libavcodec/qsvenc_h264.c > > +++ b/libavcodec/qsvenc_h264.c > > @@ -109,7 +109,7 @@ static const AVOption options[] = { > > { "max_dec_frame_buffering", "Maximum number of frames > buffered in the DPB", OFFSET(qsv.max_dec_frame_buffering), > AV_OPT_TYPE_INT, { .i64 = 0 }, 0, UINT16_MAX, VE }, > > > > #if QSV_HAVE_LA > > - { "look_ahead", "Use VBR algorithm with look ahead", > OFFSET(qsv.look_ahead), AV_OPT_TYPE_INT, { .i64 = 1 }, 0, 1, VE }, > > + { "look_ahead", "Use VBR algorithm with look ahead", > OFFSET(qsv.look_ahead), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, 1, VE }, > > { "look_ahead_depth", "Depth of look ahead in number frames", > > OFFSET(qsv.look_ahead_depth), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, 100, > > VE }, #endif #if QSV_HAVE_LA_DS > > > > I agree with everything you've said, so applied.
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