On 2/16/2017 5:15 PM, Michael Niedermayer wrote: > On Thu, Feb 16, 2017 at 05:11:54PM +0000, Mark Thompson wrote: >> On 16/02/17 16:20, Michael Niedermayer wrote: >>> Its used elsewhere for 2^p-1 cliping >>> >>> Signed-off-by: Michael Niedermayer <mich...@niedermayer.cc> >>> --- >>> libavcodec/vaapi_encode_vp8.c | 6 +++--- >>> 1 file changed, 3 insertions(+), 3 deletions(-) >>> >>> diff --git a/libavcodec/vaapi_encode_vp8.c b/libavcodec/vaapi_encode_vp8.c >>> index 4a1c85e66c..3d3831c46d 100644 >>> --- a/libavcodec/vaapi_encode_vp8.c >>> +++ b/libavcodec/vaapi_encode_vp8.c >>> @@ -161,12 +161,12 @@ static av_cold int >>> vaapi_encode_vp8_configure(AVCodecContext *avctx) >>> VAAPIEncodeContext *ctx = avctx->priv_data; >>> VAAPIEncodeVP8Context *priv = ctx->priv_data; >>> >>> - priv->q_index_p = av_clip(avctx->global_quality, 0, 127); >>> + priv->q_index_p = av_clip_uintp2(avctx->global_quality, 7); >>> if (avctx->i_quant_factor > 0.0) >>> - priv->q_index_i = av_clip((avctx->global_quality * >>> + priv->q_index_i = av_clip_uintp2((avctx->global_quality * >>> avctx->i_quant_factor + >>> avctx->i_quant_offset) + 0.5, >>> - 0, 127); >>> + 7); >>> else >>> priv->q_index_i = priv->q_index_p; >> >> IMO this makes the code less readable, not more. It doesn't really matter >> to anything, though, so commit it if you really want to. >> >> (If this is mainly objecting to the magic number being visible there then >> please do introduce a constant to hide it rather than making the constant >> smaller - VP8_QINDEX_RANGE, say, to match >> <https://tools.ietf.org/html/rfc6386#section-14.1>.) > > I just suggested it because its the only case we have in the codebase > that matches this: > git grep -E 'av_clip *\(.*, *0 *, > *(3|7|15|31|63|127|255|511|1023|2047|4095|8191|16383|32767|65535|131071|262143|524287|1048575|2097151|4194303|8388607|16777215|33554431|67108863|134217727|268435455|536870911|1073741823) > *\)' > > If we dont use the more optimized code everywhere then finding > cases where it makes a difference and isnt used is harder and not > something i would attempt.
These specialized integer av_clip* functions are optimized only for arm. On x86 i don't think anyone ever did benchmarks to see if av_clip(), when the compiler properly uses cmov, isn't faster than all the arithmetical instructions from the alternatives. Especially intp2. > > i can also move this into fate-source > (there it might even be possible to keep track of exceptions) > but previous additions to fate-source had opposition, so iam not > doing that unless theres some positive feedback in that direction > first ... > > [...] > > > > _______________________________________________ > ffmpeg-devel mailing list > ffmpeg-devel@ffmpeg.org > http://ffmpeg.org/mailman/listinfo/ffmpeg-devel > _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
