On 31/10/17 15:18, Jun Zhao wrote: > On 2017/10/31 18:26, Mark Thompson wrote: >> On 31/10/17 02:37, Jun Zhao wrote: >>> From d1e105057e93e7c2788d6d684292db9008fbf3ac Mon Sep 17 00:00:00 2001 >>> From: Jun Zhao <jun.z...@intel.com> >>> Date: Tue, 31 Oct 2017 10:19:08 +0800 >>> Subject: [PATCH 2/2] lavc/vaapi_encode_h264: correct bit_rate_scale setting. >>> >>> As H264 Spec 2012 E.2.2, bit_rate_scale means the max input bit rate. >>> >>> Signed-off-by: Jun Zhao <jun.z...@intel.com> >>> Signed-off-by: Wang, Yi A <yi.a.w...@intel.com> >>> --- >>> libavcodec/vaapi_encode_h264.c | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/libavcodec/vaapi_encode_h264.c b/libavcodec/vaapi_encode_h264.c >>> index 1d43e934ef..27a810c64e 100644 >>> --- a/libavcodec/vaapi_encode_h264.c >>> +++ b/libavcodec/vaapi_encode_h264.c >>> @@ -406,7 +406,7 @@ static int >>> vaapi_encode_h264_init_sequence_params(AVCodecContext *avctx) >>> // Try to scale these to a sensible range so that the >>> // golomb encode of the value is not overlong. >>> hrd->bit_rate_scale = >>> - av_clip_uintp2(av_log2(avctx->bit_rate) - 15 - 6, 4); >>> + av_clip_uintp2(av_log2(FFMAX(avctx->bit_rate, >>> avctx->rc_max_rate)) - 15 - 6, 4); >>> hrd->bit_rate_value_minus1[0] = >>> (avctx->bit_rate >> hrd->bit_rate_scale + 6) - 1; > > avctx->bit_rate will change with FFMAX(avctx->bit_rate, avctx->rc_max_rate) > when setting bit_rate_value_minus1.
The two values combine to specify the BitRate[0] value for this HRD instance. The same value has to be used for both the scale and the value parts. >>> >>> -- >>> 2.14.1 >>> >> Can you offer some more justification for that? I think the change is >> wrong: consider under what circumstances overflow/underflow occurs. > In VBR/CBR mode, I think max bit rate = FFMAX(bit_rate, rc_max_rate) for > bit_rate_scale/bit_rate_value_minus1. The bitrate here is how fast the CPB fills. It is not the same as the RC max rate, which will only affect how fast the CPB can be emptied. - Mark _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
