[x265] Bug report: incorrect computation of sps_max_dec_pic_buffering_minus1

[Olivier Lapicque]

This was the cmdline info used (Though I don't know which build of x265 was used):

<<
./x265 --input ~/FILES/yuv/720p50_parkrun_ter.yuv --fps 30 --input-res 1280x720 --refresh 2 -i 30 --bitrate 5000 -o parkrun_ter_720p30fps_5Mbps.hevc

Encoding info as printed by x265 is below.
yuv  [info]: 1280x720 30Hz, frames 0 - 49 of 50
x265 [info]: detected SIMD architectures SSE2 SSE3 SSSE3 SSE4.1 SSE4.2
x265 [info]: performance primitives: intrinsic
x265 [info]: Main profile, Level-3.1 (Main tier)
x265 [info]: WPP streams / pool / frames  : 12 / 8 / 1
x265 [info]: CU size                      : 64
x265 [info]: Max RQT depth inter / intra  : 3 / 3
x265 [info]: ME / range / subpel / merge  : star / 60 / 5 / 5
x265 [info]: Keyframe min / max           : 30 / 30
x265 [info]: Rate Control                 : ABR-5000 kbps
x265 [info]: Lookahead len / -b / bAdapt  : 10 / 3 / 1      [Default is max 3 consecutive B-frames, corresponding to "-b 3" option]
x265 [info]: tools: rect amp rdo rdoq lft sao sao-lcu sign-hide tskip tskip-fast rdoqts
x265 [info]: frame I:2      kb/s: 38722.20 PSNR Mean: Y:39.782 U:43.591 V:44.109
x265 [info]: frame P:32     kb/s: 5119.59  PSNR Mean: Y:27.178 U:39.095 V:40.228
x265 [info]: frame B:16     kb/s: 1147.47  PSNR Mean: Y:26.369 U:38.924 V:40.048
x265 [info]: global:        kb/s: 5192.62  PSNR Mean: Y:27.423 U:39.220 V:40.326
encoded 50 frames in 115.83s (0.43 fps), 5193.93 kb/s, Global PSNR: 30.511
>>


From: x265-devel [mailto:x265-devel-bounces at videolan.org] On Behalf Of Deepthi Devaki Akkoorath
Sent: Tuesday, September 24, 2013 2:05 AM
To: Development for x265
Subject: Re: [x265] Bug report: incorrect computation of sps_max_dec_pic_buffering_minus1


Olivier,

I couldn't reproduce the problem with b-frames enabled. I will be able to look into it better once I get the exact command line.

- Deepthi

On Tue, Sep 24, 2013 at 1:25 AM, Steve Borho <steve at borho.org<mailto:steve at borho.org>> wrote:


On Mon, Sep 23, 2013 at 2:38 PM, Olivier Lapicque <olapicque at nvidia.com<mailto:olapicque at nvidia.com>> wrote:

"(param->bframes+2)-1" seems correct for 1-backward and 1 forward reference (but seems like it would be too low for more than 2 refs).

Yeah, we haven't re-enabled multiple refs yet after plugging in the new lookahead.  It should happen soon, though.


The exact condition that was violated in the bitstream I saw is the following:

NumNegativePics(4) + NumPositivePics(1) + num_long_term_sps(0) + num_long_term_pics(0) > max_dec_pic_buffering_minus1(3)+1



I'll get the exact cmdline parameters to reproduce this, but I was told that this problem occurs any time B-frames are enabled.

Ah, ok.  The problem is probably with NumNegativePics then.  We'll take a look at this.

--
Steve Borho


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