[FFmpeg-devel] [PATCH] Fix non-rounding up to next 16-bit aligned bug in IFF decoder
Sebastian Vater
cdgs.basty
Thu Apr 29 20:34:10 CEST 2010
Ronald S. Bultje a ?crit :
> Hi,
>
> On Thu, Apr 29, 2010 at 2:22 PM, Sebastian Vater
> <cdgs.basty at googlemail.com> wrote:
>
>> Regarding your idea gcc outputs:
>> 52: 0f b6 16 movzbl (%esi),%edx
>> 55: 83 c6 01 add $0x1,%esi
>> 58: 89 d0 mov %edx,%eax
>> 5a: 83 e2 0f and $0xf,%edx
>> 5d: c1 e8 04 shr $0x4,%eax
>> 60: 8b 04 81 mov (%ecx,%eax,4),%eax
>> 63: 09 03 or %eax,(%ebx)
>> 65: 8b 04 91 mov (%ecx,%edx,4),%eax
>> 68: 09 43 04 or %eax,0x4(%ebx)
>> 6b: 83 c3 08 add $0x8,%ebx
>> 6e: 39 df cmp %ebx,%edi
>> 70: 77 e0 ja 52 <decodeplane8+0x52>
>>
>
> 12 instructions, so 2 less, as intended. Is it faster?
>
Old method:
basty at cdgs-basty:~/src/ffmpeg/build$ ./ffplay ../patches/MRLake.iff
FFplay version git-5b9f10d, Copyright (c) 2003-2010 the FFmpeg developers
built on Apr 29 2010 15:19:11 with gcc 4.2.4 (Ubuntu 4.2.4-1ubuntu4)
configuration:
libavutil 50.14. 0 / 50.14. 0
libavcodec 52.66. 0 / 52.66. 0
libavformat 52.61. 0 / 52.61. 0
libavdevice 52. 2. 0 / 52. 2. 0
libswscale 0.10. 0 / 0.10. 0
[IFF @ 0x8b32790]Estimating duration from bitrate, this may be inaccurate
Input #0, IFF, from '../patches/MRLake.iff':
Duration: N/A, bitrate: N/A
Stream #0.0: Video: iff_byterun1, pal8, 737x595, PAR 17:20 DAR
737:700, 90k tbr, 90k tbn, 90k tbc
18270 dezicycles in decodeplane8, 1 runs, 0 skips
14805 dezicycles in decodeplane8, 2 runs, 0 skips
12340 dezicycles in decodeplane8, 4 runs, 0 skips
11127 dezicycles in decodeplane8, 8 runs, 0 skips
9640 dezicycles in decodeplane8, 16 runs, 0 skips
8882 dezicycles in decodeplane8, 32 runs, 0 skips
8496 dezicycles in decodeplane8, 64 runs, 0 skips
8312 dezicycles in decodeplane8, 127 runs, 1 skips
8220 dezicycles in decodeplane8, 255 runs, 1 skips
8173 dezicycles in decodeplane8, 511 runs, 1 skips
8149 dezicycles in decodeplane8, 1023 runs, 1 skips
8135 dezicycles in decodeplane8, 2046 runs, 2 skips
8128 dezicycles in decodeplane8, 4093 runs, 3 skips
0.76 A-V: 0.000 s:0.0 aq= 0KB vq= 0KB sq= 0B f=0/0 0/0
New method with 2 instructions less:
basty at cdgs-basty:~/src/ffmpeg/build$ ./ffplay ../patches/MRLake.iff
FFplay version git-5b9f10d, Copyright (c) 2003-2010 the FFmpeg developers
built on Apr 29 2010 15:19:11 with gcc 4.2.4 (Ubuntu 4.2.4-1ubuntu4)
configuration:
libavutil 50.14. 0 / 50.14. 0
libavcodec 52.66. 0 / 52.66. 0
libavformat 52.61. 0 / 52.61. 0
libavdevice 52. 2. 0 / 52. 2. 0
libswscale 0.10. 0 / 0.10. 0
[IFF @ 0x8b32790]Estimating duration from bitrate, this may be inaccurate
Input #0, IFF, from '../patches/MRLake.iff':
Duration: N/A, bitrate: N/A
Stream #0.0: Video: iff_byterun1, pal8, 737x595, PAR 17:20 DAR
737:700, 90k tbr, 90k tbn, 90k tbc
16180 dezicycles in decodeplane8, 1 runs, 0 skips
14210 dezicycles in decodeplane8, 2 runs, 0 skips
12887 dezicycles in decodeplane8, 4 runs, 0 skips
10575 dezicycles in decodeplane8, 8 runs, 0 skips
9363 dezicycles in decodeplane8, 16 runs, 0 skips
8755 dezicycles in decodeplane8, 32 runs, 0 skips
8445 dezicycles in decodeplane8, 64 runs, 0 skips
8288 dezicycles in decodeplane8, 128 runs, 0 skips
8208 dezicycles in decodeplane8, 256 runs, 0 skips
8185 dezicycles in decodeplane8, 512 runs, 0 skips
8162 dezicycles in decodeplane8, 1024 runs, 0 skips
8148 dezicycles in decodeplane8, 2048 runs, 0 skips
8145 dezicycles in decodeplane8, 4095 runs, 1 skips
3.84 A-V: 0.000 s:0.0 aq= 0KB vq= 0KB sq= 0B f=0/0 0/0
The new method is initially faster but is 0,01% slower at the end...
Remember, I'm back at home again, so these benchmarks are again Athlon
XP+ 2100, so please don't compare them with the ones I did on the
Pentium 4.
--
Best regards,
:-) Basty/CDGS (-:
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