[x265] Adaptove GoP sizes - not sure if its working

[Deepthi Nandakumar]

Hi,

You can just set keyint to the rough periodicity of I frames you prefer.
On Aug 22, 2015 9:12 AM, "Roshantha Mendis" <hrm506 at york.ac.uk> wrote:

> Hi Deepthi,
>
> Thank you for replying.
>
> So , if I want to get the encoder to add an I-frame instead of multiple p
> frames , do I have to set another param ? Scene-cut ? What's the upper
> limit for scenecut ?
>
> Thank you
> Rosh
> On 22 Aug 2015 2:17 am, "Deepthi Nandakumar" <deepthi at multicorewareinc.com>
> wrote:
>
>> Hello,
>>
>> Without the keyint argument, the default keyframe interval reverts to
>> 250, and the encoder will try to insert I-frames only closer to this value.
>> With --keyint 50, the encoder will try to insert GOP frames closer to 50,
>> and thats what the GOP size would roughly be.
>>
>> At the points where you expected a scene change / I frame, you might find
>> that the P-frames are significantly larger, but it's likely the encoder
>> didnt deem it necessary to insert an I-frame.
>>
>>
>>
>> On Sat, Aug 22, 2015 at 4:51 AM, Roshantha Mendis <hrm506 at york.ac.uk>
>> wrote:
>>
>>> Hi,
>>>
>>> I am trying to investigate GoP size changes based on scene changes in
>>> video.
>>>
>>> i've used x265 to encode a y4m (raw) file to hevc bitstream. A standard
>>> action fight scene : high moving, fast paced, 2-3 mins). So I was hoping to
>>> get highly varying scene changes. link :
>>> https://www.youtube.com/watch?v=gQEfEeBR3-M
>>>
>>> I used this command:
>>>
>>> ./x265 --input ../../../../ffmpeg_work/vids/originals/FightScene.y4m -F
>>> 0 -o FightScene_x265.bin --csv FightScene_x265.csv --csv-log-level 2
>>>
>>> // -- more info --
>>>
>>> y4m [info]: 312x176 fps 25/1 i420p8 frames 0 - 5104 of 5105
>>> raw [info]: output file: FightScene_x265.bin
>>> x265 [info]: HEVC encoder version 1.7+431-f63273fa3137
>>> x265 [info]: build info [Linux][GCC 4.8.4][64 bit] 8bit
>>> x265 [info]: using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX AVX2
>>> FMA3 LZCNT BMI2
>>> x265 [info]: Main profile, Level-2 (Main tier)
>>> x265 [info]: Thread pool created using 4 threads
>>> x265 [info]: frame threads / pool features : 2 / wpp(3 rows)
>>> x265 [info]: Coding QT: max CU size, min CU size : 64 / 8
>>> x265 [info]: Residual QT: max TU size, max depth : 32 / 1 inter / 1 intra
>>> x265 [info]: ME / range / subpel / merge : hex / 57 / 2 / 2
>>> x265 [info]: Keyframe min / max / scenecut : 25 / 250 / 40
>>> x265 [info]: Lookahead / bframes / badapt : 20 / 4 / 2
>>> x265 [info]: b-pyramid / weightp / weightb : 1 / 1 / 0
>>> x265 [info]: References / ref-limit cu / depth : 3 / 0 / 0
>>> x265 [info]: AQ: mode / str / qg-size / cu-tree : 1 / 1.0 / 32 / 1
>>> x265 [info]: Rate Control / qCompress : CRF-28.0 / 0.60
>>> x265 [info]: tools: rd=3 psy-rd=0.30 signhide tmvp strong-intra-smoothing
>>> x265 [info]: tools: deblock sao
>>> x265 [info]: frame I: 2, Avg QP:27.50 kb/s: 919.70
>>> x265 [info]: frame P: 82, Avg QP:29.56 kb/s: 170.33
>>> x265 [info]: frame B: 195, Avg QP:35.66 kb/s: 27.40
>>> x265 [info]: Weighted P-Frames: Y:1.2% UV:1.2%
>>> x265 [info]: consecutive B-frames: 9.3% 18.6% 12.8% 44.2% 15.1%
>>>
>>>
>>> // ---------
>>>
>>>
>>> So very basic, using only the defaults.
>>>
>>> I then investgate the csv file, and check the I-SLICE to I-SLICE frame
>>> gap (I assume I-Slice --> I-Slice is a GOP)
>>>
>>> They all seem around 246 to 252 frames per GoP. I was hoping to get
>>> drastic GoP changes : e.g. GoP sizes 25, 36, 100 .. 250 etc.
>>>
>>> Any thoughts why the difference are so small ?
>>>
>>> I even tried setting the following flags to high values :
>>>
>>> --scenecut 100 --keyint 240 --min-keyint 2
>>>
>>> but the still the gop size remained around 238-242 .. not much
>>> fluctuation.
>>>
>>>
>>> Please can someone advice why ?
>>>
>>>
>>>
>>> Many thanks
>>>
>>>
>>> --
>>> Rosh Mendis
>>> Research Student - EngD in LSCITS
>>> Dept. of Computer Science
>>> University of York
>>>
>>> Disclaimer: http://www.york.ac.uk/docs/disclaimer/email.htm
>>>
>>> _______________________________________________
>>> x265-devel mailing list
>>> x265-devel at videolan.org
>>> https://mailman.videolan.org/listinfo/x265-devel
>>>
>>>
>>
>> _______________________________________________
>> x265-devel mailing list
>> x265-devel at videolan.org
>> https://mailman.videolan.org/listinfo/x265-devel
>>
>>
> _______________________________________________
> x265-devel mailing list
> x265-devel at videolan.org
> https://mailman.videolan.org/listinfo/x265-devel
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.videolan.org/pipermail/x265-devel/attachments/20150822/8d56986f/attachment.html>