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

[Roshantha Mendis]

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
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.videolan.org/pipermail/x265-devel/attachments/20150822/932be8a2/attachment.html>